An empty flush bio can have arbitrary bi_sector. The commit 2b1c6d7a890a introduced a regression that device mapper would fail an empty flush bio with -EIO if the sector pointed beyond the end of the device.
The commit introduced an optimization, that optimization would pass flushes to __split_and_process_bio and __split_and_process_bio is not prepared to handle empty bios. Fix this bug by passing only non-empty flushes to __split_and_process_bio - non-empty flushes must have valid bi_sector. Empty bios will go through __send_empty_flush, as they did before the optimization. This problem can be reproduced by running the lvm2 test: make check_local T=lvconvert-thin.sh LVM_TEST_PREFER_BRD=0 Signed-off-by: Mikulas Patocka <[email protected]> Fixes: 2b1c6d7a890a ("dm: optimize REQ_PREFLUSH with data when using the linear target") Reported-by: Zdenek Kabelac <[email protected]> --- drivers/md/dm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6/drivers/md/dm.c =================================================================== --- linux-2.6.orig/drivers/md/dm.c 2025-11-19 15:08:07.000000000 +0100 +++ linux-2.6/drivers/md/dm.c 2025-11-19 15:08:35.000000000 +0100 @@ -2005,7 +2005,7 @@ static void dm_split_and_process_bio(str * linear target or multiple linear targets pointing to the same * device), we can send the flush with data directly to it. */ - if (map->flush_bypasses_map) { + if (bio->bi_iter.bi_size && map->flush_bypasses_map) { struct list_head *devices = dm_table_get_devices(map); if (devices->next == devices->prev) goto send_preflush_with_data;
