[PATCH 2/2] Btrfs: fix reported number of inode blocks after buffered append writes

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

The patch from commit 7e3b975a0f92 ("Btrfs: fix reported number of inode
blocks") introduced a regression where if we do a buffered write starting
at position equal to or greater than the file's size and then stat(2) the
file before writeback is triggered, the number of used blocks does not
change (unless there's a prealloc/unwritten extent). Example:

  $ xfs_io -f -c "pwrite -S 0xab 0 64K" foobar
  $ du -h foobar
  0	foobar
  $ sync
  $ du -h foobar
  64K	foobar

The first version of that patch didn't had this regression and the second
version, which was the one committed, was made only to address some
performance regression detected by the intel test robots using fs_mark.

This fixes the regression by setting the new delaloc bit in the range, and
doing it at btrfs_dirty_pages() while setting the regular dealloc bit as
well, so that this way we set both bits at once avoiding navigation of the
inode's io tree twice. Doing it at btrfs_dirty_pages() is also the most
meaninful place, as we should set the new dellaloc bit when if we set the
delalloc bit, which happens only if we copied bytes into the pages at
__btrfs_buffered_write().

This was making some of LTP's du tests fail, which can be quickly run
using a command line like the following:

  $ ./runltp -q -p -l /ltp.log -f commands -s du -d /mnt

Fixes: 7e3b975a0f92 ("Btrfs: fix reported number of inode blocks")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/ctree.h                 |   1 +
 fs/btrfs/extent_io.h             |   5 +-
 fs/btrfs/file.c                  | 123 +++++++++++++++++++++------------------
 fs/btrfs/inode.c                 |   9 +--
 fs/btrfs/relocation.c            |   3 +-
 fs/btrfs/tests/extent-io-tests.c |   6 +-
 fs/btrfs/tests/inode-tests.c     |  12 ++--
 7 files changed, 86 insertions(+), 73 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8fc690384c58..51f1f3e31608 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3174,6 +3174,7 @@ int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput);
 int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int delay_iput,
 			       int nr);
 int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
+			      unsigned int extra_bits,
 			      struct extent_state **cached_state, int dedupe);
 int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root,
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index faffa28ba707..580a6c1c296c 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -365,10 +365,11 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		       struct extent_state **cached_state);
 
 static inline int set_extent_delalloc(struct extent_io_tree *tree, u64 start,
-		u64 end, struct extent_state **cached_state)
+				      u64 end, unsigned int extra_bits,
+				      struct extent_state **cached_state)
 {
 	return set_extent_bit(tree, start, end,
-			      EXTENT_DELALLOC | EXTENT_UPTODATE,
+			      EXTENT_DELALLOC | EXTENT_UPTODATE | extra_bits,
 			      NULL, cached_state, GFP_NOFS);
 }
 
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index aaab1838cece..bcac827d65f0 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -477,6 +477,47 @@ static void btrfs_drop_pages(struct page **pages, size_t num_pages)
 	}
 }
 
+static int btrfs_find_new_delalloc_bytes(struct btrfs_inode *inode,
+					 const u64 start,
+					 const u64 len,
+					 struct extent_state **cached_state)
+{
+	u64 search_start = start;
+	const u64 end = start + len - 1;
+
+	while (search_start < end) {
+		const u64 search_len = end - search_start + 1;
+		struct extent_map *em;
+		u64 em_len;
+		int ret = 0;
+
+		em = btrfs_get_extent(inode, NULL, 0, search_start,
+				      search_len, 0);
+		if (IS_ERR(em))
+			return PTR_ERR(em);
+
+		if (em->block_start != EXTENT_MAP_HOLE)
+			goto next;
+
+		em_len = em->len;
+		if (em->start < search_start)
+			em_len -= search_start - em->start;
+		if (em_len > search_len)
+			em_len = search_len;
+
+		ret = set_extent_bit(&inode->io_tree, search_start,
+				     search_start + em_len - 1,
+				     EXTENT_DELALLOC_NEW,
+				     NULL, cached_state, GFP_NOFS);
+next:
+		search_start = extent_map_end(em);
+		free_extent_map(em);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
 /*
  * after copy_from_user, pages need to be dirtied and we need to make
  * sure holes are created between the current EOF and the start of
@@ -497,14 +538,34 @@ int btrfs_dirty_pages(struct inode *inode, struct page **pages,
 	u64 end_of_last_block;
 	u64 end_pos = pos + write_bytes;
 	loff_t isize = i_size_read(inode);
+	unsigned int extra_bits = 0;
 
