[PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[Qu Wenruo]

This branch is based on subpage RW branch, as the last patch needs to
enable defrag support for subpage cases.

But despite that one, all other patches can be applied on current
misc-next.

[BACKGROUND]
In subpage rw branch, we disable defrag completely due to the fact that
current code can only work on page basis.

This could lead to problems like btrfs/062 crash.

Thus this patchset will make defrag to work on both regular and subpage
sectorsize.

[SOLUTION]
To defrag a file range, what we do is pretty much like buffered write,
except we don't really write any new data to page cache, but just mark
the range dirty.

Then let later writeback to merge the range into a larger extent.

But current defrag code is working on per-page basis, not per-sector,
thus we have to refactor it a little to make it to work properly for
subpage.

This patch will separate the code into 3 layers:
Layer 0:	btrfs_defrag_file()
		The defrag entrace
		Just do proper inode lock and split the file into
		page aligned 256K clusters to defrag

Layer 1:	defrag_one_cluster()
		Will collect the initial targets file extents, and pass
		each continuous target to defrag_one_range()

Layer 2:	defrag_one_range()
		Will prepare the needed page and extent locking.
		Then re-check the range for real target list, as initial
		target list is not consistent as it doesn't hage
		page/extent locking to prevent hole punching.

Layer 3:	defrag_one_locked_target()
		The real work, to make the extent range defrag and
		update involved page status

[BEHAVIOR CHANGE]
In the refactor, there is one behavior change:

- Defraged sector counter is based on the initial target list
  This is mostly to avoid the paremters to be passed too deep into
  defrag_one_locked_target().
  Considering the accounting is not that important, we can afford some
  difference.

[PATCH STRUTURE]
Patch 01~03:	Small independent refactor to improve readability
Patch 04~08:	Implement the more readable and subpage friendly defrag
Patch 09:	Cleanup of old infrastruture
Patch 10:	Enable defrag for subpage case

Now both regular sectorsize and subpage sectorsize can pass defrag test
group.

[CHANGELOG]
v2:
- Make sure we won't defrag hole
  This is done by re-collect the target list after have page and extent
  locked. So that we can have a consistent view of the extent map.

- Add a new layer to avoid variable naming bugs
  Since we need to handle real target list inside defrag_one_range(),
  and that function has parameters like "start" and "len", while inside
  the loop we need things like "entry->start" and "entry->len", it has
  already caused hard to debug bugs during development.

  Thus introduce a new layer, defrag_one_ragen() to prepare pages/extent
  lock then pass the entry to defrag_one_locked_target().

v3:
- Fix extent_state leak
  Now we pass the @cached_state to defrag_one_locked_target() other
  than allowing it to allocate a new one.

  This can be reproduced by enabling "TEST_FS_MODULE_RELOAD" environment
  variable for fstests and run "-g defrag" group.

- Fix a random hang in test cases like btrfs/062
  Since defrag_one_range() will lock the extent range first, then
  call defrag_collect_targets(), which will in turn call
  defrag_lookup_extent() and lock extent range again.

  This will cause a dead lock, and this only happens when the
  extent range is smaller than the original locked range.
  Thus sometimes the test can pass, but sometimes it can hang.

  Fix it by teaching defrag_collect_targets() and defrag_lookup_extent()
  to skip extent lock for certain call sites.
  Thus this needs some loops for btrfs/062.
  The hang possibility is around 1/2 ~ 1/3 when run in a loop.

Qu Wenruo (10):
  btrfs: defrag: pass file_ra_state instead of file for
    btrfs_defrag_file()
  btrfs: defrag: extract the page preparation code into one helper
  btrfs: defrag: replace hard coded PAGE_SIZE to sectorsize for
    defrag_lookup_extent()
  btrfs: defrag: introduce a new helper to collect target file extents
  btrfs: defrag: introduce a helper to defrag a continuous prepared
    range
  btrfs: defrag: introduce a helper to defrag a range
  btrfs: defrag: introduce a new helper to defrag one cluster
  btrfs: defrag: use defrag_one_cluster() to implement
    btrfs_defrag_file()
  btrfs: defrag: remove the old infrastructure
  btrfs: defrag: enable defrag for subpage case

 fs/btrfs/ctree.h |   4 +-
 fs/btrfs/ioctl.c | 921 ++++++++++++++++++++++-------------------------
 2 files changed, 432 insertions(+), 493 deletions(-)

-- 
2.31.1

[PATCH v3 01/10] btrfs: defrag: pass file_ra_state instead of file for btrfs_defrag_file()

[Qu Wenruo]

Currently btrfs_defrag_file() accepts both "struct inode" and "struct
file" as parameter, which can't be more confusing.
As we can easily grab "struct inode" from "struct file" using
file_inode() helper.

The reason why we need "struct file" is just to re-use its f_ra.

This patch will change this by passing "struct file_ra_state" parameter,
so that it's more clear what we really want.

Since we're here, also add some comment on the function
btrfs_defrag_file() to make later reader less miserable.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/ctree.h |  4 ++--
 fs/btrfs/ioctl.c | 27 ++++++++++++++++++---------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 45798e68331a..918df8877b45 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3212,9 +3212,9 @@ int btrfs_fileattr_set(struct user_namespace *mnt_userns,
 int btrfs_ioctl_get_supported_features(void __user *arg);
 void btrfs_sync_inode_flags_to_i_flags(struct inode *inode);
 int __pure btrfs_is_empty_uuid(u8 *uuid);
-int btrfs_defrag_file(struct inode *inode, struct file *file,
+int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
 		      struct btrfs_ioctl_defrag_range_args *range,
-		      u64 newer_than, unsigned long max_pages);
+		      u64 newer_than, unsigned long max_to_defrag);
 void btrfs_get_block_group_info(struct list_head *groups_list,
 				struct btrfs_ioctl_space_info *space);
 void btrfs_update_ioctl_balance_args(struct btrfs_fs_info *fs_info,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 11adf4670c55..f85ee0ac9606 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1350,13 +1350,22 @@ static int cluster_pages_for_defrag(struct inode *inode,
 
 }
 
-int btrfs_defrag_file(struct inode *inode, struct file *file,
+/*
+ * Btrfs entrace for defrag.
+ *
+ * @inode:	   Inode to be defraged
+ * @ra:		   Readahead state. If NULL, one will be allocated at runtime.
+ * @range:	   Defrag options including range and flags.
+ * @newer_than:	   Minimal transid to defrag
+ * @max_to_defrag: Max number of sectors to be defraged, if 0, the whole inode
+ * 		   will be defraged.
+ */
+int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
 		      struct btrfs_ioctl_defrag_range_args *range,
 		      u64 newer_than, unsigned long max_to_defrag)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct file_ra_state *ra = NULL;
 	unsigned long last_index;
 	u64 isize = i_size_read(inode);
 	u64 last_len = 0;
@@ -1374,6 +1383,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 	u64 new_align = ~((u64)SZ_128K - 1);
 	struct page **pages = NULL;
 	bool do_compress = range->flags & BTRFS_DEFRAG_RANGE_COMPRESS;
+	bool ra_allocated = false;
 
 	if (isize == 0)
 		return 0;
@@ -1392,16 +1402,15 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 		extent_thresh = SZ_256K;
 
 	/*
-	 * If we were not given a file, allocate a readahead context. As
+	 * If we were not given a ra, allocate a readahead context. As
 	 * readahead is just an optimization, defrag will work without it so
 	 * we don't error out.
 	 */
-	if (!file) {
+	if (!ra) {
+		ra_allocated = true;
 		ra = kzalloc(sizeof(*ra), GFP_KERNEL);
 		if (ra)
 			file_ra_state_init(ra, inode->i_mapping);
-	} else {
-		ra = &file->f_ra;
 	}
 
 	pages = kmalloc_array(max_cluster, sizeof(struct page *), GFP_KERNEL);
@@ -1483,7 +1492,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 			ra_index = max(i, ra_index);
 			if (ra)
 				page_cache_sync_readahead(inode->i_mapping, ra,
-						file, ra_index, cluster);
+						NULL, ra_index, cluster);
 			ra_index += cluster;
 		}
 
@@ -1554,7 +1563,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 		BTRFS_I(inode)->defrag_compress = BTRFS_COMPRESS_NONE;
 		btrfs_inode_unlock(inode, 0);
 	}
-	if (!file)
+	if (ra_allocated)
 		kfree(ra);
 	kfree(pages);
 	return ret;
@@ -3076,7 +3085,7 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 			/* the rest are all set to zero by kzalloc */
 			range->len = (u64)-1;
 		}
-		ret = btrfs_defrag_file(file_inode(file), file,
+		ret = btrfs_defrag_file(file_inode(file), &file->f_ra,
 					range, BTRFS_OLDEST_GENERATION, 0);
 		if (ret > 0)
 			ret = 0;
-- 
2.31.1

[PATCH v3 02/10] btrfs: defrag: extract the page preparation code into one helper

[Qu Wenruo]

In cluster_pages_for_defrag(), we have complex code block inside one
for() loop.

