[PATCH 1/2] btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents()

[PATCH 1/2] btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents()

[Qu Wenruo]

commit 8702ba9396bf7bbae2ab93c94acd4bd37cfa4f09 upstream.

[Background]
Btrfs qgroup uses two types of reserved space for METADATA space,
PERTRANS and PREALLOC.

PERTRANS is metadata space reserved for each transaction started by
btrfs_start_transaction().
While PREALLOC is for delalloc, where we reserve space before joining a
transaction, and finally it will be converted to PERTRANS after the
writeback is done.

[Inconsistency]
However there is inconsistency in how we handle PREALLOC metadata space.

The most obvious one is:
In btrfs_buffered_write():
	btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes, true);

We always free qgroup PREALLOC meta space.

While in btrfs_truncate_block():
	btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, (ret != 0));

We only free qgroup PREALLOC meta space when something went wrong.

[The Correct Behavior]
The correct behavior should be the one in btrfs_buffered_write(), we
should always free PREALLOC metadata space.

The reason is, the btrfs_delalloc_* mechanism works by:
- Reserve metadata first, even it's not necessary
  In btrfs_delalloc_reserve_metadata()

- Free the unused metadata space
  Normally in:
  btrfs_delalloc_release_extents()
  |- btrfs_inode_rsv_release()
     Here we do calculation on whether we should release or not.

E.g. for 64K buffered write, the metadata rsv works like:

/* The first page */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=0
total:		num_bytes=calc_inode_reservations()
/* The first page caused one outstanding extent, thus needs metadata
   rsv */

/* The 2nd page */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=calc_inode_reservations()
total:		not changed
/* The 2nd page doesn't cause new outstanding extent, needs no new meta
   rsv, so we free what we have reserved */

/* The 3rd~16th pages */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=calc_inode_reservations()
total:		not changed (still space for one outstanding extent)

This means, if btrfs_delalloc_release_extents() determines to free some
space, then those space should be freed NOW.
So for qgroup, we should call btrfs_qgroup_free_meta_prealloc() other
than btrfs_qgroup_convert_reserved_meta().

The good news is:
- The callers are not that hot
  The hottest caller is in btrfs_buffered_write(), which is already
  fixed by commit 336a8bb8e36a ("btrfs: Fix wrong
  btrfs_delalloc_release_extents parameter"). Thus it's not that
  easy to cause false EDQUOT.

- The trans commit in advance for qgroup would hide the bug
  Since commit f5fef4593653 ("btrfs: qgroup: Make qgroup async transaction
  commit more aggressive"), when btrfs qgroup metadata free space is slow,
  it will try to commit transaction and free the wrongly converted
  PERTRANS space, so it's not that easy to hit such bug.

[FIX]
So to fix the problem, remove the @qgroup_free parameter for
btrfs_delalloc_release_extents(), and always pass true to
btrfs_inode_rsv_release().

Reported-by: Filipe Manana <fdmanana@suse.com>
Fixes: 43b18595d660 ("btrfs: qgroup: Use separate meta reservation type for delalloc")
CC: stable@vger.kernel.org # 4.19
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
[Fix conflicts caused by delalloc-space.[ch] code move]
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/ctree.h       |  3 +--
 fs/btrfs/extent-tree.c |  5 ++---
 fs/btrfs/file.c        |  7 +++----
 fs/btrfs/inode-map.c   |  4 ++--
 fs/btrfs/inode.c       | 12 ++++++------
 fs/btrfs/ioctl.c       |  6 ++----
 fs/btrfs/relocation.c  |  7 +++----
 7 files changed, 19 insertions(+), 25 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index faca485ccd8f..ef7a352d72ed 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2747,8 +2747,7 @@ int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,
 				     int nitems, bool use_global_rsv);
 void btrfs_subvolume_release_metadata(struct btrfs_fs_info *fs_info,
 				      struct btrfs_block_rsv *rsv);
-void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes,
-				    bool qgroup_free);
+void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes);
 
 int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes);
 void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e49e29288049..7d316a31874f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5980,8 +5980,7 @@ void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes,
  * temporarily tracked outstanding_extents.  This _must_ be used in conjunction
  * with btrfs_delalloc_reserve_metadata.
  */
-void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes,
-				    bool qgroup_free)
+void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	unsigned num_extents;
@@ -5995,7 +5994,7 @@ void btrfs_delalloc_release_extents(struct btrfs_inode *inode, u64 num_bytes,
 	if (btrfs_is_testing(fs_info))
 		return;
 
