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dm-bufio: fix wrong count calculation in dm_bufio_issue_discard

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commit 422f1d4f14 upstream.

block_to_sector converts a block number to a sector number and adds
c->start to the result. It is inappropriate to use this function for
converting the number of blocks to a number to sectors because c->start
would be incorrectly added to the result.

Luckily, the only target that uses dm_bufio_issue_discard is dm-ebs,
which sets c->start to 0, so this bug is latent.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Assisted-by: Claude:claude-opus-4-6
Fixes: 6fbeb0048e ("dm bufio: implement discard")
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mikulas Patocka
2026-07-24 16:03:39 +02:00
committed by Greg Kroah-Hartman
parent 7e1822f83c
commit ae7fac9cb5
1 changed files with 3 additions and 1 deletions
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drivers/md/dm-bufio.c
+3 -1
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@@ -2189,7 +2189,9 @@ int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t c
struct dm_io_region io_reg = {
.bdev = c->bdev,
.sector = block_to_sector(c, block),
.count = block_to_sector(c, count),
.count = likely(c->sectors_per_block_bits >= 0) ?
count << c->sectors_per_block_bits :
count * (c->block_size >> SECTOR_SHIFT),
};
if (WARN_ON_ONCE(dm_bufio_in_request()))