From: Bart Van Assche <bvanassche@acm.org>
To: "Martin K . Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>,
Martin Wilck <mwilck@suse.com>, Hannes Reinecke <hare@suse.de>,
Sachin Sant <sachinp@linux.ibm.com>,
Benjamin Block <bblock@linux.ibm.com>,
Dan Carpenter <dan.carpenter@oracle.com>
Subject: [PATCH 2/2] scsi: alua: Call scsi_device_put() from non-atomic context
Date: Thu, 17 Nov 2022 10:36:26 -0800 [thread overview]
Message-ID: <20221117183626.2656196-3-bvanassche@acm.org> (raw)
In-Reply-To: <20221117183626.2656196-1-bvanassche@acm.org>
Since commit f93ed747e2c7 ("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: Martin Wilck <mwilck@suse.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/device_handler/scsi_dh_alua.c | 27 +++++++++++++++-------
1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index bd4ee294f5c7..49cc18a87473 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -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) {
- pg->interval = 0;
- pg->flags |= ALUA_PG_RUN_RTPG;
- kref_get(&pg->kref);
- pg->rtpg_sdev = sdev;
- start_queue = 1;
+ 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 */
next prev parent reply other threads:[~2022-11-17 18:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-17 18:36 [PATCH 0/2] Rework how the ALUA driver calls scsi_device_put() Bart Van Assche
2022-11-17 18:36 ` [PATCH 1/2] scsi: alua: Revert "Move a scsi_device_put() call out of alua_check_vpd()" Bart Van Assche
2022-11-18 6:11 ` Sachin Sant
2022-11-18 15:07 ` Bart Van Assche
2022-11-18 16:03 ` Sachin Sant
2022-11-18 18:54 ` Bart Van Assche
2022-11-19 9:46 ` Sachin Sant
2022-11-17 18:36 ` Bart Van Assche [this message]
2022-11-26 0:34 ` [PATCH 0/2] Rework how the ALUA driver calls scsi_device_put() Martin K. Petersen
2022-12-01 3:45 ` Martin K. Petersen
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