[PATCH v2 00/11] Metadata specific accouting and dirty writeout

[PATCH v2 00/11] Metadata specific accouting and dirty writeout

[Josef Bacik]

These patches are to support having metadata accounting and dirty handling
in a generic way.  For dirty metadata ext4 and xfs currently are limited by
their journal size, which allows them to handle dirty metadata flushing in a
relatively easy way.  Btrfs does not have this limiting factor, we can have as
much dirty metadata on the system as we have memory, so we have a dummy inode
that all of our metadat pages are allocated from so we can call
balance_dirty_pages() on it and make sure we don't overwhelm the system with
dirty metadata pages.

The problem with this is it severely limits our ability to do things like
support sub-pagesize blocksizes.  Btrfs also supports metadata blocksizes > page
size, which makes keeping track of our metadata and it's pages particularly
tricky.  We have the inode mapping with our pages, and we have another radix
tree for our actual metadata buffers.  This double accounting leads to some fun
shenanigans around reclaim and evicting pages we know we are done using.

To solve this we would like to switch to a scheme like xfs has, where we simply
have our metadata structures tied into the slab shrinking code, and we just use
alloc_page() for our pages, or kmalloc() when we add sub-pagesize blocksizes.
In order to do this we need infrastructure in place to make sure we still don't
overwhelm the system with dirty metadata pages.

Enter these patches.  Because metadata is tracked on a non-pagesize amount we
need to convert a bunch of our existing counters to bytes.  From there I've
added various counters for metadata, to keep track of overall metadata bytes,
how many are dirty and how many are under writeback.  I've added a super
operation to handle the dirty writeback, which is going to be handled mostly
inside the fs since we will need a little more smarts around what we writeback.

The last three patches are just there to show how we use the infrastructure in
the first 8 patches.  The actuall kill btree_inode patch is pretty big,
unfortunately ripping out all of the pagecache based handling and replacing it
with the new infrastructure has to be done whole-hog and can't be broken up
anymore than it already has been without making it un-bisectable.

Thanks,

Josef

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[PATCH v2 01/11] remove mapping from balance_dirty_pages*()

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

The only reason we pass in the mapping is to get the inode in order to see if
writeback cgroups is enabled, and even then it only checks the bdi and a super
block flag.  balance_dirty_pages() doesn't even use the mapping.  Since
balance_dirty_pages*() works on a bdi level, just pass in the bdi and super
block directly so we can avoid using mapping.  This will allow us to still use
balance_dirty_pages for dirty metadata pages that are not backed by an
address_mapping.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 drivers/mtd/devices/block2mtd.c | 12 ++++++++----
 fs/btrfs/disk-io.c              |  3 ++-
 fs/btrfs/file.c                 |  3 ++-
 fs/btrfs/ioctl.c                |  3 ++-
 fs/btrfs/relocation.c           |  3 ++-
 fs/buffer.c                     |  3 ++-
 fs/iomap.c                      |  6 ++++--
 fs/ntfs/attrib.c                | 11 ++++++++---
 fs/ntfs/file.c                  |  4 ++--
 include/linux/backing-dev.h     | 29 +++++++++++++++++++++++------
 include/linux/writeback.h       |  4 +++-
 mm/filemap.c                    |  4 +++-
 mm/memory.c                     |  5 ++++-
 mm/page-writeback.c             | 15 +++++++--------
 14 files changed, 72 insertions(+), 33 deletions(-)

diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
index 7c887f111a7d..7892d0b9fcb0 100644
--- a/drivers/mtd/devices/block2mtd.c
+++ b/drivers/mtd/devices/block2mtd.c
@@ -52,7 +52,8 @@ static struct page *page_read(struct address_space *mapping, int index)
 /* erase a specified part of the device */
 static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
 {
-	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
+	struct inode *inode = dev->blkdev->bd_inode;
+	struct address_space *mapping = inode->i_mapping;
 	struct page *page;
 	int index = to >> PAGE_SHIFT;	// page index
 	int pages = len >> PAGE_SHIFT;
@@ -71,7 +72,8 @@ static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
 				memset(page_address(page), 0xff, PAGE_SIZE);
 				set_page_dirty(page);
 				unlock_page(page);
-				balance_dirty_pages_ratelimited(mapping);
+				balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+								inode->i_sb);
 				break;
 			}
 
@@ -141,7 +143,8 @@ static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
 		loff_t to, size_t len, size_t *retlen)
 {
 	struct page *page;
-	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
+	struct inode *inode = dev->blkdev->bd_inode;
+	struct address_space *mapping = inode->i_mapping;
 	int index = to >> PAGE_SHIFT;	// page index
 	int offset = to & ~PAGE_MASK;	// page offset
 	int cpylen;
@@ -162,7 +165,8 @@ static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
 			memcpy(page_address(page) + offset, buf, cpylen);
 			set_page_dirty(page);
 			unlock_page(page);
-			balance_dirty_pages_ratelimited(mapping);
+			balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+							inode->i_sb);
 		}
 		put_page(page);
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 689b9913ccb5..8b6df7688d52 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4150,7 +4150,8 @@ static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
 	ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
 				     BTRFS_DIRTY_METADATA_THRESH);
 	if (ret > 0) {
-		balance_dirty_pages_ratelimited(fs_info->btree_inode->i_mapping);
+		balance_dirty_pages_ratelimited(fs_info->sb->s_bdi,
+						fs_info->sb);
 	}
 }
 
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ab1c38f2dd8c..4bc6cd6509be 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1779,7 +1779,8 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 
 		cond_resched();
 
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 		if (dirty_pages < (fs_info->nodesize >> PAGE_SHIFT) + 1)
 			btrfs_btree_balance_dirty(fs_info);
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6a07d4e12fd2..ec92fb5e2b51 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1368,7 +1368,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 		}
 
 		defrag_count += ret;
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 		inode_unlock(inode);
 
 		if (newer_than) {
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 4cf2eb67eba6..9f31c5e6c0e5 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3278,7 +3278,8 @@ static int relocate_file_extent_cluster(struct inode *inode,
 
 		index++;
 		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 		btrfs_throttle(fs_info);
 	}
 	WARN_ON(nr != cluster->nr);
diff --git a/fs/buffer.c b/fs/buffer.c
index 170df856bdb9..36be326a316c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2421,7 +2421,8 @@ static int cont_expand_zero(struct file *file, struct address_space *mapping,
 		BUG_ON(err != len);
 		err = 0;
 
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 
 		if (unlikely(fatal_signal_pending(current))) {
 			err = -EINTR;
diff --git a/fs/iomap.c b/fs/iomap.c
index 269b24a01f32..0eb1ec680f87 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -223,7 +223,8 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		written += copied;
 		length -= copied;
 
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 	} while (iov_iter_count(i) && length);
 
 	return written ? written : status;
@@ -305,7 +306,8 @@ iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		written += status;
 		length -= status;
 
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 	} while (length);
 
 	return written;
diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
index 44a39a099b54..d85368dd82e7 100644
--- a/fs/ntfs/attrib.c
+++ b/fs/ntfs/attrib.c
@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/writeback.h>
+#include <linux/backing-dev.h>
 
 #include "attrib.h"
 #include "debug.h"
@@ -2493,6 +2494,7 @@ s64 ntfs_attr_extend_allocation(ntfs_inode *ni, s64 new_alloc_size,
 int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
 {
 	ntfs_volume *vol = ni->vol;
+	struct inode *inode = VFS_I(ni);
 	struct address_space *mapping;
 	struct page *page;
 	u8 *kaddr;
@@ -2545,7 +2547,8 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
 		kunmap_atomic(kaddr);
 		set_page_dirty(page);
 		put_page(page);
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 		cond_resched();
 		if (idx == end)
 			goto done;
@@ -2586,7 +2589,8 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
 		/* Finally unlock and release the page. */
 		unlock_page(page);
 		put_page(page);
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 		cond_resched();
 	}
 	/* If there is a last partial page, need to do it the slow way. */
@@ -2603,7 +2607,8 @@ int ntfs_attr_set(ntfs_inode *ni, const s64 ofs, const s64 cnt, const u8 val)
 		kunmap_atomic(kaddr);
 		set_page_dirty(page);
 		put_page(page);
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 		cond_resched();
 	}
 done:
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index 331910fa8442..77b04be4a157 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -276,7 +276,7 @@ static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size)
 		 * number of pages we read and make dirty in the case of sparse
 		 * files.
 		 */
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(vi), vi->i_sb);
 		cond_resched();
 	} while (++index < end_index);
 	read_lock_irqsave(&ni->size_lock, flags);
@@ -1913,7 +1913,7 @@ static ssize_t ntfs_perform_write(struct file *file, struct iov_iter *i,
 		iov_iter_advance(i, copied);
 		pos += copied;
 		written += copied;
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(vi), vi->i_sb);
 		if (fatal_signal_pending(current)) {
 			status = -EINTR;
 			break;
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 854e1bdd0b2a..14e266d12620 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -228,8 +228,9 @@ void wb_blkcg_offline(struct blkcg *blkcg);
 int inode_congested(struct inode *inode, int cong_bits);
 
 /**
- * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
- * @inode: inode of interest
+ * bdi_cgwb_enabled - test wether cgroup writeback is enabled on a filesystem
+ * @bdi: the bdi we care about
+ * @sb: the super for the bdi
  *
  * cgroup writeback requires support from both the bdi and filesystem.
  * Also, both memcg and iocg have to be on the default hierarchy.  Test
@@ -238,15 +239,25 @@ int inode_congested(struct inode *inode, int cong_bits);
  * Note that the test result may change dynamically on the same inode
  * depending on how memcg and iocg are configured.
  */
-static inline bool inode_cgwb_enabled(struct inode *inode)
+static inline bool bdi_cgwb_enabled(struct backing_dev_info *bdi,
+				    struct super_block *sb)
 {
-	struct backing_dev_info *bdi = inode_to_bdi(inode);
-
 	return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
 		cgroup_subsys_on_dfl(io_cgrp_subsys) &&
 		bdi_cap_account_dirty(bdi) &&
 		(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
-		(inode->i_sb->s_iflags & SB_I_CGROUPWB);
+		(sb->s_iflags & SB_I_CGROUPWB);
+}
+
+/**
+ * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
+ * @inode: inode of interest
+ *
+ * Does the inode have cgroup writeback support.
+ */
+static inline bool inode_cgwb_enabled(struct inode *inode)
+{
+	return bdi_cgwb_enabled(inode_to_bdi(inode), inode->i_sb);
 }
 
 /**
@@ -389,6 +400,12 @@ static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
 
 #else	/* CONFIG_CGROUP_WRITEBACK */
 
+static inline bool bdi_cgwb_enabled(struct backing_dev_info *bdi,
+				    struct super_block *sb)
+{
+	return false;
+}
+
 static inline bool inode_cgwb_enabled(struct inode *inode)
 {
 	return false;
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index d5815794416c..fa799a4a7755 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -376,7 +376,9 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
 
 void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
-void balance_dirty_pages_ratelimited(struct address_space *mapping);
+void page_writeback_init(void);
+void balance_dirty_pages_ratelimited(struct backing_dev_info *bdi,
+				     struct super_block *sb);
 bool wb_over_bg_thresh(struct bdi_writeback *wb);
 
 typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
diff --git a/mm/filemap.c b/mm/filemap.c
index 870971e20967..5ea4878e9c78 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2971,6 +2971,7 @@ ssize_t generic_perform_write(struct file *file,
 				struct iov_iter *i, loff_t pos)
 {
 	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
 	const struct address_space_operations *a_ops = mapping->a_ops;
 	long status = 0;
 	ssize_t written = 0;
@@ -3044,7 +3045,8 @@ ssize_t generic_perform_write(struct file *file,
 		pos += copied;
 		written += copied;
 
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 	} while (iov_iter_count(i));
 
 	return written ? written : status;
diff --git a/mm/memory.c b/mm/memory.c
index ec4e15494901..86f31b3d54c6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -70,6 +70,7 @@
 #include <linux/userfaultfd_k.h>
 #include <linux/dax.h>
 #include <linux/oom.h>
+#include <linux/backing-dev.h>
 
 #include <asm/io.h>
 #include <asm/mmu_context.h>
@@ -2391,11 +2392,13 @@ static void fault_dirty_shared_page(struct vm_area_struct *vma,
 	unlock_page(page);
 
 	if ((dirtied || page_mkwrite) && mapping) {
+		struct inode *inode = mapping->host;
 		/*
 		 * Some device drivers do not set page.mapping
 		 * but still dirty their pages
 		 */
-		balance_dirty_pages_ratelimited(mapping);
+		balance_dirty_pages_ratelimited(inode_to_bdi(inode),
+						inode->i_sb);
 	}
 
 	if (!page_mkwrite)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0b9c5cbe8eba..1a47d4296750 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1559,8 +1559,7 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc)
  * If we're over `background_thresh' then the writeback threads are woken to
  * perform some writeout.
  */
-static void balance_dirty_pages(struct address_space *mapping,
-				struct bdi_writeback *wb,
+static void balance_dirty_pages(struct bdi_writeback *wb,
 				unsigned long pages_dirtied)
 {
 	struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) };
@@ -1850,7 +1849,8 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
 
 /**
  * balance_dirty_pages_ratelimited - balance dirty memory state
- * @mapping: address_space which was dirtied
+ * @bdi: the bdi that was dirtied
+ * @sb: the super block that was dirtied
  *
  * Processes which are dirtying memory should call in here once for each page
  * which was newly dirtied.  The function will periodically check the system's
@@ -1861,10 +1861,9 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
  * limit we decrease the ratelimiting by a lot, to prevent individual processes
  * from overshooting the limit by (ratelimit_pages) each.
  */
-void balance_dirty_pages_ratelimited(struct address_space *mapping)
+void balance_dirty_pages_ratelimited(struct backing_dev_info *bdi,
+				     struct super_block *sb)
 {
-	struct inode *inode = mapping->host;
-	struct backing_dev_info *bdi = inode_to_bdi(inode);
 	struct bdi_writeback *wb = NULL;
 	int ratelimit;
 	int *p;
@@ -1872,7 +1871,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
 	if (!bdi_cap_account_dirty(bdi))
 		return;
 
-	if (inode_cgwb_enabled(inode))
+	if (bdi_cgwb_enabled(bdi, sb))
 		wb = wb_get_create_current(bdi, GFP_KERNEL);
 	if (!wb)
 		wb = &bdi->wb;
@@ -1910,7 +1909,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
 	preempt_enable();
 
 	if (unlikely(current->nr_dirtied >= ratelimit))
-		balance_dirty_pages(mapping, wb, current->nr_dirtied);
+		balance_dirty_pages(wb, current->nr_dirtied);
 
 	wb_put(wb);
 }
-- 
2.7.5

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[PATCH v2 02/11] writeback: convert WB_WRITTEN/WB_DIRITED counters to bytes

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

These are counters that constantly go up in order to do bandwidth calculations.
It isn't important what the units are in, as long as they are consistent between
the two of them, so convert them to count bytes written/dirtied, and allow the
metadata accounting stuff to change the counters as well.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
---
 fs/fuse/file.c                   |  4 ++--
 include/linux/backing-dev-defs.h |  4 ++--
 include/linux/backing-dev.h      |  2 +-
 mm/backing-dev.c                 |  9 +++++----
 mm/page-writeback.c              | 20 ++++++++++----------
 5 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index cb7dff5c45d7..67e7c4fac28d 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1471,7 +1471,7 @@ static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
 	for (i = 0; i < req->num_pages; i++) {
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
 		dec_node_page_state(req->pages[i], NR_WRITEBACK_TEMP);
-		wb_writeout_inc(&bdi->wb);
+		wb_writeout_add(&bdi->wb, PAGE_SIZE);
 	}
 	wake_up(&fi->page_waitq);
 }
@@ -1776,7 +1776,7 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
 
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
 		dec_node_page_state(page, NR_WRITEBACK_TEMP);
-		wb_writeout_inc(&bdi->wb);
+		wb_writeout_add(&bdi->wb, PAGE_SIZE);
 		fuse_writepage_free(fc, new_req);
 		fuse_request_free(new_req);
 		goto out;
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 866c433e7d32..ded45ac2cec7 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -36,8 +36,8 @@ typedef int (congested_fn)(void *, int);
 enum wb_stat_item {
 	WB_RECLAIMABLE,
 	WB_WRITEBACK,
-	WB_DIRTIED,
-	WB_WRITTEN,
+	WB_DIRTIED_BYTES,
+	WB_WRITTEN_BYTES,
 	NR_WB_STAT_ITEMS
 };
 
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 14e266d12620..39b8dc486ea7 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -89,7 +89,7 @@ static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
 	return percpu_counter_sum_positive(&wb->stat[item]);
 }
 
-extern void wb_writeout_inc(struct bdi_writeback *wb);
+extern void wb_writeout_add(struct bdi_writeback *wb, long bytes);
 
 /*
  * maximal error of a stat counter.
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index e19606bb41a0..62a332a91b38 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -68,14 +68,15 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 	wb_thresh = wb_calc_thresh(wb, dirty_thresh);
 
 #define K(x) ((x) << (PAGE_SHIFT - 10))
+#define BtoK(x) ((x) >> 10)
 	seq_printf(m,
 		   "BdiWriteback:       %10lu kB\n"
 		   "BdiReclaimable:     %10lu kB\n"
 		   "BdiDirtyThresh:     %10lu kB\n"
 		   "DirtyThresh:        %10lu kB\n"
 		   "BackgroundThresh:   %10lu kB\n"
-		   "BdiDirtied:         %10lu kB\n"
-		   "BdiWritten:         %10lu kB\n"
+		   "BdiDirtiedBytes:    %10lu kB\n"
+		   "BdiWrittenBytes:    %10lu kB\n"
 		   "BdiWriteBandwidth:  %10lu kBps\n"
 		   "b_dirty:            %10lu\n"
 		   "b_io:               %10lu\n"
@@ -88,8 +89,8 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 		   K(wb_thresh),
 		   K(dirty_thresh),
 		   K(background_thresh),
-		   (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
-		   (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
+		   (unsigned long) BtoK(wb_stat(wb, WB_DIRTIED_BYTES)),
+		   (unsigned long) BtoK(wb_stat(wb, WB_WRITTEN_BYTES)),
 		   (unsigned long) K(wb->write_bandwidth),
 		   nr_dirty,
 		   nr_io,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 1a47d4296750..e4563645749a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -597,11 +597,11 @@ static void wb_domain_writeout_inc(struct wb_domain *dom,
  * Increment @wb's writeout completion count and the global writeout
  * completion count. Called from test_clear_page_writeback().
  */
-static inline void __wb_writeout_inc(struct bdi_writeback *wb)
+static inline void __wb_writeout_add(struct bdi_writeback *wb, long bytes)
 {
 	struct wb_domain *cgdom;
 
-	inc_wb_stat(wb, WB_WRITTEN);
+	__add_wb_stat(wb, WB_WRITTEN_BYTES, bytes);
 	wb_domain_writeout_inc(&global_wb_domain, &wb->completions,
 			       wb->bdi->max_prop_frac);
 
@@ -611,15 +611,15 @@ static inline void __wb_writeout_inc(struct bdi_writeback *wb)
 				       wb->bdi->max_prop_frac);
 }
 
-void wb_writeout_inc(struct bdi_writeback *wb)
+void wb_writeout_add(struct bdi_writeback *wb, long bytes)
 {
 	unsigned long flags;
 
 	local_irq_save(flags);
-	__wb_writeout_inc(wb);
+	__wb_writeout_add(wb, bytes);
 	local_irq_restore(flags);
 }
-EXPORT_SYMBOL_GPL(wb_writeout_inc);
+EXPORT_SYMBOL_GPL(wb_writeout_add);
 
 /*
  * On idle system, we can be called long after we scheduled because we use
@@ -1362,8 +1362,8 @@ static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc,
 	if (elapsed < BANDWIDTH_INTERVAL)
 		return;
 
-	dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]);
-	written = percpu_counter_read(&wb->stat[WB_WRITTEN]);
+	dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED_BYTES]) >> PAGE_SHIFT;
+	written = percpu_counter_read(&wb->stat[WB_WRITTEN_BYTES]) >> PAGE_SHIFT;
 
 	/*
 	 * Skip quiet periods when disk bandwidth is under-utilized.
@@ -2435,7 +2435,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
 		__inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
 		__inc_node_page_state(page, NR_DIRTIED);
 		inc_wb_stat(wb, WB_RECLAIMABLE);
-		inc_wb_stat(wb, WB_DIRTIED);
+		__add_wb_stat(wb, WB_DIRTIED_BYTES, PAGE_SIZE);
 		task_io_account_write(PAGE_SIZE);
 		current->nr_dirtied++;
 		this_cpu_inc(bdp_ratelimits);
@@ -2522,7 +2522,7 @@ void account_page_redirty(struct page *page)
 		wb = unlocked_inode_to_wb_begin(inode, &locked);
 		current->nr_dirtied--;
 		dec_node_page_state(page, NR_DIRTIED);
-		dec_wb_stat(wb, WB_DIRTIED);
+		__add_wb_stat(wb, WB_DIRTIED_BYTES, -(long)PAGE_SIZE);
 		unlocked_inode_to_wb_end(inode, locked);
 	}
 }
@@ -2744,7 +2744,7 @@ int test_clear_page_writeback(struct page *page)
 				struct bdi_writeback *wb = inode_to_wb(inode);
 
 				dec_wb_stat(wb, WB_WRITEBACK);
-				__wb_writeout_inc(wb);
+				__wb_writeout_add(wb, PAGE_SIZE);
 			}
 		}
 
-- 
2.7.5

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[PATCH v2 03/11] lib: make the fprop batch size a multiple of PAGE_SIZE

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

We are converting the writeback counters to use bytes instead of pages,
so we need to make the batch size for the percpu modifications align
properly with the new units.  Since we used pages before, just multiply
by PAGE_SIZE to get the equivalent bytes for the batch size.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 lib/flex_proportions.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
index 2cc1f94e03a1..b0343ae71f5e 100644
--- a/lib/flex_proportions.c
+++ b/lib/flex_proportions.c
@@ -166,7 +166,7 @@ void fprop_fraction_single(struct fprop_global *p,
 /*
  * ---- PERCPU ----
  */
-#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
+#define PROP_BATCH (8*PAGE_SIZE*(1+ilog2(nr_cpu_ids)))
 
 int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp)
 {
-- 
2.7.5

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[PATCH v2 04/11] lib: add a __fprop_add_percpu_max

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

This helper allows us to add an arbitrary amount to the fprop
structures.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 include/linux/flex_proportions.h | 11 +++++++++--
 lib/flex_proportions.c           |  9 +++++----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/linux/flex_proportions.h b/include/linux/flex_proportions.h
index 0d348e011a6e..9f88684bf0a0 100644
--- a/include/linux/flex_proportions.h
+++ b/include/linux/flex_proportions.h
@@ -83,8 +83,8 @@ struct fprop_local_percpu {
 int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp);
 void fprop_local_destroy_percpu(struct fprop_local_percpu *pl);
 void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl);
-void __fprop_inc_percpu_max(struct fprop_global *p, struct fprop_local_percpu *pl,
-			    int max_frac);
+void __fprop_add_percpu_max(struct fprop_global *p, struct fprop_local_percpu *pl,
+			    unsigned long nr, int max_frac);
 void fprop_fraction_percpu(struct fprop_global *p,
 	struct fprop_local_percpu *pl, unsigned long *numerator,
 	unsigned long *denominator);
@@ -99,4 +99,11 @@ void fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl)
 	local_irq_restore(flags);
 }
 
+static inline
+void __fprop_inc_percpu_max(struct fprop_global *p,
+			    struct fprop_local_percpu *pl, int max_frac)
+{
+	__fprop_add_percpu_max(p, pl, 1, max_frac);
+}
+
 #endif
diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
index b0343ae71f5e..fd95791a2c93 100644
--- a/lib/flex_proportions.c
+++ b/lib/flex_proportions.c
@@ -255,8 +255,9 @@ void fprop_fraction_percpu(struct fprop_global *p,
  * Like __fprop_inc_percpu() except that event is counted only if the given
  * type has fraction smaller than @max_frac/FPROP_FRAC_BASE
  */
-void __fprop_inc_percpu_max(struct fprop_global *p,
-			    struct fprop_local_percpu *pl, int max_frac)
+void __fprop_add_percpu_max(struct fprop_global *p,
+			    struct fprop_local_percpu *pl, unsigned long nr,
+			    int max_frac)
 {
 	if (unlikely(max_frac < FPROP_FRAC_BASE)) {
 		unsigned long numerator, denominator;
@@ -267,6 +268,6 @@ void __fprop_inc_percpu_max(struct fprop_global *p,
 			return;
 	} else
 		fprop_reflect_period_percpu(p, pl);
-	percpu_counter_add_batch(&pl->events, 1, PROP_BATCH);
-	percpu_counter_add(&p->events, 1);
+	percpu_counter_add_batch(&pl->events, nr, PROP_BATCH);
+	percpu_counter_add(&p->events, nr);
 }
-- 
2.7.5

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[PATCH v2 05/11] writeback: convert the flexible prop stuff to bytes

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

The flexible proportions were all page based, but now that we are doing
metadata writeout that can be smaller or larger than page size we need
to account for this in bytes instead of number of pages.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 mm/page-writeback.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e4563645749a..2a1994194cc1 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -574,11 +574,11 @@ static unsigned long wp_next_time(unsigned long cur_time)
 	return cur_time;
 }
 
-static void wb_domain_writeout_inc(struct wb_domain *dom,
+static void wb_domain_writeout_add(struct wb_domain *dom,
 				   struct fprop_local_percpu *completions,
-				   unsigned int max_prop_frac)
+				   long bytes, unsigned int max_prop_frac)
 {
-	__fprop_inc_percpu_max(&dom->completions, completions,
+	__fprop_add_percpu_max(&dom->completions, completions, bytes,
 			       max_prop_frac);
 	/* First event after period switching was turned off? */
 	if (unlikely(!dom->period_time)) {
@@ -602,12 +602,12 @@ static inline void __wb_writeout_add(struct bdi_writeback *wb, long bytes)
 	struct wb_domain *cgdom;
 
 	__add_wb_stat(wb, WB_WRITTEN_BYTES, bytes);
-	wb_domain_writeout_inc(&global_wb_domain, &wb->completions,
+	wb_domain_writeout_add(&global_wb_domain, &wb->completions, bytes,
 			       wb->bdi->max_prop_frac);
 
 	cgdom = mem_cgroup_wb_domain(wb);
 	if (cgdom)
-		wb_domain_writeout_inc(cgdom, wb_memcg_completions(wb),
+		wb_domain_writeout_add(cgdom, wb_memcg_completions(wb), bytes,
 				       wb->bdi->max_prop_frac);
 }
 
-- 
2.7.5

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[PATCH v2 06/11] writeback: add counters for metadata usage

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

Btrfs has no bounds except memory on the amount of dirty memory that we have in
use for metadata.  Historically we have used a special inode so we could take
advantage of the balance_dirty_pages throttling that comes with using pagecache.
However as we'd like to support different blocksizes it would be nice to not
have to rely on pagecache, but still get the balance_dirty_pages throttling
without having to do it ourselves.

