[PATCH 3.19.y-ckt 044/251] scsi_transport_srp: Fix a race condition

[Kamal Mostafa]

3.19.8-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche at sandisk.com>

commit 535fb906225fb7436cb658144d0c0cea14a26f3e upstream.

Avoid that srp_terminate_io() can get invoked while srp_queuecommand()
is in progress. This patch avoids that an I/O timeout can trigger the
following kernel warning:

WARNING: at drivers/infiniband/ulp/srp/ib_srp.c:1447 srp_terminate_io+0xef/0x100 [ib_srp]()
Call Trace:
 [<ffffffff814c65a2>] dump_stack+0x4e/0x68
 [<ffffffff81051f71>] warn_slowpath_common+0x81/0xa0
 [<ffffffff8105204a>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa075f51f>] srp_terminate_io+0xef/0x100 [ib_srp]
 [<ffffffffa07495da>] __rport_fail_io_fast+0xba/0xc0 [scsi_transport_srp]
 [<ffffffffa0749a90>] rport_fast_io_fail_timedout+0xe0/0xf0 [scsi_transport_srp]
 [<ffffffff8106e09b>] process_one_work+0x1db/0x780
 [<ffffffff8106e75b>] worker_thread+0x11b/0x450
 [<ffffffff81073c64>] kthread+0xe4/0x100
 [<ffffffff814cf26c>] ret_from_fork+0x7c/0xb0

See also patch "scsi_transport_srp: Add transport layer error
handling" (commit ID 29c17324803c).

Signed-off-by: Bart Van Assche <bart.vanassche at sandisk.com>
Cc: James Bottomley <JBottomley at Odin.com>
Cc: Sagi Grimberg <sagig at mellanox.com>
Cc: Sebastian Parschauer <sebastian.riemer at profitbricks.com>
Signed-off-by: Doug Ledford <dledford at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/scsi/scsi_transport_srp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_transport_srp.c b/drivers/scsi/scsi_transport_srp.c
index e05cd7e..f115f67 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -439,8 +439,10 @@ static void __rport_fail_io_fast(struct srp_rport *rport)
 
 	/* Involve the LLD if possible to terminate all I/O on the rport. */
 	i = to_srp_internal(shost->transportt);
-	if (i->f->terminate_rport_io)
+	if (i->f->terminate_rport_io) {
+		srp_wait_for_queuecommand(shost);
 		i->f->terminate_rport_io(rport);
+	}
 }
 
 /**
-- 
1.9.1