diff options
| author |   Dave Chen <davechen@synology.com> | 2026-06-29 15:08:43 +0800 |
|---|---|---|
| committer |   David Sterba <dsterba@suse.com> | 2026-07-14 07:04:19 +0200 |
| commit | 8b5a09ceb61b18b1f0797cd30a549d7dc85d8d50 (patch) | |
| tree | f8f11efa3f9962b9d5810d5df9f7128f2d079143 | |
| parent | btrfs: fix NULL pointer deref during assertion in btrfs_backref_free_node() (diff) | |
btrfs: fix u32 to s64 type conversion in dirty_metadata_bytes accounting
The percpu_counter dirty_metadata_bytes is updated by negating eb->len
and passing it to percpu_counter_add_batch(), whose amount parameter is
s64. Since commit 84cda1a6087d ("btrfs: cache folio size and shift in
extent_buffer"), eb->len is u32. The u32 result of -eb->len, when
widened to the s64 parameter, becomes a large positive value instead of
the intended negative value. For eb->len == 16384 the counter adds
+4294950912 instead of subtracting 16384.
The counter therefore grows on every metadata writeback instead of
shrinking by the extent buffer size, permanently exceeding
BTRFS_DIRTY_METADATA_THRESH and causing __btrfs_btree_balance_dirty()
to trigger balance_dirty_pages_ratelimited() unconditionally, adding
unnecessary writeback pressure.
Cast eb->len to s64 before negation at both call sites so the
subtraction is performed in signed 64-bit arithmetic.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Fixes: 84cda1a6087d ("btrfs: cache folio size and shift in extent_buffer")
Signed-off-by: Dave Chen <davechen@synology.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/extent_io.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 7d604524e83c..de5785117a47 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -2004,7 +2004,7 @@ static noinline_for_stack bool lock_extent_buffer_for_io(struct extent_buffer *e btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN); percpu_counter_add_batch(&fs_info->dirty_metadata_bytes, - -eb->len, + -(s64)eb->len, fs_info->dirty_metadata_batch); ret = true; } else { @@ -3774,7 +3774,7 @@ void btrfs_clear_buffer_dirty(struct btrfs_trans_handle *trans, return; buffer_tree_clear_mark(eb, PAGECACHE_TAG_DIRTY); - percpu_counter_add_batch(&fs_info->dirty_metadata_bytes, -eb->len, + percpu_counter_add_batch(&fs_info->dirty_metadata_bytes, -(s64)eb->len, fs_info->dirty_metadata_batch); for (int i = 0; i < num_extent_folios(eb); i++) { |