So introduce *METADATA_DIRTY_BYTES and *METADATA_WRITEBACK_BYTES.  These are
zone and bdi_writeback counters to keep track of how many bytes we have in
flight for METADATA.  We need to count in bytes as blocksizes could be
percentages of pagesize.  We simply convert the bytes to number of pages where
it is needed for the throttling.

Also introduce NR_METADATA_BYTES so we can keep track of the total amount of
pages used for metadata on the system.  This is also needed so things like dirty
throttling know that this is dirtyable memory as well and easily reclaimed.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 drivers/base/node.c              |   8 +++
 fs/fs-writeback.c                |   2 +
 fs/proc/meminfo.c                |   8 +++
 include/linux/backing-dev-defs.h |   2 +
 include/linux/mm.h               |   9 +++
 include/linux/mmzone.h           |   3 +
 include/trace/events/writeback.h |  13 +++-
 mm/backing-dev.c                 |   4 ++
 mm/page-writeback.c              | 142 +++++++++++++++++++++++++++++++++++----
 mm/page_alloc.c                  |  20 ++++--
 mm/util.c                        |   1 +
 mm/vmscan.c                      |  19 +++++-
 mm/vmstat.c                      |   3 +
 13 files changed, 212 insertions(+), 22 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 3855902f2c5b..a39cecc8957a 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -51,6 +51,8 @@ static DEVICE_ATTR(cpumap,  S_IRUGO, node_read_cpumask, NULL);
 static DEVICE_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL);
 
 #define K(x) ((x) << (PAGE_SHIFT - 10))
+#define BtoK(x) ((x) >> 10)
+
 static ssize_t node_read_meminfo(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
@@ -99,7 +101,10 @@ static ssize_t node_read_meminfo(struct device *dev,
 #endif
 	n += sprintf(buf + n,
 		       "Node %d Dirty:          %8lu kB\n"
+		       "Node %d MetadataDirty:	%8lu kB\n"
 		       "Node %d Writeback:      %8lu kB\n"
+		       "Node %d MetaWriteback:  %8lu kB\n"
+		       "Node %d Metadata:       %8lu kB\n"
 		       "Node %d FilePages:      %8lu kB\n"
 		       "Node %d Mapped:         %8lu kB\n"
 		       "Node %d AnonPages:      %8lu kB\n"
@@ -119,8 +124,11 @@ static ssize_t node_read_meminfo(struct device *dev,
 #endif
 			,
 		       nid, K(node_page_state(pgdat, NR_FILE_DIRTY)),
+		       nid, BtoK(node_page_state(pgdat, NR_METADATA_DIRTY_BYTES)),
 		       nid, K(node_page_state(pgdat, NR_WRITEBACK)),
+		       nid, BtoK(node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES)),
 		       nid, K(node_page_state(pgdat, NR_FILE_PAGES)),
+		       nid, BtoK(node_page_state(pgdat, NR_METADATA_BYTES)),
 		       nid, K(node_page_state(pgdat, NR_FILE_MAPPED)),
 		       nid, K(node_page_state(pgdat, NR_ANON_MAPPED)),
 		       nid, K(i.sharedram),
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 245c430a2e41..987448ed7698 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1814,6 +1814,7 @@ static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
 	return work;
 }
 
+#define BtoP(x) ((x) >> PAGE_SHIFT)
 /*
  * Add in the number of potentially dirty inodes, because each inode
  * write can dirty pagecache in the underlying blockdev.
@@ -1822,6 +1823,7 @@ static unsigned long get_nr_dirty_pages(void)
 {
 	return global_node_page_state(NR_FILE_DIRTY) +
 		global_node_page_state(NR_UNSTABLE_NFS) +
+		BtoP(global_node_page_state(NR_METADATA_DIRTY_BYTES)) +
 		get_nr_dirty_inodes();
 }
 
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index cdd979724c74..fa1fd24a4d99 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -42,6 +42,8 @@ static void show_val_kb(struct seq_file *m, const char *s, unsigned long num)
 	seq_write(m, " kB\n", 4);
 }
 
+#define BtoP(x) ((x) >> PAGE_SHIFT)
+
 static int meminfo_proc_show(struct seq_file *m, void *v)
 {
 	struct sysinfo i;
@@ -71,6 +73,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "Buffers:        ", i.bufferram);
 	show_val_kb(m, "Cached:         ", cached);
 	show_val_kb(m, "SwapCached:     ", total_swapcache_pages());
+	show_val_kb(m, "Metadata:       ",
+		    BtoP(global_node_page_state(NR_METADATA_BYTES)));
 	show_val_kb(m, "Active:         ", pages[LRU_ACTIVE_ANON] +
 					   pages[LRU_ACTIVE_FILE]);
 	show_val_kb(m, "Inactive:       ", pages[LRU_INACTIVE_ANON] +
@@ -98,8 +102,12 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "SwapFree:       ", i.freeswap);
 	show_val_kb(m, "Dirty:          ",
 		    global_node_page_state(NR_FILE_DIRTY));
+	show_val_kb(m, "MetadataDirty:  ",
+		    BtoP(global_node_page_state(NR_METADATA_DIRTY_BYTES)));
 	show_val_kb(m, "Writeback:      ",
 		    global_node_page_state(NR_WRITEBACK));
+	show_val_kb(m, "MetaWriteback:  ",
+		    BtoP(global_node_page_state(NR_METADATA_WRITEBACK_BYTES)));
 	show_val_kb(m, "AnonPages:      ",
 		    global_node_page_state(NR_ANON_MAPPED));
 	show_val_kb(m, "Mapped:         ",
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index ded45ac2cec7..78c65e2910dc 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -38,6 +38,8 @@ enum wb_stat_item {
 	WB_WRITEBACK,
 	WB_DIRTIED_BYTES,
 	WB_WRITTEN_BYTES,
+	WB_METADATA_DIRTY_BYTES,
+	WB_METADATA_WRITEBACK_BYTES,
 	NR_WB_STAT_ITEMS
 };
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f8c10d336e42..e14ada96af25 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -32,6 +32,7 @@ struct file_ra_state;
 struct user_struct;
 struct writeback_control;
 struct bdi_writeback;
+struct backing_dev_info;
 
 void init_mm_internals(void);
 
@@ -1428,6 +1429,14 @@ int redirty_page_for_writepage(struct writeback_control *wbc,
 void account_page_dirtied(struct page *page, struct address_space *mapping);
 void account_page_cleaned(struct page *page, struct address_space *mapping,
 			  struct bdi_writeback *wb);
+void account_metadata_dirtied(struct page *page, struct backing_dev_info *bdi,
+			      long bytes);
+void account_metadata_cleaned(struct page *page, struct backing_dev_info *bdi,
+			      long bytes);
+void account_metadata_writeback(struct page *page,
+				struct backing_dev_info *bdi, long bytes);
+void account_metadata_end_writeback(struct page *page,
+				    struct backing_dev_info *bdi, long bytes);
 int set_page_dirty(struct page *page);
 int set_page_dirty_lock(struct page *page);
 void cancel_dirty_page(struct page *page);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 356a814e7c8e..fd516a0f0bfe 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -179,6 +179,9 @@ enum node_stat_item {
 	NR_VMSCAN_IMMEDIATE,	/* Prioritise for reclaim when writeback ends */
 	NR_DIRTIED,		/* page dirtyings since bootup */
 	NR_WRITTEN,		/* page writings since bootup */
+	NR_METADATA_DIRTY_BYTES,	/* Metadata dirty bytes */
+	NR_METADATA_WRITEBACK_BYTES,	/* Metadata writeback bytes */
+	NR_METADATA_BYTES,	/* total metadata bytes in use. */
 	NR_VM_NODE_STAT_ITEMS
 };
 
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 9b57f014d79d..989cdae363db 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -390,6 +390,8 @@ TRACE_EVENT(writeback_queue_io,
 	)
 );
 
+#define BtoP(x) ((x) >> PAGE_SHIFT)
+
 TRACE_EVENT(global_dirty_state,
 
 	TP_PROTO(unsigned long background_thresh,
@@ -402,7 +404,9 @@ TRACE_EVENT(global_dirty_state,
 
 	TP_STRUCT__entry(
 		__field(unsigned long,	nr_dirty)
+		__field(unsigned long,	nr_metadata_dirty)
 		__field(unsigned long,	nr_writeback)
+		__field(unsigned long,	nr_metadata_writeback)
 		__field(unsigned long,	nr_unstable)
 		__field(unsigned long,	background_thresh)
 		__field(unsigned long,	dirty_thresh)
@@ -413,7 +417,9 @@ TRACE_EVENT(global_dirty_state,
 
 	TP_fast_assign(
 		__entry->nr_dirty	= global_node_page_state(NR_FILE_DIRTY);
+		__entry->nr_metadata_dirty = BtoP(global_node_page_state(NR_METADATA_DIRTY_BYTES));
 		__entry->nr_writeback	= global_node_page_state(NR_WRITEBACK);
+		__entry->nr_metadata_dirty = BtoP(global_node_page_state(NR_METADATA_WRITEBACK_BYTES));
 		__entry->nr_unstable	= global_node_page_state(NR_UNSTABLE_NFS);
 		__entry->nr_dirtied	= global_node_page_state(NR_DIRTIED);
 		__entry->nr_written	= global_node_page_state(NR_WRITTEN);
@@ -424,7 +430,8 @@ TRACE_EVENT(global_dirty_state,
 
 	TP_printk("dirty=%lu writeback=%lu unstable=%lu "
 		  "bg_thresh=%lu thresh=%lu limit=%lu "
-		  "dirtied=%lu written=%lu",
+		  "dirtied=%lu written=%lu metadata_dirty=%lu "
+		  "metadata_writeback=%lu",
 		  __entry->nr_dirty,
 		  __entry->nr_writeback,
 		  __entry->nr_unstable,
@@ -432,7 +439,9 @@ TRACE_EVENT(global_dirty_state,
 		  __entry->dirty_thresh,
 		  __entry->dirty_limit,
 		  __entry->nr_dirtied,
-		  __entry->nr_written
+		  __entry->nr_written,
+		  __entry->nr_metadata_dirty,
+		  __entry->nr_metadata_writeback
 	)
 );
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 62a332a91b38..0aad67bc0898 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -77,6 +77,8 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 		   "BackgroundThresh:   %10lu kB\n"
 		   "BdiDirtiedBytes:    %10lu kB\n"
 		   "BdiWrittenBytes:    %10lu kB\n"
+		   "BdiMetadataDirty:   %10lu kB\n"
+		   "BdiMetaWriteback:	%10lu kB\n"
 		   "BdiWriteBandwidth:  %10lu kBps\n"
 		   "b_dirty:            %10lu\n"
 		   "b_io:               %10lu\n"
@@ -91,6 +93,8 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 		   K(background_thresh),
 		   (unsigned long) BtoK(wb_stat(wb, WB_DIRTIED_BYTES)),
 		   (unsigned long) BtoK(wb_stat(wb, WB_WRITTEN_BYTES)),
+		   (unsigned long) BtoK(wb_stat(wb, WB_METADATA_DIRTY_BYTES)),
+		   (unsigned long) BtoK(wb_stat(wb, WB_METADATA_WRITEBACK_BYTES)),
 		   (unsigned long) K(wb->write_bandwidth),
 		   nr_dirty,
 		   nr_io,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2a1994194cc1..044aaa1ab090 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -249,6 +249,8 @@ static void wb_min_max_ratio(struct bdi_writeback *wb,
 
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
+#define BtoP(x) ((x) >> PAGE_SHIFT)
+
 /*
  * In a memory zone, there is a certain amount of pages we consider
  * available for the page cache, which is essentially the number of
@@ -297,6 +299,7 @@ static unsigned long node_dirtyable_memory(struct pglist_data *pgdat)
 
 	nr_pages += node_page_state(pgdat, NR_INACTIVE_FILE);
 	nr_pages += node_page_state(pgdat, NR_ACTIVE_FILE);
+	nr_pages += node_page_state(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT;
 
 	return nr_pages;
 }
@@ -373,6 +376,7 @@ static unsigned long global_dirtyable_memory(void)
 
 	x += global_node_page_state(NR_INACTIVE_FILE);
 	x += global_node_page_state(NR_ACTIVE_FILE);
+	x += global_node_page_state(NR_METADATA_BYTES) >> PAGE_SHIFT;
 
 	if (!vm_highmem_is_dirtyable)
 		x -= highmem_dirtyable_memory(x);
@@ -381,6 +385,30 @@ static unsigned long global_dirtyable_memory(void)
 }
 
 /**
+ * global_dirty_memory - the number of globally dirty pages
+ *
+ * Returns the global number of pages that are dirty in pagecache and metadata.
+ */
+static unsigned long global_dirty_memory(void)
+{
+	return global_node_page_state(NR_FILE_DIRTY) +
+		global_node_page_state(NR_UNSTABLE_NFS) +
+		(global_node_page_state(NR_METADATA_DIRTY_BYTES) >> PAGE_SHIFT);
+}
+
+/**
+ * global_writeback_memory - the number of pages under writeback globally
+ *
+ * Returns the global number of pages under writeback both in pagecache and in
+ * metadata.
+ */
+static unsigned long global_writeback_memory(void)
+{
+	return global_node_page_state(NR_WRITEBACK) +
+		(global_node_page_state(NR_METADATA_WRITEBACK_BYTES) >> PAGE_SHIFT);
+}
+
+/**
  * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain
  * @dtc: dirty_throttle_control of interest
  *
@@ -492,6 +520,7 @@ static unsigned long node_dirty_limit(struct pglist_data *pgdat)
 	return dirty;
 }
 
+
 /**
  * node_dirty_ok - tells whether a node is within its dirty limits
  * @pgdat: the node to check
@@ -507,6 +536,8 @@ bool node_dirty_ok(struct pglist_data *pgdat)
 	nr_pages += node_page_state(pgdat, NR_FILE_DIRTY);
 	nr_pages += node_page_state(pgdat, NR_UNSTABLE_NFS);
 	nr_pages += node_page_state(pgdat, NR_WRITEBACK);
+	nr_pages += BtoP(node_page_state(pgdat, NR_METADATA_DIRTY_BYTES));
+	nr_pages += BtoP(node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES));
 
 	return nr_pages <= limit;
 }
@@ -1514,7 +1545,7 @@ static long wb_min_pause(struct bdi_writeback *wb,
 static inline void wb_dirty_limits(struct dirty_throttle_control *dtc)
 {
 	struct bdi_writeback *wb = dtc->wb;
-	unsigned long wb_reclaimable;
+	unsigned long wb_reclaimable, wb_writeback;
 
 	/*
 	 * wb_thresh is not treated as some limiting factor as
@@ -1544,12 +1575,17 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc)
 	 * deltas.
 	 */
 	if (dtc->wb_thresh < 2 * wb_stat_error(wb)) {
-		wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE);
-		dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK);
+		wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE) +
+			BtoP(wb_stat_sum(wb, WB_METADATA_DIRTY_BYTES));
+		wb_writeback = wb_stat_sum(wb, WB_WRITEBACK) +
+			BtoP(wb_stat_sum(wb, WB_METADATA_WRITEBACK_BYTES));
 	} else {
-		wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE);
-		dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK);
+		wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE) +
+			BtoP(wb_stat(wb, WB_METADATA_DIRTY_BYTES));
+		wb_writeback = wb_stat(wb, WB_WRITEBACK) +
+			BtoP(wb_stat(wb, WB_METADATA_WRITEBACK_BYTES));
 	}
+	dtc->wb_dirty = wb_reclaimable + wb_writeback;
 }
 
 /*
@@ -1594,10 +1630,9 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
 		 * written to the server's write cache, but has not yet
 		 * been flushed to permanent storage.
 		 */
-		nr_reclaimable = global_node_page_state(NR_FILE_DIRTY) +
-					global_node_page_state(NR_UNSTABLE_NFS);
+		nr_reclaimable = global_dirty_memory();
 		gdtc->avail = global_dirtyable_memory();
-		gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK);
+		gdtc->dirty = nr_reclaimable + global_writeback_memory();
 
 		domain_dirty_limits(gdtc);
 
@@ -1929,20 +1964,22 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
 	struct dirty_throttle_control * const gdtc = &gdtc_stor;
 	struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ?
 						     &mdtc_stor : NULL;
+	unsigned long wb_reclaimable;
 
 	/*
 	 * Similar to balance_dirty_pages() but ignores pages being written
 	 * as we're trying to decide whether to put more under writeback.
 	 */
 	gdtc->avail = global_dirtyable_memory();
-	gdtc->dirty = global_node_page_state(NR_FILE_DIRTY) +
-		      global_node_page_state(NR_UNSTABLE_NFS);
+	gdtc->dirty = global_dirty_memory();
 	domain_dirty_limits(gdtc);
 
 	if (gdtc->dirty > gdtc->bg_thresh)
 		return true;
 
-	if (wb_stat(wb, WB_RECLAIMABLE) >
+	wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE) +
+		BtoP(wb_stat(wb, WB_METADATA_DIRTY_BYTES));
+	if (wb_reclaimable >
 	    wb_calc_thresh(gdtc->wb, gdtc->bg_thresh))
 		return true;
 
@@ -1957,7 +1994,7 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
 		if (mdtc->dirty > mdtc->bg_thresh)
 			return true;
 
-		if (wb_stat(wb, WB_RECLAIMABLE) >
+		if (wb_reclaimable >
 		    wb_calc_thresh(mdtc->wb, mdtc->bg_thresh))
 			return true;
 	}
@@ -1979,8 +2016,7 @@ int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
 void laptop_mode_timer_fn(unsigned long data)
 {
 	struct request_queue *q = (struct request_queue *)data;
-	int nr_pages = global_node_page_state(NR_FILE_DIRTY) +
-		global_node_page_state(NR_UNSTABLE_NFS);
+	int nr_pages = global_dirty_memory();
 	struct bdi_writeback *wb;
 
 	/*
@@ -2444,6 +2480,84 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
 EXPORT_SYMBOL(account_page_dirtied);
 
 /*
+ * account_metadata_dirtied
+ * @page - the page being dirited
+ * @bdi - the bdi that owns this page
+ * @bytes - the number of bytes being dirtied
+ *
+ * Do the dirty page accounting for metadata pages that aren't backed by an
+ * address_space.
+ */
+void account_metadata_dirtied(struct page *page, struct backing_dev_info *bdi,
+			      long bytes)
+{
+	mod_node_page_state(page_pgdat(page), NR_METADATA_DIRTY_BYTES,
+			    bytes);
+	__add_wb_stat(&bdi->wb, WB_DIRTIED_BYTES, bytes);
+	__add_wb_stat(&bdi->wb, WB_METADATA_DIRTY_BYTES, bytes);
+	current->nr_dirtied++;
+	task_io_account_write(bytes);
+	this_cpu_inc(bdp_ratelimits);
+}
+EXPORT_SYMBOL(account_metadata_dirtied);
+
+/*
+ * account_metadata_cleaned
+ * @page - the page being cleaned
+ * @bdi - the bdi that owns this page
+ * @bytes - the number of bytes cleaned
+ *
+ * Called on a no longer dirty metadata page.
+ */
+void account_metadata_cleaned(struct page *page, struct backing_dev_info *bdi,
+			      long bytes)
+{
+	mod_node_page_state(page_pgdat(page), NR_METADATA_DIRTY_BYTES,
+			    -bytes);
+	__add_wb_stat(&bdi->wb, WB_METADATA_DIRTY_BYTES, -bytes);
+	task_io_account_cancelled_write(bytes);
+}
+EXPORT_SYMBOL(account_metadata_cleaned);
+
+/*
+ * account_metadata_writeback
+ * @page - the page being marked as writeback
+ * @bdi - the bdi that owns this page
+ * @bytes - the number of bytes we are submitting for writeback
+ *
+ * Called on a metadata page that has been marked writeback.
+ */
+void account_metadata_writeback(struct page *page,
+				struct backing_dev_info *bdi, long bytes)
+{
+	__add_wb_stat(&bdi->wb, WB_METADATA_DIRTY_BYTES, -bytes);
+	mod_node_page_state(page_pgdat(page), NR_METADATA_DIRTY_BYTES,
+					 -bytes);
+	__add_wb_stat(&bdi->wb, WB_METADATA_WRITEBACK_BYTES, bytes);
+	mod_node_page_state(page_pgdat(page), NR_METADATA_WRITEBACK_BYTES,
+					 bytes);
+}
+EXPORT_SYMBOL(account_metadata_writeback);
+
+/*
+ * account_metadata_end_writeback
+ * @page - the page we are ending writeback on
+ * @bdi - the bdi that owns this page
+ * @bytes - the number of bytes that just ended writeback
+ *
+ * Called on a metadata page that has completed writeback.
+ */
+void account_metadata_end_writeback(struct page *page,
+				    struct backing_dev_info *bdi, long bytes)
+{
+	__add_wb_stat(&bdi->wb, WB_METADATA_WRITEBACK_BYTES, -bytes);
+	mod_node_page_state(page_pgdat(page), NR_METADATA_WRITEBACK_BYTES,
+			    -bytes);
+	__wb_writeout_add(&bdi->wb, bytes);
+}
+EXPORT_SYMBOL(account_metadata_end_writeback);
+
+/*
  * Helper function for deaccounting dirty page without writeback.
  *
  * Caller must hold lock_page_memcg().
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c841af88836a..aab0dd6aa8d7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4640,6 +4640,8 @@ static bool show_mem_node_skip(unsigned int flags, int nid, nodemask_t *nodemask
 }
 
 #define K(x) ((x) << (PAGE_SHIFT-10))
+#define BtoK(x) ((x) >> 10)
+#define BtoP(x) ((x) >> PAGE_SHIFT)
 
 static void show_migration_types(unsigned char type)
 {
@@ -4694,10 +4696,11 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 
 	printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
 		" active_file:%lu inactive_file:%lu isolated_file:%lu\n"
-		" unevictable:%lu dirty:%lu writeback:%lu unstable:%lu\n"
-		" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
-		" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
-		" free:%lu free_pcp:%lu free_cma:%lu\n",
+		" unevictable:%lu metadata:%lu dirty:%lu metadata_dirty:%lu\n"
+		" writeback:%lu unstable:%lu metadata_writeback:%lu\n"
+		" slab_reclaimable:%lu slab_unreclaimable:%lu mapped:%lu\n"
+		" shmem:%lu pagetables:%lu bounce:%lu free:%lu free_pcp:%lu\n"
+	        " free_cma:%lu\n",
 		global_node_page_state(NR_ACTIVE_ANON),
 		global_node_page_state(NR_INACTIVE_ANON),
 		global_node_page_state(NR_ISOLATED_ANON),
@@ -4705,9 +4708,12 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 		global_node_page_state(NR_INACTIVE_FILE),
 		global_node_page_state(NR_ISOLATED_FILE),
 		global_node_page_state(NR_UNEVICTABLE),
+		BtoP(global_node_page_state(NR_METADATA_BYTES)),
 		global_node_page_state(NR_FILE_DIRTY),
+		BtoP(global_node_page_state(NR_METADATA_DIRTY_BYTES)),
 		global_node_page_state(NR_WRITEBACK),
 		global_node_page_state(NR_UNSTABLE_NFS),
+		BtoP(global_node_page_state(NR_METADATA_WRITEBACK_BYTES)),
 		global_node_page_state(NR_SLAB_RECLAIMABLE),
 		global_node_page_state(NR_SLAB_UNRECLAIMABLE),
 		global_node_page_state(NR_FILE_MAPPED),
@@ -4730,9 +4736,12 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 			" unevictable:%lukB"
 			" isolated(anon):%lukB"
 			" isolated(file):%lukB"
+			" metadata:%lukB"
 			" mapped:%lukB"
 			" dirty:%lukB"
+			" metadata_dirty:%lukB"
 			" writeback:%lukB"
+			" metadata_writeback:%lukB"
 			" shmem:%lukB"
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			" shmem_thp: %lukB"
@@ -4751,9 +4760,12 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
 			K(node_page_state(pgdat, NR_UNEVICTABLE)),
 			K(node_page_state(pgdat, NR_ISOLATED_ANON)),
 			K(node_page_state(pgdat, NR_ISOLATED_FILE)),
+			BtoK(node_page_state(pgdat, NR_METADATA_BYTES)),
 			K(node_page_state(pgdat, NR_FILE_MAPPED)),
 			K(node_page_state(pgdat, NR_FILE_DIRTY)),
+			BtoK(node_page_state(pgdat, NR_METADATA_DIRTY_BYTES)),
 			K(node_page_state(pgdat, NR_WRITEBACK)),
+			BtoK(node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES)),
 			K(node_page_state(pgdat, NR_SHMEM)),
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			K(node_page_state(pgdat, NR_SHMEM_THPS) * HPAGE_PMD_NR),
diff --git a/mm/util.c b/mm/util.c
index 34e57fae959d..681d62631ee0 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -616,6 +616,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
 		free = global_zone_page_state(NR_FREE_PAGES);
 		free += global_node_page_state(NR_FILE_PAGES);
+		free += global_node_page_state(NR_METADATA_BYTES) >> PAGE_SHIFT;
 
 		/*
 		 * shmem pages shouldn't be counted as free in this
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 13d711dd8776..415b003e475c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -225,7 +225,8 @@ unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat)
 
 	nr = node_page_state_snapshot(pgdat, NR_ACTIVE_FILE) +
 	     node_page_state_snapshot(pgdat, NR_INACTIVE_FILE) +
-	     node_page_state_snapshot(pgdat, NR_ISOLATED_FILE);
+	     node_page_state_snapshot(pgdat, NR_ISOLATED_FILE) +
+	     (node_page_state_snapshot(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT);
 
 	if (get_nr_swap_pages() > 0)
 		nr += node_page_state_snapshot(pgdat, NR_ACTIVE_ANON) +
@@ -3812,6 +3813,7 @@ static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
 static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
 {
 	unsigned long nr_pagecache_reclaimable;
+	unsigned long nr_metadata_reclaimable;
 	unsigned long delta = 0;
 
 	/*
@@ -3833,7 +3835,20 @@ static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
 	if (unlikely(delta > nr_pagecache_reclaimable))
 		delta = nr_pagecache_reclaimable;
 
-	return nr_pagecache_reclaimable - delta;
+	nr_metadata_reclaimable =
+		node_page_state(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT;
+	/*
+	 * We don't do writeout through the shrinkers so subtract any
+	 * dirty/writeback metadata bytes from the reclaimable count.
+	 */
+	if (nr_metadata_reclaimable) {
+		unsigned long unreclaimable =
+			node_page_state(pgdat, NR_METADATA_DIRTY_BYTES) +
+			node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES);
+		unreclaimable >>= PAGE_SHIFT;
+		nr_metadata_reclaimable -= unreclaimable;
+	}
+	return nr_metadata_reclaimable + nr_pagecache_reclaimable - delta;
 }
 
 /*
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 4bb13e72ac97..1d8c93ec486e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1090,6 +1090,9 @@ const char * const vmstat_text[] = {
 	"nr_vmscan_immediate_reclaim",
 	"nr_dirtied",
 	"nr_written",
+	"nr_metadata_dirty_bytes",
+	"nr_metadata_writeback_bytes",
+	"nr_metadata_bytes",
 
