[PATCH 6.18 225/752] dm: remove fake timeout to avoid leak request

Sasha Levin
2026-02-28T17:51:18Z

From: Ding Hui <dinghui@sangfor.com.cn>

[ Upstream commit f3a9c95a15d2f4466acad5c68faeff79ca5e9f47 ]

Since commit 15f73f5b3e59 ("blk-mq: move failure injection out of
blk_mq_complete_request"), drivers are responsible for calling
blk_should_fake_timeout() at appropriate code paths and opportunities.

However, the dm driver does not implement its own timeout handler and
relies on the timeout handling of its slave devices.

If an io-timeout-fail error is injected to a dm device, the request
will be leaked and never completed, causing tasks to hang indefinitely.

Reproduce:
1. prepare dm which has iscsi slave device
2. inject io-timeout-fail to dm
echo 1 >/sys/class/block/dm-0/io-timeout-fail
echo 100 >/sys/kernel/debug/fail_io_timeout/probability
echo 10 >/sys/kernel/debug/fail_io_timeout/times
3. read/write dm
4. iscsiadm -m node -u

Result: hang task like below
[ 862.243768] INFO: task kworker/u514:2:151 blocked for more than 122 seconds.
[ 862.244133] Tainted: G E 6.19.0-rc1+ #51
[ 862.244337] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 862.244718] task:kworker/u514:2 state:D stack:0 pid:151 tgid:151 ppid:2 task_flags:0x4288060 flags:0x00080000
[ 862.245024] Workqueue: iscsi_ctrl_3:1 __iscsi_unbind_session [scsi_transport_iscsi]
[ 862.245264] Call Trace:
[ 862.245587] <TASK>
[ 862.245814] __schedule+0x810/0x15c0
[ 862.246557] schedule+0x69/0x180
[ 862.246760] blk_mq_freeze_queue_wait+0xde/0x120
[ 862.247688] elevator_change+0x16d/0x460
[ 862.247893] elevator_set_none+0x87/0xf0
[ 862.248798] blk_unregister_queue+0x12e/0x2a0
[ 862.248995] __del_gendisk+0x231/0x7e0
[ 862.250143] del_gendisk+0x12f/0x1d0
[ 862.250339] sd_remove+0x85/0x130 [sd_mod]
[ 862.250650] device_release_driver_internal+0x36d/0x530
[ 862.250849] bus_remove_device+0x1dd/0x3f0
[ 862.251042] device_del+0x38a/0x930
[ 862.252095] __scsi_remove_device+0x293/0x360
[ 862.252291] scsi_remove_target+0x486/0x760
[ 862.252654] __iscsi_unbind_session+0x18a/0x3e0 [scsi_transport_iscsi]
[ 862.252886] process_one_work+0x633/0xe50
[ 862.253101] worker_thread+0x6df/0xf10
[ 862.253647] kthread+0x36d/0x720
[ 862.254533] ret_from_fork+0x2a6/0x470
[ 862.255852] ret_from_fork_asm+0x1a/0x30
[ 862.256037] </TASK>

Remove the blk_should_fake_timeout() check from dm, as dm has no
native timeout handling and should not attempt to fake timeouts.

Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/dm-rq.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index a6ca92049c10e..5e08546696145 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -278,8 +278,7 @@ static void dm_complete_request(struct request *rq, blk_status_t error)
struct dm_rq_target_io *tio = tio_from_request(rq);

tio->error = error;
- if (likely(!blk_should_fake_timeout(rq->q)))
- blk_mq_complete_request(rq);
+ blk_mq_complete_request(rq);
}

/*
--
2.51.0