The code block is to prepare one page for defrag, this will ensure:
- The page is locked and set up properly
- No ordered extent exists in the page range
- The page is uptodate
- The writeback has finished

This behavior is pretty common and will be reused by later defrag
rework.

So extract the code into its own helper, defrag_prepare_one_page(), for
later usage, and cleanup the code by a little.

Since we're here, also make the page check to be subpage compatible,
which means we will also check page::private, not only page->mapping.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 151 +++++++++++++++++++++++++++--------------------
 1 file changed, 86 insertions(+), 65 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f85ee0ac9606..0b5a48274266 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1143,6 +1143,89 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
 	return ret;
 }
 
+/*
+ * Prepare one page to be defraged.
+ *
+ * This will ensure:
+ * - Returned page is locked and has been set up properly
+ * - No ordered extent exists in the page
+ * - The page is uptodate
+ * - The writeback has finished
+ */
+static struct page *defrag_prepare_one_page(struct btrfs_inode *inode,
+					    unsigned long index)
+{
+	struct address_space *mapping = inode->vfs_inode.i_mapping;
+	gfp_t mask = btrfs_alloc_write_mask(mapping);
+	u64 page_start = index << PAGE_SHIFT;
+	u64 page_end = page_start + PAGE_SIZE - 1;
+	struct extent_state *cached_state = NULL;
+	struct page *page;
+	int ret;
+
+again:
+	page = find_or_create_page(mapping, index, mask);
+	if (!page)
+		return ERR_PTR(-ENOMEM);
+
+	ret = set_page_extent_mapped(page);
+	if (ret < 0) {
+		unlock_page(page);
+		put_page(page);
+		return ERR_PTR(ret);
+	}
+
+	/* Wait for any exists ordered extent in the range */
+	while (1) {
+		struct btrfs_ordered_extent *ordered;
+
+		lock_extent_bits(&inode->io_tree, page_start, page_end,
+				 &cached_state);
+		ordered = btrfs_lookup_ordered_range(inode, page_start,
+						     PAGE_SIZE);
+		unlock_extent_cached(&inode->io_tree, page_start, page_end,
+				     &cached_state);
+		if (!ordered)
+			break;
+
+		unlock_page(page);
+		btrfs_start_ordered_extent(ordered, 1);
+		btrfs_put_ordered_extent(ordered);
+		lock_page(page);
+		/*
+		 * we unlocked the page above, so we need check if
+		 * it was released or not.
+		 */
+		if (page->mapping != mapping || !PagePrivate(page)) {
+			unlock_page(page);
+			put_page(page);
+			goto again;
+		}
+	}
+
+	/*
+	 * Now the page range has no ordered extent any more.
+	 * Read the page to make it uptodate.
+	 */
+	if (!PageUptodate(page)) {
+		btrfs_readpage(NULL, page);
+		lock_page(page);
+		if (page->mapping != mapping || !PagePrivate(page)) {
+			unlock_page(page);
+			put_page(page);
+			goto again;
+		}
+		if (!PageUptodate(page)) {
+			unlock_page(page);
+			put_page(page);
+			return ERR_PTR(-EIO);
+		}
+	}
+
+	wait_on_page_writeback(page);
+	return page;
+}
+
 /*
  * it doesn't do much good to defrag one or two pages
  * at a time.  This pulls in a nice chunk of pages
@@ -1170,11 +1253,8 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	int ret;
 	int i;
 	int i_done;
-	struct btrfs_ordered_extent *ordered;
 	struct extent_state *cached_state = NULL;
-	struct extent_io_tree *tree;
 	struct extent_changeset *data_reserved = NULL;
-	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
 
 	file_end = (isize - 1) >> PAGE_SHIFT;
 	if (!isize || start_index > file_end)
@@ -1187,68 +1267,16 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	if (ret)
 		return ret;
 	i_done = 0;
-	tree = &BTRFS_I(inode)->io_tree;
 
 	/* step one, lock all the pages */
 	for (i = 0; i < page_cnt; i++) {
 		struct page *page;
-again:
-		page = find_or_create_page(inode->i_mapping,
-					   start_index + i, mask);
-		if (!page)
-			break;
 
-		ret = set_page_extent_mapped(page);
-		if (ret < 0) {
-			unlock_page(page);
-			put_page(page);
+		page = defrag_prepare_one_page(BTRFS_I(inode), start_index + i);
+		if (IS_ERR(page)) {
+			ret = PTR_ERR(page);
 			break;
 		}
-
-		page_start = page_offset(page);
-		page_end = page_start + PAGE_SIZE - 1;
-		while (1) {
-			lock_extent_bits(tree, page_start, page_end,
-					 &cached_state);
-			ordered = btrfs_lookup_ordered_extent(BTRFS_I(inode),
-							      page_start);
-			unlock_extent_cached(tree, page_start, page_end,
-					     &cached_state);
-			if (!ordered)
-				break;
-
-			unlock_page(page);
-			btrfs_start_ordered_extent(ordered, 1);
-			btrfs_put_ordered_extent(ordered);
-			lock_page(page);
-			/*
-			 * we unlocked the page above, so we need check if
-			 * it was released or not.
-			 */
-			if (page->mapping != inode->i_mapping) {
-				unlock_page(page);
-				put_page(page);
-				goto again;
-			}
-		}
-
-		if (!PageUptodate(page)) {
-			btrfs_readpage(NULL, page);
-			lock_page(page);
-			if (!PageUptodate(page)) {
-				unlock_page(page);
-				put_page(page);
-				ret = -EIO;
-				break;
-			}
-		}
-
-		if (page->mapping != inode->i_mapping) {
-			unlock_page(page);
-			put_page(page);
-			goto again;
-		}
-
 		pages[i] = page;
 		i_done++;
 	}
@@ -1258,13 +1286,6 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	if (!(inode->i_sb->s_flags & SB_ACTIVE))
 		goto out;
 
-	/*
-	 * so now we have a nice long stream of locked
-	 * and up to date pages, lets wait on them
-	 */
-	for (i = 0; i < i_done; i++)
-		wait_on_page_writeback(pages[i]);
-
 	page_start = page_offset(pages[0]);
 	page_end = page_offset(pages[i_done - 1]) + PAGE_SIZE;
 
-- 
2.31.1

[PATCH v3 03/10] btrfs: defrag: replace hard coded PAGE_SIZE to sectorsize for defrag_lookup_extent()

[Qu Wenruo]

When testing subpage defrag support, I always find some strange inode
nbytes error, after a lot of debugging, it turns out that
defrag_lookup_extent() is using PAGE_SIZE as size for
lookup_extent_mapping().

Since lookup_extent_mapping() is calling __lookup_extent_mapping() with
@strict == 1, this means any extent map smaller than one page will be
ignored, prevent subpage defrag to grab a correct extent map.

There are quite some PAGE_SIZE usage in ioctl.c, but most of them are
correct usages, and can be one of the following cases:

- ioctl structure size check
  We want ioctl structure be contained inside one page.

- real page opeartions

There is one special case left untouched, check_defrag_in_cache().
This function will later be removed completely, thus there is not much
meaning to change it now.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0b5a48274266..24b0dc1325d3 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1037,23 +1037,24 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
 	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct extent_map *em;
-	u64 len = PAGE_SIZE;
+	const u32 sectorsize = BTRFS_I(inode)->root->fs_info->sectorsize;
 
 	/*
 	 * hopefully we have this extent in the tree already, try without
 	 * the full extent lock
 	 */
 	read_lock(&em_tree->lock);
-	em = lookup_extent_mapping(em_tree, start, len);
+	em = lookup_extent_mapping(em_tree, start, sectorsize);
 	read_unlock(&em_tree->lock);
 
 	if (!em) {
 		struct extent_state *cached = NULL;
-		u64 end = start + len - 1;
+		u64 end = start + sectorsize - 1;
 
 		/* get the big lock and read metadata off disk */
 		lock_extent_bits(io_tree, start, end, &cached);
-		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
+		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start,
+				      sectorsize);
 		unlock_extent_cached(io_tree, start, end, &cached);
 
 		if (IS_ERR(em))
-- 
2.31.1

[PATCH v3 04/10] btrfs: defrag: introduce a new helper to collect target file extents

[Qu Wenruo]

Introduce a new helper, defrag_collect_targets(), to collect all
possible targets to be defraged.

This function will not consider things like max_sectors_to_defrag, thus
caller should be responsible to ensure we don't exceed the limit.