 	/* enum writeback_stat_item counters */
 	"nr_dirty_threshold",
-- 
2.7.5

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[PATCH v2 07/11] writeback: introduce super_operations->write_metadata

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

Now that we have metadata counters in the VM, we need to provide a way to kick
writeback on dirty metadata.  Introduce super_operations->write_metadata.  This
allows file systems to deal with writing back any dirty metadata we need based
on the writeback needs of the system.  Since there is no inode to key off of we
need a list in the bdi for dirty super blocks to be added.  From there we can
find any dirty sb's on the bdi we are currently doing writeback on and call into
their ->write_metadata callback.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Tejun Heo <tj@kernel.org>
---
 fs/fs-writeback.c                | 72 ++++++++++++++++++++++++++++++++++++----
 fs/super.c                       |  6 ++++
 include/linux/backing-dev-defs.h |  2 ++
 include/linux/fs.h               |  4 +++
 mm/backing-dev.c                 |  2 ++
 5 files changed, 80 insertions(+), 6 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 987448ed7698..fba703dff678 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1479,6 +1479,31 @@ static long writeback_chunk_size(struct bdi_writeback *wb,
 	return pages;
 }
 
+static long writeback_sb_metadata(struct super_block *sb,
+				  struct bdi_writeback *wb,
+				  struct wb_writeback_work *work)
+{
+	struct writeback_control wbc = {
+		.sync_mode		= work->sync_mode,
+		.tagged_writepages	= work->tagged_writepages,
+		.for_kupdate		= work->for_kupdate,
+		.for_background		= work->for_background,
+		.for_sync		= work->for_sync,
+		.range_cyclic		= work->range_cyclic,
+		.range_start		= 0,
+		.range_end		= LLONG_MAX,
+	};
+	long write_chunk;
+
+	write_chunk = writeback_chunk_size(wb, work);
+	wbc.nr_to_write = write_chunk;
+	sb->s_op->write_metadata(sb, &wbc);
+	work->nr_pages -= write_chunk - wbc.nr_to_write;
+
+	return write_chunk - wbc.nr_to_write;
+}
+
+
 /*
  * Write a portion of b_io inodes which belong to @sb.
  *
@@ -1505,6 +1530,7 @@ static long writeback_sb_inodes(struct super_block *sb,
 	unsigned long start_time = jiffies;
 	long write_chunk;
 	long wrote = 0;  /* count both pages and inodes */
+	bool done = false;
 
 	while (!list_empty(&wb->b_io)) {
 		struct inode *inode = wb_inode(wb->b_io.prev);
@@ -1621,12 +1647,18 @@ static long writeback_sb_inodes(struct super_block *sb,
 		 * background threshold and other termination conditions.
 		 */
 		if (wrote) {
-			if (time_is_before_jiffies(start_time + HZ / 10UL))
-				break;
-			if (work->nr_pages <= 0)
+			if (time_is_before_jiffies(start_time + HZ / 10UL) ||
+			    work->nr_pages <= 0) {
+				done = true;
 				break;
+			}
 		}
 	}
+	if (!done && sb->s_op->write_metadata) {
+		spin_unlock(&wb->list_lock);
+		wrote += writeback_sb_metadata(sb, wb, work);
+		spin_lock(&wb->list_lock);
+	}
 	return wrote;
 }
 
@@ -1635,6 +1667,7 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb,
 {
 	unsigned long start_time = jiffies;
 	long wrote = 0;
+	bool done = false;
 
 	while (!list_empty(&wb->b_io)) {
 		struct inode *inode = wb_inode(wb->b_io.prev);
@@ -1654,12 +1687,39 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb,
 
 		/* refer to the same tests at the end of writeback_sb_inodes */
 		if (wrote) {
-			if (time_is_before_jiffies(start_time + HZ / 10UL))
-				break;
-			if (work->nr_pages <= 0)
+			if (time_is_before_jiffies(start_time + HZ / 10UL) ||
+			    work->nr_pages <= 0) {
+				done = true;
 				break;
+			}
 		}
 	}
+
+	if (!done && wb_stat(wb, WB_METADATA_DIRTY_BYTES)) {
+		LIST_HEAD(list);
+
+		spin_unlock(&wb->list_lock);
+		spin_lock(&wb->bdi->sb_list_lock);
+		list_splice_init(&wb->bdi->dirty_sb_list, &list);
+		while (!list_empty(&list)) {
+			struct super_block *sb;
+
+			sb = list_first_entry(&list, struct super_block,
+					      s_bdi_dirty_list);
+			list_move_tail(&sb->s_bdi_dirty_list,
+				       &wb->bdi->dirty_sb_list);
+			if (!sb->s_op->write_metadata)
+				continue;
+			if (!trylock_super(sb))
+				continue;
+			spin_unlock(&wb->bdi->sb_list_lock);
+			wrote += writeback_sb_metadata(sb, wb, work);
+			spin_lock(&wb->bdi->sb_list_lock);
+			up_read(&sb->s_umount);
+		}
+		spin_unlock(&wb->bdi->sb_list_lock);
+		spin_lock(&wb->list_lock);
+	}
 	/* Leave any unwritten inodes on b_io */
 	return wrote;
 }
diff --git a/fs/super.c b/fs/super.c
index 166c4ee0d0ed..2290bef486a3 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -214,6 +214,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
 	spin_lock_init(&s->s_inode_list_lock);
 	INIT_LIST_HEAD(&s->s_inodes_wb);
 	spin_lock_init(&s->s_inode_wblist_lock);
+	INIT_LIST_HEAD(&s->s_bdi_dirty_list);
 
 	if (list_lru_init_memcg(&s->s_dentry_lru))
 		goto fail;
@@ -446,6 +447,11 @@ void generic_shutdown_super(struct super_block *sb)
 	spin_unlock(&sb_lock);
 	up_write(&sb->s_umount);
 	if (sb->s_bdi != &noop_backing_dev_info) {
+		if (!list_empty(&sb->s_bdi_dirty_list)) {
+			spin_lock(&sb->s_bdi->sb_list_lock);
+			list_del_init(&sb->s_bdi_dirty_list);
+			spin_unlock(&sb->s_bdi->sb_list_lock);
+		}
 		bdi_put(sb->s_bdi);
 		sb->s_bdi = &noop_backing_dev_info;
 	}
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 78c65e2910dc..a961f9a51a38 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -176,6 +176,8 @@ struct backing_dev_info {
 
 	struct timer_list laptop_mode_wb_timer;
 
+	spinlock_t sb_list_lock;
+	struct list_head dirty_sb_list;
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debug_dir;
 	struct dentry *debug_stats;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 339e73742e73..298a28eaed2b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1440,6 +1440,8 @@ struct super_block {
 
 	spinlock_t		s_inode_wblist_lock;
 	struct list_head	s_inodes_wb;	/* writeback inodes */
+
+	struct list_head        s_bdi_dirty_list;
 } __randomize_layout;
 
 /* Helper functions so that in most cases filesystems will
@@ -1830,6 +1832,8 @@ struct super_operations {
 				  struct shrink_control *);
 	long (*free_cached_objects)(struct super_block *,
 				    struct shrink_control *);
+	void (*write_metadata)(struct super_block *sb,
+			       struct writeback_control *wbc);
 };
 
 /*
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 0aad67bc0898..e3aa4e0dd15e 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -839,6 +839,8 @@ static int bdi_init(struct backing_dev_info *bdi)
 	bdi->max_prop_frac = FPROP_FRAC_BASE;
 	INIT_LIST_HEAD(&bdi->bdi_list);
 	INIT_LIST_HEAD(&bdi->wb_list);
+	INIT_LIST_HEAD(&bdi->dirty_sb_list);
+	spin_lock_init(&bdi->sb_list_lock);
 	init_waitqueue_head(&bdi->wb_waitq);
 
 	ret = cgwb_bdi_init(bdi);
-- 
2.7.5

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[PATCH v2 08/11] export radix_tree_iter_tag_set

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

We use this in btrfs for metadata writeback.

Acked-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 lib/radix-tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 8b1feca1230a..0c1cde9fcb69 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1459,6 +1459,7 @@ void radix_tree_iter_tag_set(struct radix_tree_root *root,
 {
 	node_tag_set(root, iter->node, tag, iter_offset(iter));
 }
+EXPORT_SYMBOL(radix_tree_iter_tag_set);
 
 static void node_tag_clear(struct radix_tree_root *root,
 				struct radix_tree_node *node,
-- 
2.7.5

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[PATCH v2 09/11] Btrfs: kill the btree_inode

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

In order to more efficiently support sub-page blocksizes we need to stop
allocating pages from pagecache for our metadata.  Instead switch to using the
account_metadata* counters for making sure we are keeping the system aware of
how much dirty metadata we have, and use the ->free_cached_objects super
operation in order to handle freeing up extent buffers.  This greatly simplifies
how we deal with extent buffers as now we no longer have to tie the page cache
reclaimation stuff to the extent buffer stuff.  This will also allow us to
simply kmalloc() our data for sub-page blocksizes.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 fs/btrfs/btrfs_inode.h                 |   1 -
 fs/btrfs/ctree.c                       |  18 +-
 fs/btrfs/ctree.h                       |  17 +-
 fs/btrfs/dir-item.c                    |   2 +-
 fs/btrfs/disk-io.c                     | 386 ++++----------
 fs/btrfs/extent-tree.c                 |  14 +-
 fs/btrfs/extent_io.c                   | 906 ++++++++++++++++++---------------
 fs/btrfs/extent_io.h                   |  51 +-
 fs/btrfs/inode.c                       |   6 +-
 fs/btrfs/print-tree.c                  |  13 +-
 fs/btrfs/reada.c                       |   2 +-
 fs/btrfs/root-tree.c                   |   2 +-
 fs/btrfs/super.c                       |  31 +-
 fs/btrfs/tests/btrfs-tests.c           |  36 +-
 fs/btrfs/tests/extent-buffer-tests.c   |   3 +-
 fs/btrfs/tests/extent-io-tests.c       |   4 +-
 fs/btrfs/tests/free-space-tree-tests.c |   3 +-
 fs/btrfs/tests/inode-tests.c           |   4 +-
 fs/btrfs/tests/qgroup-tests.c          |   3 +-
 fs/btrfs/transaction.c                 |  13 +-
 20 files changed, 744 insertions(+), 771 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index f9c6887a8b6c..24582650622d 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -241,7 +241,6 @@ static inline u64 btrfs_ino(const struct btrfs_inode *inode)
 	u64 ino = inode->location.objectid;
 
 	/*
-	 * !ino: btree_inode
 	 * type == BTRFS_ROOT_ITEM_KEY: subvol dir
 	 */
 	if (!ino || inode->location.type == BTRFS_ROOT_ITEM_KEY)
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 531e0a8645b0..3c6610b5d0d3 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1361,7 +1361,8 @@ tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
 
 	if (tm->op == MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
 		BUG_ON(tm->slot != 0);
-		eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
+		eb_rewin = alloc_dummy_extent_buffer(fs_info->eb_info,
+						     eb->start, eb->len);
 		if (!eb_rewin) {
 			btrfs_tree_read_unlock_blocking(eb);
 			free_extent_buffer(eb);
@@ -1444,7 +1445,8 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
 	} else if (old_root) {
 		btrfs_tree_read_unlock(eb_root);
 		free_extent_buffer(eb_root);
-		eb = alloc_dummy_extent_buffer(fs_info, logical);
+		eb = alloc_dummy_extent_buffer(root->fs_info->eb_info, logical,
+					       root->fs_info->nodesize);
 	} else {
 		btrfs_set_lock_blocking_rw(eb_root, BTRFS_READ_LOCK);
 		eb = btrfs_clone_extent_buffer(eb_root);
@@ -1675,7 +1677,7 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
 			continue;
 		}
 
-		cur = find_extent_buffer(fs_info, blocknr);
+		cur = find_extent_buffer(fs_info->eb_info, blocknr);
 		if (cur)
 			uptodate = btrfs_buffer_uptodate(cur, gen, 0);
 		else
@@ -1748,7 +1750,7 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
 	int err;
 
 	if (low > high) {
-		btrfs_err(eb->fs_info,
+		btrfs_err(eb->eb_info->fs_info,
 		 "%s: low (%d) > high (%d) eb %llu owner %llu level %d",
 			  __func__, low, high, eb->start,
 			  btrfs_header_owner(eb), btrfs_header_level(eb));
@@ -2260,7 +2262,7 @@ static void reada_for_search(struct btrfs_fs_info *fs_info,
 
 	search = btrfs_node_blockptr(node, slot);
 	blocksize = fs_info->nodesize;
-	eb = find_extent_buffer(fs_info, search);
+	eb = find_extent_buffer(fs_info->eb_info, search);
 	if (eb) {
 		free_extent_buffer(eb);
 		return;
@@ -2319,7 +2321,7 @@ static noinline void reada_for_balance(struct btrfs_fs_info *fs_info,
 	if (slot > 0) {
 		block1 = btrfs_node_blockptr(parent, slot - 1);
 		gen = btrfs_node_ptr_generation(parent, slot - 1);
-		eb = find_extent_buffer(fs_info, block1);
+		eb = find_extent_buffer(fs_info->eb_info, block1);
 		/*
 		 * if we get -eagain from btrfs_buffer_uptodate, we
 		 * don't want to return eagain here.  That will loop
@@ -2332,7 +2334,7 @@ static noinline void reada_for_balance(struct btrfs_fs_info *fs_info,
 	if (slot + 1 < nritems) {
 		block2 = btrfs_node_blockptr(parent, slot + 1);
 		gen = btrfs_node_ptr_generation(parent, slot + 1);
-		eb = find_extent_buffer(fs_info, block2);
+		eb = find_extent_buffer(fs_info->eb_info, block2);
 		if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
 			block2 = 0;
 		free_extent_buffer(eb);
@@ -2450,7 +2452,7 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
 	blocknr = btrfs_node_blockptr(b, slot);
 	gen = btrfs_node_ptr_generation(b, slot);
 
-	tmp = find_extent_buffer(fs_info, blocknr);
+	tmp = find_extent_buffer(fs_info->eb_info, blocknr);
 	if (tmp) {
 		/* first we do an atomic uptodate check */
 		if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4ffbe9f07cf7..a7c764a1ee48 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -40,6 +40,7 @@
 #include <linux/sizes.h>
 #include <linux/dynamic_debug.h>
 #include <linux/refcount.h>
+#include <linux/list_lru.h>
 #include "extent_io.h"
 #include "extent_map.h"
 #include "async-thread.h"
@@ -701,6 +702,7 @@ struct btrfs_device;
 struct btrfs_fs_devices;
 struct btrfs_balance_control;
 struct btrfs_delayed_root;
+struct btrfs_eb_info;
 
 #define BTRFS_FS_BARRIER			1
 #define BTRFS_FS_CLOSING_START			2
@@ -818,7 +820,7 @@ struct btrfs_fs_info {
 	struct btrfs_super_block *super_copy;
 	struct btrfs_super_block *super_for_commit;
 	struct super_block *sb;
-	struct inode *btree_inode;
+	struct btrfs_eb_info *eb_info;
 	struct mutex tree_log_mutex;
 	struct mutex transaction_kthread_mutex;
 	struct mutex cleaner_mutex;
@@ -1060,10 +1062,6 @@ struct btrfs_fs_info {
 	/* readahead works cnt */
 	atomic_t reada_works_cnt;
 
-	/* Extent buffer radix tree */
-	spinlock_t buffer_lock;
-	struct radix_tree_root buffer_radix;
-
 	/* next backup root to be overwritten */
 	int backup_root_index;
 
@@ -1563,7 +1561,7 @@ static inline void btrfs_set_device_total_bytes(struct extent_buffer *eb,
 {
 	BUILD_BUG_ON(sizeof(u64) !=
 		     sizeof(((struct btrfs_dev_item *)0))->total_bytes);
-	WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
+	WARN_ON(!IS_ALIGNED(val, eb->eb_info->fs_info->sectorsize));
 	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);
 }
 
@@ -2962,6 +2960,10 @@ static inline int btrfs_need_cleaner_sleep(struct btrfs_fs_info *fs_info)
 
 static inline void free_fs_info(struct btrfs_fs_info *fs_info)
 {
+	if (fs_info->eb_info) {
+		list_lru_destroy(&fs_info->eb_info->lru_list);
+		kfree(fs_info->eb_info);
+	}
 	kfree(fs_info->balance_ctl);
 	kfree(fs_info->delayed_root);
 	kfree(fs_info->extent_root);
@@ -3185,9 +3187,6 @@ int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root,
 			     struct btrfs_root *parent_root,
 			     u64 new_dirid);
-int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
-			 size_t size, struct bio *bio,
-			 unsigned long bio_flags);
 void btrfs_set_range_writeback(void *private_data, u64 start, u64 end);
 int btrfs_page_mkwrite(struct vm_fault *vmf);
 int btrfs_readpage(struct file *file, struct page *page);
diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index 41cb9196eaa8..f5782523e723 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -496,7 +496,7 @@ int verify_dir_item(struct btrfs_fs_info *fs_info,
 bool btrfs_is_name_len_valid(struct extent_buffer *leaf, int slot,
 			     unsigned long start, u16 name_len)
 {
-	struct btrfs_fs_info *fs_info = leaf->fs_info;
+	struct btrfs_fs_info *fs_info = leaf->eb_info->fs_info;
 	struct btrfs_key key;
 	u32 read_start;
 	u32 read_end;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8b6df7688d52..d9d69e181942 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -215,56 +215,6 @@ void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb,
 
 #endif
 
-/*
- * extents on the btree inode are pretty simple, there's one extent
- * that covers the entire device
- */
-static struct extent_map *btree_get_extent(struct btrfs_inode *inode,
-		struct page *page, size_t pg_offset, u64 start, u64 len,
-		int create)
-{
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
-	struct extent_map_tree *em_tree = &inode->extent_tree;
-	struct extent_map *em;
-	int ret;
-
-	read_lock(&em_tree->lock);
-	em = lookup_extent_mapping(em_tree, start, len);
-	if (em) {
-		em->bdev = fs_info->fs_devices->latest_bdev;
-		read_unlock(&em_tree->lock);
-		goto out;
-	}
-	read_unlock(&em_tree->lock);
-
-	em = alloc_extent_map();
-	if (!em) {
-		em = ERR_PTR(-ENOMEM);
-		goto out;
-	}
-	em->start = 0;
-	em->len = (u64)-1;
-	em->block_len = (u64)-1;
-	em->block_start = 0;
-	em->bdev = fs_info->fs_devices->latest_bdev;
-
-	write_lock(&em_tree->lock);
-	ret = add_extent_mapping(em_tree, em, 0);
-	if (ret == -EEXIST) {
-		free_extent_map(em);
-		em = lookup_extent_mapping(em_tree, start, len);
-		if (!em)
-			em = ERR_PTR(-EIO);
-	} else if (ret) {
-		free_extent_map(em);
-		em = ERR_PTR(ret);
-	}
-	write_unlock(&em_tree->lock);
-
-out:
-	return em;
-}
-
 u32 btrfs_csum_data(const char *data, u32 seed, size_t len)
 {
 	return btrfs_crc32c(seed, data, len);
@@ -346,11 +296,11 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
  * detect blocks that either didn't get written at all or got written
  * in the wrong place.
  */
-static int verify_parent_transid(struct extent_io_tree *io_tree,
-				 struct extent_buffer *eb, u64 parent_transid,
+static int verify_parent_transid(struct extent_buffer *eb, u64 parent_transid,
 				 int atomic)
 {
 	struct extent_state *cached_state = NULL;
+	struct extent_io_tree *io_tree = &eb->eb_info->io_tree;
 	int ret;
 	bool need_lock = (current->journal_info == BTRFS_SEND_TRANS_STUB);
 
@@ -372,7 +322,7 @@ static int verify_parent_transid(struct extent_io_tree *io_tree,
 		ret = 0;
 		goto out;
 	}
-	btrfs_err_rl(eb->fs_info,
+	btrfs_err_rl(eb->eb_info->fs_info,
 		"parent transid verify failed on %llu wanted %llu found %llu",
 			eb->start,
 			parent_transid, btrfs_header_generation(eb));
@@ -443,7 +393,6 @@ static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
 					  struct extent_buffer *eb,
 					  u64 parent_transid)
 {
-	struct extent_io_tree *io_tree;
 	int failed = 0;
 	int ret;
 	int num_copies = 0;
@@ -451,13 +400,10 @@ static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
 	int failed_mirror = 0;
 
 	clear_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
-	io_tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
 	while (1) {
-		ret = read_extent_buffer_pages(io_tree, eb, WAIT_COMPLETE,
-					       btree_get_extent, mirror_num);
+		ret = read_extent_buffer_pages(eb, WAIT_COMPLETE, mirror_num);
 		if (!ret) {
-			if (!verify_parent_transid(io_tree, eb,
-						   parent_transid, 0))
+			if (!verify_parent_transid(eb, parent_transid, 0))
 				break;
 			else
 				ret = -EIO;
@@ -502,24 +448,11 @@ static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
 
 static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
 {
-	u64 start = page_offset(page);
-	u64 found_start;
 	struct extent_buffer *eb;
 
 	eb = (struct extent_buffer *)page->private;
 	if (page != eb->pages[0])
 		return 0;
-
-	found_start = btrfs_header_bytenr(eb);
-	/*
-	 * Please do not consolidate these warnings into a single if.
-	 * It is useful to know what went wrong.
-	 */
-	if (WARN_ON(found_start != start))
-		return -EUCLEAN;
-	if (WARN_ON(!PageUptodate(page)))
-		return -EUCLEAN;
-
 	ASSERT(memcmp_extent_buffer(eb, fs_info->fsid,
 			btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);
 
@@ -829,8 +762,8 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	u64 found_start;
 	int found_level;
 	struct extent_buffer *eb;
-	struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
-	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_root *root;
+	struct btrfs_fs_info *fs_info;
 	int ret = 0;
 	int reads_done;
 
@@ -843,6 +776,8 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	 * in memory.  Make sure we have a ref for all this other checks
 	 */
 	extent_buffer_get(eb);
+	fs_info = eb->eb_info->fs_info;
+	root = fs_info->tree_root;
 
 	reads_done = atomic_dec_and_test(&eb->io_pages);
 	if (!reads_done)
@@ -906,11 +841,19 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 		/*
 		 * our io error hook is going to dec the io pages
 		 * again, we have to make sure it has something
-		 * to decrement
+		 * to decrement.
+		 *
+		 * TODO: Kill this, we've re-arranged how this works now so we
+		 * don't need to do this io_pages dance.
 		 */
 		atomic_inc(&eb->io_pages);
 		clear_extent_buffer_uptodate(eb);
 	}
+	if (reads_done) {
+		clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
+		smp_mb__after_atomic();
+		wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
+	}
 	free_extent_buffer(eb);
 out:
 	return ret;
@@ -1075,16 +1018,14 @@ blk_status_t btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 	return 0;
 }
 
-static blk_status_t btree_csum_one_bio(struct bio *bio)
+static blk_status_t btree_csum_one_bio(struct btrfs_fs_info *fs_info, struct bio *bio)
 {
 	struct bio_vec *bvec;
-	struct btrfs_root *root;
 	int i, ret = 0;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
 	bio_for_each_segment_all(bvec, bio, i) {
-		root = BTRFS_I(bvec->bv_page->mapping->host)->root;
-		ret = csum_dirty_buffer(root->fs_info, bvec->bv_page);
+		ret = csum_dirty_buffer(fs_info, bvec->bv_page);
 		if (ret)
 			break;
 	}
@@ -1096,25 +1037,26 @@ static blk_status_t __btree_submit_bio_start(void *private_data, struct bio *bio
 					     int mirror_num, unsigned long bio_flags,
 					     u64 bio_offset)
 {
+	struct btrfs_eb_info *eb_info = private_data;
 	/*
 	 * when we're called for a write, we're already in the async
 	 * submission context.  Just jump into btrfs_map_bio
 	 */
-	return btree_csum_one_bio(bio);
+	return btree_csum_one_bio(eb_info->fs_info, bio);
 }
 
 static blk_status_t __btree_submit_bio_done(void *private_data, struct bio *bio,
 					    int mirror_num, unsigned long bio_flags,
 					    u64 bio_offset)
 {
-	struct inode *inode = private_data;
-	blk_status_t ret;
+	struct btrfs_eb_info *eb_info = private_data;
+	int ret;
 
 	/*
 	 * when we're called for a write, we're already in the async
 	 * submission context.  Just jump into btrfs_map_bio
 	 */
-	ret = btrfs_map_bio(btrfs_sb(inode->i_sb), bio, mirror_num, 1);
+	ret = btrfs_map_bio(eb_info->fs_info, bio, mirror_num, 1);
 	if (ret) {
 		bio->bi_status = ret;
 		bio_endio(bio);
@@ -1122,9 +1064,10 @@ static blk_status_t __btree_submit_bio_done(void *private_data, struct bio *bio,
 	return ret;
 }
 
-static int check_async_write(struct btrfs_inode *bi)
+static int check_async_write(void)
 {
-	if (atomic_read(&bi->sync_writers))
+	/* If we are fsync we can be under a trans handle. */
+	if (current->journal_info)
 		return 0;
 #ifdef CONFIG_X86
 	if (static_cpu_has(X86_FEATURE_XMM4_2))
@@ -1137,9 +1080,9 @@ static blk_status_t btree_submit_bio_hook(void *private_data, struct bio *bio,
 					  int mirror_num, unsigned long bio_flags,
 					  u64 bio_offset)
 {
-	struct inode *inode = private_data;
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	int async = check_async_write(BTRFS_I(inode));
+	struct btrfs_eb_info *eb_info = private_data;
+	struct btrfs_fs_info *fs_info = eb_info->fs_info;
+	int async = check_async_write();
 	blk_status_t ret;
 
 	if (bio_op(bio) != REQ_OP_WRITE) {
@@ -1153,7 +1096,7 @@ static blk_status_t btree_submit_bio_hook(void *private_data, struct bio *bio,
 			goto out_w_error;
 		ret = btrfs_map_bio(fs_info, bio, mirror_num, 0);
 	} else if (!async) {
-		ret = btree_csum_one_bio(bio);
+		ret = btree_csum_one_bio(eb_info->fs_info, bio);
 		if (ret)
 			goto out_w_error;
 		ret = btrfs_map_bio(fs_info, bio, mirror_num, 0);
@@ -1178,118 +1121,14 @@ static blk_status_t btree_submit_bio_hook(void *private_data, struct bio *bio,
 	return ret;
 }
 
