Commit 50759b88 authored by Bart Van Assche's avatar Bart Van Assche Committed by Martin K. Petersen
Browse files

scsi: device_handler: alua: Call scsi_device_put() from non-atomic context 



Since commit f93ed747 ("scsi: core: Release SCSI devices
synchronously"), scsi_device_put() might sleep. Avoid calling it from
alua_rtpg_queue() with the pg_lock held. The lock only pretects h->pg,
anyway. To avoid the pg being freed under us, because of a race with
another thread, take a temporary reference. In alua_rtpg_queue(), verify
that the pg still belongs to the sdev being passed before actually queueing
the RTPG.

This patch fixes the following smatch warning:

drivers/scsi/device_handler/scsi_dh_alua.c:1013 alua_rtpg_queue() warn: sleeping in atomic context

alua_check_vpd() <- disables preempt
-> alua_rtpg_queue()
   -> scsi_device_put()

Cc: Martin Wilck <mwilck@suse.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Sachin Sant <sachinp@linux.ibm.com>
Cc: Benjamin Block <bblock@linux.ibm.com>
Suggested-by: default avatarMartin Wilck <mwilck@suse.com>
Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20221117183626.2656196-3-bvanassche@acm.org


Tested-by: default avatarSachin Sant <sachinp@linux.ibm.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent a500c4cc

drivers/scsi/device_handler/scsi_dh_alua.c

+19 −8
Original line number Diff line number Diff line
@@ -354,6 +354,8 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h, 
			    "%s: port group %x rel port %x\n",

			    ALUA_DH_NAME, group_id, rel_port);



	kref_get(&pg->kref);



	/* Check for existing port group references */

	spin_lock(&h->pg_lock);

	old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
@@ -373,11 +375,11 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h, 
		list_add_rcu(&h->node, &pg->dh_list);

	spin_unlock_irqrestore(&pg->lock, flags);



	alua_rtpg_queue(rcu_dereference_protected(h->pg,

						  lockdep_is_held(&h->pg_lock)),

			sdev, NULL, true);

	spin_unlock(&h->pg_lock);



	alua_rtpg_queue(pg, sdev, NULL, true);

	kref_put(&pg->kref, release_port_group);



	if (old_pg)

		kref_put(&old_pg->kref, release_port_group);
@@ -986,6 +988,9 @@ static bool alua_rtpg_queue(struct alua_port_group *pg, 
{

	int start_queue = 0;

	unsigned long flags;



	might_sleep();



	if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))

		return false;
@@ -996,11 +1001,17 @@ static bool alua_rtpg_queue(struct alua_port_group *pg, 
		force = true;

	}

	if (pg->rtpg_sdev == NULL) {

		struct alua_dh_data *h = sdev->handler_data;



		rcu_read_lock();

		if (h && rcu_dereference(h->pg) == pg) {

			pg->interval = 0;

			pg->flags |= ALUA_PG_RUN_RTPG;

			kref_get(&pg->kref);

			pg->rtpg_sdev = sdev;

			start_queue = 1;

		}

		rcu_read_unlock();

	} else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {

		pg->flags |= ALUA_PG_RUN_RTPG;

		/* Do not queue if the worker is already running */