[PATCH 3.2 104/125] [SCSI] Stop accepting SCSI requests before removing a device

Ben Hutchings
2014-07-08T19:27:43Z

From: Bart Van Assche <bvanassche@acm.org>

commit b485462aca7df4e32bcf7efb6f84a69e8b640243 upstream.

Avoid that the code for requeueing SCSI requests triggers a
crash by making sure that that code isn't scheduled anymore
after a device has been removed.

Also, source code inspection of __scsi_remove_device() revealed
a race condition in this function: no new SCSI requests must be
accepted for a SCSI device after device removal started.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/scsi/scsi_lib.c | 7 ++++---
drivers/scsi/scsi_sysfs.c | 11 +++++++++--
2 files changed, 13 insertions(+), 5 deletions(-)

--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -155,13 +155,14 @@ static int __scsi_queue_insert(struct sc

/*
* Requeue this command. It will go before all other commands
- * that are already in the queue.
+ * that are already in the queue. Schedule requeue work under
+ * lock such that the kblockd_schedule_work() call happens
+ * before blk_cleanup_queue() finishes.
*/
spin_lock_irqsave(q->queue_lock, flags);
blk_requeue_request(q, cmd->request);
- spin_unlock_irqrestore(q->queue_lock, flags);
-
kblockd_schedule_work(q, &device->requeue_work);
+ spin_unlock_irqrestore(q->queue_lock, flags);

return 0;
}
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -963,13 +963,20 @@ void __scsi_remove_device(struct scsi_de
device_del(dev);
} else
put_device(&sdev->sdev_dev);
+
+ /*
+ * Stop accepting new requests and wait until all queuecommand() and
+ * scsi_run_queue() invocations have finished before tearing down the
+ * device.
+ */
scsi_device_set_state(sdev, SDEV_DEL);
+ blk_cleanup_queue(sdev->request_queue);
+ cancel_work_sync(&sdev->requeue_work);
+
if (sdev->host->hostt->slave_destroy)
sdev->host->hostt->slave_destroy(sdev);
transport_destroy_device(dev);

- /* Freeing the queue signals to block that we're done */
- blk_cleanup_queue(sdev->request_queue);
put_device(dev);
}