 	start_pos = pos & ~((u64) fs_info->sectorsize - 1);
 	num_bytes = round_up(write_bytes + pos - start_pos,
 			     fs_info->sectorsize);
 
 	end_of_last_block = start_pos + num_bytes - 1;
+
+	if (!btrfs_is_free_space_inode(BTRFS_I(inode))) {
+		if (start_pos >= isize &&
+		    !(BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC)) {
+			/*
+			 * There can't be any extents following eof in this case
+			 * so just set the delalloc new bit for the range
+			 * directly.
+			 */
+			extra_bits |= EXTENT_DELALLOC_NEW;
+		} else {
+			err = btrfs_find_new_delalloc_bytes(BTRFS_I(inode),
+							    start_pos,
+							    num_bytes, cached);
+			if (err)
+				return err;
+		}
+	}
+
 	err = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block,
-					cached, 0);
+					extra_bits, cached, 0);
 	if (err)
 		return err;
 
@@ -1404,47 +1465,6 @@ static noinline int prepare_pages(struct inode *inode, struct page **pages,
 
 }
 
-static int btrfs_find_new_delalloc_bytes(struct btrfs_inode *inode,
-					 const u64 start,
-					 const u64 len,
-					 struct extent_state **cached_state)
-{
-	u64 search_start = start;
-	const u64 end = start + len - 1;
-
-	while (search_start < end) {
-		const u64 search_len = end - search_start + 1;
-		struct extent_map *em;
-		u64 em_len;
-		int ret = 0;
-
-		em = btrfs_get_extent(inode, NULL, 0, search_start,
-				      search_len, 0);
-		if (IS_ERR(em))
-			return PTR_ERR(em);
-
-		if (em->block_start != EXTENT_MAP_HOLE)
-			goto next;
-
-		em_len = em->len;
-		if (em->start < search_start)
-			em_len -= search_start - em->start;
-		if (em_len > search_len)
-			em_len = search_len;
-
-		ret = set_extent_bit(&inode->io_tree, search_start,
-				     search_start + em_len - 1,
-				     EXTENT_DELALLOC_NEW,
-				     NULL, cached_state, GFP_NOFS);
-next:
-		search_start = extent_map_end(em);
-		free_extent_map(em);
-		if (ret)
-			return ret;
-	}
-	return 0;
-}
-
 /*
  * This function locks the extent and properly waits for data=ordered extents
  * to finish before allowing the pages to be modified if need.
@@ -1473,10 +1493,8 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
 		+ round_up(pos + write_bytes - start_pos,
 			   fs_info->sectorsize) - 1;
 
-	if (start_pos < inode->vfs_inode.i_size ||
-	    (inode->flags & BTRFS_INODE_PREALLOC)) {
+	if (start_pos < inode->vfs_inode.i_size) {
 		struct btrfs_ordered_extent *ordered;
-		unsigned int clear_bits;
 
