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scsi: add non-sleeping variant of scsi_device_put() and use it in alua

Message ID 20230124120734.15806-1-mwilck@suse.com
State New
Headers show
Series scsi: add non-sleeping variant of scsi_device_put() and use it in alua | expand

Commit Message

Martin Wilck Jan. 24, 2023, 12:07 p.m. UTC 
From: Martin Wilck <mwilck@suse.com>

Since the might_sleep() annotation was added in scsi_device_put() and
alua_rtpg_queue(), we have seen repeated reports of "BUG: sleeping function
called from invalid context" [1], [2]. alua_rtpg_queue() is always called
from contexts where the caller must hold at least one reference to the
scsi device in question. This means that the reference taken by
alua_rtpg_queue() itself can't be the last one, and thus can be dropped
without entering the code path in which scsi_device_put() might actually
sleep.

Add a new helper function, scsi_device_put_nosleep() for cases like this,
where a device reference is put from atomic context, and at the same time
it is certain that this reference is not the last one, and use it from
alua_rtpg_queue().

[1] https://lore.kernel.org/linux-scsi/b49e37d5-edfb-4c56-3eeb-62c7d5855c00@linux.ibm.com/
[2] https://lore.kernel.org/linux-scsi/55c35e64-a7d4-9072-46fd-e8eae6a90e96@linux.ibm.com/

Fixes: f93ed747e2c7 ("scsi: core: Release SCSI devices synchronously")
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Sachin Sant <sachinp@linux.ibm.com>
Cc: Benjamin Block <bblock@linux.ibm.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c |  4 +---
 drivers/scsi/scsi.c                        | 23 ++++++++++++++++++----
 include/scsi/scsi_device.h                 |  1 +
 3 files changed, 21 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 49cc18a87473..bdfcea1c16cb 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -989,8 +989,6 @@  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;
 
@@ -1031,7 +1029,7 @@  static bool alua_rtpg_queue(struct alua_port_group *pg,
 			kref_put(&pg->kref, release_port_group);
 	}
 	if (sdev)
-		scsi_device_put(sdev);
+		scsi_device_put_nosleep(sdev);
 
 	return true;
 }
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 1426b9b03612..eec52bb298a7 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -576,6 +576,24 @@  int scsi_device_get(struct scsi_device *sdev)
 }
 EXPORT_SYMBOL(scsi_device_get);
 
+/**
+ * scsi_device_put_nosleep  -  release a reference to a scsi_device
+ * @sdev:	device to release a reference on.
+ *
+ * Description: Release a reference to the scsi_device and decrements the use
+ * count of the underlying LLDD module. This function may only be called from
+ * a call context where it is certain that the reference dropped is not the
+ * last one.
+ */
+void scsi_device_put_nosleep(struct scsi_device *sdev)
+{
+	struct module *mod = sdev->host->hostt->module;
+
+	put_device(&sdev->sdev_gendev);
+	module_put(mod);
+}
+EXPORT_SYMBOL(scsi_device_put);
+
 /**
  * scsi_device_put  -  release a reference to a scsi_device
  * @sdev:	device to release a reference on.
@@ -586,12 +604,9 @@  EXPORT_SYMBOL(scsi_device_get);
  */
 void scsi_device_put(struct scsi_device *sdev)
 {
-	struct module *mod = sdev->host->hostt->module;
-
 	might_sleep();
 
-	put_device(&sdev->sdev_gendev);
-	module_put(mod);
+	scsi_device_put_nosleep(sdev);
 }
 EXPORT_SYMBOL(scsi_device_put);
 
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 3642b8e3928b..85cffa07f2c0 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -365,6 +365,7 @@  void scsi_attach_vpd(struct scsi_device *sdev);
 
 extern struct scsi_device *scsi_device_from_queue(struct request_queue *q);
 extern int __must_check scsi_device_get(struct scsi_device *);
+extern void scsi_device_put_nosleep(struct scsi_device *);
 extern void scsi_device_put(struct scsi_device *);
 extern struct scsi_device *scsi_device_lookup(struct Scsi_Host *,
 					      uint, uint, u64);