From cb72e03dd55e887babae215568b8f9dfc59a50e4 Mon Sep 17 00:00:00 2001
From: Jeff Moyer <jmoyer@redhat.com>
Date: Mon, 15 Aug 2011 21:37:25 +0200
Subject: [PATCH] --- yaml --- r: 263150 b: refs/heads/master c:
 4853abaae7e4a2af938115ce9071ef8684fb7af4 h: refs/heads/master v: v3

---
 [refs]                       |  2 +-
 trunk/block/blk-core.c       |  8 ++++++--
 trunk/block/blk-flush.c      | 20 ++++++++++++++++----
 trunk/block/blk.h            |  2 ++
 trunk/include/linux/blkdev.h |  1 +
 5 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index ffaffea7a1a1..25524e4b2173 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: bcf30e75b773b60379338768677a1301ef602ff9
+refs/heads/master: 4853abaae7e4a2af938115ce9071ef8684fb7af4
diff --git a/trunk/block/blk-core.c b/trunk/block/blk-core.c
index b850bedad229..7c59b0f5eae8 100644
--- a/trunk/block/blk-core.c
+++ b/trunk/block/blk-core.c
@@ -1700,6 +1700,7 @@ EXPORT_SYMBOL_GPL(blk_rq_check_limits);
 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
 {
 	unsigned long flags;
+	int where = ELEVATOR_INSERT_BACK;
 
 	if (blk_rq_check_limits(q, rq))
 		return -EIO;
@@ -1716,7 +1717,10 @@ int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
 	 */
 	BUG_ON(blk_queued_rq(rq));
 
-	add_acct_request(q, rq, ELEVATOR_INSERT_BACK);
+	if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
+		where = ELEVATOR_INSERT_FLUSH;
+
+	add_acct_request(q, rq, where);
 	spin_unlock_irqrestore(q->queue_lock, flags);
 
 	return 0;
@@ -2273,7 +2277,7 @@ static bool blk_end_bidi_request(struct request *rq, int error,
  *     %false - we are done with this request
  *     %true  - still buffers pending for this request
  **/
-static bool __blk_end_bidi_request(struct request *rq, int error,
+bool __blk_end_bidi_request(struct request *rq, int error,
 				   unsigned int nr_bytes, unsigned int bidi_bytes)
 {
 	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
diff --git a/trunk/block/blk-flush.c b/trunk/block/blk-flush.c
index 2d162bd840d3..491eb30a242d 100644
--- a/trunk/block/blk-flush.c
+++ b/trunk/block/blk-flush.c
@@ -123,7 +123,7 @@ static void blk_flush_restore_request(struct request *rq)
 
 	/* make @rq a normal request */
 	rq->cmd_flags &= ~REQ_FLUSH_SEQ;
-	rq->end_io = NULL;
+	rq->end_io = rq->flush.saved_end_io;
 }
 
 /**
@@ -301,9 +301,6 @@ void blk_insert_flush(struct request *rq)
 	unsigned int fflags = q->flush_flags;	/* may change, cache */
 	unsigned int policy = blk_flush_policy(fflags, rq);
 
-	BUG_ON(rq->end_io);
-	BUG_ON(!rq->bio || rq->bio != rq->biotail);
-
 	/*
 	 * @policy now records what operations need to be done.  Adjust
 	 * REQ_FLUSH and FUA for the driver.
@@ -312,6 +309,19 @@ void blk_insert_flush(struct request *rq)
 	if (!(fflags & REQ_FUA))
 		rq->cmd_flags &= ~REQ_FUA;
 
+	/*
+	 * An empty flush handed down from a stacking driver may
+	 * translate into nothing if the underlying device does not
+	 * advertise a write-back cache.  In this case, simply
+	 * complete the request.
+	 */
+	if (!policy) {
+		__blk_end_bidi_request(rq, 0, 0, 0);
+		return;
+	}
+
+	BUG_ON(!rq->bio || rq->bio != rq->biotail);
+
 	/*
 	 * If there's data but flush is not necessary, the request can be
 	 * processed directly without going through flush machinery.  Queue
@@ -320,6 +330,7 @@ void blk_insert_flush(struct request *rq)
 	if ((policy & REQ_FSEQ_DATA) &&
 	    !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
 		list_add_tail(&rq->queuelist, &q->queue_head);
+		blk_run_queue_async(q);
 		return;
 	}
 
@@ -330,6 +341,7 @@ void blk_insert_flush(struct request *rq)
 	memset(&rq->flush, 0, sizeof(rq->flush));
 	INIT_LIST_HEAD(&rq->flush.list);
 	rq->cmd_flags |= REQ_FLUSH_SEQ;
+	rq->flush.saved_end_io = rq->end_io; /* Usually NULL */
 	rq->end_io = flush_data_end_io;
 
 	blk_flush_complete_seq(rq, REQ_FSEQ_ACTIONS & ~policy, 0);
diff --git a/trunk/block/blk.h b/trunk/block/blk.h
index d6586287adc9..20b900a377c9 100644
--- a/trunk/block/blk.h
+++ b/trunk/block/blk.h
@@ -17,6 +17,8 @@ int blk_rq_append_bio(struct request_queue *q, struct request *rq,
 		      struct bio *bio);
 void blk_dequeue_request(struct request *rq);
 void __blk_queue_free_tags(struct request_queue *q);
+bool __blk_end_bidi_request(struct request *rq, int error,
+			    unsigned int nr_bytes, unsigned int bidi_bytes);
 
 void blk_rq_timed_out_timer(unsigned long data);
 void blk_delete_timer(struct request *);
diff --git a/trunk/include/linux/blkdev.h b/trunk/include/linux/blkdev.h
index 847928546076..84b15d54f8c2 100644
--- a/trunk/include/linux/blkdev.h
+++ b/trunk/include/linux/blkdev.h
@@ -118,6 +118,7 @@ struct request {
 		struct {
 			unsigned int		seq;
 			struct list_head	list;
+			rq_end_io_fn		*saved_end_io;
 		} flush;
 	};