From 422f1d4f141eaa3a6e4199ceec86cc6b9bf26570 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 10 Jul 2026 18:32:49 +0200 Subject: [PATCH] dm-bufio: fix wrong count calculation in dm_bufio_issue_discard 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 Assisted-by: Claude:claude-opus-4-6 Fixes: 6fbeb0048e6b ("dm bufio: implement discard") Cc: stable@vger.kernel.org --- drivers/md/dm-bufio.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 26fedf5883ef..a458b9fd2fcd 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -2238,7 +2238,9 @@ 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()))