-#ifdef CONFIG_MIGRATION
-static int btree_migratepage(struct address_space *mapping,
-			struct page *newpage, struct page *page,
-			enum migrate_mode mode)
-{
-	/*
-	 * we can't safely write a btree page from here,
-	 * we haven't done the locking hook
-	 */
-	if (PageDirty(page))
-		return -EAGAIN;
-	/*
-	 * Buffers may be managed in a filesystem specific way.
-	 * We must have no buffers or drop them.
-	 */
-	if (page_has_private(page) &&
-	    !try_to_release_page(page, GFP_KERNEL))
-		return -EAGAIN;
-	return migrate_page(mapping, newpage, page, mode);
-}
-#endif
-
-
-static int btree_writepages(struct address_space *mapping,
-			    struct writeback_control *wbc)
-{
-	struct btrfs_fs_info *fs_info;
-	int ret;
-
-	if (wbc->sync_mode == WB_SYNC_NONE) {
-
-		if (wbc->for_kupdate)
-			return 0;
-
-		fs_info = BTRFS_I(mapping->host)->root->fs_info;
-		/* this is a bit racy, but that's ok */
-		ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
-					     BTRFS_DIRTY_METADATA_THRESH);
-		if (ret < 0)
-			return 0;
-	}
-	return btree_write_cache_pages(mapping, wbc);
-}
-
-static int btree_readpage(struct file *file, struct page *page)
-{
-	struct extent_io_tree *tree;
-	tree = &BTRFS_I(page->mapping->host)->io_tree;
-	return extent_read_full_page(tree, page, btree_get_extent, 0);
-}
-
-static int btree_releasepage(struct page *page, gfp_t gfp_flags)
-{
-	if (PageWriteback(page) || PageDirty(page))
-		return 0;
-
-	return try_release_extent_buffer(page);
-}
-
-static void btree_invalidatepage(struct page *page, unsigned int offset,
-				 unsigned int length)
-{
-	struct extent_io_tree *tree;
-	tree = &BTRFS_I(page->mapping->host)->io_tree;
-	extent_invalidatepage(tree, page, offset);
-	btree_releasepage(page, GFP_NOFS);
-	if (PagePrivate(page)) {
-		btrfs_warn(BTRFS_I(page->mapping->host)->root->fs_info,
-			   "page private not zero on page %llu",
-			   (unsigned long long)page_offset(page));
-		ClearPagePrivate(page);
-		set_page_private(page, 0);
-		put_page(page);
-	}
-}
-
-static int btree_set_page_dirty(struct page *page)
-{
-#ifdef DEBUG
-	struct extent_buffer *eb;
-
-	BUG_ON(!PagePrivate(page));
-	eb = (struct extent_buffer *)page->private;
-	BUG_ON(!eb);
-	BUG_ON(!test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
-	BUG_ON(!atomic_read(&eb->refs));
-	btrfs_assert_tree_locked(eb);
-#endif
-	return __set_page_dirty_nobuffers(page);
-}
-
-static const struct address_space_operations btree_aops = {
-	.readpage	= btree_readpage,
-	.writepages	= btree_writepages,
-	.releasepage	= btree_releasepage,
-	.invalidatepage = btree_invalidatepage,
-#ifdef CONFIG_MIGRATION
-	.migratepage	= btree_migratepage,
-#endif
-	.set_page_dirty = btree_set_page_dirty,
-};
-
 void readahead_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr)
 {
 	struct extent_buffer *buf = NULL;
-	struct inode *btree_inode = fs_info->btree_inode;
 
 	buf = btrfs_find_create_tree_block(fs_info, bytenr);
 	if (IS_ERR(buf))
 		return;
-	read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
-				 buf, WAIT_NONE, btree_get_extent, 0);
+	read_extent_buffer_pages(buf, WAIT_NONE, 0);
 	free_extent_buffer(buf);
 }
 
@@ -1297,8 +1136,6 @@ int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr,
 			 int mirror_num, struct extent_buffer **eb)
 {
 	struct extent_buffer *buf = NULL;
-	struct inode *btree_inode = fs_info->btree_inode;
-	struct extent_io_tree *io_tree = &BTRFS_I(btree_inode)->io_tree;
 	int ret;
 
 	buf = btrfs_find_create_tree_block(fs_info, bytenr);
@@ -1307,8 +1144,7 @@ int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr,
 
 	set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);
 
-	ret = read_extent_buffer_pages(io_tree, buf, WAIT_PAGE_LOCK,
-				       btree_get_extent, mirror_num);
+	ret = read_extent_buffer_pages(buf, WAIT_PAGE_LOCK, mirror_num);
 	if (ret) {
 		free_extent_buffer(buf);
 		return ret;
@@ -1330,21 +1166,22 @@ struct extent_buffer *btrfs_find_create_tree_block(
 						u64 bytenr)
 {
 	if (btrfs_is_testing(fs_info))
-		return alloc_test_extent_buffer(fs_info, bytenr);
+		return alloc_test_extent_buffer(fs_info->eb_info, bytenr,
+						fs_info->nodesize);
 	return alloc_extent_buffer(fs_info, bytenr);
 }
 
 
 int btrfs_write_tree_block(struct extent_buffer *buf)
 {
-	return filemap_fdatawrite_range(buf->pages[0]->mapping, buf->start,
-					buf->start + buf->len - 1);
+	return btree_write_range(buf->eb_info->fs_info, buf->start,
+				 buf->start + buf->len - 1);
 }
 
 void btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
 {
-	filemap_fdatawait_range(buf->pages[0]->mapping,
-			        buf->start, buf->start + buf->len - 1);
+	btree_wait_range(buf->eb_info->fs_info, buf->start,
+			 buf->start + buf->len - 1);
 }
 
 struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
@@ -1372,15 +1209,10 @@ void clean_tree_block(struct btrfs_fs_info *fs_info,
 	if (btrfs_header_generation(buf) ==
 	    fs_info->running_transaction->transid) {
 		btrfs_assert_tree_locked(buf);
-
-		if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &buf->bflags)) {
+		if (clear_extent_buffer_dirty(buf))
 			percpu_counter_add_batch(&fs_info->dirty_metadata_bytes,
 						 -buf->len,
 						 fs_info->dirty_metadata_batch);
-			/* ugh, clear_extent_buffer_dirty needs to lock the page */
-			btrfs_set_lock_blocking(buf);
-			clear_extent_buffer_dirty(buf);
-		}
 	}
 }
 
@@ -2412,31 +2244,20 @@ static void btrfs_init_balance(struct btrfs_fs_info *fs_info)
 	init_waitqueue_head(&fs_info->balance_wait_q);
 }
 
-static void btrfs_init_btree_inode(struct btrfs_fs_info *fs_info)
+int btrfs_init_eb_info(struct btrfs_fs_info *fs_info)
 {
-	struct inode *inode = fs_info->btree_inode;
-
-	inode->i_ino = BTRFS_BTREE_INODE_OBJECTID;
-	set_nlink(inode, 1);
-	/*
-	 * we set the i_size on the btree inode to the max possible int.
-	 * the real end of the address space is determined by all of
-	 * the devices in the system
-	 */
-	inode->i_size = OFFSET_MAX;
-	inode->i_mapping->a_ops = &btree_aops;
-
-	RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
-	extent_io_tree_init(&BTRFS_I(inode)->io_tree, inode);
-	BTRFS_I(inode)->io_tree.track_uptodate = 0;
-	extent_map_tree_init(&BTRFS_I(inode)->extent_tree);
-
-	BTRFS_I(inode)->io_tree.ops = &btree_extent_io_ops;
-
-	BTRFS_I(inode)->root = fs_info->tree_root;
-	memset(&BTRFS_I(inode)->location, 0, sizeof(struct btrfs_key));
-	set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
-	btrfs_insert_inode_hash(inode);
+	struct btrfs_eb_info *eb_info = fs_info->eb_info;
+
+	eb_info->fs_info = fs_info;
+	extent_io_tree_init(&eb_info->io_tree, eb_info);
+	eb_info->io_tree.track_uptodate = 0;
+	eb_info->io_tree.ops = &btree_extent_io_ops;
+	extent_io_tree_init(&eb_info->io_failure_tree, eb_info);
+	INIT_RADIX_TREE(&eb_info->buffer_radix, GFP_ATOMIC);
+	spin_lock_init(&eb_info->buffer_lock);
+	if (list_lru_init(&eb_info->lru_list))
+		return -ENOMEM;
+	return 0;
 }
 
 static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info)
@@ -2725,7 +2546,6 @@ int open_ctree(struct super_block *sb,
 	}
 
 	INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
-	INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
 	INIT_LIST_HEAD(&fs_info->trans_list);
 	INIT_LIST_HEAD(&fs_info->dead_roots);
 	INIT_LIST_HEAD(&fs_info->delayed_iputs);
@@ -2739,7 +2559,6 @@ int open_ctree(struct super_block *sb,
 	spin_lock_init(&fs_info->tree_mod_seq_lock);
 	spin_lock_init(&fs_info->super_lock);
 	spin_lock_init(&fs_info->qgroup_op_lock);
-	spin_lock_init(&fs_info->buffer_lock);
 	spin_lock_init(&fs_info->unused_bgs_lock);
 	rwlock_init(&fs_info->tree_mod_log_lock);
 	mutex_init(&fs_info->unused_bg_unpin_mutex);
@@ -2785,18 +2604,11 @@ int open_ctree(struct super_block *sb,
 	INIT_LIST_HEAD(&fs_info->ordered_roots);
 	spin_lock_init(&fs_info->ordered_root_lock);
 
-	fs_info->btree_inode = new_inode(sb);
-	if (!fs_info->btree_inode) {
-		err = -ENOMEM;
-		goto fail_bio_counter;
-	}
-	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
-
 	fs_info->delayed_root = kmalloc(sizeof(struct btrfs_delayed_root),
 					GFP_KERNEL);
 	if (!fs_info->delayed_root) {
 		err = -ENOMEM;
-		goto fail_iput;
+		goto fail_alloc;
 	}
 	btrfs_init_delayed_root(fs_info->delayed_root);
 
@@ -2810,7 +2622,15 @@ int open_ctree(struct super_block *sb,
 	sb->s_blocksize = BTRFS_BDEV_BLOCKSIZE;
 	sb->s_blocksize_bits = blksize_bits(BTRFS_BDEV_BLOCKSIZE);
 
-	btrfs_init_btree_inode(fs_info);
+	fs_info->eb_info = kzalloc(sizeof(struct btrfs_eb_info), GFP_KERNEL);
+	if (!fs_info->eb_info) {
+		err = -ENOMEM;
+		goto fail_alloc;
+	}
+	if (btrfs_init_eb_info(fs_info)) {
+		err = -ENOMEM;
+		goto fail_alloc;
+	}
 
 	spin_lock_init(&fs_info->block_group_cache_lock);
 	fs_info->block_group_cache_tree = RB_ROOT;
@@ -3243,6 +3063,14 @@ int open_ctree(struct super_block *sb,
 	if (sb_rdonly(sb))
 		return 0;
 
+	/*
+	 * We need to make sure we are on the bdi's dirty list so we get
+	 * writeback requests for our fs properly.
+	 */
+	spin_lock(&sb->s_bdi->sb_list_lock);
+	list_add_tail(&sb->s_bdi->dirty_sb_list, &sb->s_bdi_dirty_list);
+	spin_unlock(&sb->s_bdi->sb_list_lock);
+
 	if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
 	    btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
 		clear_free_space_tree = 1;
@@ -3346,7 +3174,8 @@ int open_ctree(struct super_block *sb,
 	 * make sure we're done with the btree inode before we stop our
 	 * kthreads
 	 */
-	filemap_write_and_wait(fs_info->btree_inode->i_mapping);
+	btree_write_range(fs_info, 0, (u64)-1);
+	btree_wait_range(fs_info, 0, (u64)-1);
 
 fail_sysfs:
 	btrfs_sysfs_remove_mounted(fs_info);
@@ -3359,17 +3188,12 @@ int open_ctree(struct super_block *sb,
 
 fail_tree_roots:
 	free_root_pointers(fs_info, 1);
-	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
-
+	btrfs_invalidate_eb_info(fs_info->eb_info);
 fail_sb_buffer:
 	btrfs_stop_all_workers(fs_info);
 	btrfs_free_block_groups(fs_info);
 fail_alloc:
-fail_iput:
 	btrfs_mapping_tree_free(&fs_info->mapping_tree);
-
-	iput(fs_info->btree_inode);
-fail_bio_counter:
 	percpu_counter_destroy(&fs_info->bio_counter);
 fail_delalloc_bytes:
 	percpu_counter_destroy(&fs_info->delalloc_bytes);
@@ -4041,7 +3865,6 @@ void close_ctree(struct btrfs_fs_info *fs_info)
 	 * we must make sure there is not any read request to
 	 * submit after we stopping all workers.
 	 */
-	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
 	btrfs_stop_all_workers(fs_info);
 
 	btrfs_free_block_groups(fs_info);
@@ -4049,8 +3872,6 @@ void close_ctree(struct btrfs_fs_info *fs_info)
 	clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
 	free_root_pointers(fs_info, 1);
 
-	iput(fs_info->btree_inode);
-
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(fs_info, CHECK_INTEGRITY))
 		btrfsic_unmount(fs_info->fs_devices);
@@ -4059,6 +3880,8 @@ void close_ctree(struct btrfs_fs_info *fs_info)
 	btrfs_close_devices(fs_info->fs_devices);
 	btrfs_mapping_tree_free(&fs_info->mapping_tree);
 
+	btrfs_invalidate_eb_info(fs_info->eb_info);
+
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
 	percpu_counter_destroy(&fs_info->delalloc_bytes);
 	percpu_counter_destroy(&fs_info->bio_counter);
@@ -4084,14 +3907,12 @@ int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,
 			  int atomic)
 {
 	int ret;
-	struct inode *btree_inode = buf->pages[0]->mapping->host;
 
 	ret = extent_buffer_uptodate(buf);
 	if (!ret)
 		return ret;
 
-	ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf,
-				    parent_transid, atomic);
+	ret = verify_parent_transid(buf, parent_transid, atomic);
 	if (ret == -EAGAIN)
 		return ret;
 	return !ret;
@@ -4113,8 +3934,8 @@ void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
 	if (unlikely(test_bit(EXTENT_BUFFER_DUMMY, &buf->bflags)))
 		return;
 #endif
-	root = BTRFS_I(buf->pages[0]->mapping->host)->root;
-	fs_info = root->fs_info;
+	fs_info = buf->eb_info->fs_info;
+	root = fs_info->tree_root;
 	btrfs_assert_tree_locked(buf);
 	if (transid != fs_info->generation)
 		WARN(1, KERN_CRIT "btrfs transid mismatch buffer %llu, found %llu running %llu\n",
@@ -4140,6 +3961,7 @@ static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
 	 * this code, they end up stuck in balance_dirty_pages forever
 	 */
 	int ret;
+	struct super_block *sb = fs_info->sb;
 
 	if (current->flags & PF_MEMALLOC)
 		return;
@@ -4149,10 +3971,8 @@ static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
 
 	ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
 				     BTRFS_DIRTY_METADATA_THRESH);
-	if (ret > 0) {
-		balance_dirty_pages_ratelimited(fs_info->sb->s_bdi,
-						fs_info->sb);
-	}
+	if (ret > 0)
+		balance_dirty_pages_ratelimited(sb->s_bdi, sb);
 }
 
 void btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info)
@@ -4167,9 +3987,7 @@ void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info)
 
 int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)
 {
-	struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
-	struct btrfs_fs_info *fs_info = root->fs_info;
-
+	struct btrfs_fs_info *fs_info = buf->eb_info->fs_info;
 	return btree_read_extent_buffer_pages(fs_info, buf, parent_transid);
 }
 
@@ -4513,15 +4331,12 @@ static int btrfs_destroy_marked_extents(struct btrfs_fs_info *fs_info,
 
 		clear_extent_bits(dirty_pages, start, end, mark);
 		while (start <= end) {
-			eb = find_extent_buffer(fs_info, start);
+			eb = find_extent_buffer(fs_info->eb_info, start);
 			start += fs_info->nodesize;
 			if (!eb)
 				continue;
 			wait_on_extent_buffer_writeback(eb);
-
-			if (test_and_clear_bit(EXTENT_BUFFER_DIRTY,
-					       &eb->bflags))
-				clear_extent_buffer_dirty(eb);
+			clear_extent_buffer_dirty(eb);
 			free_extent_buffer_stale(eb);
 		}
 	}
@@ -4710,16 +4525,37 @@ static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info)
 
 static struct btrfs_fs_info *btree_fs_info(void *private_data)
 {
-	struct inode *inode = private_data;
-	return btrfs_sb(inode->i_sb);
+	struct btrfs_eb_info *eb_info = private_data;
+	return eb_info->fs_info;
+}
+
+static int btree_merge_bio_hook(struct page *page, unsigned long offset,
+				size_t size, struct bio *bio,
+				unsigned long bio_flags)
+{
+	struct extent_buffer *eb = (struct extent_buffer *)page->private;
+	struct btrfs_fs_info *fs_info = eb->eb_info->fs_info;
+	u64 logical = (u64)bio->bi_iter.bi_sector << 9;
+	u64 length = 0;
+	u64 map_length;
+	int ret;
+
+	length = bio->bi_iter.bi_size;
+	map_length = length;
+	ret = btrfs_map_block(fs_info, bio_op(bio), logical, &map_length,
+			      NULL, 0);
+	if (ret < 0)
+		return ret;
+	if (map_length < length + size)
+		return 1;
+	return 0;
 }
 
 static const struct extent_io_ops btree_extent_io_ops = {
 	/* mandatory callbacks */
 	.submit_bio_hook = btree_submit_bio_hook,
 	.readpage_end_io_hook = btree_readpage_end_io_hook,
-	/* note we're sharing with inode.c for the merge bio hook */
-	.merge_bio_hook = btrfs_merge_bio_hook,
+	.merge_bio_hook = btree_merge_bio_hook,
 	.readpage_io_failed_hook = btree_io_failed_hook,
 	.set_range_writeback = btrfs_set_range_writeback,
 	.tree_fs_info = btree_fs_info,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0bdc10b453b9..a48fb3abed0c 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1158,28 +1158,30 @@ int btrfs_get_extent_inline_ref_type(const struct extent_buffer *eb,
 			if (type == BTRFS_TREE_BLOCK_REF_KEY)
 				return type;
 			if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
-				ASSERT(eb->fs_info);
+				ASSERT(eb->eb_info);
 				/*
 				 * Every shared one has parent tree
 				 * block, which must be aligned to
 				 * nodesize.
 				 */
 				if (offset &&
-				    IS_ALIGNED(offset, eb->fs_info->nodesize))
+				    IS_ALIGNED(offset,
+					       eb->eb_info->fs_info->nodesize))
 					return type;
 			}
 		} else if (is_data == BTRFS_REF_TYPE_DATA) {
 			if (type == BTRFS_EXTENT_DATA_REF_KEY)
 				return type;
 			if (type == BTRFS_SHARED_DATA_REF_KEY) {
-				ASSERT(eb->fs_info);
+				ASSERT(eb->eb_info->fs_info);
 				/*
 				 * Every shared one has parent tree
 				 * block, which must be aligned to
 				 * nodesize.
 				 */
 				if (offset &&
-				    IS_ALIGNED(offset, eb->fs_info->nodesize))
+				    IS_ALIGNED(offset,
+					       eb->eb_info->fs_info->nodesize))
 					return type;
 			}
 		} else {
@@ -1189,7 +1191,7 @@ int btrfs_get_extent_inline_ref_type(const struct extent_buffer *eb,
 	}
 
 	btrfs_print_leaf((struct extent_buffer *)eb);
-	btrfs_err(eb->fs_info, "eb %llu invalid extent inline ref type %d",
+	btrfs_err(eb->eb_info->fs_info, "eb %llu invalid extent inline ref type %d",
 		  eb->start, type);
 	WARN_ON(1);
 
@@ -8731,7 +8733,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
 	bytenr = btrfs_node_blockptr(path->nodes[level], path->slots[level]);
 	blocksize = fs_info->nodesize;
 
-	next = find_extent_buffer(fs_info, bytenr);
+	next = find_extent_buffer(fs_info->eb_info, bytenr);
 	if (!next) {
 		next = btrfs_find_create_tree_block(fs_info, bytenr);
 		if (IS_ERR(next))
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0538bf85adc3..bb10dc6f4e41 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2768,6 +2768,7 @@ static int submit_extent_page(unsigned int opf, struct extent_io_tree *tree,
 			      int mirror_num,
 			      unsigned long prev_bio_flags,
 			      unsigned long bio_flags,
+			      enum rw_hint io_hint,
 			      bool force_bio_submit)
 {
 	int ret = 0;
@@ -2804,7 +2805,7 @@ static int submit_extent_page(unsigned int opf, struct extent_io_tree *tree,
 	bio_add_page(bio, page, page_size, offset);
 	bio->bi_end_io = end_io_func;
 	bio->bi_private = tree;
-	bio->bi_write_hint = page->mapping->host->i_write_hint;
+	bio->bi_write_hint = io_hint;
 	bio->bi_opf = opf;
 	if (wbc) {
 		wbc_init_bio(wbc, bio);
@@ -3065,7 +3066,7 @@ static int __do_readpage(struct extent_io_tree *tree,
 					 bdev, bio,
 					 end_bio_extent_readpage, mirror_num,
 					 *bio_flags,
-					 this_bio_flag,
+					 this_bio_flag, inode->i_write_hint,
 					 force_bio_submit);
 		if (!ret) {
 			nr++;
@@ -3433,7 +3434,7 @@ static noinline_for_stack int __extent_writepage_io(struct inode *inode,
 					 page, sector, iosize, pg_offset,
 					 bdev, &epd->bio,
 					 end_bio_extent_writepage,
-					 0, 0, 0, false);
+					 0, 0, 0, inode->i_write_hint, false);
 		if (ret) {
 			SetPageError(page);
 			if (PageWriteback(page))
@@ -3539,7 +3540,7 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 			  struct btrfs_fs_info *fs_info,
 			  struct extent_page_data *epd)
 {
-	unsigned long i, num_pages;
+	struct btrfs_eb_info *eb_info = fs_info->eb_info;
 	int flush = 0;
 	int ret = 0;
 
@@ -3586,37 +3587,42 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 
 	btrfs_tree_unlock(eb);
 
-	if (!ret)
-		return ret;
-
-	num_pages = num_extent_pages(eb->start, eb->len);
-	for (i = 0; i < num_pages; i++) {
-		struct page *p = eb->pages[i];
-
-		if (!trylock_page(p)) {
-			if (!flush) {
-				flush_write_bio(epd);
-				flush = 1;
-			}
-			lock_page(p);
-		}
+	/*
+	 * We cleared dirty on this buffer, we need to adjust the radix tags.
+	 * We do the actual page accounting in write_one_eb.
+	 */
+	if (ret) {
+		spin_lock_irq(&eb_info->buffer_lock);
+		radix_tree_tag_set(&eb_info->buffer_radix, eb_index(eb),
+				   PAGECACHE_TAG_WRITEBACK);
+		radix_tree_tag_clear(&eb_info->buffer_radix, eb_index(eb),
+				     PAGECACHE_TAG_DIRTY);
+		radix_tree_tag_clear(&eb_info->buffer_radix, eb_index(eb),
+				     PAGECACHE_TAG_TOWRITE);
+		spin_unlock_irq(&eb_info->buffer_lock);
 	}
-
 	return ret;
 }
 
 static void end_extent_buffer_writeback(struct extent_buffer *eb)
 {
-	clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
-	smp_mb__after_atomic();
-	wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK);
+	if (test_and_clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags)) {
+		struct btrfs_eb_info *eb_info = eb->eb_info;
+		unsigned long flags;
+
+		spin_lock_irqsave(&eb_info->buffer_lock, flags);
+		radix_tree_tag_clear(&eb_info->buffer_radix, eb_index(eb),
+				     PAGECACHE_TAG_WRITEBACK);
+		spin_unlock_irqrestore(&eb_info->buffer_lock, flags);
+		wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK);
+	}
 }
 
 static void set_btree_ioerr(struct page *page)
 {
 	struct extent_buffer *eb = (struct extent_buffer *)page->private;
+	struct btrfs_fs_info *fs_info = eb->eb_info->fs_info;
 
-	SetPageError(page);
 	if (test_and_set_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))
 		return;
 
@@ -3625,8 +3631,7 @@ static void set_btree_ioerr(struct page *page)
 	 * failed, increment the counter transaction->eb_write_errors.
 	 * We do this because while the transaction is running and before it's
 	 * committing (when we call filemap_fdata[write|wait]_range against
-	 * the btree inode), we might have
-	 * btree_inode->i_mapping->a_ops->writepages() called by the VM - if it
+	 * the btree inode), we might have write_metadata() called - if it
 	 * returns an error or an error happens during writeback, when we're
 	 * committing the transaction we wouldn't know about it, since the pages
 	 * can be no longer dirty nor marked anymore for writeback (if a
@@ -3660,13 +3665,13 @@ static void set_btree_ioerr(struct page *page)
 	 */
 	switch (eb->log_index) {
 	case -1:
-		set_bit(BTRFS_FS_BTREE_ERR, &eb->fs_info->flags);
+		set_bit(BTRFS_FS_BTREE_ERR, &fs_info->flags);
 		break;
 	case 0:
-		set_bit(BTRFS_FS_LOG1_ERR, &eb->fs_info->flags);
+		set_bit(BTRFS_FS_LOG1_ERR, &fs_info->flags);
 		break;
 	case 1:
-		set_bit(BTRFS_FS_LOG2_ERR, &eb->fs_info->flags);
+		set_bit(BTRFS_FS_LOG2_ERR, &fs_info->flags);
 		break;
 	default:
 		BUG(); /* unexpected, logic error */
@@ -3682,22 +3687,20 @@ static void end_bio_extent_buffer_writepage(struct bio *bio)
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
 	bio_for_each_segment_all(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
+		struct super_block *sb;
 
 		eb = (struct extent_buffer *)page->private;
 		BUG_ON(!eb);
 		done = atomic_dec_and_test(&eb->io_pages);
 
 		if (bio->bi_status ||
-		    test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags)) {
-			ClearPageUptodate(page);
+		    test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))
 			set_btree_ioerr(page);
-		}
-
-		end_page_writeback(page);
 
+		sb = eb->eb_info->fs_info->sb;
+		account_metadata_end_writeback(page, sb->s_bdi, PAGE_SIZE);
 		if (!done)
 			continue;
-
 		end_extent_buffer_writeback(eb);
 	}
 
@@ -3710,7 +3713,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
 			struct extent_page_data *epd)
 {
 	struct block_device *bdev = fs_info->fs_devices->latest_bdev;
-	struct extent_io_tree *tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
+	struct extent_io_tree *tree = &fs_info->eb_info->io_tree;
 	u64 offset = eb->start;
 	u32 nritems;
 	unsigned long i, num_pages;
@@ -3741,44 +3744,105 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
 	for (i = 0; i < num_pages; i++) {
 		struct page *p = eb->pages[i];
 