This function will be the first stage of later defrag rework.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 24b0dc1325d3..6af37a9e0738 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1372,6 +1372,126 @@ static int cluster_pages_for_defrag(struct inode *inode,
 
 }
 
+struct defrag_target_range {
+	struct list_head list;
+	u64 start;
+	u64 len;
+};
+
+/*
+ * Helper to collect all valid target extents.
+ *
+ * @start:	   The file offset to lookup
+ * @len:	   The length to lookup
+ * @extent_thresh: File extent size threshold, any extent size >= this value
+ * 		   will be ignored
+ * @newer_than:    Only defrag extents newer than this value
+ * @do_compress:   Whether the defrag is doing compression
+ * 		   If true, @extent_thresh will be ignored and all regular
+ * 		   file extents meeting @newer_than will be targets.
+ * @target_list:   The list of targets file extents
+ */
+static int defrag_collect_targets(struct btrfs_inode *inode,
+				  u64 start, u64 len, u32 extent_thresh,
+				  u64 newer_than, bool do_compress,
+				  struct list_head *target_list)
+{
+	u64 cur = start;
+	int ret = 0;
+
+	while (cur < start + len) {
+		struct extent_map *em;
+		struct defrag_target_range *new;
+		bool next_mergeable = true;
+		u64 range_len;
+
+		em = defrag_lookup_extent(&inode->vfs_inode, cur);
+		if (!em)
+			break;
+
+		/* Skip hole/inline/preallocated extents */
+		if (em->block_start >= EXTENT_MAP_LAST_BYTE ||
+		    test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
+			goto next;
+
+		/* Skip older extent */
+		if (em->generation < newer_than)
+			goto next;
+
+		/*
+		 * For do_compress case, we want to compress all valid file
+		 * extents, thus no @extent_thresh or mergable check.
+		 */
+		if (do_compress)
+			goto add;
+
+		/* Skip too large extent */
+		if (em->len >= extent_thresh)
+			goto next;
+
+		next_mergeable = defrag_check_next_extent(&inode->vfs_inode, em);
+		if (!next_mergeable) {
+			struct defrag_target_range *last;
+
+			/* Empty target list, no way to merge with last entry */
+			if (list_empty(target_list))
+				goto next;
+			last = list_entry(target_list->prev,
+					struct defrag_target_range, list);
+			/* Not mergable with last entry */
+			if (last->start + last->len != cur)
+				goto next;
+
+			/* Mergable, fall throught to add it to @target_list. */
+		}
+
+add:
+		range_len = min(extent_map_end(em), start + len) - cur;
+		/*
+		 * This one is a good target, check if it can be merged into
+		 * last range of the target list
+		 */
+		if (!list_empty(target_list)) {
+			struct defrag_target_range *last;
+
+			last = list_entry(target_list->prev,
+					struct defrag_target_range, list);
+			ASSERT(last->start + last->len <= cur);
+			if (last->start + last->len == cur) {
+				/* Mergable, enlarge the last entry */
+				last->len += range_len;
+				goto next;
+			}
+			/* Fall through to allocate a new entry */
+		}
+
+		/* Allocate new defrag_target_range */
+		new = kmalloc(sizeof(*new), GFP_NOFS);
+		if (!new) {
+			free_extent_map(em);
+			ret = -ENOMEM;
+			break;
+		}
+		new->start = cur;
+		new->len = range_len;
+		list_add_tail(&new->list, target_list);
+
+next:
+		cur = extent_map_end(em);
+		free_extent_map(em);
+	}
+	if (ret < 0) {
+		struct defrag_target_range *entry;
+		struct defrag_target_range *tmp;
+
+		list_for_each_entry_safe(entry, tmp, target_list, list) {
+			list_del_init(&entry->list);
+			kfree(entry);
+		}
+	}
+	return ret;
+}
+
 /*
  * Btrfs entrace for defrag.
  *
-- 
2.31.1

[PATCH v3 05/10] btrfs: defrag: introduce a helper to defrag a continuous prepared range

[Qu Wenruo]

A new helper, defrag_one_locked_target(), introduced to do the real part
of defrag.

The caller needs to ensure both page and extents bits are locked, and no
ordered extent for the range, and all writeback is finished.

The core defrag part is pretty straight-forward:

- Reserve space
- Set extent bits to defrag
- Update involved pages to be dirty

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6af37a9e0738..42e757dfdd7b 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -47,6 +47,7 @@
 #include "space-info.h"
 #include "delalloc-space.h"
 #include "block-group.h"
+#include "subpage.h"
 
 #ifdef CONFIG_64BIT
 /* If we have a 32-bit userspace and 64-bit kernel, then the UAPI
@@ -1492,6 +1493,61 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
 	return ret;
 }
 
+#define CLUSTER_SIZE	(SZ_256K)
+
+/*
+ * Defrag one continuous target range.
+ *
+ * @inode:	Target inode
+ * @target:	Target range to defrag
+ * @pages:	Locked pages covering the defrag range
+ * @nr_pages:	Number of locked pages
+ *
+ * Caller should ensure:
+ *
+ * - Pages are prepared
+ *   Pages should be locked, no ordered extent in the pages range,
+ *   no writeback.
+ *
+ * - Extent bits are locked
+ */
+static int defrag_one_locked_target(struct btrfs_inode *inode,
+				    struct defrag_target_range *target,
+				    struct page **pages, int nr_pages,
+				    struct extent_state **cached_state)
+{
+	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	struct extent_changeset *data_reserved = NULL;
+	const u64 start = target->start;
+	const u64 len = target->len;
+	unsigned long last_index = (start + len - 1) >> PAGE_SHIFT;
+	unsigned long start_index = start >> PAGE_SHIFT;
+	unsigned long first_index = page_index(pages[0]);
+	int ret = 0;
+	int i;
+
+	ASSERT(last_index - first_index + 1 <= nr_pages);
+
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, start, len);
+	if (ret < 0)
+		return ret;
+	clear_extent_bit(&inode->io_tree, start, start + len - 1,
+			 EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
+			 EXTENT_DEFRAG, 0, 0, cached_state);
+	set_extent_defrag(&inode->io_tree, start, start + len - 1,
+			  cached_state);
+
+	/* Update the page status */
+	for (i = start_index - first_index; i <= last_index - first_index;
+	     i++) {
+		ClearPageChecked(pages[i]);
+		btrfs_page_clamp_set_dirty(fs_info, pages[i], start, len);
+	}
+	btrfs_delalloc_release_extents(inode, len);
+	extent_changeset_free(data_reserved);
+	return ret;
+}
+
 /*
  * Btrfs entrace for defrag.
  *
-- 
2.31.1

[PATCH v3 06/10] btrfs: defrag: introduce a helper to defrag a range

[Qu Wenruo]

A new helper, defrag_one_range(), is introduced to defrag one range.

This function will mostly prepare the needed pages and extent status for
defrag_one_locked_target().

As we can only have a consistent view of extent map with page and
extent bits locked, we need to re-check the range passed in to get a
real target list for defrag_one_locked_target().

Since defrag_collect_targets() will call defrag_lookup_extent() and lock
extent range, we also need to teach those two functions to skip extent
lock.
Thus new parameter, @locked, is introruced to skip extent lock if the
caller has already locked the range.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 94 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 87 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 42e757dfdd7b..8259ad102469 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1033,7 +1033,8 @@ static int find_new_extents(struct btrfs_root *root,
 	return -ENOENT;
 }
 
-static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
+static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start,
+					       bool locked)
 {
 	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
@@ -1053,10 +1054,12 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
 		u64 end = start + sectorsize - 1;
 
 		/* get the big lock and read metadata off disk */
-		lock_extent_bits(io_tree, start, end, &cached);
+		if (!locked)
+			lock_extent_bits(io_tree, start, end, &cached);
 		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start,
 				      sectorsize);
-		unlock_extent_cached(io_tree, start, end, &cached);
+		if (!locked)
+			unlock_extent_cached(io_tree, start, end, &cached);
 
 		if (IS_ERR(em))
 			return NULL;
@@ -1074,7 +1077,7 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
 	if (em->start + em->len >= i_size_read(inode))
 		return false;
 
-	next = defrag_lookup_extent(inode, em->start + em->len);
+	next = defrag_lookup_extent(inode, em->start + em->len, false);
 	if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE)
 		ret = false;
 	else if ((em->block_start + em->block_len == next->block_start) &&
@@ -1103,7 +1106,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
 
 	*skip = 0;
 
-	em = defrag_lookup_extent(inode, start);
+	em = defrag_lookup_extent(inode, start, false);
 	if (!em)
 		return 0;
 
@@ -1390,12 +1393,13 @@ struct defrag_target_range {
  * @do_compress:   Whether the defrag is doing compression
  * 		   If true, @extent_thresh will be ignored and all regular
  * 		   file extents meeting @newer_than will be targets.
+ * @locked:	   If the range has already hold extent lock
  * @target_list:   The list of targets file extents
  */
 static int defrag_collect_targets(struct btrfs_inode *inode,
 				  u64 start, u64 len, u32 extent_thresh,
 				  u64 newer_than, bool do_compress,
-				  struct list_head *target_list)
+				  bool locked, struct list_head *target_list)
 {
 	u64 cur = start;
 	int ret = 0;
@@ -1406,7 +1410,7 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
 		bool next_mergeable = true;
 		u64 range_len;
 
