[PATCH 5/9] block: introduce blk_drain_queue()

[Ming Lei]

So that we can support legacy version of freezing queue,
which is required by safe SCSI quiescing.

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 block/blk-core.c       | 16 ++++++++++++++++
 include/linux/blkdev.h |  1 +
 2 files changed, 17 insertions(+)

diff --git a/block/blk-core.c b/block/blk-core.c
index d579501f24ba..636452f151ea 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -530,6 +530,22 @@ static void __blk_drain_queue(struct request_queue *q, 
bool drain_all)
 }
 
 /**
+ * blk_drain_queue - drain requests from request_queue
+ * @q: queue to drain
+ *
+ * Drain requests from @q.  All pending requests are drained.
+ * The caller is responsible for ensuring that no new requests
+ * which need to be drained are queued.
+ */
+void blk_drain_queue(struct request_queue *q)
+{
+       spin_lock_irq(q->queue_lock);
+       __blk_drain_queue(q, true);
+       spin_unlock_irq(q->queue_lock);
+}
+EXPORT_SYMBOL(blk_drain_queue);
+
+/**
  * blk_queue_bypass_start - enter queue bypass mode
  * @q: queue of interest
  *
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f45f157b2910..02959ca03b66 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1146,6 +1146,7 @@ extern struct request_queue 
*blk_init_queue_node(request_fn_proc *rfn,
 extern struct request_queue *blk_init_queue(request_fn_proc *, spinlock_t *);
 extern int blk_init_allocated_queue(struct request_queue *);
 extern void blk_cleanup_queue(struct request_queue *);
+extern void blk_drain_queue(struct request_queue *);
 extern void blk_queue_make_request(struct request_queue *, make_request_fn *);
 extern void blk_queue_bounce_limit(struct request_queue *, u64);
 extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);
-- 
2.9.5