 		lock_extent_bits(&inode->io_tree, start_pos, last_pos,
 				cached_state);
@@ -1498,19 +1516,10 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
 		}
 		if (ordered)
 			btrfs_put_ordered_extent(ordered);
-		ret = btrfs_find_new_delalloc_bytes(inode, start_pos,
-						    last_pos - start_pos + 1,
-						    cached_state);
-		clear_bits = EXTENT_DIRTY | EXTENT_DELALLOC |
-			EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG;
-		if (ret)
-			clear_bits |= EXTENT_DELALLOC_NEW | EXTENT_LOCKED;
 		clear_extent_bit(&inode->io_tree, start_pos,
-				 last_pos, clear_bits,
-				 (clear_bits & EXTENT_LOCKED) ? 1 : 0,
-				 0, cached_state, GFP_NOFS);
-		if (ret)
-			return ret;
+				 last_pos, EXTENT_DIRTY | EXTENT_DELALLOC |
+				 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
+				 0, 0, cached_state, GFP_NOFS);
 		*lockstart = start_pos;
 		*lockend = last_pos;
 		ret = 1;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d94e3f68b9b1..185cdc904856 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2036,11 +2036,12 @@ static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
 }
 
 int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
+			      unsigned int extra_bits,
 			      struct extent_state **cached_state, int dedupe)
 {
 	WARN_ON((end & (PAGE_SIZE - 1)) == 0);
 	return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
-				   cached_state);
+				   extra_bits, cached_state);
 }
 
 /* see btrfs_writepage_start_hook for details on why this is required */
@@ -2101,7 +2102,7 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
 		goto out;
 	 }
 
-	btrfs_set_extent_delalloc(inode, page_start, page_end, &cached_state,
+	btrfs_set_extent_delalloc(inode, page_start, page_end, 0, &cached_state,
 				  0);
 	ClearPageChecked(page);
 	set_page_dirty(page);
@@ -4853,7 +4854,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 			  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
 			  0, 0, &cached_state, GFP_NOFS);
 
-	ret = btrfs_set_extent_delalloc(inode, block_start, block_end,
+	ret = btrfs_set_extent_delalloc(inode, block_start, block_end, 0,
 					&cached_state, 0);
 	if (ret) {
 		unlock_extent_cached(io_tree, block_start, block_end,
@@ -9252,7 +9253,7 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 			  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
 			  0, 0, &cached_state, GFP_NOFS);
 
-	ret = btrfs_set_extent_delalloc(inode, page_start, end,
+	ret = btrfs_set_extent_delalloc(inode, page_start, end, 0,
 					&cached_state, 0);
 	if (ret) {
 		unlock_extent_cached(io_tree, page_start, page_end,
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 9841faef08ea..6432817906c7 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3266,7 +3266,8 @@ static int relocate_file_extent_cluster(struct inode *inode,
 			nr++;
 		}
 
-		btrfs_set_extent_delalloc(inode, page_start, page_end, NULL, 0);
+		btrfs_set_extent_delalloc(inode, page_start, page_end, 0, NULL,
+					  0);
 		set_page_dirty(page);
 
 		unlock_extent(&BTRFS_I(inode)->io_tree,
diff --git a/fs/btrfs/tests/extent-io-tests.c b/fs/btrfs/tests/extent-io-tests.c
index d06b1c931d05..2e7f64a3b22b 100644
--- a/fs/btrfs/tests/extent-io-tests.c
+++ b/fs/btrfs/tests/extent-io-tests.c
@@ -114,7 +114,7 @@ static int test_find_delalloc(u32 sectorsize)
 	 * |--- delalloc ---|
 	 * |---  search  ---|
 	 */
-	set_extent_delalloc(&tmp, 0, sectorsize - 1, NULL);
+	set_extent_delalloc(&tmp, 0, sectorsize - 1, 0, NULL);
 	start = 0;
 	end = 0;
 	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
@@ -145,7 +145,7 @@ static int test_find_delalloc(u32 sectorsize)
 		test_msg("Couldn't find the locked page\n");
 		goto out_bits;
 	}
-	set_extent_delalloc(&tmp, sectorsize, max_bytes - 1, NULL);
+	set_extent_delalloc(&tmp, sectorsize, max_bytes - 1, 0, NULL);
 	start = test_start;
 	end = 0;
 	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
@@ -200,7 +200,7 @@ static int test_find_delalloc(u32 sectorsize)
 	 *
 	 * We are re-using our test_start from above since it works out well.
 	 */
-	set_extent_delalloc(&tmp, max_bytes, total_dirty - 1, NULL);
+	set_extent_delalloc(&tmp, max_bytes, total_dirty - 1, 0, NULL);
 	start = test_start;
 	end = 0;
 	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c
index 8c91d03cc82d..5c329321c936 100644
--- a/fs/btrfs/tests/inode-tests.c
+++ b/fs/btrfs/tests/inode-tests.c
@@ -969,7 +969,7 @@ static int test_extent_accounting(u32 sectorsize, u32 nodesize)
 
