Patch "target: Use system workqueue for ALUA transitions" has been added to the 4.9-stable tree

Patch "target: Use system workqueue for ALUA transitions" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    target: Use system workqueue for ALUA transitions

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     target-use-system-workqueue-for-alua-transitions.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Dec 18 14:12:34 CET 2017
From: Mike Christie <mchristi@redhat.com>
Date: Wed, 1 Mar 2017 23:13:26 -0600
Subject: target: Use system workqueue for ALUA transitions

From: Mike Christie <mchristi@redhat.com>


[ Upstream commit 207ee84133c00a8a2a5bdec94df4a5b37d78881c ]

If tcmu-runner is processing a STPG and needs to change the kernel's
ALUA state then we cannot use the same work queue for task management
requests and ALUA transitions, because we could deadlock. The problem
occurs when a STPG times out before tcmu-runner is able to
call into target_tg_pt_gp_alua_access_state_store->
core_alua_do_port_transition -> core_alua_do_transition_tg_pt ->
queue_work. In this case, the tmr is on the work queue waiting for
the STPG to complete, but the STPG transition is now queued behind
the waiting tmr.

Note:
This bug will also be fixed by this patch:
http://www.spinics.net/lists/target-devel/msg14560.html
which switches the tmr code to use the system workqueues.

For both, I am not sure if we need a dedicated workqueue since
it is not a performance path and I do not think we need WQ_MEM_RECLAIM
to make forward progress to free up memory like the block layer does.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/target/target_core_alua.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/drivers/target/target_core_alua.c
+++ b/drivers/target/target_core_alua.c
@@ -1118,13 +1118,11 @@ static int core_alua_do_transition_tg_pt
 		unsigned long transition_tmo;
 
 		transition_tmo = tg_pt_gp->tg_pt_gp_implicit_trans_secs * HZ;
-		queue_delayed_work(tg_pt_gp->tg_pt_gp_dev->tmr_wq,
-				   &tg_pt_gp->tg_pt_gp_transition_work,
-				   transition_tmo);
+		schedule_delayed_work(&tg_pt_gp->tg_pt_gp_transition_work,
+				      transition_tmo);
 	} else {
 		tg_pt_gp->tg_pt_gp_transition_complete = &wait;
-		queue_delayed_work(tg_pt_gp->tg_pt_gp_dev->tmr_wq,
-				   &tg_pt_gp->tg_pt_gp_transition_work, 0);
+		schedule_delayed_work(&tg_pt_gp->tg_pt_gp_transition_work, 0);
 		wait_for_completion(&wait);
 		tg_pt_gp->tg_pt_gp_transition_complete = NULL;
 	}


Patches currently in stable-queue which might be from mchristi@redhat.com are

queue-4.9/target-use-system-workqueue-for-alua-transitions.patch
queue-4.9/target-iscsi-fix-a-race-condition-in-iscsit_add_reject_from_cmd.patch
queue-4.9/target-fix-alua-transition-timeout-handling.patch
queue-4.9/target-fix-race-during-implicit-transition-work-flushes.patch