Commit a612d24e authored by Mikulas Patocka's avatar Mikulas Patocka
Browse files

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 2b1c6d7a
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: default avatarMikulas Patocka <mpatocka@redhat.com>
Fixes: 2b1c6d7a ("dm: optimize REQ_PREFLUSH with data when using the linear target")
Reported-by: default avatarZdenek Kabelac <zkabelac@redhat.com>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
parent a6ee8422

drivers/md/dm.c

+1 −1
Original line number Diff line number Diff line
@@ -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;