6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
[ Upstream commit c8691cd0fc11197515ed148de0780d927bfca38b ]
This reverts commit fa247089de9936a46e290d4724cb5f0b845600f5.
The following sequence of commands causes a livelock - there will be
workqueue process looping and consuming 100% CPU:
dmsetup create --notable test
truncate -s 1MiB testdata
losetup /dev/loop0 testdata
dmsetup load test --table '0 2048 linear /dev/loop0 0'
dd if=/dev/zero of=/dev/dm-0 bs=16k count=1 conv=fdatasync
The livelock is caused by the commit fa247089de99. The commit claims that
it fixes a race condition, however, it is unknown what the actual race
condition is and what program is involved in the race condition.
When the inactive table is loaded, the nodes /dev/dm-0 and
/sys/block/dm-0 are created. /dev/dm-0 has zero size at this point. When
the device is suspended and resumed, the nodes /dev/mapper/test and
/dev/disk/* are created.
If some program opens a block device before it is created by dmsetup or
lvm, the program is buggy, so dm could just report an error as it used to
do before.
Reported-by: Zdenek Kabelac <zkabelac@xxxxxxxxxx>
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Fixes: fa247089de99 ("dm: requeue IO if mapping table not yet available")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/md/dm-rq.c | 4 +++-
drivers/md/dm.c | 11 ++++++++---
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 80f46e01bca44..6685dc3b8b448 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -493,8 +493,10 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
map = dm_get_live_table(md, &srcu_idx);
if (unlikely(!map)) {
+ DMERR_LIMIT("%s: mapping table unavailable, erroring io",
+ dm_device_name(md));
dm_put_live_table(md, srcu_idx);
- return BLK_STS_RESOURCE;
+ return BLK_STS_IOERR;
}
ti = dm_table_find_target(map, 0);
dm_put_live_table(md, srcu_idx);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ddd44a7f79dbf..f70129bc703b8 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1789,10 +1789,15 @@ static void dm_submit_bio(struct bio *bio)
struct dm_table *map;
map = dm_get_live_table(md, &srcu_idx);
+ if (unlikely(!map)) {
+ DMERR_LIMIT("%s: mapping table unavailable, erroring io",
+ dm_device_name(md));
+ bio_io_error(bio);
+ goto out;
+ }
- /* If suspended, or map not yet available, queue this IO for later */
- if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) ||
- unlikely(!map)) {
+ /* If suspended, queue this IO for later */
+ if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) {
if (bio->bi_opf & REQ_NOWAIT)
bio_wouldblock_error(bio);
else if (bio->bi_opf & REQ_RAHEAD)
--
2.43.0
