releases/5.10.227/revert-dm-requeue-io-if-mapping-table-not-yet-availa.patch

From 68b795015c9be8cdaf9881ff77e7f8bd161fdcc6 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Fri, 13 Sep 2024 15:05:18 +0200
Subject: Revert "dm: requeue IO if mapping table not yet available"

From: Mikulas Patocka <mpatocka@redhat.com>

[ 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@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: fa247089de99 ("dm: requeue IO if mapping table not yet available")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 5f933dbb0152c..7762bde40963e 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -496,8 +496,10 @@ 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 b56ea42ab7d2b..4fdf0e666777a 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1696,10 +1696,15 @@ static blk_qc_t 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