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

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>
Link: https://lore.kernel.org/r/20221117183626.2656196-3-bvanassche@acm.org
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index bd4ee29..49cc18a 100644 (file)
--- 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 */