-		em = defrag_lookup_extent(&inode->vfs_inode, cur);
+		em = defrag_lookup_extent(&inode->vfs_inode, cur, locked);
 		if (!em)
 			break;
 
@@ -1548,6 +1552,82 @@ static int defrag_one_locked_target(struct btrfs_inode *inode,
 	return ret;
 }
 
+static int defrag_one_range(struct btrfs_inode *inode,
+			    u64 start, u32 len,
+			    u32 extent_thresh, u64 newer_than,
+			    bool do_compress)
+{
+	struct extent_state *cached_state = NULL;
+	struct defrag_target_range *entry;
+	struct defrag_target_range *tmp;
+	LIST_HEAD(target_list);
+	struct page **pages;
+	const u32 sectorsize = inode->root->fs_info->sectorsize;
+	unsigned long last_index = (start + len - 1) >> PAGE_SHIFT;
+	unsigned long start_index = start >> PAGE_SHIFT;
+	unsigned int nr_pages = last_index - start_index + 1;
+	int ret = 0;
+	int i;
+
+	ASSERT(nr_pages <= CLUSTER_SIZE / PAGE_SIZE);
+	ASSERT(IS_ALIGNED(start, sectorsize) && IS_ALIGNED(len, sectorsize));
+
+	pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS);
+	if (!pages)
+		return -ENOMEM;
+
+	/* Prepare all pages */
+	for (i = 0; i < nr_pages; i++) {
+		pages[i] = defrag_prepare_one_page(inode, start_index + i);
+		if (IS_ERR(pages[i])) {
+			ret = PTR_ERR(pages[i]);
+			pages[i] = NULL;
+			goto free_pages;
+		}
+	}
+	/* Also lock the pages range */
+	lock_extent_bits(&inode->io_tree, start_index << PAGE_SHIFT,
+			 (last_index << PAGE_SHIFT) + PAGE_SIZE - 1,
+			 &cached_state);
+	/*
+	 * Now we have a consistent view about the extent map, re-check
+	 * which range really need to be defraged.
+	 *
+	 * And this time we have extent locked already, pass @locked = true
+	 * so that we won't re-lock the extent range and cause deadlock.
+	 */
+	ret = defrag_collect_targets(inode, start, len, extent_thresh,
+				     newer_than, do_compress, true,
+				     &target_list);
+	if (ret < 0)
+		goto unlock_extent;
+
+	list_for_each_entry(entry, &target_list, list) {
+		ret = defrag_one_locked_target(inode, entry, pages, nr_pages,
+					       &cached_state);
+		if (ret < 0)
+			break;
+	}
+
+	list_for_each_entry_safe(entry, tmp, &target_list, list) {
+		list_del_init(&entry->list);
+		kfree(entry);
+	}
+unlock_extent:
+	unlock_extent_cached(&inode->io_tree, start_index << PAGE_SHIFT,
+			     (last_index << PAGE_SHIFT) + PAGE_SIZE - 1,
+			     &cached_state);
+free_pages:
+	for (i = 0; i < nr_pages; i++) {
+		if (pages[i]) {
+			unlock_page(pages[i]);
+			put_page(pages[i]);
+		}
+	}
+	kfree(pages);
+	return ret;
+}
+
 /*
  * Btrfs entrace for defrag.
  *
-- 
2.31.1

[PATCH v3 07/10] btrfs: defrag: introduce a new helper to defrag one cluster

[Qu Wenruo]

This new helper, defrag_one_cluster(), will defrag one cluster (at most
256K) by:

- Collect all initial targets

- Kick in readahead when possible

- Call defrag_one_range() on each initial target
  With some extra range clamping.

- Update @sectors_defraged parameter

This involves one behavior change, the defraged sectors accounting is
no longer as accurate as old behavior, as the initial targets are not
consistent.

We can have new holes punched inside the initial target, and we will
skip such holes later.
But the defraged sectors accounting doesn't need to be that accurate
anyway, thus I don't want to pass those extra accounting burden into
defrag_one_range().

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8259ad102469..cccecb5aec33 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1628,6 +1628,62 @@ static int defrag_one_range(struct btrfs_inode *inode,
 	return ret;
 }
 
+static int defrag_one_cluster(struct btrfs_inode *inode,
+			      struct file_ra_state *ra,
+			      u64 start, u32 len, u32 extent_thresh,
+			      u64 newer_than, bool do_compress,
+			      unsigned long *sectors_defraged,
+			      unsigned long max_sectors)
+{
+	const u32 sectorsize = inode->root->fs_info->sectorsize;
+	struct defrag_target_range *entry;
+	struct defrag_target_range *tmp;
+	LIST_HEAD(target_list);
+	int ret;
+
+	BUILD_BUG_ON(!IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE));
+	ret = defrag_collect_targets(inode, start, len, extent_thresh,
+				     newer_than, do_compress, false,
+				     &target_list);
+	if (ret < 0)
+		goto out;
+
+	list_for_each_entry(entry, &target_list, list) {
+		u32 range_len = entry->len;
+
+		/* Reached the limit */
+		if (max_sectors && max_sectors == *sectors_defraged)
+			break;
+
+		if (max_sectors)
+			range_len = min_t(u32, range_len,
+				(max_sectors - *sectors_defraged) * sectorsize);
+
+		if (ra)
+			page_cache_sync_readahead(inode->vfs_inode.i_mapping,
+				ra, NULL, entry->start >> PAGE_SHIFT,
+				((entry->start + range_len - 1) >> PAGE_SHIFT) -
+				(entry->start >> PAGE_SHIFT) + 1);
+		/*
+		 * Here we may not defrag any range if holes are punched before
+		 * we locked the pages.
+		 * But that's fine, it only affects the @sectors_defraged
+		 * accounting.
+		 */
+		ret = defrag_one_range(inode, entry->start, range_len,
+					extent_thresh, newer_than, do_compress);
+		if (ret < 0)
+			break;
+		*sectors_defraged += range_len;
+	}
+out:
+	list_for_each_entry_safe(entry, tmp, &target_list, list) {
+		list_del_init(&entry->list);
+		kfree(entry);
+	}
+	return ret;
+}
+
 /*
  * Btrfs entrace for defrag.
  *
-- 
2.31.1

[PATCH v3 08/10] btrfs: defrag: use defrag_one_cluster() to implement btrfs_defrag_file()

[Qu Wenruo]

The function defrag_one_cluster() is able to defrag one range well
enough, we only need to do prepration for it, including:

- Clamp and align the defrag range
- Exclude invalid cases
- Proper inode locking

The old infrastructures will not be removed in this patch, as it would
be too noisy to review.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 219 ++++++++++++++---------------------------------
 1 file changed, 63 insertions(+), 156 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index cccecb5aec33..709e2d23b74d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1699,25 +1699,15 @@ int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
 		      u64 newer_than, unsigned long max_to_defrag)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	unsigned long last_index;
+	unsigned long sectors_defraged = 0;
 	u64 isize = i_size_read(inode);
-	u64 last_len = 0;
-	u64 skip = 0;
-	u64 defrag_end = 0;
-	u64 newer_off = range->start;
-	unsigned long i;
-	unsigned long ra_index = 0;
-	int ret;
-	int defrag_count = 0;
-	int compress_type = BTRFS_COMPRESS_ZLIB;
-	u32 extent_thresh = range->extent_thresh;
-	unsigned long max_cluster = SZ_256K >> PAGE_SHIFT;
-	unsigned long cluster = max_cluster;
-	u64 new_align = ~((u64)SZ_128K - 1);
-	struct page **pages = NULL;
+	u64 cur;
+	u64 last_byte;
 	bool do_compress = range->flags & BTRFS_DEFRAG_RANGE_COMPRESS;
 	bool ra_allocated = false;
+	int compress_type = BTRFS_COMPRESS_ZLIB;
+	int ret;
+	u32 extent_thresh = range->extent_thresh;
 
 	if (isize == 0)
 		return 0;
@@ -1735,6 +1725,14 @@ int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
 	if (extent_thresh == 0)
 		extent_thresh = SZ_256K;
 
+	if (range->start + range->len > range->start) {
+		/* Got a specific range */
+		last_byte = min(isize, range->start + range->len) - 1;
+	} else {
+		/* Defrag until file end */
+		last_byte = isize - 1;
+	}
+
 	/*
 	 * If we were not given a ra, allocate a readahead context. As
 	 * readahead is just an optimization, defrag will work without it so
@@ -1747,159 +1745,68 @@ int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
 			file_ra_state_init(ra, inode->i_mapping);
 	}
 
