[PATCH] scsi: core: run queue in case of IO queueing failure

[Ming Lei <ming.lei@redhat.com>]

IO requests may be held in scheduler queue because of resource contention.
However, not like normal completion, when queueing request failed, we don't
ask block layer to queue these requests, so IO hang[1] is caused.

Fix this issue by run queue when IO request failure happens.

[1] IO hang log by running heavy IO with removing scsi device

[   39.054963] scsi 13:0:0:0: rejecting I/O to dead device
[   39.058700] scsi 13:0:0:0: rejecting I/O to dead device
[   39.087855] sd 13:0:0:1: [sdd] Synchronizing SCSI cache
[   39.088909] scsi 13:0:0:1: rejecting I/O to dead device
[   39.095351] scsi 13:0:0:1: rejecting I/O to dead device
[   39.096962] scsi 13:0:0:1: rejecting I/O to dead device
[  247.021859] INFO: task scsi-stress-rem:813 blocked for more than 122 seconds.
[  247.023258]       Not tainted 5.8.0-rc2 #8
[  247.024069] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  247.025331] scsi-stress-rem D    0   813    802 0x00004000
[  247.025334] Call Trace:
[  247.025354]  __schedule+0x504/0x55f
[  247.027987]  schedule+0x72/0xa8
[  247.027991]  blk_mq_freeze_queue_wait+0x63/0x8c
[  247.027994]  ? do_wait_intr_irq+0x7a/0x7a
[  247.027996]  blk_cleanup_queue+0x4b/0xc9
[  247.028000]  __scsi_remove_device+0xf6/0x14e
[  247.028002]  scsi_remove_device+0x21/0x2b
[  247.029037]  sdev_store_delete+0x58/0x7c
[  247.029041]  kernfs_fop_write+0x10d/0x14f
[  247.031281]  vfs_write+0xa2/0xdf
[  247.032670]  ksys_write+0x6b/0xb3
[  247.032673]  do_syscall_64+0x56/0x82
[  247.034053]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  247.034059] RIP: 0033:0x7f69f39e9008
[  247.036330] Code: Bad RIP value.
[  247.036331] RSP: 002b:00007ffdd8116498 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[  247.037613] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f69f39e9008
[  247.039714] RDX: 0000000000000002 RSI: 000055cde92a0ab0 RDI: 0000000000000001
[  247.039715] RBP: 000055cde92a0ab0 R08: 000000000000000a R09: 00007f69f3a79e80
[  247.039716] R10: 000000000000000a R11: 0000000000000246 R12: 00007f69f3abb780
[  247.039717] R13: 0000000000000002 R14: 00007f69f3ab6740 R15: 0000000000000002

Cc: linux-block@vger.kernel.org
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/scsi_lib.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 534b85e87c80..4d7fab9e8af9 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1694,6 +1694,16 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 		 */
 		if (req->rq_flags & RQF_DONTPREP)
 			scsi_mq_uninit_cmd(cmd);
+
+		/*
+		 * Requests may be held in block layer queue because of
+		 * resource contention. We usually run queue in normal
+		 * completion for queuing these requests again. Block layer
+		 * will finish this failed request simply, run queue in case
+		 * of IO queueing failure so that requests can get chance to
+		 * be finished.
+		 */
+		scsi_run_queue(q);
 		break;
 	}
 	return ret;
-- 
2.25.2