-		clear_page_dirty_for_io(p);
-		set_page_writeback(p);
 		ret = submit_extent_page(REQ_OP_WRITE | write_flags, tree, wbc,
 					 p, offset >> 9, PAGE_SIZE, 0, bdev,
 					 &epd->bio,
 					 end_bio_extent_buffer_writepage,
-					 0, 0, 0, false);
+					 0, 0, 0, 0, false);
 		if (ret) {
 			set_btree_ioerr(p);
-			if (PageWriteback(p))
-				end_page_writeback(p);
 			if (atomic_sub_and_test(num_pages - i, &eb->io_pages))
 				end_extent_buffer_writeback(eb);
 			ret = -EIO;
 			break;
 		}
+		account_metadata_writeback(p, fs_info->sb->s_bdi, PAGE_SIZE);
 		offset += PAGE_SIZE;
 		update_nr_written(wbc, 1);
-		unlock_page(p);
 	}
 
-	if (unlikely(ret)) {
-		for (; i < num_pages; i++) {
-			struct page *p = eb->pages[i];
-			clear_page_dirty_for_io(p);
-			unlock_page(p);
-		}
+	return ret;
+}
+
+static void tag_ebs_for_writeback(struct btrfs_eb_info *eb_info, pgoff_t start,
+				  pgoff_t end)
+{
+#define EB_TAG_BATCH 4096
+	unsigned long tagged = 0;
+	struct radix_tree_iter iter;
+	void **slot;
+
+	spin_lock_irq(&eb_info->buffer_lock);
+	radix_tree_for_each_tagged(slot, &eb_info->buffer_radix, &iter, start,
+				   PAGECACHE_TAG_DIRTY) {
+		if (iter.index > end)
+			break;
+		radix_tree_iter_tag_set(&eb_info->buffer_radix, &iter,
+					PAGECACHE_TAG_TOWRITE);
+		tagged++;
+		if ((tagged % EB_TAG_BATCH) != 0)
+			continue;
+		slot = radix_tree_iter_resume(slot, &iter);
+		spin_unlock_irq(&eb_info->buffer_lock);
+		cond_resched();
+		spin_lock_irq(&eb_info->buffer_lock);
 	}
+	spin_unlock_irq(&eb_info->buffer_lock);
+}
+
+static unsigned eb_lookup_tag(struct btrfs_eb_info *eb_info,
+			      struct extent_buffer **ebs, pgoff_t *index,
+			      int tag, unsigned nr)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+	unsigned ret = 0;
 
+	if (unlikely(!nr))
+		return 0;
+
+	rcu_read_lock();
+	radix_tree_for_each_tagged(slot, &eb_info->buffer_radix, &iter, *index,
+				   tag) {
+		struct extent_buffer *eb;
+repeat:
+		eb = radix_tree_deref_slot(slot);
+		if (unlikely(!eb))
+			continue;
+
+		if (radix_tree_exception(eb)) {
+			if (radix_tree_deref_retry(eb)) {
+				slot = radix_tree_iter_retry(&iter);
+				continue;
+			}
+			continue;
+		}
+
+		if (unlikely(!atomic_inc_not_zero(&eb->refs)))
+			continue;
+
+		if (unlikely(eb != *slot)) {
+			free_extent_buffer(eb);
+			goto repeat;
+		}
+
+		ebs[ret] = eb;
+		if (++ret == nr)
+			break;
+	}
+	rcu_read_unlock();
+	if (ret)
+		*index = (ebs[ret - 1]->start >> PAGE_SHIFT) + 1;
 	return ret;
 }
 
-int btree_write_cache_pages(struct address_space *mapping,
+#define EBVEC_SIZE 16
+static int btree_write_cache_pages(struct btrfs_fs_info *fs_info,
 				   struct writeback_control *wbc)
 {
-	struct extent_io_tree *tree = &BTRFS_I(mapping->host)->io_tree;
-	struct btrfs_fs_info *fs_info = BTRFS_I(mapping->host)->root->fs_info;
-	struct extent_buffer *eb, *prev_eb = NULL;
+	struct btrfs_eb_info *eb_info = fs_info->eb_info;
+	struct extent_io_tree *tree = &eb_info->io_tree;
+	struct extent_buffer *eb;
 	struct extent_page_data epd = {
 		.bio = NULL,
 		.tree = tree,
@@ -3788,16 +3852,16 @@ int btree_write_cache_pages(struct address_space *mapping,
 	int ret = 0;
 	int done = 0;
 	int nr_to_write_done = 0;
-	struct pagevec pvec;
-	int nr_pages;
+	struct extent_buffer *ebs[EBVEC_SIZE];
+	int nr_ebs;
 	pgoff_t index;
 	pgoff_t end;		/* Inclusive */
+	pgoff_t done_index = 0;
 	int scanned = 0;
 	int tag;
 
-	pagevec_init(&pvec, 0);
 	if (wbc->range_cyclic) {
-		index = mapping->writeback_index; /* Start from prev offset */
+		index = eb_info->writeback_index; /* Start from prev offset */
 		end = -1;
 	} else {
 		index = wbc->range_start >> PAGE_SHIFT;
@@ -3810,53 +3874,27 @@ int btree_write_cache_pages(struct address_space *mapping,
 		tag = PAGECACHE_TAG_DIRTY;
 retry:
 	if (wbc->sync_mode == WB_SYNC_ALL)
-		tag_pages_for_writeback(mapping, index, end);
+		tag_ebs_for_writeback(fs_info->eb_info, index, end);
 	while (!done && !nr_to_write_done && (index <= end) &&
-	       (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
-			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
+	       (nr_ebs = eb_lookup_tag(eb_info, ebs, &index, tag,
+			min(end - index, (pgoff_t)EBVEC_SIZE-1) + 1))) {
 		unsigned i;
 
 		scanned = 1;
-		for (i = 0; i < nr_pages; i++) {
-			struct page *page = pvec.pages[i];
-
-			if (!PagePrivate(page))
-				continue;
-
-			if (!wbc->range_cyclic && page->index > end) {
-				done = 1;
-				break;
-			}
-
-			spin_lock(&mapping->private_lock);
-			if (!PagePrivate(page)) {
-				spin_unlock(&mapping->private_lock);
-				continue;
-			}
-
-			eb = (struct extent_buffer *)page->private;
-
-			/*
-			 * Shouldn't happen and normally this would be a BUG_ON
-			 * but no sense in crashing the users box for something
-			 * we can survive anyway.
-			 */
-			if (WARN_ON(!eb)) {
-				spin_unlock(&mapping->private_lock);
+		for (i = 0; i < nr_ebs; i++) {
+			eb = ebs[i];
+			if (done) {
+				free_extent_buffer(eb);
 				continue;
 			}
 
-			if (eb == prev_eb) {
-				spin_unlock(&mapping->private_lock);
+			if (!wbc->range_cyclic && eb->start > wbc->range_end) {
+				done = 1;
+				free_extent_buffer(eb);
 				continue;
 			}
 
-			ret = atomic_inc_not_zero(&eb->refs);
-			spin_unlock(&mapping->private_lock);
-			if (!ret)
-				continue;
-
-			prev_eb = eb;
+			done_index = eb_index(eb);
 			ret = lock_extent_buffer_for_io(eb, fs_info, &epd);
 			if (!ret) {
 				free_extent_buffer(eb);
@@ -3864,12 +3902,11 @@ int btree_write_cache_pages(struct address_space *mapping,
 			}
 
 			ret = write_one_eb(eb, fs_info, wbc, &epd);
+			free_extent_buffer(eb);
 			if (ret) {
 				done = 1;
-				free_extent_buffer(eb);
-				break;
+				continue;
 			}
-			free_extent_buffer(eb);
 
 			/*
 			 * the filesystem may choose to bump up nr_to_write.
@@ -3878,7 +3915,6 @@ int btree_write_cache_pages(struct address_space *mapping,
 			 */
 			nr_to_write_done = wbc->nr_to_write <= 0;
 		}
-		pagevec_release(&pvec);
 		cond_resched();
 	}
 	if (!scanned && !done) {
@@ -3890,10 +3926,77 @@ int btree_write_cache_pages(struct address_space *mapping,
 		index = 0;
 		goto retry;
 	}
+	if (wbc->range_cyclic)
+		fs_info->eb_info->writeback_index = done_index;
 	flush_write_bio(&epd);
 	return ret;
 }
 
+void btrfs_write_ebs(struct super_block *sb, struct writeback_control *wbc)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
+	btree_write_cache_pages(fs_info, wbc);
+}
+
+static int __btree_write_range(struct btrfs_fs_info *fs_info, u64 start,
+			       u64 end, int sync_mode)
+{
+	struct writeback_control wbc = {
+		.sync_mode = sync_mode,
+		.nr_to_write = LONG_MAX,
+		.range_start = start,
+		.range_end = end,
+	};
+
+	return btree_write_cache_pages(fs_info, &wbc);
+}
+
+void btree_flush(struct btrfs_fs_info *fs_info)
+{
+	__btree_write_range(fs_info, 0, (u64)-1, WB_SYNC_NONE);
+}
+
+int btree_write_range(struct btrfs_fs_info *fs_info, u64 start, u64 end)
+{
+	return __btree_write_range(fs_info, start, end, WB_SYNC_ALL);
+}
+
+int btree_wait_range(struct btrfs_fs_info *fs_info, u64 start, u64 end)
+{
+	struct extent_buffer *ebs[EBVEC_SIZE];
+	pgoff_t index = start >> PAGE_SHIFT;
+	pgoff_t end_index = end >> PAGE_SHIFT;
+	unsigned nr_ebs;
+	int ret = 0;
+
+	if (end < start)
+		return ret;
+
+	while ((index <= end) &&
+	       (nr_ebs = eb_lookup_tag(fs_info->eb_info, ebs, &index,
+				       PAGECACHE_TAG_WRITEBACK,
+				       min(end_index - index,
+					   (pgoff_t)EBVEC_SIZE-1) + 1)) != 0) {
+		unsigned i;
+
+		for (i = 0; i < nr_ebs; i++) {
+			struct extent_buffer *eb = ebs[i];
+
+			if (eb->start > end) {
+				free_extent_buffer(eb);
+				continue;
+			}
+
+			wait_on_extent_buffer_writeback(eb);
+			if (test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))
+				ret = -EIO;
+			free_extent_buffer(eb);
+		}
+		cond_resched();
+	}
+	return ret;
+}
+
 /**
  * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
  * @mapping: address space structure to write
@@ -4680,7 +4783,6 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
 {
 	unsigned long index;
 	struct page *page;
-	int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
 
 	BUG_ON(extent_buffer_under_io(eb));
 
@@ -4688,39 +4790,21 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
 	if (index == 0)
 		return;
 
+	ASSERT(!test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
 	do {
 		index--;
 		page = eb->pages[index];
 		if (!page)
 			continue;
-		if (mapped)
-			spin_lock(&page->mapping->private_lock);
-		/*
-		 * We do this since we'll remove the pages after we've
-		 * removed the eb from the radix tree, so we could race
-		 * and have this page now attached to the new eb.  So
-		 * only clear page_private if it's still connected to
-		 * this eb.
-		 */
-		if (PagePrivate(page) &&
-		    page->private == (unsigned long)eb) {
-			BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
-			BUG_ON(PageDirty(page));
-			BUG_ON(PageWriteback(page));
-			/*
-			 * We need to make sure we haven't be attached
-			 * to a new eb.
-			 */
-			ClearPagePrivate(page);
-			set_page_private(page, 0);
-			/* One for the page private */
-			put_page(page);
-		}
+		ASSERT(PagePrivate(page));
+		ASSERT(page->private == (unsigned long)eb);
+		ClearPagePrivate(page);
+		set_page_private(page, 0);
 
-		if (mapped)
-			spin_unlock(&page->mapping->private_lock);
+		/* Once for the page private. */
+		put_page(page);
 
-		/* One for when we allocated the page */
+		/* Once for the alloc_page. */
 		put_page(page);
 	} while (index != 0);
 }
@@ -4735,7 +4819,7 @@ static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
 }
 
 static struct extent_buffer *
-__alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
+__alloc_extent_buffer(struct btrfs_eb_info *eb_info, u64 start,
 		      unsigned long len)
 {
 	struct extent_buffer *eb = NULL;
@@ -4743,7 +4827,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS|__GFP_NOFAIL);
 	eb->start = start;
 	eb->len = len;
-	eb->fs_info = fs_info;
+	eb->eb_info = eb_info;
 	eb->bflags = 0;
 	rwlock_init(&eb->lock);
 	atomic_set(&eb->write_locks, 0);
@@ -4755,6 +4839,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	eb->lock_nested = 0;
 	init_waitqueue_head(&eb->write_lock_wq);
 	init_waitqueue_head(&eb->read_lock_wq);
+	INIT_LIST_HEAD(&eb->lru);
 
 	btrfs_leak_debug_add(&eb->leak_list, &buffers);
 
@@ -4779,7 +4864,7 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
 	struct extent_buffer *new;
 	unsigned long num_pages = num_extent_pages(src->start, src->len);
 
-	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
+	new = __alloc_extent_buffer(src->eb_info, src->start, src->len);
 	if (new == NULL)
 		return NULL;
 
@@ -4790,8 +4875,6 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
 			return NULL;
 		}
 		attach_extent_buffer_page(new, p);
-		WARN_ON(PageDirty(p));
-		SetPageUptodate(p);
 		new->pages[i] = p;
 		copy_page(page_address(p), page_address(src->pages[i]));
 	}
@@ -4802,8 +4885,8 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
 	return new;
 }
 
-struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
-						  u64 start, unsigned long len)
+struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_eb_info *eb_info,
+						u64 start, unsigned long len)
 {
 	struct extent_buffer *eb;
 	unsigned long num_pages;
@@ -4811,7 +4894,7 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 
 	num_pages = num_extent_pages(start, len);
 
-	eb = __alloc_extent_buffer(fs_info, start, len);
+	eb = __alloc_extent_buffer(eb_info, start, len);
 	if (!eb)
 		return NULL;
 
@@ -4819,6 +4902,7 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 		eb->pages[i] = alloc_page(GFP_NOFS);
 		if (!eb->pages[i])
 			goto err;
+		attach_extent_buffer_page(eb, eb->pages[i]);
 	}
 	set_extent_buffer_uptodate(eb);
 	btrfs_set_header_nritems(eb, 0);
@@ -4826,18 +4910,10 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 
 	return eb;
 err:
-	for (; i > 0; i--)
-		__free_page(eb->pages[i - 1]);
-	__free_extent_buffer(eb);
+	btrfs_release_extent_buffer(eb);
 	return NULL;
 }
 
-struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
-						u64 start)
-{
-	return __alloc_dummy_extent_buffer(fs_info, start, fs_info->nodesize);
-}
-
 static void check_buffer_tree_ref(struct extent_buffer *eb)
 {
 	int refs;
@@ -4887,13 +4963,13 @@ static void mark_extent_buffer_accessed(struct extent_buffer *eb,
 	}
 }
 
-struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
+struct extent_buffer *find_extent_buffer(struct btrfs_eb_info *eb_info,
 					 u64 start)
 {
 	struct extent_buffer *eb;
 
 	rcu_read_lock();
-	eb = radix_tree_lookup(&fs_info->buffer_radix,
+	eb = radix_tree_lookup(&eb_info->buffer_radix,
 			       start >> PAGE_SHIFT);
 	if (eb && atomic_inc_not_zero(&eb->refs)) {
 		rcu_read_unlock();
@@ -4925,30 +5001,30 @@ struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
 }
 
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
-struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
-					u64 start)
+struct extent_buffer *alloc_test_extent_buffer(struct btrfs_eb_info *eb_info,
+					       u64 start, u32 nodesize)
 {
 	struct extent_buffer *eb, *exists = NULL;
 	int ret;
 
-	eb = find_extent_buffer(fs_info, start);
+	eb = find_extent_buffer(eb_info, start);
 	if (eb)
 		return eb;
-	eb = alloc_dummy_extent_buffer(fs_info, start);
+	eb = alloc_dummy_extent_buffer(eb_info, start, nodesize);
 	if (!eb)
 		return NULL;
-	eb->fs_info = fs_info;
+	eb->eb_info = eb_info;
 again:
 	ret = radix_tree_preload(GFP_NOFS);
 	if (ret)
 		goto free_eb;
-	spin_lock(&fs_info->buffer_lock);
-	ret = radix_tree_insert(&fs_info->buffer_radix,
+	spin_lock_irq(&eb_info->buffer_lock);
+	ret = radix_tree_insert(&eb_info->buffer_radix,
 				start >> PAGE_SHIFT, eb);
-	spin_unlock(&fs_info->buffer_lock);
+	spin_unlock_irq(&eb_info->buffer_lock);
 	radix_tree_preload_end();
 	if (ret == -EEXIST) {
-		exists = find_extent_buffer(fs_info, start);
+		exists = find_extent_buffer(eb_info, start);
 		if (exists)
 			goto free_eb;
 		else
@@ -4964,6 +5040,7 @@ struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
 	 * bump the ref count again.
 	 */
 	atomic_inc(&eb->refs);
+	set_extent_buffer_uptodate(eb);
 	return eb;
 free_eb:
 	btrfs_release_extent_buffer(eb);
@@ -4977,12 +5054,10 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 	unsigned long len = fs_info->nodesize;
 	unsigned long num_pages = num_extent_pages(start, len);
 	unsigned long i;
-	unsigned long index = start >> PAGE_SHIFT;
 	struct extent_buffer *eb;
 	struct extent_buffer *exists = NULL;
 	struct page *p;
-	struct address_space *mapping = fs_info->btree_inode->i_mapping;
-	int uptodate = 1;
+	struct btrfs_eb_info *eb_info = fs_info->eb_info;
 	int ret;
 
 	if (!IS_ALIGNED(start, fs_info->sectorsize)) {
@@ -4990,62 +5065,23 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 		return ERR_PTR(-EINVAL);
 	}
 
-	eb = find_extent_buffer(fs_info, start);
+	eb = find_extent_buffer(eb_info, start);
 	if (eb)
 		return eb;
 
-	eb = __alloc_extent_buffer(fs_info, start, len);
+	eb = __alloc_extent_buffer(eb_info, start, len);
 	if (!eb)
 		return ERR_PTR(-ENOMEM);
 
-	for (i = 0; i < num_pages; i++, index++) {
-		p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
+	for (i = 0; i < num_pages; i++) {
+		p = alloc_page(GFP_NOFS|__GFP_NOFAIL);
 		if (!p) {
 			exists = ERR_PTR(-ENOMEM);
 			goto free_eb;
 		}
-
-		spin_lock(&mapping->private_lock);
-		if (PagePrivate(p)) {
-			/*
-			 * We could have already allocated an eb for this page
-			 * and attached one so lets see if we can get a ref on
-			 * the existing eb, and if we can we know it's good and
-			 * we can just return that one, else we know we can just
-			 * overwrite page->private.
-			 */
-			exists = (struct extent_buffer *)p->private;
-			if (atomic_inc_not_zero(&exists->refs)) {
-				spin_unlock(&mapping->private_lock);
-				unlock_page(p);
-				put_page(p);
-				mark_extent_buffer_accessed(exists, p);
-				goto free_eb;
-			}
-			exists = NULL;
-
-			/*
-			 * Do this so attach doesn't complain and we need to
-			 * drop the ref the old guy had.
-			 */
-			ClearPagePrivate(p);
-			WARN_ON(PageDirty(p));
-			put_page(p);
-		}
 		attach_extent_buffer_page(eb, p);
-		spin_unlock(&mapping->private_lock);
-		WARN_ON(PageDirty(p));
 		eb->pages[i] = p;
-		if (!PageUptodate(p))
-			uptodate = 0;
-
-		/*
-		 * see below about how we avoid a nasty race with release page
-		 * and why we unlock later
-		 */
 	}
-	if (uptodate)
-		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
 again:
 	ret = radix_tree_preload(GFP_NOFS);
 	if (ret) {
@@ -5053,13 +5089,13 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 		goto free_eb;
 	}
 
-	spin_lock(&fs_info->buffer_lock);
-	ret = radix_tree_insert(&fs_info->buffer_radix,
+	spin_lock_irq(&eb_info->buffer_lock);
+	ret = radix_tree_insert(&eb_info->buffer_radix,
 				start >> PAGE_SHIFT, eb);
-	spin_unlock(&fs_info->buffer_lock);
+	spin_unlock_irq(&eb_info->buffer_lock);
 	radix_tree_preload_end();
 	if (ret == -EEXIST) {
-		exists = find_extent_buffer(fs_info, start);
+		exists = find_extent_buffer(eb_info, start);
 		if (exists)
 			goto free_eb;
 		else
@@ -5069,31 +5105,10 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 	check_buffer_tree_ref(eb);
 	set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
 
-	/*
-	 * there is a race where release page may have
-	 * tried to find this extent buffer in the radix
-	 * but failed.  It will tell the VM it is safe to
-	 * reclaim the, and it will clear the page private bit.
-	 * We must make sure to set the page private bit properly
-	 * after the extent buffer is in the radix tree so
-	 * it doesn't get lost
-	 */
-	SetPageChecked(eb->pages[0]);
-	for (i = 1; i < num_pages; i++) {
-		p = eb->pages[i];
-		ClearPageChecked(p);
-		unlock_page(p);
-	}
-	unlock_page(eb->pages[0]);
 	return eb;
 
 free_eb:
 	WARN_ON(!atomic_dec_and_test(&eb->refs));
-	for (i = 0; i < num_pages; i++) {
-		if (eb->pages[i])
-			unlock_page(eb->pages[i]);
-	}
-
 	btrfs_release_extent_buffer(eb);
 	return exists;
 }
@@ -5109,17 +5124,19 @@ static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
 /* Expects to have eb->eb_lock already held */
 static int release_extent_buffer(struct extent_buffer *eb)
 {
+	struct btrfs_eb_info *eb_info = eb->eb_info;
+
 	WARN_ON(atomic_read(&eb->refs) == 0);
 	if (atomic_dec_and_test(&eb->refs)) {
+		if (eb_info)
+			list_lru_del(&eb_info->lru_list, &eb->lru);
 		if (test_and_clear_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags)) {
-			struct btrfs_fs_info *fs_info = eb->fs_info;
-
 			spin_unlock(&eb->refs_lock);
 
-			spin_lock(&fs_info->buffer_lock);
-			radix_tree_delete(&fs_info->buffer_radix,
-					  eb->start >> PAGE_SHIFT);
-			spin_unlock(&fs_info->buffer_lock);
+			spin_lock_irq(&eb_info->buffer_lock);
+			radix_tree_delete(&eb_info->buffer_radix,
+					  eb_index(eb));
+			spin_unlock_irq(&eb_info->buffer_lock);
 		} else {
 			spin_unlock(&eb->refs_lock);
 		}
@@ -5134,6 +5151,8 @@ static int release_extent_buffer(struct extent_buffer *eb)
 #endif
 		call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
 		return 1;
+	} else if (eb_info && atomic_read(&eb->refs) == 1) {
+		list_lru_add(&eb_info->lru_list, &eb->lru);
 	}
 	spin_unlock(&eb->refs_lock);
 
@@ -5167,10 +5186,6 @@ void free_extent_buffer(struct extent_buffer *eb)
 	    test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
 		atomic_dec(&eb->refs);
 
-	/*
-	 * I know this is terrible, but it's temporary until we stop tracking
-	 * the uptodate bits and such for the extent buffers.
-	 */
 	release_extent_buffer(eb);
 }
 
@@ -5188,82 +5203,156 @@ void free_extent_buffer_stale(struct extent_buffer *eb)
 	release_extent_buffer(eb);
 }
 
-void clear_extent_buffer_dirty(struct extent_buffer *eb)
+long btrfs_nr_ebs(struct super_block *sb, struct shrink_control *sc)
 {
-	unsigned long i;
-	unsigned long num_pages;
-	struct page *page;
+	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
+	struct btrfs_eb_info *eb_info = fs_info->eb_info;
 
-	num_pages = num_extent_pages(eb->start, eb->len);
+	return list_lru_shrink_count(&eb_info->lru_list, sc);
+}
 
-	for (i = 0; i < num_pages; i++) {
-		page = eb->pages[i];
-		if (!PageDirty(page))
-			continue;
+static enum lru_status eb_lru_isolate(struct list_head *item,
+				      struct list_lru_one *lru,
+				      spinlock_t *lru_lock, void *arg)
+{
+	struct list_head *freeable = (struct list_head *)arg;
+	struct extent_buffer *eb = container_of(item, struct extent_buffer,
+						lru);
+	enum lru_status ret;
+	int refs;
 
-		lock_page(page);
-		WARN_ON(!PagePrivate(page));
+	if (!spin_trylock(&eb->refs_lock))
+		return LRU_SKIP;
 
-		clear_page_dirty_for_io(page);
-		spin_lock_irq(&page->mapping->tree_lock);
-		if (!PageDirty(page)) {
-			radix_tree_tag_clear(&page->mapping->page_tree,
-						page_index(page),
-						PAGECACHE_TAG_DIRTY);
-		}
-		spin_unlock_irq(&page->mapping->tree_lock);
-		ClearPageError(page);
-		unlock_page(page);
+	if (extent_buffer_under_io(eb)) {
+		ret = LRU_ROTATE;
+		goto out;
+	}
+
+	refs = atomic_read(&eb->refs);
+	/* We can race with somebody freeing us, just skip if this happens. */
+	if (refs == 0) {
+		ret = LRU_SKIP;
+		goto out;
+	}
+
+	/* Eb is in use, don't kill it. */
+	if (refs > 1) {
+		ret = LRU_ROTATE;
+		goto out;
+	}
+
+	/*
+	 * If we don't clear the TREE_REF flag then this eb is going to
+	 * disappear soon anyway.  Otherwise we become responsible for dropping
+	 * the last ref on this eb and we know it'll survive until we call
+	 * dispose_list.
+	 */
+	if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
+		ret = LRU_SKIP;
+		goto out;
+	}
+	list_lru_isolate_move(lru, &eb->lru, freeable);
+	ret = LRU_REMOVED;
+out:
+	spin_unlock(&eb->refs_lock);
+	return ret;
+}
+
+static void dispose_list(struct list_head *list)
+{
+	struct extent_buffer *eb;
+
+	while (!list_empty(list)) {
+		eb = list_first_entry(list, struct extent_buffer, lru);
+
+		spin_lock(&eb->refs_lock);
+		list_del_init(&eb->lru);
+		spin_unlock(&eb->refs_lock);
+		free_extent_buffer(eb);
+		cond_resched();
 	}
+}
+
+long btrfs_free_ebs(struct super_block *sb, struct shrink_control *sc)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
+	struct btrfs_eb_info *eb_info = fs_info->eb_info;
+	LIST_HEAD(freeable);
+	long freed;
+
+	freed = list_lru_shrink_walk(&eb_info->lru_list, sc, eb_lru_isolate,
+				     &freeable);
+	dispose_list(&freeable);
+	return freed;
+}
+
+void btrfs_invalidate_eb_info(struct btrfs_eb_info *eb_info)
+{
+	LIST_HEAD(freeable);
+
+	/*
+	 * We should be able to free all the extent buffers at this point, if we
+	 * can't there's a problem and we should complain loudly about it.
+	 */
+	do {
+		list_lru_walk(&eb_info->lru_list, eb_lru_isolate, &freeable, LONG_MAX);
+	} while (WARN_ON(list_lru_count(&eb_info->lru_list)));
+	dispose_list(&freeable);
+	synchronize_rcu();
+}
+
+int clear_extent_buffer_dirty(struct extent_buffer *eb)
+{
+	struct btrfs_eb_info *eb_info = eb->eb_info;
+	struct super_block *sb = eb_info->fs_info->sb;
+	unsigned long num_pages;
+
+	if (!test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->bflags))
+		return 0;
+
+	spin_lock_irq(&eb_info->buffer_lock);
+	radix_tree_tag_clear(&eb_info->buffer_radix, eb_index(eb),
+			     PAGECACHE_TAG_DIRTY);
+	spin_unlock_irq(&eb_info->buffer_lock);
+
+	num_pages = num_extent_pages(eb->start, eb->len);
+	account_metadata_cleaned(eb->pages[0], sb->s_bdi, eb->len);
 	WARN_ON(atomic_read(&eb->refs) == 0);
+	return 1;
 }
 
 int set_extent_buffer_dirty(struct extent_buffer *eb)
 {
-	unsigned long i;
+	struct btrfs_eb_info *eb_info = eb->eb_info;
+	struct super_block *sb = eb_info->fs_info->sb;
 	unsigned long num_pages;
 	int was_dirty = 0;
 
 	check_buffer_tree_ref(eb);
 