 	/* [BTRFS_MAX_EXTENT_SIZE] */
 	BTRFS_I(inode)->outstanding_extents++;
-	ret = btrfs_set_extent_delalloc(inode, 0, BTRFS_MAX_EXTENT_SIZE - 1,
+	ret = btrfs_set_extent_delalloc(inode, 0, BTRFS_MAX_EXTENT_SIZE - 1, 0,
 					NULL, 0);
 	if (ret) {
 		test_msg("btrfs_set_extent_delalloc returned %d\n", ret);
@@ -986,7 +986,7 @@ static int test_extent_accounting(u32 sectorsize, u32 nodesize)
 	BTRFS_I(inode)->outstanding_extents++;
 	ret = btrfs_set_extent_delalloc(inode, BTRFS_MAX_EXTENT_SIZE,
 					BTRFS_MAX_EXTENT_SIZE + sectorsize - 1,
-					NULL, 0);
+					0, NULL, 0);
 	if (ret) {
 		test_msg("btrfs_set_extent_delalloc returned %d\n", ret);
 		goto out;
@@ -1021,7 +1021,7 @@ static int test_extent_accounting(u32 sectorsize, u32 nodesize)
 	ret = btrfs_set_extent_delalloc(inode, BTRFS_MAX_EXTENT_SIZE >> 1,
 					(BTRFS_MAX_EXTENT_SIZE >> 1)
 					+ sectorsize - 1,
-					NULL, 0);
+					0, NULL, 0);
 	if (ret) {
 		test_msg("btrfs_set_extent_delalloc returned %d\n", ret);
 		goto out;
@@ -1044,7 +1044,7 @@ static int test_extent_accounting(u32 sectorsize, u32 nodesize)
 	ret = btrfs_set_extent_delalloc(inode,
 			BTRFS_MAX_EXTENT_SIZE + 2 * sectorsize,
 			(BTRFS_MAX_EXTENT_SIZE << 1) + 3 * sectorsize - 1,
-			NULL, 0);
+			0, NULL, 0);
 	if (ret) {
 		test_msg("btrfs_set_extent_delalloc returned %d\n", ret);
 		goto out;
@@ -1062,7 +1062,7 @@ static int test_extent_accounting(u32 sectorsize, u32 nodesize)
 	BTRFS_I(inode)->outstanding_extents++;
 	ret = btrfs_set_extent_delalloc(inode,
 			BTRFS_MAX_EXTENT_SIZE + sectorsize,
-			BTRFS_MAX_EXTENT_SIZE + 2 * sectorsize - 1, NULL, 0);
+			BTRFS_MAX_EXTENT_SIZE + 2 * sectorsize - 1, 0, NULL, 0);
 	if (ret) {
 		test_msg("btrfs_set_extent_delalloc returned %d\n", ret);
 		goto out;
@@ -1099,7 +1099,7 @@ static int test_extent_accounting(u32 sectorsize, u32 nodesize)
 	BTRFS_I(inode)->outstanding_extents++;
 	ret = btrfs_set_extent_delalloc(inode,
 			BTRFS_MAX_EXTENT_SIZE + sectorsize,
-			BTRFS_MAX_EXTENT_SIZE + 2 * sectorsize - 1, NULL, 0);
+			BTRFS_MAX_EXTENT_SIZE + 2 * sectorsize - 1, 0, NULL, 0);
 	if (ret) {
 		test_msg("btrfs_set_extent_delalloc returned %d\n", ret);
 		goto out;
-- 
2.11.0