From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Mon, 28 Aug 2006 08:15:59 -0400
Add a real API for dealing with blk_congestion_wait()

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---

 block/ll_rw_blk.c         |   12 ++++++++++++
 fs/nfs/write.c            |    1 +
 include/linux/blkdev.h    |    1 +
 include/linux/writeback.h |    1 +
 mm/page-writeback.c       |    9 +++++++++
 5 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index ddd9253..dcbd6ff 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -2734,6 +2734,18 @@ long blk_congestion_wait(int rw, long ti
 
 EXPORT_SYMBOL(blk_congestion_wait);
 
+/**
+ * blk_congestion_end - wake up sleepers on a congestion queue
+ * @rw: READ or WRITE
+ */
+void blk_congestion_end(int rw)
+{
+	wait_queue_head_t *wqh = &congestion_wqh[rw];
+
+	if (waitqueue_active(wqh))
+		wake_up(wqh);
+}
+
 /*
  * Has to be called with the request spinlock acquired
  */
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 453d446..38ba5c0 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -396,6 +396,7 @@ int nfs_writepages(struct address_space 
 out:
 	clear_bit(BDI_write_congested, &bdi->state);
 	wake_up_all(&nfs_write_congestion);
+	writeback_congestion_end();
 	return err;
 }
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index aafe827..96c9040 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -746,6 +746,7 @@ extern void blk_queue_free_tags(request_
 extern int blk_queue_resize_tags(request_queue_t *, int);
 extern void blk_queue_invalidate_tags(request_queue_t *);
 extern long blk_congestion_wait(int rw, long timeout);
+extern void blk_congestion_end(int rw);
 
 extern void blk_rq_bio_prep(request_queue_t *, struct request *, struct bio *);
 extern int blkdev_issue_flush(struct block_device *, sector_t *);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 9e38b56..0422036 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -85,6 +85,7 @@ int wakeup_pdflush(long nr_pages);
 void laptop_io_completion(void);
 void laptop_sync_completion(void);
 void throttle_vm_writeout(void);
+void writeback_congestion_end(void);
 
 /* These are exported to sysctl. */
 extern int dirty_background_ratio;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e630188..77a0bc4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -803,6 +803,15 @@ int test_set_page_writeback(struct page 
 EXPORT_SYMBOL(test_set_page_writeback);
 
 /*
+ * Wakes up tasks that are being throttled due to writeback congestion
+ */
+void writeback_congestion_end(void)
+{
+	blk_congestion_end(WRITE);
+}
+EXPORT_SYMBOL(writeback_congestion_end);
+
+/*
  * Return true if any of the pages in the mapping are marged with the
  * passed tag.
  */