[SCSI] make blk layer set REQ_SOFTBARRIER on defer and requeue
This is the reworked version of the patch. It sets REQ_SOFTBARRIER
in two places - in elv_next_request() on BLKPREP_DEFER and in
blk_requeue_request().
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
index 6b79b43..8c51d1c 100644
--- a/drivers/block/elevator.c
+++ b/drivers/block/elevator.c
@@ -291,6 +291,13 @@
}
/*
+ * the request is prepped and may have some resources allocated.
+ * allowing unprepped requests to pass this one may cause resource
+ * deadlock. turn on softbarrier.
+ */
+ rq->flags |= REQ_SOFTBARRIER;
+
+ /*
* if iosched has an explicit requeue hook, then use that. otherwise
* just put the request at the front of the queue
*/
@@ -386,6 +393,12 @@
if (ret == BLKPREP_OK) {
break;
} else if (ret == BLKPREP_DEFER) {
+ /*
+ * the request may have been (partially) prepped.
+ * we need to keep this request in the front to
+ * avoid resource deadlock. turn on softbarrier.
+ */
+ rq->flags |= REQ_SOFTBARRIER;
rq = NULL;
break;
} else if (ret == BLKPREP_KILL) {