-	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
-
-	num_pages = num_extent_pages(eb->start, eb->len);
 	WARN_ON(atomic_read(&eb->refs) == 0);
 	WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
+	if (test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags))
+		return 1;
 
-	for (i = 0; i < num_pages; i++)
-		set_page_dirty(eb->pages[i]);
+	num_pages = num_extent_pages(eb->start, eb->len);
+	account_metadata_dirtied(eb->pages[0], sb->s_bdi, eb->len);
+	spin_lock_irq(&eb_info->buffer_lock);
+	radix_tree_tag_set(&eb_info->buffer_radix, eb_index(eb),
+			   PAGECACHE_TAG_DIRTY);
+	spin_unlock_irq(&eb_info->buffer_lock);
 	return was_dirty;
 }
 
 void clear_extent_buffer_uptodate(struct extent_buffer *eb)
 {
-	unsigned long i;
-	struct page *page;
-	unsigned long num_pages;
-
 	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-	num_pages = num_extent_pages(eb->start, eb->len);
-	for (i = 0; i < num_pages; i++) {
-		page = eb->pages[i];
-		if (page)
-			ClearPageUptodate(page);
-	}
 }
 
 void set_extent_buffer_uptodate(struct extent_buffer *eb)
 {
-	unsigned long i;
-	struct page *page;
-	unsigned long num_pages;
-
 	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-	num_pages = num_extent_pages(eb->start, eb->len);
-	for (i = 0; i < num_pages; i++) {
-		page = eb->pages[i];
-		SetPageUptodate(page);
-	}
 }
 
 int extent_buffer_uptodate(struct extent_buffer *eb)
@@ -5271,112 +5360,165 @@ int extent_buffer_uptodate(struct extent_buffer *eb)
 	return test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
 }
 
-int read_extent_buffer_pages(struct extent_io_tree *tree,
-			     struct extent_buffer *eb, int wait,
-			     get_extent_t *get_extent, int mirror_num)
+static void end_bio_extent_buffer_readpage(struct bio *bio)
 {
+	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
+	struct extent_io_tree *tree = NULL;
+	struct bio_vec *bvec;
+	u64 unlock_start = 0, unlock_len = 0;
+	int mirror_num = io_bio->mirror_num;
+	int uptodate = !bio->bi_status;
+	int i, ret;
+
+	bio_for_each_segment_all(bvec, bio, i) {
+		struct page *page = bvec->bv_page;
+		struct btrfs_eb_info *eb_info;
+		struct extent_buffer *eb;
+
+		eb = (struct extent_buffer *)page->private;
+		if (WARN_ON(!eb))
+			continue;
+
+		eb_info = eb->eb_info;
+		if (!tree)
+			tree = &eb_info->io_tree;
+		if (uptodate) {
+			/*
+			 * btree_readpage_end_io_hook doesn't care about
+			 * start/end so just pass 0.  We'll kill this later.
+			 */
+			ret = tree->ops->readpage_end_io_hook(io_bio, 0,
+							      page, 0, 0,
+							      mirror_num);
+			if (ret) {
+				uptodate = 0;
+			} else {
+				u64 start = eb->start;
+				int c, num_pages;
+
+				num_pages = num_extent_pages(eb->start,
+							     eb->len);
+				for (c = 0; c < num_pages; c++) {
+					if (eb->pages[c] == page)
+						break;
+					start += PAGE_SIZE;
+				}
+				clean_io_failure(eb_info->fs_info,
+						 &eb_info->io_failure_tree,
+						 tree, start, page, 0, 0);
+			}
+		}
+		/*
+		 * We never fix anything in btree_io_failed_hook.
+		 *
+		 * TODO: rework the io failed hook to not assume we can fix
+		 * anything.
+		 */
+		if (!uptodate)
+			tree->ops->readpage_io_failed_hook(page, mirror_num);
+
+		if (unlock_start == 0) {
+			unlock_start = eb->start;
+			unlock_len = PAGE_SIZE;
+		} else {
+			unlock_len += PAGE_SIZE;
+		}
+	}
+
+	if (unlock_start)
+		unlock_extent(tree, unlock_start,
+			      unlock_start + unlock_len - 1);
+	if (io_bio->end_io)
+		io_bio->end_io(io_bio, blk_status_to_errno(bio->bi_status));
+	bio_put(bio);
+}
+
+int read_extent_buffer_pages(struct extent_buffer *eb, int wait,
+			     int mirror_num)
+{
+	struct btrfs_eb_info *eb_info = eb->eb_info;
+	struct extent_io_tree *io_tree = &eb_info->io_tree;
+	struct block_device *bdev = eb_info->fs_info->fs_devices->latest_bdev;
+	struct bio *bio = NULL;
+	u64 offset = eb->start;
+	u64 unlock_start = 0, unlock_len = 0;
 	unsigned long i;
 	struct page *page;
 	int err;
 	int ret = 0;
-	int locked_pages = 0;
-	int all_uptodate = 1;
 	unsigned long num_pages;
-	unsigned long num_reads = 0;
-	struct bio *bio = NULL;
-	unsigned long bio_flags = 0;
 
 	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
 		return 0;
 
-	num_pages = num_extent_pages(eb->start, eb->len);
-	for (i = 0; i < num_pages; i++) {
-		page = eb->pages[i];
-		if (wait == WAIT_NONE) {
-			if (!trylock_page(page))
-				goto unlock_exit;
-		} else {
-			lock_page(page);
-		}
-		locked_pages++;
-	}
-	/*
-	 * We need to firstly lock all pages to make sure that
-	 * the uptodate bit of our pages won't be affected by
-	 * clear_extent_buffer_uptodate().
-	 */
-	for (i = 0; i < num_pages; i++) {
-		page = eb->pages[i];
-		if (!PageUptodate(page)) {
-			num_reads++;
-			all_uptodate = 0;
-		}
-	}
-
-	if (all_uptodate) {
-		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-		goto unlock_exit;
+	if (test_and_set_bit(EXTENT_BUFFER_READING, &eb->bflags)) {
+		if (wait != WAIT_COMPLETE)
+			return 0;
+		wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_READING,
+			       TASK_UNINTERRUPTIBLE);
+		if (!test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
+			ret = -EIO;
+		return ret;
 	}
 
+	lock_extent(io_tree, eb->start, eb->start + eb->len - 1);
+	num_pages = num_extent_pages(eb->start, eb->len);
 	clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
 	eb->read_mirror = 0;
-	atomic_set(&eb->io_pages, num_reads);
+	atomic_set(&eb->io_pages, num_pages);
 	for (i = 0; i < num_pages; i++) {
 		page = eb->pages[i];
-
-		if (!PageUptodate(page)) {
-			if (ret) {
-				atomic_dec(&eb->io_pages);
-				unlock_page(page);
-				continue;
+		if (ret) {
+			unlock_len += PAGE_SIZE;
+			if (atomic_dec_and_test(&eb->io_pages)) {
+				clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
+				smp_mb__after_atomic();
+				wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
 			}
+			continue;
+		}
 
-			ClearPageError(page);
-			err = __extent_read_full_page(tree, page,
-						      get_extent, &bio,
-						      mirror_num, &bio_flags,
-						      REQ_META);
-			if (err) {
-				ret = err;
-				/*
-				 * We use &bio in above __extent_read_full_page,
-				 * so we ensure that if it returns error, the
-				 * current page fails to add itself to bio and
-				 * it's been unlocked.
-				 *
-				 * We must dec io_pages by ourselves.
-				 */
-				atomic_dec(&eb->io_pages);
+		err = submit_extent_page(REQ_OP_READ | REQ_META, io_tree, NULL,
+					 page, offset >> 9, PAGE_SIZE, 0, bdev,
+					 &bio, end_bio_extent_buffer_readpage,
+					 mirror_num, 0, 0, 0, false);
+		if (err) {
+			ret = err;
+			/*
+			 * We use &bio in above submit_extent_page
+			 * so we ensure that if it returns error, the
+			 * current page fails to add itself to bio and
+			 * it's been unlocked.
+			 *
+			 * We must dec io_pages by ourselves.
+			 */
+			if (atomic_dec_and_test(&eb->io_pages)) {
+				clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
+				smp_mb__after_atomic();
+				wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
 			}
-		} else {
-			unlock_page(page);
+			unlock_start = eb->start;
+			unlock_len = PAGE_SIZE;
 		}
+		offset += PAGE_SIZE;
 	}
 
 	if (bio) {
-		err = submit_one_bio(bio, mirror_num, bio_flags);
+		err = submit_one_bio(bio, mirror_num, 0);
 		if (err)
 			return err;
 	}
 
+	if (ret && unlock_start)
+		unlock_extent(io_tree, unlock_start,
+			      unlock_start + unlock_len - 1);
 	if (ret || wait != WAIT_COMPLETE)
 		return ret;
 
-	for (i = 0; i < num_pages; i++) {
-		page = eb->pages[i];
-		wait_on_page_locked(page);
-		if (!PageUptodate(page))
-			ret = -EIO;
-	}
-
-	return ret;
-
-unlock_exit:
-	while (locked_pages > 0) {
-		locked_pages--;
-		page = eb->pages[locked_pages];
-		unlock_page(page);
-	}
+	wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_READING,
+		       TASK_UNINTERRUPTIBLE);
+	if (!test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
+		ret = -EIO;
 	return ret;
 }
 
@@ -5533,7 +5675,6 @@ void write_extent_buffer_chunk_tree_uuid(struct extent_buffer *eb,
 {
 	char *kaddr;
 
-	WARN_ON(!PageUptodate(eb->pages[0]));
 	kaddr = page_address(eb->pages[0]);
 	memcpy(kaddr + offsetof(struct btrfs_header, chunk_tree_uuid), srcv,
 			BTRFS_FSID_SIZE);
@@ -5543,7 +5684,6 @@ void write_extent_buffer_fsid(struct extent_buffer *eb, const void *srcv)
 {
 	char *kaddr;
 
-	WARN_ON(!PageUptodate(eb->pages[0]));
 	kaddr = page_address(eb->pages[0]);
 	memcpy(kaddr + offsetof(struct btrfs_header, fsid), srcv,
 			BTRFS_FSID_SIZE);
@@ -5567,7 +5707,6 @@ void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
 
 	while (len > 0) {
 		page = eb->pages[i];
-		WARN_ON(!PageUptodate(page));
 
 		cur = min(len, PAGE_SIZE - offset);
 		kaddr = page_address(page);
@@ -5597,7 +5736,6 @@ void memzero_extent_buffer(struct extent_buffer *eb, unsigned long start,
 
 	while (len > 0) {
 		page = eb->pages[i];
-		WARN_ON(!PageUptodate(page));
 
 		cur = min(len, PAGE_SIZE - offset);
 		kaddr = page_address(page);
@@ -5642,7 +5780,6 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
 
 	while (len > 0) {
 		page = dst->pages[i];
-		WARN_ON(!PageUptodate(page));
 
 		cur = min(len, (unsigned long)(PAGE_SIZE - offset));
 
@@ -5745,7 +5882,6 @@ int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,
 
 	eb_bitmap_offset(eb, start, nr, &i, &offset);
 	page = eb->pages[i];
-	WARN_ON(!PageUptodate(page));
 	kaddr = page_address(page);
 	return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));
 }
@@ -5770,7 +5906,6 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
 
 	eb_bitmap_offset(eb, start, pos, &i, &offset);
 	page = eb->pages[i];
-	WARN_ON(!PageUptodate(page));
 	kaddr = page_address(page);
 
 	while (len >= bits_to_set) {
@@ -5781,7 +5916,6 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
 		if (++offset >= PAGE_SIZE && len > 0) {
 			offset = 0;
 			page = eb->pages[++i];
-			WARN_ON(!PageUptodate(page));
 			kaddr = page_address(page);
 		}
 	}
@@ -5812,7 +5946,6 @@ void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
 
 	eb_bitmap_offset(eb, start, pos, &i, &offset);
 	page = eb->pages[i];
-	WARN_ON(!PageUptodate(page));
 	kaddr = page_address(page);
 
 	while (len >= bits_to_clear) {
@@ -5823,7 +5956,6 @@ void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
 		if (++offset >= PAGE_SIZE && len > 0) {
 			offset = 0;
 			page = eb->pages[++i];
-			WARN_ON(!PageUptodate(page));
 			kaddr = page_address(page);
 		}
 	}
@@ -5864,7 +5996,7 @@ static void copy_pages(struct page *dst_page, struct page *src_page,
 void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
 			   unsigned long src_offset, unsigned long len)
 {
-	struct btrfs_fs_info *fs_info = dst->fs_info;
+	struct btrfs_fs_info *fs_info = dst->eb_info->fs_info;
 	size_t cur;
 	size_t dst_off_in_page;
 	size_t src_off_in_page;
@@ -5911,7 +6043,7 @@ void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
 void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
 			   unsigned long src_offset, unsigned long len)
 {
-	struct btrfs_fs_info *fs_info = dst->fs_info;
+	struct btrfs_fs_info *fs_info = dst->eb_info->fs_info;
 	size_t cur;
 	size_t dst_off_in_page;
 	size_t src_off_in_page;
@@ -5957,45 +6089,3 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
 		len -= cur;
 	}
 }
-
-int try_release_extent_buffer(struct page *page)
-{
-	struct extent_buffer *eb;
-
-	/*
-	 * We need to make sure nobody is attaching this page to an eb right
-	 * now.
-	 */
-	spin_lock(&page->mapping->private_lock);
-	if (!PagePrivate(page)) {
-		spin_unlock(&page->mapping->private_lock);
-		return 1;
-	}
-
-	eb = (struct extent_buffer *)page->private;
-	BUG_ON(!eb);
-
-	/*
-	 * This is a little awful but should be ok, we need to make sure that
-	 * the eb doesn't disappear out from under us while we're looking at
-	 * this page.
-	 */
-	spin_lock(&eb->refs_lock);
-	if (atomic_read(&eb->refs) != 1 || extent_buffer_under_io(eb)) {
-		spin_unlock(&eb->refs_lock);
-		spin_unlock(&page->mapping->private_lock);
-		return 0;
-	}
-	spin_unlock(&page->mapping->private_lock);
-
-	/*
-	 * If tree ref isn't set then we know the ref on this eb is a real ref,
-	 * so just return, this page will likely be freed soon anyway.
-	 */
-	if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
-		spin_unlock(&eb->refs_lock);
-		return 0;
-	}
-
-	return release_extent_buffer(eb);
-}
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 861dacb371c7..f18cbce1f2f1 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -47,6 +47,8 @@
 #define EXTENT_BUFFER_DUMMY 9
 #define EXTENT_BUFFER_IN_TREE 10
 #define EXTENT_BUFFER_WRITE_ERR 11    /* write IO error */
+#define EXTENT_BUFFER_MIXED_PAGES 12	/* the pages span multiple zones or numa nodes. */
+#define EXTENT_BUFFER_READING 13 /* currently reading this eb. */
 
 /* these are flags for __process_pages_contig */
 #define PAGE_UNLOCK		(1 << 0)
@@ -160,13 +162,25 @@ struct extent_state {
 #endif
 };
 
+struct btrfs_eb_info {
+	struct btrfs_fs_info *fs_info;
+	struct extent_io_tree io_tree;
+	struct extent_io_tree io_failure_tree;
+
+	/* Extent buffer radix tree */
+	spinlock_t buffer_lock;
+	struct radix_tree_root buffer_radix;
+	struct list_lru lru_list;
+	pgoff_t writeback_index;
+};
+
 #define INLINE_EXTENT_BUFFER_PAGES 16
 #define MAX_INLINE_EXTENT_BUFFER_SIZE (INLINE_EXTENT_BUFFER_PAGES * PAGE_SIZE)
 struct extent_buffer {
 	u64 start;
 	unsigned long len;
 	unsigned long bflags;
-	struct btrfs_fs_info *fs_info;
+	struct btrfs_eb_info *eb_info;
 	spinlock_t refs_lock;
 	atomic_t refs;
 	atomic_t io_pages;
@@ -201,6 +215,7 @@ struct extent_buffer {
 #ifdef CONFIG_BTRFS_DEBUG
 	struct list_head leak_list;
 #endif
+	struct list_head lru;
 };
 
 /*
@@ -408,8 +423,6 @@ int extent_writepages(struct extent_io_tree *tree,
 		      struct address_space *mapping,
 		      get_extent_t *get_extent,
 		      struct writeback_control *wbc);
-int btree_write_cache_pages(struct address_space *mapping,
-			    struct writeback_control *wbc);
 int extent_readpages(struct extent_io_tree *tree,
 		     struct address_space *mapping,
 		     struct list_head *pages, unsigned nr_pages,
@@ -420,21 +433,18 @@ void set_page_extent_mapped(struct page *page);
 
 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 					  u64 start);
-struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
-						  u64 start, unsigned long len);
-struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
-						u64 start);
+struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_eb_info *eb_info,
+						u64 start, unsigned long len);
 struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src);
-struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
+struct extent_buffer *find_extent_buffer(struct btrfs_eb_info *eb_info,
 					 u64 start);
 void free_extent_buffer(struct extent_buffer *eb);
 void free_extent_buffer_stale(struct extent_buffer *eb);
 #define WAIT_NONE	0
 #define WAIT_COMPLETE	1
 #define WAIT_PAGE_LOCK	2
-int read_extent_buffer_pages(struct extent_io_tree *tree,
-			     struct extent_buffer *eb, int wait,
-			     get_extent_t *get_extent, int mirror_num);
+int read_extent_buffer_pages(struct extent_buffer *eb, int wait,
+			     int mirror_num);
 void wait_on_extent_buffer_writeback(struct extent_buffer *eb);
 
 static inline unsigned long num_extent_pages(u64 start, u64 len)
@@ -448,6 +458,11 @@ static inline void extent_buffer_get(struct extent_buffer *eb)
 	atomic_inc(&eb->refs);
 }
 
+static inline unsigned long eb_index(struct extent_buffer *eb)
+{
+	return eb->start >> PAGE_SHIFT;
+}
+
 int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
 			 unsigned long start, unsigned long len);
 void read_extent_buffer(const struct extent_buffer *eb, void *dst,
@@ -478,7 +493,7 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
 			      unsigned long pos, unsigned long len);
 void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
 				unsigned long pos, unsigned long len);
-void clear_extent_buffer_dirty(struct extent_buffer *eb);
+int clear_extent_buffer_dirty(struct extent_buffer *eb);
 int set_extent_buffer_dirty(struct extent_buffer *eb);
 void set_extent_buffer_uptodate(struct extent_buffer *eb);
 void clear_extent_buffer_uptodate(struct extent_buffer *eb);
@@ -512,6 +527,14 @@ int clean_io_failure(struct btrfs_fs_info *fs_info,
 void end_extent_writepage(struct page *page, int err, u64 start, u64 end);
 int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
 			 struct extent_buffer *eb, int mirror_num);
+void btree_flush(struct btrfs_fs_info *fs_info);
+int btree_write_range(struct btrfs_fs_info *fs_info, u64 start, u64 end);
+int btree_wait_range(struct btrfs_fs_info *fs_info, u64 start, u64 end);
+long btrfs_free_ebs(struct super_block *sb, struct shrink_control *sc);
+long btrfs_nr_ebs(struct super_block *sb, struct shrink_control *sc);
+void btrfs_write_ebs(struct super_block *sb, struct writeback_control *wbc);
+void btrfs_invalidate_eb_info(struct btrfs_eb_info *eb_info);
+int btrfs_init_eb_info(struct btrfs_fs_info *fs_info);
 
 /*
  * When IO fails, either with EIO or csum verification fails, we
@@ -552,6 +575,6 @@ noinline u64 find_lock_delalloc_range(struct inode *inode,
 				      struct page *locked_page, u64 *start,
 				      u64 *end, u64 max_bytes);
 #endif
-struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
-					       u64 start);
+struct extent_buffer *alloc_test_extent_buffer(struct btrfs_eb_info *eb_info,
+					       u64 start, u32 nodesize);
 #endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 46b5632a7c6d..27bc64fb6d3e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1877,9 +1877,9 @@ static void btrfs_clear_bit_hook(void *private_data,
  * return 0 if page can be merged to bio
  * return error otherwise
  */
-int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
-			 size_t size, struct bio *bio,
-			 unsigned long bio_flags)
+static int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
+				size_t size, struct bio *bio,
+				unsigned long bio_flags)
 {
 	struct inode *inode = page->mapping->host;
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index 569205e651c7..f912c8166d94 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -102,6 +102,7 @@ static void print_extent_item(struct extent_buffer *eb, int slot, int type)
 	ptr = (unsigned long)iref;
 	end = (unsigned long)ei + item_size;
 	while (ptr < end) {
+		struct btrfs_fs_info *fs_info = eb->eb_info->fs_info;
 		iref = (struct btrfs_extent_inline_ref *)ptr;
 		type = btrfs_extent_inline_ref_type(eb, iref);
 		offset = btrfs_extent_inline_ref_offset(eb, iref);
@@ -116,9 +117,9 @@ static void print_extent_item(struct extent_buffer *eb, int slot, int type)
 			 * offset is supposed to be a tree block which
 			 * must be aligned to nodesize.
 			 */
-			if (!IS_ALIGNED(offset, eb->fs_info->nodesize))
+			if (!IS_ALIGNED(offset, fs_info->nodesize))
 				pr_info("\t\t\t(parent %llu is NOT ALIGNED to nodesize %llu)\n",
-					offset, (unsigned long long)eb->fs_info->nodesize);
+					offset, (unsigned long long)fs_info->nodesize);
 			break;
 		case BTRFS_EXTENT_DATA_REF_KEY:
 			dref = (struct btrfs_extent_data_ref *)(&iref->offset);
@@ -132,9 +133,9 @@ static void print_extent_item(struct extent_buffer *eb, int slot, int type)
 			 * offset is supposed to be a tree block which
 			 * must be aligned to nodesize.
 			 */
-			if (!IS_ALIGNED(offset, eb->fs_info->nodesize))
+			if (!IS_ALIGNED(offset, fs_info->nodesize))
 				pr_info("\t\t\t(parent %llu is NOT ALIGNED to nodesize %llu)\n",
-				     offset, (unsigned long long)eb->fs_info->nodesize);
+				     offset, (unsigned long long)fs_info->nodesize);
 			break;
 		default:
 			pr_cont("(extent %llu has INVALID ref type %d)\n",
@@ -199,7 +200,7 @@ void btrfs_print_leaf(struct extent_buffer *l)
 	if (!l)
 		return;
 
-	fs_info = l->fs_info;
+	fs_info = l->eb_info->fs_info;
 	nr = btrfs_header_nritems(l);
 
 	btrfs_info(fs_info, "leaf %llu total ptrs %d free space %d",
@@ -347,7 +348,7 @@ void btrfs_print_tree(struct extent_buffer *c)
 
 	if (!c)
 		return;
-	fs_info = c->fs_info;
+	fs_info = c->eb_info->fs_info;
 	nr = btrfs_header_nritems(c);
 	level = btrfs_header_level(c);
 	if (level == 0) {
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index ab852b8e3e37..c6244890085f 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -210,7 +210,7 @@ static void __readahead_hook(struct btrfs_fs_info *fs_info,
 
 int btree_readahead_hook(struct extent_buffer *eb, int err)
 {
-	struct btrfs_fs_info *fs_info = eb->fs_info;
+	struct btrfs_fs_info *fs_info = eb->eb_info->fs_info;
 	int ret = 0;
 	struct reada_extent *re;
 
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 3338407ef0f0..e40bd9a910dd 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -45,7 +45,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
 	if (!need_reset && btrfs_root_generation(item)
 		!= btrfs_root_generation_v2(item)) {
 		if (btrfs_root_generation_v2(item) != 0) {
-			btrfs_warn(eb->fs_info,
+			btrfs_warn(eb->eb_info->fs_info,
 					"mismatching generation and generation_v2 found in root item. This root was probably mounted with an older kernel. Resetting all new fields.");
 		}
 		need_reset = 1;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 8e74f7029e12..3b5fe791639d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1198,7 +1198,7 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 	trace_btrfs_sync_fs(fs_info, wait);
 
 	if (!wait) {
-		filemap_flush(fs_info->btree_inode->i_mapping);
+		btree_flush(fs_info);
 		return 0;
 	}
 
@@ -2284,19 +2284,22 @@ static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
 }
 
 static const struct super_operations btrfs_super_ops = {
-	.drop_inode	= btrfs_drop_inode,
-	.evict_inode	= btrfs_evict_inode,
-	.put_super	= btrfs_put_super,
-	.sync_fs	= btrfs_sync_fs,
-	.show_options	= btrfs_show_options,
-	.show_devname	= btrfs_show_devname,
-	.write_inode	= btrfs_write_inode,
-	.alloc_inode	= btrfs_alloc_inode,
-	.destroy_inode	= btrfs_destroy_inode,
-	.statfs		= btrfs_statfs,
-	.remount_fs	= btrfs_remount,
-	.freeze_fs	= btrfs_freeze,
-	.unfreeze_fs	= btrfs_unfreeze,
+	.drop_inode		= btrfs_drop_inode,
+	.evict_inode		= btrfs_evict_inode,
+	.put_super		= btrfs_put_super,
+	.sync_fs		= btrfs_sync_fs,
+	.show_options		= btrfs_show_options,
+	.show_devname		= btrfs_show_devname,
+	.write_inode		= btrfs_write_inode,
+	.alloc_inode		= btrfs_alloc_inode,
+	.destroy_inode		= btrfs_destroy_inode,
+	.statfs			= btrfs_statfs,
+	.remount_fs		= btrfs_remount,
+	.freeze_fs		= btrfs_freeze,
+	.unfreeze_fs		= btrfs_unfreeze,
+	.nr_cached_objects	= btrfs_nr_ebs,
+	.free_cached_objects	= btrfs_free_ebs,
+	.write_metadata		= btrfs_write_ebs,
 };
 
 static const struct file_operations btrfs_ctl_fops = {
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index d3f25376a0f8..dbf05b2ab9ee 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -102,15 +102,32 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize)
 
 	fs_info->nodesize = nodesize;
 	fs_info->sectorsize = sectorsize;
+	fs_info->eb_info = kzalloc(sizeof(struct btrfs_eb_info),
+				   GFP_KERNEL);
+	if (!fs_info->eb_info) {
+		kfree(fs_info->fs_devices);
+		kfree(fs_info->super_copy);
+		kfree(fs_info);
+		return NULL;
+	}
+
+	if (btrfs_init_eb_info(fs_info)) {
+		kfree(fs_info->eb_info);
+		kfree(fs_info->fs_devices);
+		kfree(fs_info->super_copy);
+		kfree(fs_info);
+		return NULL;
+	}
 
 	if (init_srcu_struct(&fs_info->subvol_srcu)) {
+		list_lru_destroy(&fs_info->eb_info->lru_list);
+		kfree(fs_info->eb_info);
 		kfree(fs_info->fs_devices);
 		kfree(fs_info->super_copy);
 		kfree(fs_info);
 		return NULL;
 	}
 
