From a612d24e850b28c16384cf071636034935447e43 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 20 Nov 2025 12:08:47 +0100 Subject: [PATCH] dm: fix failure when empty flush's bi_sector points beyond the device end 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 Fixes: 2b1c6d7a890a ("dm: optimize REQ_PREFLUSH with data when using the linear target") Reported-by: Zdenek Kabelac Reviewed-by: Bart Van Assche --- drivers/md/dm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index f5e5e59b232b..6c83ab940af7 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2005,7 +2005,7 @@ static void dm_split_and_process_bio(struct mapped_device *md, * 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; -- 2.47.3