-	btrfs_inode_rsv_release(inode, qgroup_free);
+	btrfs_inode_rsv_release(inode, true);
 }
 
 /**
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index c84186563c31..1b7b599f7caf 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1692,7 +1692,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
 				    force_page_uptodate);
 		if (ret) {
 			btrfs_delalloc_release_extents(BTRFS_I(inode),
-						       reserve_bytes, true);
+						       reserve_bytes);
 			break;
 		}
 
@@ -1704,7 +1704,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
 			if (extents_locked == -EAGAIN)
 				goto again;
 			btrfs_delalloc_release_extents(BTRFS_I(inode),
-						       reserve_bytes, true);
+						       reserve_bytes);
 			ret = extents_locked;
 			break;
 		}
@@ -1761,8 +1761,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
 		if (extents_locked)
 			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
 					     lockstart, lockend, &cached_state);
-		btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes,
-					       true);
+		btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes);
 		if (ret) {
 			btrfs_drop_pages(pages, num_pages);
 			break;
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index ffca2abf13d0..ba9566cabc94 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -483,12 +483,12 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, prealloc,
 					      prealloc, prealloc, &alloc_hint);
 	if (ret) {
-		btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc, true);
+		btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc);
 		goto out_put;
 	}
 
 	ret = btrfs_write_out_ino_cache(root, trans, path, inode);
-	btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc, false);
+	btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc);
 out_put:
 	iput(inode);
 out_release:
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 37332f83a3a9..9aea9381ceeb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2166,7 +2166,7 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
 
 	ClearPageChecked(page);
 	set_page_dirty(page);
-	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, false);
+	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
 out:
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end,
 			     &cached_state);
@@ -4918,7 +4918,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	if (!page) {
 		btrfs_delalloc_release_space(inode, data_reserved,
 					     block_start, blocksize, true);
-		btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, true);
+		btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize);
 		ret = -ENOMEM;
 		goto out;
 	}
@@ -4986,7 +4986,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	if (ret)
 		btrfs_delalloc_release_space(inode, data_reserved, block_start,
 					     blocksize, true);
-	btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, (ret != 0));
+	btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize);
 	unlock_page(page);
 	put_page(page);
 out:
@@ -8660,7 +8660,7 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 		} else if (ret >= 0 && (size_t)ret < count)
 			btrfs_delalloc_release_space(inode, data_reserved,
 					offset, count - (size_t)ret, true);
-		btrfs_delalloc_release_extents(BTRFS_I(inode), count, false);
+		btrfs_delalloc_release_extents(BTRFS_I(inode), count);
 	}
 out:
 	if (wakeup)
@@ -9013,7 +9013,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 	unlock_extent_cached(io_tree, page_start, page_end, &cached_state);
 
 	if (!ret2) {
-		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, true);
+		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
 		sb_end_pagefault(inode->i_sb);
 		extent_changeset_free(data_reserved);
 		return VM_FAULT_LOCKED;
@@ -9022,7 +9022,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
 out_unlock:
 	unlock_page(page);
 out:
-	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE, (ret != 0));
+	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
 	btrfs_delalloc_release_space(inode, data_reserved, page_start,
 				     reserved_space, (ret != 0));
 out_noreserve:
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0eb333c62fe4..7592beb53fc4 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1359,8 +1359,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 		unlock_page(pages[i]);
 		put_page(pages[i]);
 	}
-	btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT,
-				       false);
+	btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT);
 	extent_changeset_free(data_reserved);
 	return i_done;
 out:
@@ -1371,8 +1370,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	btrfs_delalloc_release_space(inode, data_reserved,
 			start_index << PAGE_SHIFT,
 			page_cnt << PAGE_SHIFT, true);
-	btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT,
-				       true);
+	btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT);
 	extent_changeset_free(data_reserved);
 	return ret;
 
