[PATCH 5.14 017/432] btrfs: zoned: fix double counting of split ordered extent

Greg Kroah-Hartman
2021-09-16T17:10:29Z

From: Naohiro Aota <naohiro.aota@wdc.com>

commit f79645df806565a03abb2847a1d20e6930b25e7e upstream.

btrfs_add_ordered_extent_*() add num_bytes to fs_info->ordered_bytes.
Then, splitting an ordered extent will call btrfs_add_ordered_extent_*()
again for split extents, leading to double counting of the region of
a split extent. These leaked bytes are finally reported at unmount time
as follow:

BTRFS info (device dm-1): at unmount dio bytes count 364544

Fix the double counting by subtracting split extent's size from
fs_info->ordered_bytes.

Fixes: d22002fd37bd ("btrfs: zoned: split ordered extent when bio is sent")
CC: stable@vger.kernel.org # 5.12+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/ordered-data.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -1052,6 +1052,7 @@ static int clone_ordered_extent(struct b
u64 len)
{
struct inode *inode = ordered->inode;
+ struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
u64 file_offset = ordered->file_offset + pos;
u64 disk_bytenr = ordered->disk_bytenr + pos;
u64 num_bytes = len;
@@ -1069,6 +1070,13 @@ static int clone_ordered_extent(struct b
else
type = __ffs(flags_masked);

+ /*
+ * The splitting extent is already counted and will be added again
+ * in btrfs_add_ordered_extent_*(). Subtract num_bytes to avoid
+ * double counting.
+ */
+ percpu_counter_add_batch(&fs_info->ordered_bytes, -num_bytes,
+ fs_info->delalloc_batch);
if (test_bit(BTRFS_ORDERED_COMPRESSED, &ordered->flags)) {
WARN_ON_ONCE(1);
ret = btrfs_add_ordered_extent_compress(BTRFS_I(inode),