[PATCH] separate bdi congestion functions from queue congestion functions

Separate out the concept of "queue congestion" from "backing-dev congestion".
Congestion is a backing-dev concept, not a queue concept.

The blk_* congestion functions are retained, as wrappers around the core
backing-dev congestion functions.

This proper layering is needed so that NFS can cleanly use the congestion
functions, and so that CONFIG_BLOCK=n actually links.

Cc: "Thomas Maier" <balagi@justmail.de>
Cc: "Jens Axboe" <jens.axboe@oracle.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: David Howells <dhowells@redhat.com>
Cc: Peter Osterlund <petero2@telia.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 27 insertions, 5 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index f7a1390d67f5..7011d6255593 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -10,6 +10,8 @@
 
 #include <asm/atomic.h>
 
+struct page;
+
 /*
  * Bits in backing_dev_info.state
  */
@@ -88,6 +90,11 @@ static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 				  (1 << BDI_write_congested));
 }
 
+void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
+void set_bdi_congested(struct backing_dev_info *bdi, int rw);
+long congestion_wait(int rw, long timeout);
+void congestion_end(int rw);
+
 #define bdi_cap_writeback_dirty(bdi) \
 	(!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9575e3a5ff2a..7bfcde2d5578 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -651,8 +651,26 @@ extern void blk_recount_segments(request_queue_t *, struct bio *);
 extern int scsi_cmd_ioctl(struct file *, struct gendisk *, unsigned int, void __user *);
 extern int sg_scsi_ioctl(struct file *, struct request_queue *,
 		struct gendisk *, struct scsi_ioctl_command __user *);
-extern void blk_clear_queue_congested(request_queue_t *q, int rw);
-extern void blk_set_queue_congested(request_queue_t *q, int rw);
+
+/*
+ * A queue has just exitted congestion.  Note this in the global counter of
+ * congested queues, and wake up anyone who was waiting for requests to be
+ * put back.
+ */
+static inline void blk_clear_queue_congested(request_queue_t *q, int rw)
+{
+	clear_bdi_congested(&q->backing_dev_info, rw);
+}
+
+/*
+ * A queue has just entered congestion.  Flag that in the queue's VM-visible
+ * state flags and increment the global gounter of congested queues.
+ */
+static inline void blk_set_queue_congested(request_queue_t *q, int rw)
+{
+	set_bdi_congested(&q->backing_dev_info, rw);
+}
+
 extern void blk_start_queue(request_queue_t *q);
 extern void blk_stop_queue(request_queue_t *q);
 extern void blk_sync_queue(struct request_queue *q);
@@ -767,10 +785,8 @@ extern int blk_queue_init_tags(request_queue_t *, int, struct blk_queue_tag *);
 extern void blk_queue_free_tags(request_queue_t *);
 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 struct blk_queue_tag *blk_init_tags(int);
 extern void blk_free_tags(struct blk_queue_tag *);
-extern void blk_congestion_end(int rw);
 
 static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
 						int tag)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index a341c8032866..fc35e6bdfb93 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -85,7 +85,6 @@ 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;