-	spin_lock_init(&fs_info->buffer_lock);
 	spin_lock_init(&fs_info->qgroup_lock);
 	spin_lock_init(&fs_info->qgroup_op_lock);
 	spin_lock_init(&fs_info->super_lock);
@@ -126,7 +143,6 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize)
 	INIT_LIST_HEAD(&fs_info->dirty_qgroups);
 	INIT_LIST_HEAD(&fs_info->dead_roots);
 	INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
-	INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
 	INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
 	extent_io_tree_init(&fs_info->freed_extents[0], NULL);
 	extent_io_tree_init(&fs_info->freed_extents[1], NULL);
@@ -140,6 +156,7 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize)
 
 void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
 {
+	struct btrfs_eb_info *eb_info;
 	struct radix_tree_iter iter;
 	void **slot;
 
@@ -150,13 +167,14 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
 			      &fs_info->fs_state)))
 		return;
 
+	eb_info = fs_info->eb_info;
 	test_mnt->mnt_sb->s_fs_info = NULL;
 
-	spin_lock(&fs_info->buffer_lock);
-	radix_tree_for_each_slot(slot, &fs_info->buffer_radix, &iter, 0) {
+	spin_lock_irq(&eb_info->buffer_lock);
+	radix_tree_for_each_slot(slot, &eb_info->buffer_radix, &iter, 0) {
 		struct extent_buffer *eb;
 
-		eb = radix_tree_deref_slot_protected(slot, &fs_info->buffer_lock);
+		eb = radix_tree_deref_slot_protected(slot, &eb_info->buffer_lock);
 		if (!eb)
 			continue;
 		/* Shouldn't happen but that kind of thinking creates CVE's */
@@ -166,15 +184,17 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
 			continue;
 		}
 		slot = radix_tree_iter_resume(slot, &iter);
-		spin_unlock(&fs_info->buffer_lock);
+		spin_unlock_irq(&eb_info->buffer_lock);
 		free_extent_buffer_stale(eb);
-		spin_lock(&fs_info->buffer_lock);
+		spin_lock_irq(&eb_info->buffer_lock);
 	}
-	spin_unlock(&fs_info->buffer_lock);
+	spin_unlock_irq(&eb_info->buffer_lock);
 
 	btrfs_free_qgroup_config(fs_info);
 	btrfs_free_fs_roots(fs_info);
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
+	list_lru_destroy(&eb_info->lru_list);
+	kfree(fs_info->eb_info);
 	kfree(fs_info->super_copy);
 	kfree(fs_info->fs_devices);
 	kfree(fs_info);
diff --git a/fs/btrfs/tests/extent-buffer-tests.c b/fs/btrfs/tests/extent-buffer-tests.c
index b9142c614114..9a264b81a7b4 100644
--- a/fs/btrfs/tests/extent-buffer-tests.c
+++ b/fs/btrfs/tests/extent-buffer-tests.c
@@ -61,7 +61,8 @@ static int test_btrfs_split_item(u32 sectorsize, u32 nodesize)
 		goto out;
 	}
 
-	path->nodes[0] = eb = alloc_dummy_extent_buffer(fs_info, nodesize);
+	path->nodes[0] = eb = alloc_dummy_extent_buffer(fs_info->eb_info, 0,
+							nodesize);
 	if (!eb) {
 		test_msg("Could not allocate dummy buffer\n");
 		ret = -ENOMEM;
diff --git a/fs/btrfs/tests/extent-io-tests.c b/fs/btrfs/tests/extent-io-tests.c
index d06b1c931d05..600c01ddf0d0 100644
--- a/fs/btrfs/tests/extent-io-tests.c
+++ b/fs/btrfs/tests/extent-io-tests.c
@@ -406,7 +406,7 @@ static int test_eb_bitmaps(u32 sectorsize, u32 nodesize)
 		return -ENOMEM;
 	}
 
-	eb = __alloc_dummy_extent_buffer(fs_info, 0, len);
+	eb = alloc_dummy_extent_buffer(NULL, 0, len);
 	if (!eb) {
 		test_msg("Couldn't allocate test extent buffer\n");
 		kfree(bitmap);
@@ -419,7 +419,7 @@ static int test_eb_bitmaps(u32 sectorsize, u32 nodesize)
 
 	/* Do it over again with an extent buffer which isn't page-aligned. */
 	free_extent_buffer(eb);
-	eb = __alloc_dummy_extent_buffer(NULL, nodesize / 2, len);
+	eb = alloc_dummy_extent_buffer(NULL, nodesize / 2, len);
 	if (!eb) {
 		test_msg("Couldn't allocate test extent buffer\n");
 		kfree(bitmap);
diff --git a/fs/btrfs/tests/free-space-tree-tests.c b/fs/btrfs/tests/free-space-tree-tests.c
index 8444a018cca2..afba937f4365 100644
--- a/fs/btrfs/tests/free-space-tree-tests.c
+++ b/fs/btrfs/tests/free-space-tree-tests.c
@@ -474,7 +474,8 @@ static int run_test(test_func_t test_func, int bitmaps, u32 sectorsize,
 	root->fs_info->free_space_root = root;
 	root->fs_info->tree_root = root;
 
-	root->node = alloc_test_extent_buffer(root->fs_info, nodesize);
+	root->node = alloc_test_extent_buffer(fs_info->eb_info, nodesize,
+					      nodesize);
 	if (!root->node) {
 		test_msg("Couldn't allocate dummy buffer\n");
 		ret = -ENOMEM;
diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c
index 11c77eafde00..486aa7fbfce2 100644
--- a/fs/btrfs/tests/inode-tests.c
+++ b/fs/btrfs/tests/inode-tests.c
@@ -261,7 +261,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 		goto out;
 	}
 
-	root->node = alloc_dummy_extent_buffer(fs_info, nodesize);
+	root->node = alloc_dummy_extent_buffer(fs_info->eb_info, 0, nodesize);
 	if (!root->node) {
 		test_msg("Couldn't allocate dummy buffer\n");
 		goto out;
@@ -867,7 +867,7 @@ static int test_hole_first(u32 sectorsize, u32 nodesize)
 		goto out;
 	}
 
-	root->node = alloc_dummy_extent_buffer(fs_info, nodesize);
+	root->node = alloc_dummy_extent_buffer(fs_info->eb_info, 0, nodesize);
 	if (!root->node) {
 		test_msg("Couldn't allocate dummy buffer\n");
 		goto out;
diff --git a/fs/btrfs/tests/qgroup-tests.c b/fs/btrfs/tests/qgroup-tests.c
index 0f4ce970d195..0ba27cd9ae4c 100644
--- a/fs/btrfs/tests/qgroup-tests.c
+++ b/fs/btrfs/tests/qgroup-tests.c
@@ -486,7 +486,8 @@ int btrfs_test_qgroups(u32 sectorsize, u32 nodesize)
 	 * Can't use bytenr 0, some things freak out
 	 * *cough*backref walking code*cough*
 	 */
-	root->node = alloc_test_extent_buffer(root->fs_info, nodesize);
+	root->node = alloc_test_extent_buffer(fs_info->eb_info, nodesize,
+					      nodesize);
 	if (!root->node) {
 		test_msg("Couldn't allocate dummy buffer\n");
 		ret = -ENOMEM;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 9fed8c67b6e8..5df3963c413e 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -293,8 +293,7 @@ static noinline int join_transaction(struct btrfs_fs_info *fs_info,
 	INIT_LIST_HEAD(&cur_trans->deleted_bgs);
 	spin_lock_init(&cur_trans->dropped_roots_lock);
 	list_add_tail(&cur_trans->list, &fs_info->trans_list);
-	extent_io_tree_init(&cur_trans->dirty_pages,
-			     fs_info->btree_inode);
+	extent_io_tree_init(&cur_trans->dirty_pages, NULL);
 	fs_info->generation++;
 	cur_trans->transid = fs_info->generation;
 	fs_info->running_transaction = cur_trans;
@@ -944,12 +943,10 @@ int btrfs_write_marked_extents(struct btrfs_fs_info *fs_info,
 {
 	int err = 0;
 	int werr = 0;
-	struct address_space *mapping = fs_info->btree_inode->i_mapping;
 	struct extent_state *cached_state = NULL;
 	u64 start = 0;
 	u64 end;
 
-	atomic_inc(&BTRFS_I(fs_info->btree_inode)->sync_writers);
 	while (!find_first_extent_bit(dirty_pages, start, &start, &end,
 				      mark, &cached_state)) {
 		bool wait_writeback = false;
@@ -975,17 +972,16 @@ int btrfs_write_marked_extents(struct btrfs_fs_info *fs_info,
 			wait_writeback = true;
 		}
 		if (!err)
-			err = filemap_fdatawrite_range(mapping, start, end);
+			err = btree_write_range(fs_info, start, end);
 		if (err)
 			werr = err;
 		else if (wait_writeback)
-			werr = filemap_fdatawait_range(mapping, start, end);
+			werr = btree_wait_range(fs_info, start, end);
 		free_extent_state(cached_state);
 		cached_state = NULL;
 		cond_resched();
 		start = end + 1;
 	}
-	atomic_dec(&BTRFS_I(fs_info->btree_inode)->sync_writers);
 	return werr;
 }
 
@@ -1000,7 +996,6 @@ static int __btrfs_wait_marked_extents(struct btrfs_fs_info *fs_info,
 {
 	int err = 0;
 	int werr = 0;
-	struct address_space *mapping = fs_info->btree_inode->i_mapping;
 	struct extent_state *cached_state = NULL;
 	u64 start = 0;
 	u64 end;
@@ -1021,7 +1016,7 @@ static int __btrfs_wait_marked_extents(struct btrfs_fs_info *fs_info,
 		if (err == -ENOMEM)
 			err = 0;
 		if (!err)
-			err = filemap_fdatawait_range(mapping, start, end);
+			err = btree_wait_range(fs_info, start, end);
 		if (err)
 			werr = err;
 		free_extent_state(cached_state);
-- 
2.7.5

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[PATCH v2 10/11] btrfs: rework end io for extent buffer reads

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

Now that the only thing that keeps eb's alive is io_pages and it's
refcount we need to hold the eb ref for the entire end io call so we
don't get it removed out from underneath us.  Also the hooks make no
sense for us now, so rework this to be cleaner.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 fs/btrfs/disk-io.c   | 63 ++++---------------------------------------------
 fs/btrfs/disk-io.h   |  1 +
 fs/btrfs/extent_io.c | 66 +++++++++++++++++++++++++++-------------------------
 3 files changed, 40 insertions(+), 90 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d9d69e181942..1a890f8c78c8 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -755,33 +755,13 @@ static int check_node(struct btrfs_root *root, struct extent_buffer *node)
 	return ret;
 }
 
-static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
-				      u64 phy_offset, struct page *page,
-				      u64 start, u64 end, int mirror)
+int btrfs_extent_buffer_end_read(struct extent_buffer *eb, int mirror)
 {
+	struct btrfs_fs_info *fs_info = eb->eb_info->fs_info;
+	struct btrfs_root *root = fs_info->tree_root;
 	u64 found_start;
 	int found_level;
-	struct extent_buffer *eb;
-	struct btrfs_root *root;
-	struct btrfs_fs_info *fs_info;
 	int ret = 0;
-	int reads_done;
-
-	if (!page->private)
-		goto out;
-
-	eb = (struct extent_buffer *)page->private;
-
-	/* the pending IO might have been the only thing that kept this buffer
-	 * in memory.  Make sure we have a ref for all this other checks
-	 */
-	extent_buffer_get(eb);
-	fs_info = eb->eb_info->fs_info;
-	root = fs_info->tree_root;
-
-	reads_done = atomic_dec_and_test(&eb->io_pages);
-	if (!reads_done)
-		goto err;
 
 	eb->read_mirror = mirror;
 	if (test_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags)) {
@@ -833,45 +813,14 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	if (!ret)
 		set_extent_buffer_uptodate(eb);
 err:
-	if (reads_done &&
-	    test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
+	if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
 		btree_readahead_hook(eb, ret);
 
-	if (ret) {
-		/*
-		 * our io error hook is going to dec the io pages
-		 * again, we have to make sure it has something
-		 * to decrement.
-		 *
-		 * TODO: Kill this, we've re-arranged how this works now so we
-		 * don't need to do this io_pages dance.
-		 */
-		atomic_inc(&eb->io_pages);
+	if (ret)
 		clear_extent_buffer_uptodate(eb);
-	}
-	if (reads_done) {
-		clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
-		smp_mb__after_atomic();
-		wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
-	}
-	free_extent_buffer(eb);
-out:
 	return ret;
 }
 
-static int btree_io_failed_hook(struct page *page, int failed_mirror)
-{
-	struct extent_buffer *eb;
-
-	eb = (struct extent_buffer *)page->private;
-	set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
-	eb->read_mirror = failed_mirror;
-	atomic_dec(&eb->io_pages);
-	if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
-		btree_readahead_hook(eb, -EIO);
-	return -EIO;	/* we fixed nothing */
-}
-
 static void end_workqueue_bio(struct bio *bio)
 {
 	struct btrfs_end_io_wq *end_io_wq = bio->bi_private;
@@ -4554,9 +4503,7 @@ static int btree_merge_bio_hook(struct page *page, unsigned long offset,
 static const struct extent_io_ops btree_extent_io_ops = {
 	/* mandatory callbacks */
 	.submit_bio_hook = btree_submit_bio_hook,
-	.readpage_end_io_hook = btree_readpage_end_io_hook,
 	.merge_bio_hook = btree_merge_bio_hook,
-	.readpage_io_failed_hook = btree_io_failed_hook,
 	.set_range_writeback = btrfs_set_range_writeback,
 	.tree_fs_info = btree_fs_info,
 
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 7f7c35d6347a..e1f4fef91547 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -152,6 +152,7 @@ int btree_lock_page_hook(struct page *page, void *data,
 int btrfs_get_num_tolerated_disk_barrier_failures(u64 flags);
 int __init btrfs_end_io_wq_init(void);
 void btrfs_end_io_wq_exit(void);
+int btrfs_extent_buffer_end_read(struct extent_buffer *eb, int mirror);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void btrfs_init_lockdep(void);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index bb10dc6f4e41..e11372455fb0 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -20,6 +20,7 @@
 #include "locking.h"
 #include "rcu-string.h"
 #include "backref.h"
+#include "disk-io.h"
 
 static struct kmem_cache *extent_state_cache;
 static struct kmem_cache *extent_buffer_cache;
@@ -5360,6 +5361,14 @@ int extent_buffer_uptodate(struct extent_buffer *eb)
 	return test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
 }
 
+static void mark_eb_failed(struct extent_buffer *eb, int failed_mirror)
+{
+	set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
+	eb->read_mirror = failed_mirror;
+	if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
+		btree_readahead_hook(eb, -EIO);
+}
+
 static void end_bio_extent_buffer_readpage(struct bio *bio)
 {
 	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
@@ -5368,12 +5377,13 @@ static void end_bio_extent_buffer_readpage(struct bio *bio)
 	u64 unlock_start = 0, unlock_len = 0;
 	int mirror_num = io_bio->mirror_num;
 	int uptodate = !bio->bi_status;
-	int i, ret;
+	int i;
 
 	bio_for_each_segment_all(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
 		struct btrfs_eb_info *eb_info;
 		struct extent_buffer *eb;
+		int reads_done;
 
 		eb = (struct extent_buffer *)page->private;
 		if (WARN_ON(!eb))
@@ -5382,41 +5392,33 @@ static void end_bio_extent_buffer_readpage(struct bio *bio)
 		eb_info = eb->eb_info;
 		if (!tree)
 			tree = &eb_info->io_tree;
+		extent_buffer_get(eb);
+		reads_done = atomic_dec_and_test(&eb->io_pages);
 		if (uptodate) {
-			/*
-			 * btree_readpage_end_io_hook doesn't care about
-			 * start/end so just pass 0.  We'll kill this later.
-			 */
-			ret = tree->ops->readpage_end_io_hook(io_bio, 0,
-							      page, 0, 0,
-							      mirror_num);
-			if (ret) {
-				uptodate = 0;
-			} else {
-				u64 start = eb->start;
-				int c, num_pages;
-
-				num_pages = num_extent_pages(eb->start,
-							     eb->len);
-				for (c = 0; c < num_pages; c++) {
-					if (eb->pages[c] == page)
-						break;
-					start += PAGE_SIZE;
-				}
-				clean_io_failure(eb_info->fs_info,
-						 &eb_info->io_failure_tree,
-						 tree, start, page, 0, 0);
+			u64 start = eb->start;
+			int c, num_pages;
+
+			num_pages = num_extent_pages(eb->start,
+						     eb->len);
+			for (c = 0; c < num_pages; c++) {
+				if (eb->pages[c] == page)
+					break;
+				start += PAGE_SIZE;
 			}
+			clean_io_failure(eb_info->fs_info,
+					 &eb_info->io_failure_tree,
+					 tree, start, page, 0, 0);
 		}
-		/*
-		 * We never fix anything in btree_io_failed_hook.
-		 *
-		 * TODO: rework the io failed hook to not assume we can fix
-		 * anything.
-		 */
+		if (reads_done && btrfs_extent_buffer_end_read(eb, mirror_num))
+			uptodate = 0;
 		if (!uptodate)
-			tree->ops->readpage_io_failed_hook(page, mirror_num);
-
+			mark_eb_failed(eb, mirror_num);
+		if (reads_done) {
+			clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
+			smp_mb__after_atomic();
+			wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
+		}
+		free_extent_buffer(eb);
 		if (unlock_start == 0) {
 			unlock_start = eb->start;
 			unlock_len = PAGE_SIZE;
-- 
2.7.5

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[PATCH v2 11/11] btrfs: add NR_METADATA_BYTES accounting

[Josef Bacik]

From: Josef Bacik <jbacik@fb.com>

Now that we have these counters, account for the private pages we
allocate in NR_METADATA_BYTES.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 fs/btrfs/extent_io.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index e11372455fb0..7536352f424d 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4802,6 +4802,8 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
 		ClearPagePrivate(page);
 		set_page_private(page, 0);
 
+		mod_node_page_state(page_pgdat(page), NR_METADATA_BYTES,
+				    -(long)PAGE_SIZE);
 		/* Once for the page private. */
 		put_page(page);
 
@@ -5081,6 +5083,8 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 			goto free_eb;
 		}
 		attach_extent_buffer_page(eb, p);
+		mod_node_page_state(page_pgdat(p), NR_METADATA_BYTES,
+				    PAGE_SIZE);
 		eb->pages[i] = p;
 	}
 again:
-- 
2.7.5

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Re: [PATCH v2 00/11] Metadata specific accouting and dirty writeout

[David Sterba]

On Wed, Nov 22, 2017 at 04:15:55PM -0500, Josef Bacik wrote:
> These patches are to support having metadata accounting and dirty handling
> in a generic way.  For dirty metadata ext4 and xfs currently are limited by
> their journal size, which allows them to handle dirty metadata flushing in a
> relatively easy way.  Btrfs does not have this limiting factor, we can have as
> much dirty metadata on the system as we have memory, so we have a dummy inode
> that all of our metadat pages are allocated from so we can call
> balance_dirty_pages() on it and make sure we don't overwhelm the system with
> dirty metadata pages.
> 
> The problem with this is it severely limits our ability to do things like
> support sub-pagesize blocksizes.  Btrfs also supports metadata blocksizes > page
> size, which makes keeping track of our metadata and it's pages particularly
> tricky.  We have the inode mapping with our pages, and we have another radix
> tree for our actual metadata buffers.  This double accounting leads to some fun
> shenanigans around reclaim and evicting pages we know we are done using.
> 
> To solve this we would like to switch to a scheme like xfs has, where we simply
> have our metadata structures tied into the slab shrinking code, and we just use
> alloc_page() for our pages, or kmalloc() when we add sub-pagesize blocksizes.
> In order to do this we need infrastructure in place to make sure we still don't
> overwhelm the system with dirty metadata pages.
> 
> Enter these patches.  Because metadata is tracked on a non-pagesize amount we
> need to convert a bunch of our existing counters to bytes.  From there I've
> added various counters for metadata, to keep track of overall metadata bytes,
> how many are dirty and how many are under writeback.  I've added a super
> operation to handle the dirty writeback, which is going to be handled mostly
> inside the fs since we will need a little more smarts around what we writeback.

The text relevant for btrfs should also go to the btree_inode removal
patch changelog. The cover letter gets lost but we still might need to
refer to the overall logic that's going to be changed in that patch.

And possibly more documentation should go to the code itself, there are
some scattered comments in the tricky parts but the overall logic is not
described and the key functions lack comments.

What's your merge plan? There are other subsystem changes needed, before
the btree_inode removal can happen and can be tested within our for-next
branches. The 4.15 target is out of reach, so I assume 4.16 for the
dependencies and 4.17 for the btree_inode. We can of course test them
earlier, but 4.16 does not seem realistic for the whole patchset.

> The last three patches are just there to show how we use the infrastructure in
> the first 8 patches.  The actuall kill btree_inode patch is pretty big,
> unfortunately ripping out all of the pagecache based handling and replacing it
> with the new infrastructure has to be done whole-hog and can't be broken up
> anymore than it already has been without making it un-bisectable.

I don't completely agree that it cannot be split. I went through it a
few times, the patch is too big for review. It mixes the core part and
cleanups that do not necessarily need to be in the patch. I'd like to
see the core part minimized further, at the cost of leaving some dead
code behind (like the old callbacks).

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Re: [PATCH v2 09/11] Btrfs: kill the btree_inode

[David Sterba]

On Wed, Nov 22, 2017 at 04:16:04PM -0500, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> @@ -4802,8 +4885,8 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
>  	return new;
>  }
>  
> -struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
> -						  u64 start, unsigned long len)
> +struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_eb_info *eb_info,
> +						u64 start, unsigned long len)

The __alloc_dummy_extent_buffer takes the length parameter because it's
used in tests that need to pass different values.
I've removed nodesize from alloc_dummy_extent_buffer and the callchain
because we know that it's always going to be fs_info->nodesize.
Reintroducing it does not look like a good idea.