-	pages = kmalloc_array(max_cluster, sizeof(struct page *), GFP_KERNEL);
-	if (!pages) {
-		ret = -ENOMEM;
-		goto out_ra;
-	}
+	/* Align the range */
+	cur = round_down(range->start, fs_info->sectorsize);
+	last_byte = round_up(last_byte, fs_info->sectorsize) - 1;
 
-	/* find the last page to defrag */
-	if (range->start + range->len > range->start) {
-		last_index = min_t(u64, isize - 1,
-			 range->start + range->len - 1) >> PAGE_SHIFT;
-	} else {
-		last_index = (isize - 1) >> PAGE_SHIFT;
-	}
+	while (cur < last_byte) {
+		u64 cluster_end;
 
-	if (newer_than) {
-		ret = find_new_extents(root, inode, newer_than,
-				       &newer_off, SZ_64K);
-		if (!ret) {
-			range->start = newer_off;
-			/*
-			 * we always align our defrag to help keep
-			 * the extents in the file evenly spaced
-			 */
-			i = (newer_off & new_align) >> PAGE_SHIFT;
-		} else
-			goto out_ra;
-	} else {
-		i = range->start >> PAGE_SHIFT;
-	}
-	if (!max_to_defrag)
-		max_to_defrag = last_index - i + 1;
-
-	/*
-	 * make writeback starts from i, so the defrag range can be
-	 * written sequentially.
-	 */
-	if (i < inode->i_mapping->writeback_index)
-		inode->i_mapping->writeback_index = i;
-
-	while (i <= last_index && defrag_count < max_to_defrag &&
-	       (i < DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE))) {
-		/*
-		 * make sure we stop running if someone unmounts
-		 * the FS
-		 */
-		if (!(inode->i_sb->s_flags & SB_ACTIVE))
-			break;
+		/* The cluster size 256K should always be page aligned */
+		BUILD_BUG_ON(!IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE));
 
-		if (btrfs_defrag_cancelled(fs_info)) {
-			btrfs_debug(fs_info, "defrag_file cancelled");
-			ret = -EAGAIN;
-			goto error;
-		}
-
-		if (!should_defrag_range(inode, (u64)i << PAGE_SHIFT,
-					 extent_thresh, &last_len, &skip,
-					 &defrag_end, do_compress)){
-			unsigned long next;
-			/*
-			 * the should_defrag function tells us how much to skip
-			 * bump our counter by the suggested amount
-			 */
-			next = DIV_ROUND_UP(skip, PAGE_SIZE);
-			i = max(i + 1, next);
-			continue;
-		}
-
-		if (!newer_than) {
-			cluster = (PAGE_ALIGN(defrag_end) >>
-				   PAGE_SHIFT) - i;
-			cluster = min(cluster, max_cluster);
-		} else {
-			cluster = max_cluster;
-		}
+		/* We want the cluster ends at page boundary when possible */
+		cluster_end = (((cur >> PAGE_SHIFT) +
+			       (SZ_256K >> PAGE_SHIFT)) << PAGE_SHIFT) - 1;
+		cluster_end = min(cluster_end, last_byte);
 
-		if (i + cluster > ra_index) {
-			ra_index = max(i, ra_index);
-			if (ra)
-				page_cache_sync_readahead(inode->i_mapping, ra,
-						NULL, ra_index, cluster);
-			ra_index += cluster;
-		}
-
-		btrfs_inode_lock(inode, 0);
-		if (IS_SWAPFILE(inode)) {
+ 		btrfs_inode_lock(inode, 0);
+ 		if (IS_SWAPFILE(inode)) {
 			ret = -ETXTBSY;
-		} else {
-			if (do_compress)
-				BTRFS_I(inode)->defrag_compress = compress_type;
-			ret = cluster_pages_for_defrag(inode, pages, i, cluster);
+			btrfs_inode_unlock(inode, 0);
+			break;
 		}
-		if (ret < 0) {
+		if (!(inode->i_sb->s_flags & SB_ACTIVE)) {
 			btrfs_inode_unlock(inode, 0);
-			goto out_ra;
+			break;
 		}
-
-		defrag_count += ret;
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		if (do_compress)
+			BTRFS_I(inode)->defrag_compress = compress_type;
+		ret = defrag_one_cluster(BTRFS_I(inode), ra, cur,
+				cluster_end + 1 - cur, extent_thresh,
+				newer_than, do_compress,
+				&sectors_defraged, max_to_defrag);
 		btrfs_inode_unlock(inode, 0);
-
-		if (newer_than) {
-			if (newer_off == (u64)-1)
-				break;
-
-			if (ret > 0)
-				i += ret;
-
-			newer_off = max(newer_off + 1,
-					(u64)i << PAGE_SHIFT);
-
-			ret = find_new_extents(root, inode, newer_than,
-					       &newer_off, SZ_64K);
-			if (!ret) {
-				range->start = newer_off;
-				i = (newer_off & new_align) >> PAGE_SHIFT;
-			} else {
-				break;
-			}
-		} else {
-			if (ret > 0) {
-				i += ret;
-				last_len += ret << PAGE_SHIFT;
-			} else {
-				i++;
-				last_len = 0;
-			}
-		}
-	}
-
-	ret = defrag_count;
-error:
-	if ((range->flags & BTRFS_DEFRAG_RANGE_START_IO)) {
-		filemap_flush(inode->i_mapping);
-		if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
-			     &BTRFS_I(inode)->runtime_flags))
-			filemap_flush(inode->i_mapping);
-	}
-
-	if (range->compress_type == BTRFS_COMPRESS_LZO) {
-		btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
-	} else if (range->compress_type == BTRFS_COMPRESS_ZSTD) {
-		btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
+		if (ret < 0)
+			break;
+		cur = cluster_end + 1;
 	}
 
-out_ra:
-	if (do_compress) {
-		btrfs_inode_lock(inode, 0);
-		BTRFS_I(inode)->defrag_compress = BTRFS_COMPRESS_NONE;
-		btrfs_inode_unlock(inode, 0);
-	}
 	if (ra_allocated)
 		kfree(ra);
-	kfree(pages);
+	if (sectors_defraged) {
+		/*
+		 * We have defraged some sectors, for compression case
+		 * they need to be written back immediately.
+		 */
+		if (range->flags & BTRFS_DEFRAG_RANGE_START_IO) {
+			filemap_flush(inode->i_mapping);
+			if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
+				     &BTRFS_I(inode)->runtime_flags))
+				filemap_flush(inode->i_mapping);
+		}
+		if (range->compress_type == BTRFS_COMPRESS_LZO) {
+			btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
+		} else if (range->compress_type == BTRFS_COMPRESS_ZSTD) {
+			btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
+		}
+		ret = sectors_defraged;
+ 	}
+ 	if (do_compress) {
+ 		btrfs_inode_lock(inode, 0);
+ 		BTRFS_I(inode)->defrag_compress = BTRFS_COMPRESS_NONE;
+ 		btrfs_inode_unlock(inode, 0);
+ 	}
 	return ret;
 }
 
-- 
2.31.1

[PATCH v3 09/10] btrfs: defrag: remove the old infrastructure

[Qu Wenruo]

Now the old infrastructure can all be removed.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 305 -----------------------------------------------
 1 file changed, 305 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 709e2d23b74d..6de1293da45f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -933,106 +933,6 @@ static noinline int btrfs_mksnapshot(const struct path *parent,
 	return ret;
 }
 
