[SCSI] Make scsi_free_queue() kill pending SCSI commands

Make sure that SCSI device removal via scsi_remove_host() does finish
all pending SCSI commands. Currently that's not the case and hence
removal of a SCSI host during I/O can cause a deadlock. See also
"blkdev_issue_discard() hangs forever if underlying storage device is
removed" (http://bugzilla.kernel.org/show_bug.cgi?id=40472). See also
http://lkml.org/lkml/2011/8/27/6.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: <stable@kernel.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 4f7a5829ea4c..351dc0b86fab 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -286,6 +286,7 @@ static void scsi_host_dev_release(struct device *dev)
 {
         struct Scsi_Host *shost = dev_to_shost(dev);
         struct device *parent = dev->parent;
+        struct request_queue *q;
 
         scsi_proc_hostdir_rm(shost->hostt);
 
@@ -293,9 +294,11 @@ static void scsi_host_dev_release(struct device *dev)
                 kthread_stop(shost->ehandler);
         if (shost->work_q)
                 destroy_workqueue(shost->work_q);
-        if (shost->uspace_req_q) {
-                kfree(shost->uspace_req_q->queuedata);
-                scsi_free_queue(shost->uspace_req_q);
+        q = shost->uspace_req_q;
+        if (q) {
+                kfree(q->queuedata);
+                q->queuedata = NULL;
+                scsi_free_queue(q);
         }
 
         scsi_destroy_command_freelist(shost);