>  {
>  	struct extent_buffer *eb;
>  	unsigned long num_pages;

> @@ -160,13 +162,25 @@ struct extent_state {
>  #endif
>  };
>  
> +struct btrfs_eb_info {
> +	struct btrfs_fs_info *fs_info;
> +	struct extent_io_tree io_tree;
> +	struct extent_io_tree io_failure_tree;
> +
> +	/* Extent buffer radix tree */
> +	spinlock_t buffer_lock;
> +	struct radix_tree_root buffer_radix;
> +	struct list_lru lru_list;
> +	pgoff_t writeback_index;
> +};
> +
>  #define INLINE_EXTENT_BUFFER_PAGES 16
>  #define MAX_INLINE_EXTENT_BUFFER_SIZE (INLINE_EXTENT_BUFFER_PAGES * PAGE_SIZE)
>  struct extent_buffer {
>  	u64 start;
>  	unsigned long len;
>  	unsigned long bflags;
> -	struct btrfs_fs_info *fs_info;
> +	struct btrfs_eb_info *eb_info;

This single change increases the patch size just because all the
callers need to be updated. I suggest to keep fs_info in extent_buffer,
we're not going to lose much in terms of memory:

currently there are 14 eb objects in a 4k slab page, with the additional
fs_info it's still 14,

280 * 14 = 3920, unused 176 bytes
288 * 14 = 4032, unused 64 bytes

>  	spinlock_t refs_lock;
>  	atomic_t refs;
>  	atomic_t io_pages;

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Re: [PATCH v2 02/11] writeback: convert WB_WRITTEN/WB_DIRITED counters to bytes

[Jan Kara]

On Wed 22-11-17 16:15:57, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> These are counters that constantly go up in order to do bandwidth calculations.
> It isn't important what the units are in, as long as they are consistent between
> the two of them, so convert them to count bytes written/dirtied, and allow the
> metadata accounting stuff to change the counters as well.
> 
> Signed-off-by: Josef Bacik <jbacik@fb.com>
> Acked-by: Tejun Heo <tj@kernel.org>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/fuse/file.c                   |  4 ++--
>  include/linux/backing-dev-defs.h |  4 ++--
>  include/linux/backing-dev.h      |  2 +-
>  mm/backing-dev.c                 |  9 +++++----
>  mm/page-writeback.c              | 20 ++++++++++----------
>  5 files changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index cb7dff5c45d7..67e7c4fac28d 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1471,7 +1471,7 @@ static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
>  	for (i = 0; i < req->num_pages; i++) {
>  		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
>  		dec_node_page_state(req->pages[i], NR_WRITEBACK_TEMP);
> -		wb_writeout_inc(&bdi->wb);
> +		wb_writeout_add(&bdi->wb, PAGE_SIZE);
>  	}
>  	wake_up(&fi->page_waitq);
>  }
> @@ -1776,7 +1776,7 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
>  
>  		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
>  		dec_node_page_state(page, NR_WRITEBACK_TEMP);
> -		wb_writeout_inc(&bdi->wb);
> +		wb_writeout_add(&bdi->wb, PAGE_SIZE);
>  		fuse_writepage_free(fc, new_req);
>  		fuse_request_free(new_req);
>  		goto out;
> diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
> index 866c433e7d32..ded45ac2cec7 100644
> --- a/include/linux/backing-dev-defs.h
> +++ b/include/linux/backing-dev-defs.h
> @@ -36,8 +36,8 @@ typedef int (congested_fn)(void *, int);
>  enum wb_stat_item {
>  	WB_RECLAIMABLE,
>  	WB_WRITEBACK,
> -	WB_DIRTIED,
> -	WB_WRITTEN,
> +	WB_DIRTIED_BYTES,
> +	WB_WRITTEN_BYTES,
>  	NR_WB_STAT_ITEMS
>  };
>  
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index 14e266d12620..39b8dc486ea7 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -89,7 +89,7 @@ static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
>  	return percpu_counter_sum_positive(&wb->stat[item]);
>  }
>  
> -extern void wb_writeout_inc(struct bdi_writeback *wb);
> +extern void wb_writeout_add(struct bdi_writeback *wb, long bytes);
>  
>  /*
>   * maximal error of a stat counter.
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index e19606bb41a0..62a332a91b38 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -68,14 +68,15 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
>  	wb_thresh = wb_calc_thresh(wb, dirty_thresh);
>  
>  #define K(x) ((x) << (PAGE_SHIFT - 10))
> +#define BtoK(x) ((x) >> 10)
>  	seq_printf(m,
>  		   "BdiWriteback:       %10lu kB\n"
>  		   "BdiReclaimable:     %10lu kB\n"
>  		   "BdiDirtyThresh:     %10lu kB\n"
>  		   "DirtyThresh:        %10lu kB\n"
>  		   "BackgroundThresh:   %10lu kB\n"
> -		   "BdiDirtied:         %10lu kB\n"
> -		   "BdiWritten:         %10lu kB\n"
> +		   "BdiDirtiedBytes:    %10lu kB\n"
> +		   "BdiWrittenBytes:    %10lu kB\n"
>  		   "BdiWriteBandwidth:  %10lu kBps\n"
>  		   "b_dirty:            %10lu\n"
>  		   "b_io:               %10lu\n"
> @@ -88,8 +89,8 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
>  		   K(wb_thresh),
>  		   K(dirty_thresh),
>  		   K(background_thresh),
> -		   (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
> -		   (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
> +		   (unsigned long) BtoK(wb_stat(wb, WB_DIRTIED_BYTES)),
> +		   (unsigned long) BtoK(wb_stat(wb, WB_WRITTEN_BYTES)),
>  		   (unsigned long) K(wb->write_bandwidth),
>  		   nr_dirty,
>  		   nr_io,
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 1a47d4296750..e4563645749a 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -597,11 +597,11 @@ static void wb_domain_writeout_inc(struct wb_domain *dom,
>   * Increment @wb's writeout completion count and the global writeout
>   * completion count. Called from test_clear_page_writeback().
>   */
> -static inline void __wb_writeout_inc(struct bdi_writeback *wb)
> +static inline void __wb_writeout_add(struct bdi_writeback *wb, long bytes)
>  {
>  	struct wb_domain *cgdom;
>  
> -	inc_wb_stat(wb, WB_WRITTEN);
> +	__add_wb_stat(wb, WB_WRITTEN_BYTES, bytes);
>  	wb_domain_writeout_inc(&global_wb_domain, &wb->completions,
>  			       wb->bdi->max_prop_frac);
>  
> @@ -611,15 +611,15 @@ static inline void __wb_writeout_inc(struct bdi_writeback *wb)
>  				       wb->bdi->max_prop_frac);
>  }
>  
> -void wb_writeout_inc(struct bdi_writeback *wb)
> +void wb_writeout_add(struct bdi_writeback *wb, long bytes)
>  {
>  	unsigned long flags;
>  
>  	local_irq_save(flags);
> -	__wb_writeout_inc(wb);
> +	__wb_writeout_add(wb, bytes);
>  	local_irq_restore(flags);
>  }
> -EXPORT_SYMBOL_GPL(wb_writeout_inc);
> +EXPORT_SYMBOL_GPL(wb_writeout_add);
>  
>  /*
>   * On idle system, we can be called long after we scheduled because we use
> @@ -1362,8 +1362,8 @@ static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc,
>  	if (elapsed < BANDWIDTH_INTERVAL)
>  		return;
>  
> -	dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]);
> -	written = percpu_counter_read(&wb->stat[WB_WRITTEN]);
> +	dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED_BYTES]) >> PAGE_SHIFT;
> +	written = percpu_counter_read(&wb->stat[WB_WRITTEN_BYTES]) >> PAGE_SHIFT;
>  
>  	/*
>  	 * Skip quiet periods when disk bandwidth is under-utilized.
> @@ -2435,7 +2435,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
>  		__inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
>  		__inc_node_page_state(page, NR_DIRTIED);
>  		inc_wb_stat(wb, WB_RECLAIMABLE);
> -		inc_wb_stat(wb, WB_DIRTIED);
> +		__add_wb_stat(wb, WB_DIRTIED_BYTES, PAGE_SIZE);
>  		task_io_account_write(PAGE_SIZE);
>  		current->nr_dirtied++;
>  		this_cpu_inc(bdp_ratelimits);
> @@ -2522,7 +2522,7 @@ void account_page_redirty(struct page *page)
>  		wb = unlocked_inode_to_wb_begin(inode, &locked);
>  		current->nr_dirtied--;
>  		dec_node_page_state(page, NR_DIRTIED);
> -		dec_wb_stat(wb, WB_DIRTIED);
> +		__add_wb_stat(wb, WB_DIRTIED_BYTES, -(long)PAGE_SIZE);
>  		unlocked_inode_to_wb_end(inode, locked);
>  	}
>  }
> @@ -2744,7 +2744,7 @@ int test_clear_page_writeback(struct page *page)
>  				struct bdi_writeback *wb = inode_to_wb(inode);
>  
>  				dec_wb_stat(wb, WB_WRITEBACK);
> -				__wb_writeout_inc(wb);
> +				__wb_writeout_add(wb, PAGE_SIZE);
>  			}
>  		}
>  
> -- 
> 2.7.5
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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Re: [PATCH v2 03/11] lib: make the fprop batch size a multiple of PAGE_SIZE

[Jan Kara]

On Wed 22-11-17 16:15:58, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> We are converting the writeback counters to use bytes instead of pages,
> so we need to make the batch size for the percpu modifications align
> properly with the new units.  Since we used pages before, just multiply
> by PAGE_SIZE to get the equivalent bytes for the batch size.
> 
> Signed-off-by: Josef Bacik <jbacik@fb.com>

Looks good to me, just please make this part of patch 5/11. Otherwise
bisection may get broken by too large errors in per-cpu counters of IO
completions... Thanks!

								Honza

> ---
>  lib/flex_proportions.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
> index 2cc1f94e03a1..b0343ae71f5e 100644
> --- a/lib/flex_proportions.c
> +++ b/lib/flex_proportions.c
> @@ -166,7 +166,7 @@ void fprop_fraction_single(struct fprop_global *p,
>  /*
>   * ---- PERCPU ----
>   */
> -#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
> +#define PROP_BATCH (8*PAGE_SIZE*(1+ilog2(nr_cpu_ids)))
>  
>  int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp)
>  {
> -- 
> 2.7.5
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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Re: [PATCH v2 04/11] lib: add a __fprop_add_percpu_max

[Jan Kara]

On Wed 22-11-17 16:15:59, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> This helper allows us to add an arbitrary amount to the fprop
> structures.
> 
> Signed-off-by: Josef Bacik <jbacik@fb.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  include/linux/flex_proportions.h | 11 +++++++++--
>  lib/flex_proportions.c           |  9 +++++----
>  2 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/flex_proportions.h b/include/linux/flex_proportions.h
> index 0d348e011a6e..9f88684bf0a0 100644
> --- a/include/linux/flex_proportions.h
> +++ b/include/linux/flex_proportions.h
> @@ -83,8 +83,8 @@ struct fprop_local_percpu {
>  int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp);
>  void fprop_local_destroy_percpu(struct fprop_local_percpu *pl);
>  void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl);
> -void __fprop_inc_percpu_max(struct fprop_global *p, struct fprop_local_percpu *pl,
> -			    int max_frac);
> +void __fprop_add_percpu_max(struct fprop_global *p, struct fprop_local_percpu *pl,
> +			    unsigned long nr, int max_frac);
>  void fprop_fraction_percpu(struct fprop_global *p,
>  	struct fprop_local_percpu *pl, unsigned long *numerator,
>  	unsigned long *denominator);
> @@ -99,4 +99,11 @@ void fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl)
>  	local_irq_restore(flags);
>  }
>  
> +static inline
> +void __fprop_inc_percpu_max(struct fprop_global *p,
> +			    struct fprop_local_percpu *pl, int max_frac)
> +{
> +	__fprop_add_percpu_max(p, pl, 1, max_frac);
> +}
> +
>  #endif
> diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
> index b0343ae71f5e..fd95791a2c93 100644
> --- a/lib/flex_proportions.c
> +++ b/lib/flex_proportions.c
> @@ -255,8 +255,9 @@ void fprop_fraction_percpu(struct fprop_global *p,
>   * Like __fprop_inc_percpu() except that event is counted only if the given
>   * type has fraction smaller than @max_frac/FPROP_FRAC_BASE
>   */
> -void __fprop_inc_percpu_max(struct fprop_global *p,
> -			    struct fprop_local_percpu *pl, int max_frac)
> +void __fprop_add_percpu_max(struct fprop_global *p,
> +			    struct fprop_local_percpu *pl, unsigned long nr,
> +			    int max_frac)
>  {
>  	if (unlikely(max_frac < FPROP_FRAC_BASE)) {
>  		unsigned long numerator, denominator;
> @@ -267,6 +268,6 @@ void __fprop_inc_percpu_max(struct fprop_global *p,
>  			return;
>  	} else
>  		fprop_reflect_period_percpu(p, pl);
> -	percpu_counter_add_batch(&pl->events, 1, PROP_BATCH);
> -	percpu_counter_add(&p->events, 1);
> +	percpu_counter_add_batch(&pl->events, nr, PROP_BATCH);
> +	percpu_counter_add(&p->events, nr);
>  }
> -- 
> 2.7.5
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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Re: [PATCH v2 05/11] writeback: convert the flexible prop stuff to bytes

[Jan Kara]

On Wed 22-11-17 16:16:00, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> The flexible proportions were all page based, but now that we are doing
> metadata writeout that can be smaller or larger than page size we need
> to account for this in bytes instead of number of pages.
> 
> Signed-off-by: Josef Bacik <jbacik@fb.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  mm/page-writeback.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index e4563645749a..2a1994194cc1 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -574,11 +574,11 @@ static unsigned long wp_next_time(unsigned long cur_time)
>  	return cur_time;
>  }
>  
> -static void wb_domain_writeout_inc(struct wb_domain *dom,
> +static void wb_domain_writeout_add(struct wb_domain *dom,
>  				   struct fprop_local_percpu *completions,
> -				   unsigned int max_prop_frac)
> +				   long bytes, unsigned int max_prop_frac)
>  {
> -	__fprop_inc_percpu_max(&dom->completions, completions,
> +	__fprop_add_percpu_max(&dom->completions, completions, bytes,
>  			       max_prop_frac);
>  	/* First event after period switching was turned off? */
>  	if (unlikely(!dom->period_time)) {
> @@ -602,12 +602,12 @@ static inline void __wb_writeout_add(struct bdi_writeback *wb, long bytes)
>  	struct wb_domain *cgdom;
>  
>  	__add_wb_stat(wb, WB_WRITTEN_BYTES, bytes);
> -	wb_domain_writeout_inc(&global_wb_domain, &wb->completions,
> +	wb_domain_writeout_add(&global_wb_domain, &wb->completions, bytes,
>  			       wb->bdi->max_prop_frac);
>  
>  	cgdom = mem_cgroup_wb_domain(wb);
>  	if (cgdom)
> -		wb_domain_writeout_inc(cgdom, wb_memcg_completions(wb),
> +		wb_domain_writeout_add(cgdom, wb_memcg_completions(wb), bytes,
>  				       wb->bdi->max_prop_frac);
>  }
>  
> -- 
> 2.7.5
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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Re: [PATCH v2 03/11] lib: make the fprop batch size a multiple of PAGE_SIZE

[David Sterba]

On Wed, Nov 29, 2017 at 06:04:43PM +0100, Jan Kara wrote:
> On Wed 22-11-17 16:15:58, Josef Bacik wrote:
> > From: Josef Bacik <jbacik@fb.com>
> > 
> > We are converting the writeback counters to use bytes instead of pages,
> > so we need to make the batch size for the percpu modifications align
> > properly with the new units.  Since we used pages before, just multiply
> > by PAGE_SIZE to get the equivalent bytes for the batch size.
> > 
> > Signed-off-by: Josef Bacik <jbacik@fb.com>
> 
> Looks good to me, just please make this part of patch 5/11. Otherwise
> bisection may get broken by too large errors in per-cpu counters of IO
> completions... Thanks!
> 
> 								Honza
> 
> > ---
> >  lib/flex_proportions.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
> > index 2cc1f94e03a1..b0343ae71f5e 100644
> > --- a/lib/flex_proportions.c
> > +++ b/lib/flex_proportions.c
> > @@ -166,7 +166,7 @@ void fprop_fraction_single(struct fprop_global *p,
> >  /*
> >   * ---- PERCPU ----
> >   */
> > -#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
> > +#define PROP_BATCH (8*PAGE_SIZE*(1+ilog2(nr_cpu_ids)))

So when the patch is going to be updated, please fix the coding style here.

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Re: [PATCH v2 06/11] writeback: add counters for metadata usage

[Jan Kara]

On Wed 22-11-17 16:16:01, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
> 
> Btrfs has no bounds except memory on the amount of dirty memory that we have in
> use for metadata.  Historically we have used a special inode so we could take
> advantage of the balance_dirty_pages throttling that comes with using pagecache.
> However as we'd like to support different blocksizes it would be nice to not
> have to rely on pagecache, but still get the balance_dirty_pages throttling
> without having to do it ourselves.
> 
> So introduce *METADATA_DIRTY_BYTES and *METADATA_WRITEBACK_BYTES.  These are
> zone and bdi_writeback counters to keep track of how many bytes we have in
> flight for METADATA.  We need to count in bytes as blocksizes could be
> percentages of pagesize.  We simply convert the bytes to number of pages where
> it is needed for the throttling.
> 
> Also introduce NR_METADATA_BYTES so we can keep track of the total amount of
> pages used for metadata on the system.  This is also needed so things like dirty
> throttling know that this is dirtyable memory as well and easily reclaimed.

I'll defer to mm guys for final decision but the fact is the memory for
metadata is likely to be allocated from some slab cache and that actually
goes against the 'easily reclaimed' statement. Granted these are going to
be relatively large objects (1k at least I assume) so fragmentation issues
are not as bad but still getting actual free pages out of slab cache isn't
that easy... More on this below.

> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 356a814e7c8e..fd516a0f0bfe 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -179,6 +179,9 @@ enum node_stat_item {
>  	NR_VMSCAN_IMMEDIATE,	/* Prioritise for reclaim when writeback ends */
>  	NR_DIRTIED,		/* page dirtyings since bootup */
>  	NR_WRITTEN,		/* page writings since bootup */
> +	NR_METADATA_DIRTY_BYTES,	/* Metadata dirty bytes */
> +	NR_METADATA_WRITEBACK_BYTES,	/* Metadata writeback bytes */
> +	NR_METADATA_BYTES,	/* total metadata bytes in use. */
>  	NR_VM_NODE_STAT_ITEMS
>  };

I think you didn't address my comment from last version of the series.

1) Per-cpu node-stat batching will be basically useless for these counters
as the batch size is <128. Maybe we don't care but it would deserve a
comment.

2) These counters are tracked in atomic_long_t type. That means max 2GB of
metadata on 32-bit machines. I *guess* that should be OK since you would
not be able to address that much of slab cache on such machine anyway but 
still worth a comment I think.

> diff --git a/mm/util.c b/mm/util.c
> index 34e57fae959d..681d62631ee0 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -616,6 +616,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
>  	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
>  		free = global_zone_page_state(NR_FREE_PAGES);
>  		free += global_node_page_state(NR_FILE_PAGES);
> +		free += global_node_page_state(NR_METADATA_BYTES) >> PAGE_SHIFT;


I'm not really sure this is OK. It depends on whether mm is really able to
reclaim these pages easily enough... Summon mm people for help :)

> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 13d711dd8776..415b003e475c 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -225,7 +225,8 @@ unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat)
>  
>  	nr = node_page_state_snapshot(pgdat, NR_ACTIVE_FILE) +
>  	     node_page_state_snapshot(pgdat, NR_INACTIVE_FILE) +
> -	     node_page_state_snapshot(pgdat, NR_ISOLATED_FILE);
> +	     node_page_state_snapshot(pgdat, NR_ISOLATED_FILE) +
> +	     (node_page_state_snapshot(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT);
>  
>  	if (get_nr_swap_pages() > 0)
>  		nr += node_page_state_snapshot(pgdat, NR_ACTIVE_ANON) +

Just drop this hunk. The function is going away (and is currently unused).

> @@ -3812,6 +3813,7 @@ static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
>  static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
>  {
>  	unsigned long nr_pagecache_reclaimable;
> +	unsigned long nr_metadata_reclaimable;
>  	unsigned long delta = 0;
>  
>  	/*
> @@ -3833,7 +3835,20 @@ static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
>  	if (unlikely(delta > nr_pagecache_reclaimable))
>  		delta = nr_pagecache_reclaimable;
>  
> -	return nr_pagecache_reclaimable - delta;
> +	nr_metadata_reclaimable =
> +		node_page_state(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT;
> +	/*
> +	 * We don't do writeout through the shrinkers so subtract any
> +	 * dirty/writeback metadata bytes from the reclaimable count.
> +	 */
> +	if (nr_metadata_reclaimable) {
> +		unsigned long unreclaimable =
> +			node_page_state(pgdat, NR_METADATA_DIRTY_BYTES) +
> +			node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES);
> +		unreclaimable >>= PAGE_SHIFT;
> +		nr_metadata_reclaimable -= unreclaimable;
> +	}
> +	return nr_metadata_reclaimable + nr_pagecache_reclaimable - delta;
>  }

Ditto as with __vm_enough_memory(). In particular I'm unsure whether the
watermarks like min_unmapped_pages or min_slab_pages would still work as
designed.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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Re: [PATCH v2 06/11] writeback: add counters for metadata usage

[Josef Bacik]

On Mon, Dec 04, 2017 at 02:06:30PM +0100, Jan Kara wrote:
> On Wed 22-11-17 16:16:01, Josef Bacik wrote:
> > From: Josef Bacik <jbacik@fb.com>
> > 
> > Btrfs has no bounds except memory on the amount of dirty memory that we have in
> > use for metadata.  Historically we have used a special inode so we could take
> > advantage of the balance_dirty_pages throttling that comes with using pagecache.
> > However as we'd like to support different blocksizes it would be nice to not
> > have to rely on pagecache, but still get the balance_dirty_pages throttling
> > without having to do it ourselves.
> > 
> > So introduce *METADATA_DIRTY_BYTES and *METADATA_WRITEBACK_BYTES.  These are
> > zone and bdi_writeback counters to keep track of how many bytes we have in
> > flight for METADATA.  We need to count in bytes as blocksizes could be
> > percentages of pagesize.  We simply convert the bytes to number of pages where
> > it is needed for the throttling.
> > 
> > Also introduce NR_METADATA_BYTES so we can keep track of the total amount of
> > pages used for metadata on the system.  This is also needed so things like dirty
> > throttling know that this is dirtyable memory as well and easily reclaimed.
> 
> I'll defer to mm guys for final decision but the fact is the memory for
> metadata is likely to be allocated from some slab cache and that actually
> goes against the 'easily reclaimed' statement. Granted these are going to
> be relatively large objects (1k at least I assume) so fragmentation issues
> are not as bad but still getting actual free pages out of slab cache isn't
> that easy... More on this below.
> 
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 356a814e7c8e..fd516a0f0bfe 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -179,6 +179,9 @@ enum node_stat_item {
> >  	NR_VMSCAN_IMMEDIATE,	/* Prioritise for reclaim when writeback ends */
> >  	NR_DIRTIED,		/* page dirtyings since bootup */
> >  	NR_WRITTEN,		/* page writings since bootup */
> > +	NR_METADATA_DIRTY_BYTES,	/* Metadata dirty bytes */
> > +	NR_METADATA_WRITEBACK_BYTES,	/* Metadata writeback bytes */
> > +	NR_METADATA_BYTES,	/* total metadata bytes in use. */
> >  	NR_VM_NODE_STAT_ITEMS
> >  };
> 
> I think you didn't address my comment from last version of the series.
> 
> 1) Per-cpu node-stat batching will be basically useless for these counters
> as the batch size is <128. Maybe we don't care but it would deserve a
> comment.
> 
> 2) These counters are tracked in atomic_long_t type. That means max 2GB of
> metadata on 32-bit machines. I *guess* that should be OK since you would
> not be able to address that much of slab cache on such machine anyway but 
> still worth a comment I think.
> 

You're right I missed this, sorry about that.  I've resolved the batching
problem, and I'll add a comment about the 32bit machines problem.

> > diff --git a/mm/util.c b/mm/util.c
> > index 34e57fae959d..681d62631ee0 100644
> > --- a/mm/util.c
> > +++ b/mm/util.c
> > @@ -616,6 +616,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> >  	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
> >  		free = global_zone_page_state(NR_FREE_PAGES);
> >  		free += global_node_page_state(NR_FILE_PAGES);
> > +		free += global_node_page_state(NR_METADATA_BYTES) >> PAGE_SHIFT;
> 
> 
> I'm not really sure this is OK. It depends on whether mm is really able to
> reclaim these pages easily enough... Summon mm people for help :)
> 

Well we count NR_SLAB_RECLAIMABLE here, so it's no different than that.  The
point is that it's theoretically reclaimable, and we should at least try.

> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 13d711dd8776..415b003e475c 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -225,7 +225,8 @@ unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat)
> >  
> >  	nr = node_page_state_snapshot(pgdat, NR_ACTIVE_FILE) +
> >  	     node_page_state_snapshot(pgdat, NR_INACTIVE_FILE) +
> > -	     node_page_state_snapshot(pgdat, NR_ISOLATED_FILE);
> > +	     node_page_state_snapshot(pgdat, NR_ISOLATED_FILE) +
> > +	     (node_page_state_snapshot(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT);
> >  
> >  	if (get_nr_swap_pages() > 0)
> >  		nr += node_page_state_snapshot(pgdat, NR_ACTIVE_ANON) +
> 
> Just drop this hunk. The function is going away (and is currently unused).
> 

Will do.

> > @@ -3812,6 +3813,7 @@ static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
> >  static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
> >  {
> >  	unsigned long nr_pagecache_reclaimable;
> > +	unsigned long nr_metadata_reclaimable;
> >  	unsigned long delta = 0;
> >  
> >  	/*
> > @@ -3833,7 +3835,20 @@ static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
> >  	if (unlikely(delta > nr_pagecache_reclaimable))
> >  		delta = nr_pagecache_reclaimable;
> >  
> > -	return nr_pagecache_reclaimable - delta;
> > +	nr_metadata_reclaimable =
> > +		node_page_state(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT;
> > +	/*
> > +	 * We don't do writeout through the shrinkers so subtract any
> > +	 * dirty/writeback metadata bytes from the reclaimable count.
> > +	 */
> > +	if (nr_metadata_reclaimable) {
> > +		unsigned long unreclaimable =
> > +			node_page_state(pgdat, NR_METADATA_DIRTY_BYTES) +
> > +			node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES);
> > +		unreclaimable >>= PAGE_SHIFT;
> > +		nr_metadata_reclaimable -= unreclaimable;
> > +	}
> > +	return nr_metadata_reclaimable + nr_pagecache_reclaimable - delta;
> >  }
> 
> Ditto as with __vm_enough_memory(). In particular I'm unsure whether the
> watermarks like min_unmapped_pages or min_slab_pages would still work as
> designed.
> 

Yeah agreed I'd like an MM person's thoughts on this as well.  We don't count
SLAB_RECLAIMABLE here, but that's because it's just not related to pagecache.  I
guess it only matters for node reclaim and we have our node reclaim stuff turned
off, which means it doesn't help us anyway, so I'm happy to just drop it and let
somebody who cares about node reclaim think about it later ;).  Thanks,

Josef

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Re: [PATCH v2 06/11] writeback: add counters for metadata usage

[Johannes Weiner]

On Wed, Dec 06, 2017 at 03:18:35PM -0500, Josef Bacik wrote:
> On Mon, Dec 04, 2017 at 02:06:30PM +0100, Jan Kara wrote:
> > On Wed 22-11-17 16:16:01, Josef Bacik wrote:
> > > diff --git a/mm/util.c b/mm/util.c
> > > index 34e57fae959d..681d62631ee0 100644
> > > --- a/mm/util.c
> > > +++ b/mm/util.c
> > > @@ -616,6 +616,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> > >  	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
> > >  		free = global_zone_page_state(NR_FREE_PAGES);
> > >  		free += global_node_page_state(NR_FILE_PAGES);
> > > +		free += global_node_page_state(NR_METADATA_BYTES) >> PAGE_SHIFT;
> > 
> > 
> > I'm not really sure this is OK. It depends on whether mm is really able to
> > reclaim these pages easily enough... Summon mm people for help :)
> > 
> 
> Well we count NR_SLAB_RECLAIMABLE here, so it's no different than that.  The
> point is that it's theoretically reclaimable, and we should at least try.

I agree with including metadata in the equation. The (somewhat dusty)
overcommit code is mostly for containing swap storms, which is why it
adds up all the reclaimable pools that aren't backed by swap. The
metadata pool belongs in that category.

> > > @@ -3812,6 +3813,7 @@ static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat)
> > >  static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
> > >  {
> > >  	unsigned long nr_pagecache_reclaimable;
> > > +	unsigned long nr_metadata_reclaimable;
> > >  	unsigned long delta = 0;
> > >  
> > >  	/*
> > > @@ -3833,7 +3835,20 @@ static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat)
> > >  	if (unlikely(delta > nr_pagecache_reclaimable))
> > >  		delta = nr_pagecache_reclaimable;
> > >  
> > > -	return nr_pagecache_reclaimable - delta;
> > > +	nr_metadata_reclaimable =
> > > +		node_page_state(pgdat, NR_METADATA_BYTES) >> PAGE_SHIFT;
> > > +	/*
> > > +	 * We don't do writeout through the shrinkers so subtract any
> > > +	 * dirty/writeback metadata bytes from the reclaimable count.
> > > +	 */
> > > +	if (nr_metadata_reclaimable) {
> > > +		unsigned long unreclaimable =
> > > +			node_page_state(pgdat, NR_METADATA_DIRTY_BYTES) +
> > > +			node_page_state(pgdat, NR_METADATA_WRITEBACK_BYTES);
> > > +		unreclaimable >>= PAGE_SHIFT;
> > > +		nr_metadata_reclaimable -= unreclaimable;
> > > +	}
> > > +	return nr_metadata_reclaimable + nr_pagecache_reclaimable - delta;
> > >  }
> > 
> > Ditto as with __vm_enough_memory(). In particular I'm unsure whether the
> > watermarks like min_unmapped_pages or min_slab_pages would still work as
> > designed.
> > 
> 
> Yeah agreed I'd like an MM person's thoughts on this as well.  We don't count
> SLAB_RECLAIMABLE here, but that's because it's just not related to pagecache.  I
> guess it only matters for node reclaim and we have our node reclaim stuff turned
> off, which means it doesn't help us anyway, so I'm happy to just drop it and let
> somebody who cares about node reclaim think about it later ;).  Thanks,

Few people care about node reclaim at this point, see 4f9b16a64753
("mm: disable zone_reclaim_mode by default"), and it's honestly a bit
baffling why we made min_slab_ratio a tunable in the first place. Who
knows how/if anybody relies on that behavior. I'd just leave it alone.

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