-/*
- * When we're defragging a range, we don't want to kick it off again
- * if it is really just waiting for delalloc to send it down.
- * If we find a nice big extent or delalloc range for the bytes in the
- * file you want to defrag, we return 0 to let you know to skip this
- * part of the file
- */
-static int check_defrag_in_cache(struct inode *inode, u64 offset, u32 thresh)
-{
-	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
-	struct extent_map *em = NULL;
-	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
-	u64 end;
-
-	read_lock(&em_tree->lock);
-	em = lookup_extent_mapping(em_tree, offset, PAGE_SIZE);
-	read_unlock(&em_tree->lock);
-
-	if (em) {
-		end = extent_map_end(em);
-		free_extent_map(em);
-		if (end - offset > thresh)
-			return 0;
-	}
-	/* if we already have a nice delalloc here, just stop */
-	thresh /= 2;
-	end = count_range_bits(io_tree, &offset, offset + thresh,
-			       thresh, EXTENT_DELALLOC, 1);
-	if (end >= thresh)
-		return 0;
-	return 1;
-}
-
-/*
- * helper function to walk through a file and find extents
- * newer than a specific transid, and smaller than thresh.
- *
- * This is used by the defragging code to find new and small
- * extents
- */
-static int find_new_extents(struct btrfs_root *root,
-			    struct inode *inode, u64 newer_than,
-			    u64 *off, u32 thresh)
-{
-	struct btrfs_path *path;
-	struct btrfs_key min_key;
-	struct extent_buffer *leaf;
-	struct btrfs_file_extent_item *extent;
-	int type;
-	int ret;
-	u64 ino = btrfs_ino(BTRFS_I(inode));
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	min_key.objectid = ino;
-	min_key.type = BTRFS_EXTENT_DATA_KEY;
-	min_key.offset = *off;
-
-	while (1) {
-		ret = btrfs_search_forward(root, &min_key, path, newer_than);
-		if (ret != 0)
-			goto none;
-process_slot:
-		if (min_key.objectid != ino)
-			goto none;
-		if (min_key.type != BTRFS_EXTENT_DATA_KEY)
-			goto none;
-
-		leaf = path->nodes[0];
-		extent = btrfs_item_ptr(leaf, path->slots[0],
-					struct btrfs_file_extent_item);
-
-		type = btrfs_file_extent_type(leaf, extent);
-		if (type == BTRFS_FILE_EXTENT_REG &&
-		    btrfs_file_extent_num_bytes(leaf, extent) < thresh &&
-		    check_defrag_in_cache(inode, min_key.offset, thresh)) {
-			*off = min_key.offset;
-			btrfs_free_path(path);
-			return 0;
-		}
-
-		path->slots[0]++;
-		if (path->slots[0] < btrfs_header_nritems(leaf)) {
-			btrfs_item_key_to_cpu(leaf, &min_key, path->slots[0]);
-			goto process_slot;
-		}
-
-		if (min_key.offset == (u64)-1)
-			goto none;
-
-		min_key.offset++;
-		btrfs_release_path(path);
-	}
-none:
-	btrfs_free_path(path);
-	return -ENOENT;
-}
-
 static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start,
 					       bool locked)
 {
@@ -1088,66 +988,6 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
 	return ret;
 }
 
-static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
-			       u64 *last_len, u64 *skip, u64 *defrag_end,
-			       int compress)
-{
-	struct extent_map *em;
-	int ret = 1;
-	bool next_mergeable = true;
-	bool prev_mergeable = true;
-
-	/*
-	 * make sure that once we start defragging an extent, we keep on
-	 * defragging it
-	 */
-	if (start < *defrag_end)
-		return 1;
-
-	*skip = 0;
-
-	em = defrag_lookup_extent(inode, start, false);
-	if (!em)
-		return 0;
-
-	/* this will cover holes, and inline extents */
-	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
-		ret = 0;
-		goto out;
-	}
-
-	if (!*defrag_end)
-		prev_mergeable = false;
-
-	next_mergeable = defrag_check_next_extent(inode, em);
-	/*
-	 * we hit a real extent, if it is big or the next extent is not a
-	 * real extent, don't bother defragging it
-	 */
-	if (!compress && (*last_len == 0 || *last_len >= thresh) &&
-	    (em->len >= thresh || (!next_mergeable && !prev_mergeable)))
-		ret = 0;
-out:
-	/*
-	 * last_len ends up being a counter of how many bytes we've defragged.
-	 * every time we choose not to defrag an extent, we reset *last_len
-	 * so that the next tiny extent will force a defrag.
-	 *
-	 * The end result of this is that tiny extents before a single big
-	 * extent will force at least part of that big extent to be defragged.
-	 */
-	if (ret) {
-		*defrag_end = extent_map_end(em);
-	} else {
-		*last_len = 0;
-		*skip = extent_map_end(em);
-		*defrag_end = 0;
-	}
-
-	free_extent_map(em);
-	return ret;
-}
-
 /*
  * Prepare one page to be defraged.
  *
@@ -1231,151 +1071,6 @@ static struct page *defrag_prepare_one_page(struct btrfs_inode *inode,
 	return page;
 }
 
-/*
- * it doesn't do much good to defrag one or two pages
- * at a time.  This pulls in a nice chunk of pages
- * to COW and defrag.
- *
- * It also makes sure the delalloc code has enough
- * dirty data to avoid making new small extents as part
- * of the defrag
- *
- * It's a good idea to start RA on this range
- * before calling this.
- */
-static int cluster_pages_for_defrag(struct inode *inode,
-				    struct page **pages,
-				    unsigned long start_index,
-				    unsigned long num_pages)
-{
-	unsigned long file_end;
-	u64 isize = i_size_read(inode);
-	u64 page_start;
-	u64 page_end;
-	u64 page_cnt;
-	u64 start = (u64)start_index << PAGE_SHIFT;
-	u64 search_start;
-	int ret;
-	int i;
-	int i_done;
-	struct extent_state *cached_state = NULL;
-	struct extent_changeset *data_reserved = NULL;
-
-	file_end = (isize - 1) >> PAGE_SHIFT;
-	if (!isize || start_index > file_end)
-		return 0;
-
-	page_cnt = min_t(u64, (u64)num_pages, (u64)file_end - start_index + 1);
-
-	ret = btrfs_delalloc_reserve_space(BTRFS_I(inode), &data_reserved,
-			start, page_cnt << PAGE_SHIFT);
-	if (ret)
-		return ret;
-	i_done = 0;
-
-	/* step one, lock all the pages */
-	for (i = 0; i < page_cnt; i++) {
-		struct page *page;
-
-		page = defrag_prepare_one_page(BTRFS_I(inode), start_index + i);
-		if (IS_ERR(page)) {
-			ret = PTR_ERR(page);
-			break;
-		}
-		pages[i] = page;
-		i_done++;
-	}
-	if (!i_done || ret)
-		goto out;
-
-	if (!(inode->i_sb->s_flags & SB_ACTIVE))
-		goto out;
-
-	page_start = page_offset(pages[0]);
-	page_end = page_offset(pages[i_done - 1]) + PAGE_SIZE;
-
-	lock_extent_bits(&BTRFS_I(inode)->io_tree,
-			 page_start, page_end - 1, &cached_state);
-
-	/*
-	 * When defragmenting we skip ranges that have holes or inline extents,
-	 * (check should_defrag_range()), to avoid unnecessary IO and wasting
-	 * space. At btrfs_defrag_file(), we check if a range should be defragged
-	 * before locking the inode and then, if it should, we trigger a sync
-	 * page cache readahead - we lock the inode only after that to avoid
-	 * blocking for too long other tasks that possibly want to operate on
-	 * other file ranges. But before we were able to get the inode lock,
-	 * some other task may have punched a hole in the range, or we may have
-	 * now an inline extent, in which case we should not defrag. So check
-	 * for that here, where we have the inode and the range locked, and bail
-	 * out if that happened.
-	 */
-	search_start = page_start;
-	while (search_start < page_end) {
-		struct extent_map *em;
-
-		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, search_start,
-				      page_end - search_start);
-		if (IS_ERR(em)) {
-			ret = PTR_ERR(em);
-			goto out_unlock_range;
-		}
-		if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
-			free_extent_map(em);
-			/* Ok, 0 means we did not defrag anything */
-			ret = 0;
-			goto out_unlock_range;
-		}
-		search_start = extent_map_end(em);
-		free_extent_map(em);
-	}
-
-	clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start,
-			  page_end - 1, EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
-			  EXTENT_DEFRAG, 0, 0, &cached_state);
-
-	if (i_done != page_cnt) {
-		spin_lock(&BTRFS_I(inode)->lock);
-		btrfs_mod_outstanding_extents(BTRFS_I(inode), 1);
-		spin_unlock(&BTRFS_I(inode)->lock);
-		btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved,
-				start, (page_cnt - i_done) << PAGE_SHIFT, true);
-	}
-
-
-	set_extent_defrag(&BTRFS_I(inode)->io_tree, page_start, page_end - 1,
-			  &cached_state);
-
-	unlock_extent_cached(&BTRFS_I(inode)->io_tree,
-			     page_start, page_end - 1, &cached_state);
-
-	for (i = 0; i < i_done; i++) {
-		clear_page_dirty_for_io(pages[i]);
-		ClearPageChecked(pages[i]);
-		set_page_dirty(pages[i]);
-		unlock_page(pages[i]);
-		put_page(pages[i]);
-	}
-	btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT);
-	extent_changeset_free(data_reserved);
-	return i_done;
-
-out_unlock_range:
-	unlock_extent_cached(&BTRFS_I(inode)->io_tree,
-			     page_start, page_end - 1, &cached_state);
-out:
-	for (i = 0; i < i_done; i++) {
-		unlock_page(pages[i]);
-		put_page(pages[i]);
-	}
-	btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved,
-			start, page_cnt << PAGE_SHIFT, true);
-	btrfs_delalloc_release_extents(BTRFS_I(inode), page_cnt << PAGE_SHIFT);
-	extent_changeset_free(data_reserved);
-	return ret;
-
-}
-
 struct defrag_target_range {
 	struct list_head list;
 	u64 start;
-- 
2.31.1

[PATCH v3 10/10] btrfs: defrag: enable defrag for subpage case

[Qu Wenruo]

