linux-kernel - [PATCH 5.10] btrfs: fix region size in count_bitmap

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Date:   Thu, 14 Sep 2023 12:45:55 +0300
From:   Anastasia Belova <abelova@...ralinux.ru>
To:     Chris Mason <clm@...com>
Cc:     Anastasia Belova <abelova@...ralinux.ru>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>,
        Dennis Zhou <dennis@...nel.org>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org
Subject: [PATCH 5.10] btrfs: fix region size in count_bitmap_extents

count_bitmap_extents was deleted in version 5.11, but
there is possible mistake in versions 5.6-5.10.

Region size should be calculated by subtracting
the end from the beginning.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: dfb79ddb130e ("btrfs: track discardable extents for async discard")
Signed-off-by: Anastasia Belova <abelova@...ralinux.ru>
---
 fs/btrfs/free-space-cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 4989c60b1df9..a34e266a0969 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1930,7 +1930,7 @@ static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
 
 	bitmap_for_each_set_region(bitmap_info->bitmap, rs, re, 0,
 				   BITS_PER_BITMAP) {
-		bytes -= (rs - re) * ctl->unit;
+		bytes -= (re - rs) * ctl->unit;
 		count++;
 
 		if (!bytes)
-- 
2.30.2