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 5d57ed629345..725febe2b36e 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3207,7 +3207,7 @@ static int relocate_file_extent_cluster(struct inode *inode,
 				btrfs_delalloc_release_metadata(BTRFS_I(inode),
 							PAGE_SIZE, true);
 				btrfs_delalloc_release_extents(BTRFS_I(inode),
-							       PAGE_SIZE, true);
+							       PAGE_SIZE);
 				ret = -EIO;
 				goto out;
 			}
@@ -3236,7 +3236,7 @@ static int relocate_file_extent_cluster(struct inode *inode,
 			btrfs_delalloc_release_metadata(BTRFS_I(inode),
 							 PAGE_SIZE, true);
 			btrfs_delalloc_release_extents(BTRFS_I(inode),
-			                               PAGE_SIZE, true);
+			                               PAGE_SIZE);
 
 			clear_extent_bits(&BTRFS_I(inode)->io_tree,
 					  page_start, page_end,
@@ -3252,8 +3252,7 @@ static int relocate_file_extent_cluster(struct inode *inode,
 		put_page(page);
 
 		index++;
-		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE,
-					       false);
+		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
 		balance_dirty_pages_ratelimited(inode->i_mapping);
 		btrfs_throttle(fs_info);
 	}
-- 
2.23.0

[PATCH 2/2] btrfs: tracepoints: Fix wrong parameter order for qgroup events

[Qu Wenruo]

commit fd2b007eaec898564e269d1f478a2da0380ecf51 upstream.

[BUG]
For btrfs:qgroup_meta_reserve event, the trace event can output garbage:

  qgroup_meta_reserve: 9c7f6acc-b342-4037-bc47-7f6e4d2232d7: refroot=5(FS_TREE) type=DATA diff=2

The diff should always be alinged to sector size (4k), so there is
definitely something wrong.

[CAUSE]
For the wrong @diff, it's caused by wrong parameter order.
The correct parameters are:

  struct btrfs_root, s64 diff, int type.

However the parameters used are:

  struct btrfs_root, int type, s64 diff.

Fixes: 4ee0d8832c2e ("btrfs: qgroup: Update trace events for metadata reservation")
CC: stable@vger.kernel.org # 4.19
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
[Fix conflcits caused by parameter refactor]
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/qgroup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 3ea2008dcde3..cdd6d5021000 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3259,7 +3259,7 @@ int __btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
 		return 0;
 
 	BUG_ON(num_bytes != round_down(num_bytes, fs_info->nodesize));
-	trace_qgroup_meta_reserve(root, type, (s64)num_bytes);
+	trace_qgroup_meta_reserve(root, (s64)num_bytes, type);
 	ret = qgroup_reserve(root, num_bytes, enforce, type);
 	if (ret < 0)
 		return ret;
@@ -3306,7 +3306,7 @@ void __btrfs_qgroup_free_meta(struct btrfs_root *root, int num_bytes,
 	 */
 	num_bytes = sub_root_meta_rsv(root, num_bytes, type);
 	BUG_ON(num_bytes != round_down(num_bytes, fs_info->nodesize));
-	trace_qgroup_meta_reserve(root, type, -(s64)num_bytes);
+	trace_qgroup_meta_reserve(root, -(s64)num_bytes, type);
 	btrfs_qgroup_free_refroot(fs_info, root->objectid, num_bytes, type);
 }
 
-- 
2.23.0

Re: [PATCH 1/2] btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents()

[David Sterba]

On Mon, Oct 28, 2019 at 02:51:48PM +0800, Qu Wenruo wrote:
> commit 8702ba9396bf7bbae2ab93c94acd4bd37cfa4f09 upstream.

Please don't forget to note for which stable version the backport is,
ideally in the subject in the [PATCH ...] section or at least somewhere
in the tag section.