With the new infrasturture which has taken subpage into consideration,
now we should be safe to allow defrag to work for subpage case.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ioctl.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6de1293da45f..dd0a633cec8d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2973,12 +2973,6 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 		goto out;
 	}
 
-	/* Subpage defrag will be supported in later commits */
-	if (root->fs_info->sectorsize < PAGE_SIZE) {
-		ret = -ENOTTY;
-		goto out;
-	}
-
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFDIR:
 		if (!capable(CAP_SYS_ADMIN)) {
-- 
2.31.1

Re: [PATCH v3 06/10] btrfs: defrag: introduce a helper to defrag a range

[Qu Wenruo]

On 2021/6/8 上午10:59, Qu Wenruo wrote:
> A new helper, defrag_one_range(), is introduced to defrag one range.
> 
> This function will mostly prepare the needed pages and extent status for
> defrag_one_locked_target().
> 
> As we can only have a consistent view of extent map with page and
> extent bits locked, we need to re-check the range passed in to get a
> real target list for defrag_one_locked_target().
> 
> Since defrag_collect_targets() will call defrag_lookup_extent() and lock
> extent range, we also need to teach those two functions to skip extent
> lock.
> Thus new parameter, @locked, is introruced to skip extent lock if the
> caller has already locked the range.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>   fs/btrfs/ioctl.c | 94 ++++++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 87 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 42e757dfdd7b..8259ad102469 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1033,7 +1033,8 @@ static int find_new_extents(struct btrfs_root *root,
>   	return -ENOENT;
>   }
>   
> -static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
> +static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start,
> +					       bool locked)
>   {
>   	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
>   	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
> @@ -1053,10 +1054,12 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
>   		u64 end = start + sectorsize - 1;
>   
>   		/* get the big lock and read metadata off disk */
> -		lock_extent_bits(io_tree, start, end, &cached);
> +		if (!locked)
> +			lock_extent_bits(io_tree, start, end, &cached);
>   		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start,
>   				      sectorsize);
> -		unlock_extent_cached(io_tree, start, end, &cached);
> +		if (!locked)
> +			unlock_extent_cached(io_tree, start, end, &cached);
>   
>   		if (IS_ERR(em))
>   			return NULL;
> @@ -1074,7 +1077,7 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
>   	if (em->start + em->len >= i_size_read(inode))
>   		return false;
>   
> -	next = defrag_lookup_extent(inode, em->start + em->len);
> +	next = defrag_lookup_extent(inode, em->start + em->len, false);

Here the fixed false parameter is causing another hang.

As defrag_check_next_extent() can be called inside 
defrag_collect_targets(), which can be called with extent locked.

Will fix it in next update.

Thanks,
Qu

>   	if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE)
>   		ret = false;
>   	else if ((em->block_start + em->block_len == next->block_start) &&
> @@ -1103,7 +1106,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
>   
>   	*skip = 0;
>   
> -	em = defrag_lookup_extent(inode, start);
> +	em = defrag_lookup_extent(inode, start, false);
>   	if (!em)
>   		return 0;
>   
> @@ -1390,12 +1393,13 @@ struct defrag_target_range {
>    * @do_compress:   Whether the defrag is doing compression
>    * 		   If true, @extent_thresh will be ignored and all regular
>    * 		   file extents meeting @newer_than will be targets.
> + * @locked:	   If the range has already hold extent lock
>    * @target_list:   The list of targets file extents
>    */
>   static int defrag_collect_targets(struct btrfs_inode *inode,
>   				  u64 start, u64 len, u32 extent_thresh,
>   				  u64 newer_than, bool do_compress,
> -				  struct list_head *target_list)
> +				  bool locked, struct list_head *target_list)
>   {
>   	u64 cur = start;
>   	int ret = 0;
> @@ -1406,7 +1410,7 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
>   		bool next_mergeable = true;
>   		u64 range_len;
>   
> -		em = defrag_lookup_extent(&inode->vfs_inode, cur);
> +		em = defrag_lookup_extent(&inode->vfs_inode, cur, locked);
>   		if (!em)
>   			break;
>   
> @@ -1548,6 +1552,82 @@ static int defrag_one_locked_target(struct btrfs_inode *inode,
>   	return ret;
>   }
>   
> +static int defrag_one_range(struct btrfs_inode *inode,
> +			    u64 start, u32 len,
> +			    u32 extent_thresh, u64 newer_than,
> +			    bool do_compress)
> +{
> +	struct extent_state *cached_state = NULL;
> +	struct defrag_target_range *entry;
> +	struct defrag_target_range *tmp;
> +	LIST_HEAD(target_list);
> +	struct page **pages;
> +	const u32 sectorsize = inode->root->fs_info->sectorsize;
> +	unsigned long last_index = (start + len - 1) >> PAGE_SHIFT;
> +	unsigned long start_index = start >> PAGE_SHIFT;
> +	unsigned int nr_pages = last_index - start_index + 1;
> +	int ret = 0;
> +	int i;
> +
> +	ASSERT(nr_pages <= CLUSTER_SIZE / PAGE_SIZE);
> +	ASSERT(IS_ALIGNED(start, sectorsize) && IS_ALIGNED(len, sectorsize));
> +
> +	pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS);
> +	if (!pages)
> +		return -ENOMEM;
> +
> +	/* Prepare all pages */
> +	for (i = 0; i < nr_pages; i++) {
> +		pages[i] = defrag_prepare_one_page(inode, start_index + i);
> +		if (IS_ERR(pages[i])) {
> +			ret = PTR_ERR(pages[i]);
> +			pages[i] = NULL;
> +			goto free_pages;
> +		}
> +	}
> +	/* Also lock the pages range */
> +	lock_extent_bits(&inode->io_tree, start_index << PAGE_SHIFT,
> +			 (last_index << PAGE_SHIFT) + PAGE_SIZE - 1,
> +			 &cached_state);
> +	/*
> +	 * Now we have a consistent view about the extent map, re-check
> +	 * which range really need to be defraged.
> +	 *
> +	 * And this time we have extent locked already, pass @locked = true
> +	 * so that we won't re-lock the extent range and cause deadlock.
> +	 */
> +	ret = defrag_collect_targets(inode, start, len, extent_thresh,
> +				     newer_than, do_compress, true,
> +				     &target_list);
> +	if (ret < 0)
> +		goto unlock_extent;
> +
> +	list_for_each_entry(entry, &target_list, list) {
> +		ret = defrag_one_locked_target(inode, entry, pages, nr_pages,
> +					       &cached_state);
> +		if (ret < 0)
> +			break;
> +	}
> +
> +	list_for_each_entry_safe(entry, tmp, &target_list, list) {
> +		list_del_init(&entry->list);
> +		kfree(entry);
> +	}
> +unlock_extent:
> +	unlock_extent_cached(&inode->io_tree, start_index << PAGE_SHIFT,
> +			     (last_index << PAGE_SHIFT) + PAGE_SIZE - 1,
> +			     &cached_state);
> +free_pages:
> +	for (i = 0; i < nr_pages; i++) {
> +		if (pages[i]) {
> +			unlock_page(pages[i]);
> +			put_page(pages[i]);
> +		}
> +	}
> +	kfree(pages);
> +	return ret;
> +}
> +
>   /*
>    * Btrfs entrace for defrag.
>    *
> 

Re: [PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[David Sterba]

On Tue, Jun 08, 2021 at 10:59:17AM +0800, Qu Wenruo wrote:
> This branch is based on subpage RW branch, as the last patch needs to
> enable defrag support for subpage cases.
> 
> But despite that one, all other patches can be applied on current
> misc-next.
> 
> [BACKGROUND]
> In subpage rw branch, we disable defrag completely due to the fact that
> current code can only work on page basis.
> 
> This could lead to problems like btrfs/062 crash.
> 
> Thus this patchset will make defrag to work on both regular and subpage
> sectorsize.
> 
> [SOLUTION]
> To defrag a file range, what we do is pretty much like buffered write,
> except we don't really write any new data to page cache, but just mark
> the range dirty.
> 
> Then let later writeback to merge the range into a larger extent.
> 
> But current defrag code is working on per-page basis, not per-sector,
> thus we have to refactor it a little to make it to work properly for
> subpage.
> 
> This patch will separate the code into 3 layers:
> Layer 0:	btrfs_defrag_file()
> 		The defrag entrace
> 		Just do proper inode lock and split the file into
> 		page aligned 256K clusters to defrag
> 
> Layer 1:	defrag_one_cluster()
> 		Will collect the initial targets file extents, and pass
> 		each continuous target to defrag_one_range()
> 
> Layer 2:	defrag_one_range()
> 		Will prepare the needed page and extent locking.
> 		Then re-check the range for real target list, as initial
> 		target list is not consistent as it doesn't hage
> 		page/extent locking to prevent hole punching.
> 
> Layer 3:	defrag_one_locked_target()
> 		The real work, to make the extent range defrag and
> 		update involved page status
> 
> [BEHAVIOR CHANGE]
> In the refactor, there is one behavior change:
> 
> - Defraged sector counter is based on the initial target list
>   This is mostly to avoid the paremters to be passed too deep into
>   defrag_one_locked_target().
>   Considering the accounting is not that important, we can afford some
>   difference.

