[PATCH 3.13 133/187] IB/srp: Fix deadlock between host removal and multipathd

Kamal Mostafa
2014-09-15T23:07:58Z

From: Bart Van Assche <bvanassche@acm.org>

commit bcc05910359183b431da92713e98eed478edf83a upstream.

If scsi_remove_host() is invoked after a SCSI device has been blocked,
if the fast_io_fail_tmo or dev_loss_tmo work gets scheduled on the
workqueue executing srp_remove_work() and if an I/O request is
scheduled after the SCSI device had been blocked by e.g. multipathd
then the following deadlock can occur:

kworker/6:1 D ffff880831f3c460 0 195 2 0x00000000
Call Trace:
[<ffffffff814aafd9>] schedule+0x29/0x70
[<ffffffff814aa0ef>] schedule_timeout+0x10f/0x2a0
[<ffffffff8105af6f>] msleep+0x2f/0x40
[<ffffffff8123b0ae>] __blk_drain_queue+0x4e/0x180
[<ffffffff8123d2d5>] blk_cleanup_queue+0x225/0x230
[<ffffffffa0010732>] __scsi_remove_device+0x62/0xe0 [scsi_mod]
[<ffffffffa000ed2f>] scsi_forget_host+0x6f/0x80 [scsi_mod]
[<ffffffffa0002eba>] scsi_remove_host+0x7a/0x130 [scsi_mod]
[<ffffffffa07cf5c5>] srp_remove_work+0x95/0x180 [ib_srp]
[<ffffffff8106d7aa>] process_one_work+0x1ea/0x6c0
[<ffffffff8106dd9b>] worker_thread+0x11b/0x3a0
[<ffffffff810758bd>] kthread+0xed/0x110
[<ffffffff814b972c>] ret_from_fork+0x7c/0xb0
multipathd D ffff880096acc460 0 5340 1 0x00000000
Call Trace:
[<ffffffff814aafd9>] schedule+0x29/0x70
[<ffffffff814aa0ef>] schedule_timeout+0x10f/0x2a0
[<ffffffff814ab79b>] io_schedule_timeout+0x9b/0xf0
[<ffffffff814abe1c>] wait_for_completion_io_timeout+0xdc/0x110
[<ffffffff81244b9b>] blk_execute_rq+0x9b/0x100
[<ffffffff8124f665>] sg_io+0x1a5/0x450
[<ffffffff8124fd21>] scsi_cmd_ioctl+0x2a1/0x430
[<ffffffff8124fef2>] scsi_cmd_blk_ioctl+0x42/0x50
[<ffffffffa00ec97e>] sd_ioctl+0xbe/0x140 [sd_mod]
[<ffffffff8124bd04>] blkdev_ioctl+0x234/0x840
[<ffffffff811cb491>] block_ioctl+0x41/0x50
[<ffffffff811a0df0>] do_vfs_ioctl+0x300/0x520
[<ffffffff811a1051>] SyS_ioctl+0x41/0x80
[<ffffffff814b9962>] tracesys+0xd0/0xd5

Fix this by scheduling removal work on another workqueue than the
transport layer timers.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: David Dillow <dave@thedillows.org>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/infiniband/ulp/srp/ib_srp.c | 38 +++++++++++++++++++++++++++----------
1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index c74d8b6..a7d51c5 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -120,6 +120,7 @@ static void srp_send_completion(struct ib_cq *cq, void *target_ptr);
static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);

static struct scsi_transport_template *ib_srp_transport_template;
+static struct workqueue_struct *srp_remove_wq;

static struct ib_client srp_client = {
.name = "srp",
@@ -539,7 +540,7 @@ static bool srp_queue_remove_work(struct srp_target_port *target)
spin_unlock_irq(&target->lock);

if (changed)
- queue_work(system_long_wq, &target->remove_work);
+ queue_work(srp_remove_wq, &target->remove_work);

return changed;
}
@@ -2885,9 +2886,10 @@ static void srp_remove_one(struct ib_device *device)
spin_unlock(&host->target_lock);

/*
- * Wait for target port removal tasks.
+ * Wait for tl_err and target port removal tasks.
*/
flush_workqueue(system_long_wq);
+ flush_workqueue(srp_remove_wq);

kfree(host);
}
@@ -2939,16 +2941,22 @@ static int __init srp_init_module(void)
indirect_sg_entries = cmd_sg_entries;
}

+ srp_remove_wq = create_workqueue("srp_remove");
+ if (IS_ERR(srp_remove_wq)) {
+ ret = PTR_ERR(srp_remove_wq);
+ goto out;
+ }
+
+ ret = -ENOMEM;
ib_srp_transport_template =
srp_attach_transport(&ib_srp_transport_functions);
if (!ib_srp_transport_template)
- return -ENOMEM;
+ goto destroy_wq;

ret = class_register(&srp_class);
if (ret) {
pr_err("couldn't register class infiniband_srp\n");
- srp_release_transport(ib_srp_transport_template);
- return ret;
+ goto release_tr;
}

ib_sa_register_client(&srp_sa_client);
@@ -2956,13 +2964,22 @@ static int __init srp_init_module(void)
ret = ib_register_client(&srp_client);
if (ret) {
pr_err("couldn't register IB client\n");
- srp_release_transport(ib_srp_transport_template);
- ib_sa_unregister_client(&srp_sa_client);
- class_unregister(&srp_class);
- return ret;
+ goto unreg_sa;
}

- return 0;
+out:
+ return ret;
+
+unreg_sa:
+ ib_sa_unregister_client(&srp_sa_client);
+ class_unregister(&srp_class);
+
+release_tr:
+ srp_release_transport(ib_srp_transport_template);
+
+destroy_wq:
+ destroy_workqueue(srp_remove_wq);
+ goto out;
}

static void __exit srp_cleanup_module(void)
@@ -2971,6 +2988,7 @@ static void __exit srp_cleanup_module(void)
ib_sa_unregister_client(&srp_sa_client);
class_unregister(&srp_class);
srp_release_transport(ib_srp_transport_template);
+ destroy_workqueue(srp_remove_wq);
}

module_init(srp_init_module);
--
1.9.1