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Petersen" Cc: linux-scsi@vger.kernel.org, Bart Van Assche , Martin Wilck , Hannes Reinecke , Sachin Sant , Benjamin Block , Dan Carpenter Subject: [PATCH 2/2] scsi: alua: Call scsi_device_put() from non-atomic context Date: Thu, 17 Nov 2022 10:36:26 -0800 Message-Id: <20221117183626.2656196-3-bvanassche@acm.org> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog In-Reply-To: <20221117183626.2656196-1-bvanassche@acm.org> References: <20221117183626.2656196-1-bvanassche@acm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.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 Cc: Hannes Reinecke Cc: Sachin Sant Cc: Benjamin Block Suggested-by: Martin Wilck Reported-by: Dan Carpenter Signed-off-by: Bart Van Assche --- 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 */