As you're going to resend, please fix all occurences of 'defraged' to
'defragged'.

I'll give the patchset some testing bug am not sure if it isn't too
risky to put it to the 5.14 queue as it's about time to do only safe
changes.

Re: [PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[Neal Gompa]

On Wed, Jun 9, 2021 at 12:23 PM David Sterba <dsterba@suse.cz> wrote:
>
> On Tue, Jun 08, 2021 at 10:59:17AM +0800, Qu Wenruo wrote:
> > This branch is based on subpage RW branch, as the last patch needs to
> > enable defrag support for subpage cases.
> >
> > But despite that one, all other patches can be applied on current
> > misc-next.
> >
> > [BACKGROUND]
> > In subpage rw branch, we disable defrag completely due to the fact that
> > current code can only work on page basis.
> >
> > This could lead to problems like btrfs/062 crash.
> >
> > Thus this patchset will make defrag to work on both regular and subpage
> > sectorsize.
> >
> > [SOLUTION]
> > To defrag a file range, what we do is pretty much like buffered write,
> > except we don't really write any new data to page cache, but just mark
> > the range dirty.
> >
> > Then let later writeback to merge the range into a larger extent.
> >
> > But current defrag code is working on per-page basis, not per-sector,
> > thus we have to refactor it a little to make it to work properly for
> > subpage.
> >
> > This patch will separate the code into 3 layers:
> > Layer 0:      btrfs_defrag_file()
> >               The defrag entrace
> >               Just do proper inode lock and split the file into
> >               page aligned 256K clusters to defrag
> >
> > Layer 1:      defrag_one_cluster()
> >               Will collect the initial targets file extents, and pass
> >               each continuous target to defrag_one_range()
> >
> > Layer 2:      defrag_one_range()
> >               Will prepare the needed page and extent locking.
> >               Then re-check the range for real target list, as initial
> >               target list is not consistent as it doesn't hage
> >               page/extent locking to prevent hole punching.
> >
> > Layer 3:      defrag_one_locked_target()
> >               The real work, to make the extent range defrag and
> >               update involved page status
> >
> > [BEHAVIOR CHANGE]
> > In the refactor, there is one behavior change:
> >
> > - Defraged sector counter is based on the initial target list
> >   This is mostly to avoid the paremters to be passed too deep into
> >   defrag_one_locked_target().
> >   Considering the accounting is not that important, we can afford some
> >   difference.
>
> As you're going to resend, please fix all occurences of 'defraged' to
> 'defragged'.
>
> I'll give the patchset some testing bug am not sure if it isn't too
> risky to put it to the 5.14 queue as it's about time to do only safe
> changes.

This patch set makes it possible to do compression and balance in
subpage cases, right? At least, that's what I understood of it (defrag
code is used for balance and compression...).


-- 
真実はいつも一つ！/ Always, there's only one truth!

Re: [PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[David Sterba]

On Wed, Jun 09, 2021 at 06:48:31PM -0400, Neal Gompa wrote:
> On Wed, Jun 9, 2021 at 12:23 PM David Sterba <dsterba@suse.cz> wrote:
> > On Tue, Jun 08, 2021 at 10:59:17AM +0800, Qu Wenruo wrote:
> > > [BEHAVIOR CHANGE]
> > > In the refactor, there is one behavior change:
> > >
> > > - Defraged sector counter is based on the initial target list
> > >   This is mostly to avoid the paremters to be passed too deep into
> > >   defrag_one_locked_target().
> > >   Considering the accounting is not that important, we can afford some
> > >   difference.
> >
> > As you're going to resend, please fix all occurences of 'defraged' to
> > 'defragged'.
> >
> > I'll give the patchset some testing bug am not sure if it isn't too
> > risky to put it to the 5.14 queue as it's about time to do only safe
> > changes.
> 
> This patch set makes it possible to do compression and balance in
> subpage cases, right? At least, that's what I understood of it (defrag
> code is used for balance and compression...).

No it's just to do defragmentation in subpage case. Defrag and balance
code are indpendent, and only defrag can do compression, balance just
moves chunks of data but does not do changes to the data itself (it
could write them in a different way eg. the stripes or copies).

Re: [PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[Qu Wenruo]

On 2021/6/9 下午11:26, David Sterba wrote:
> On Tue, Jun 08, 2021 at 10:59:17AM +0800, Qu Wenruo wrote:
>> This branch is based on subpage RW branch, as the last patch needs to
>> enable defrag support for subpage cases.
>>
>> But despite that one, all other patches can be applied on current
>> misc-next.
>>
>> [BACKGROUND]
>> In subpage rw branch, we disable defrag completely due to the fact that
>> current code can only work on page basis.
>>
>> This could lead to problems like btrfs/062 crash.
>>
>> Thus this patchset will make defrag to work on both regular and subpage
>> sectorsize.
>>
>> [SOLUTION]
>> To defrag a file range, what we do is pretty much like buffered write,
>> except we don't really write any new data to page cache, but just mark
>> the range dirty.
>>
>> Then let later writeback to merge the range into a larger extent.
>>
>> But current defrag code is working on per-page basis, not per-sector,
>> thus we have to refactor it a little to make it to work properly for
>> subpage.
>>
>> This patch will separate the code into 3 layers:
>> Layer 0:	btrfs_defrag_file()
>> 		The defrag entrace
>> 		Just do proper inode lock and split the file into
>> 		page aligned 256K clusters to defrag
>>
>> Layer 1:	defrag_one_cluster()
>> 		Will collect the initial targets file extents, and pass
>> 		each continuous target to defrag_one_range()
>>
>> Layer 2:	defrag_one_range()
>> 		Will prepare the needed page and extent locking.
>> 		Then re-check the range for real target list, as initial
>> 		target list is not consistent as it doesn't hage
>> 		page/extent locking to prevent hole punching.
>>
>> Layer 3:	defrag_one_locked_target()
>> 		The real work, to make the extent range defrag and
>> 		update involved page status
>>
>> [BEHAVIOR CHANGE]
>> In the refactor, there is one behavior change:
>>
>> - Defraged sector counter is based on the initial target list
>>    This is mostly to avoid the paremters to be passed too deep into
>>    defrag_one_locked_target().
>>    Considering the accounting is not that important, we can afford some
>>    difference.
>
> As you're going to resend, please fix all occurences of 'defraged' to
> 'defragged'.
>
> I'll give the patchset some testing bug am not sure if it isn't too
> risky to put it to the 5.14 queue as it's about time to do only safe
> changes.
>

Please keep the branch out of the 5.14 queue.
It's safe to test, but I don't think the current test coverage is
acceptable enough for defrag.

The latest branch in my github is safe enough for now, but considering
how few test cases there are dedicated for defrag, and I'm not yet
convinced even the existing defrag code is safe.

Thanks,
Qu

Re: [PATCH v3 00/10] btrfs: defrag: rework to support sector perfect defrag

[Qu Wenruo]

On 2021/6/10 上午7:02, David Sterba wrote:
> On Wed, Jun 09, 2021 at 06:48:31PM -0400, Neal Gompa wrote:
>> On Wed, Jun 9, 2021 at 12:23 PM David Sterba <dsterba@suse.cz> wrote:
>>> On Tue, Jun 08, 2021 at 10:59:17AM +0800, Qu Wenruo wrote:
>>>> [BEHAVIOR CHANGE]
>>>> In the refactor, there is one behavior change:
>>>>
>>>> - Defraged sector counter is based on the initial target list
>>>>    This is mostly to avoid the paremters to be passed too deep into
>>>>    defrag_one_locked_target().
>>>>    Considering the accounting is not that important, we can afford some
>>>>    difference.
>>>
>>> As you're going to resend, please fix all occurences of 'defraged' to
>>> 'defragged'.
>>>
>>> I'll give the patchset some testing bug am not sure if it isn't too
>>> risky to put it to the 5.14 queue as it's about time to do only safe
>>> changes.
>>
>> This patch set makes it possible to do compression and balance in
>> subpage cases, right? At least, that's what I understood of it (defrag
>> code is used for balance and compression...).
>
> No it's just to do defragmentation in subpage case. Defrag and balance
> code are indpendent, and only defrag can do compression, balance just
> moves chunks of data but does not do changes to the data itself (it
> could write them in a different way eg. the stripes or copies).
>
Furthermore, defrag code doesn't do compression by itself.

The compression is done during writeback, defrag just tells writeback
code to do compression.

But for subpage enablement right now, compression is disabled
completely, thus no matter what setting you use, compression will not be
enabled.

Thanks,
Qu