[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>

17 files changed, 126 insertions, 104 deletions

diff --git a/arch/i386/lib/usercopy.c b/arch/i386/lib/usercopy.c
index 258df6b4d7d7..d22cfc9d656c 100644
--- a/arch/i386/lib/usercopy.c
+++ b/arch/i386/lib/usercopy.c
@@ -9,6 +9,7 @@
 #include <linux/highmem.h>
 #include <linux/blkdev.h>
 #include <linux/module.h>
+#include <linux/backing-dev.h>
 #include <asm/uaccess.h>
 #include <asm/mmx.h>
 
@@ -741,7 +742,7 @@ survive:
 
                         if (retval == -ENOMEM && is_init(current)) {
                                 up_read(&current->mm->mmap_sem);
-                                blk_congestion_wait(WRITE, HZ/50);
+                                congestion_wait(WRITE, HZ/50);
                                 goto survive;
                         }
 
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 132a858ce2c5..136066583c68 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -56,11 +56,6 @@ static kmem_cache_t *requestq_cachep;
  */
 static kmem_cache_t *iocontext_cachep;
 
-static wait_queue_head_t congestion_wqh[2] = {
-                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
-                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
-        };
-
 /*
  * Controlling structure to kblockd
  */
@@ -112,37 +107,6 @@ static void blk_queue_congestion_threshold(struct request_queue *q)
         q->nr_congestion_off = nr;
 }
 
-/*
- * 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.
- */
-void blk_clear_queue_congested(request_queue_t *q, int rw)
-{
-        enum bdi_state bit;
-        wait_queue_head_t *wqh = &congestion_wqh[rw];
-
-        bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
-        clear_bit(bit, &q->backing_dev_info.state);
-        smp_mb__after_clear_bit();
-        if (waitqueue_active(wqh))
-                wake_up(wqh);
-}
-EXPORT_SYMBOL(blk_clear_queue_congested);
-
-/*
- * A queue has just entered congestion.  Flag that in the queue's VM-visible
- * state flags and increment the global gounter of congested queues.
- */
-void blk_set_queue_congested(request_queue_t *q, int rw)
-{
-        enum bdi_state bit;
-
-        bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
-        set_bit(bit, &q->backing_dev_info.state);
-}
-EXPORT_SYMBOL(blk_set_queue_congested);
-
 /**
  * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
  * @bdev:       device
@@ -2755,41 +2719,6 @@ void blk_end_sync_rq(struct request *rq, int error)
 }
 EXPORT_SYMBOL(blk_end_sync_rq);
 
-/**
- * blk_congestion_wait - wait for a queue to become uncongested
- * @rw: READ or WRITE
- * @timeout: timeout in jiffies
- *
- * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
- * If no queues are congested then just wait for the next request to be
- * returned.
- */
-long blk_congestion_wait(int rw, long timeout)
-{
-        long ret;
-        DEFINE_WAIT(wait);
-        wait_queue_head_t *wqh = &congestion_wqh[rw];
-
-        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
-        ret = io_schedule_timeout(timeout);
-        finish_wait(wqh, &wait);
-        return ret;
-}
-
-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/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 655d816760e5..a625576fdeeb 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -16,6 +16,7 @@
 #include <linux/slab.h>
 #include <linux/crypto.h>
 #include <linux/workqueue.h>
+#include <linux/backing-dev.h>
 #include <asm/atomic.h>
 #include <linux/scatterlist.h>
 #include <asm/page.h>
@@ -602,7 +603,7 @@ static void process_write(struct crypt_io *io)
 
                 /* out of memory -> run queues */
                 if (remaining)
-                        blk_congestion_wait(bio_data_dir(clone), HZ/100);
+                        congestion_wait(bio_data_dir(clone), HZ/100);
         }
 }
 
diff --git a/fs/fat/file.c b/fs/fat/file.c
index f4b8f8b3fbdd..8337451e7897 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -13,6 +13,7 @@
 #include <linux/smp_lock.h>
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
+#include <linux/backing-dev.h>
 #include <linux/blkdev.h>
 
 int fat_generic_ioctl(struct inode *inode, struct file *filp,
@@ -118,7 +119,7 @@ static int fat_file_release(struct inode *inode, struct file *filp)
         if ((filp->f_mode & FMODE_WRITE) &&
              MSDOS_SB(inode->i_sb)->options.flush) {
                 fat_flush_inodes(inode->i_sb, inode, NULL);
-                blk_congestion_wait(WRITE, HZ/10);
+                congestion_wait(WRITE, HZ/10);
         }
         return 0;
 }
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index f6675d2c386c..ca92ac36fe9d 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -57,6 +57,8 @@
 #include <linux/nfs_fs.h>
 #include <linux/nfs_mount.h>
 #include <linux/nfs_page.h>
+#include <linux/backing-dev.h>
+
 #include <asm/uaccess.h>
 #include <linux/smp_lock.h>
 
@@ -395,7 +397,7 @@ int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
 out:
         clear_bit(BDI_write_congested, &bdi->state);
         wake_up_all(&nfs_write_congestion);
-        writeback_congestion_end();
+        congestion_end(WRITE);
         return err;
 }
 
diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index ad8cbc49883a..85ce23268302 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -53,6 +53,7 @@
 #include <linux/workqueue.h>
 #include <linux/writeback.h>
 #include <linux/blkdev.h>
+#include <linux/backing-dev.h>
 
 /* gets a struct reiserfs_journal_list * from a list head */
 #define JOURNAL_LIST_ENTRY(h) (list_entry((h), struct reiserfs_journal_list, \
@@ -970,7 +971,7 @@ int reiserfs_async_progress_wait(struct super_block *s)
         DEFINE_WAIT(wait);
         struct reiserfs_journal *j = SB_JOURNAL(s);
         if (atomic_read(&j->j_async_throttle))
-                blk_congestion_wait(WRITE, HZ / 10);
+                congestion_wait(WRITE, HZ / 10);
         return 0;
 }
 
diff --git a/fs/xfs/linux-2.6/kmem.c b/fs/xfs/linux-2.6/kmem.c
index d59737589815..004baf600611 100644
--- a/fs/xfs/linux-2.6/kmem.c
+++ b/fs/xfs/linux-2.6/kmem.c
@@ -21,6 +21,7 @@
 #include <linux/highmem.h>
 #include <linux/swap.h>
 #include <linux/blkdev.h>
+#include <linux/backing-dev.h>
 #include "time.h"
 #include "kmem.h"
 
@@ -53,7 +54,7 @@ kmem_alloc(size_t size, unsigned int __nocast flags)
                         printk(KERN_ERR "XFS: possible memory allocation "
                                         "deadlock in %s (mode:0x%x)\n",
                                         __FUNCTION__, lflags);
-                blk_congestion_wait(WRITE, HZ/50);
+                congestion_wait(WRITE, HZ/50);
         } while (1);
 }
 
@@ -131,7 +132,7 @@ kmem_zone_alloc(kmem_zone_t *zone, unsigned int __nocast flags)
                         printk(KERN_ERR "XFS: possible memory allocation "
                                         "deadlock in %s (mode:0x%x)\n",
                                         __FUNCTION__, lflags);
-                blk_congestion_wait(WRITE, HZ/50);
+                congestion_wait(WRITE, HZ/50);
         } while (1);
 }
 
diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 9bbadafdcb00..db5f5a3608ca 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -30,6 +30,7 @@
 #include <linux/hash.h>
 #include <linux/kthread.h>
 #include <linux/migrate.h>
+#include <linux/backing-dev.h>
 #include "xfs_linux.h"
 
 STATIC kmem_zone_t *xfs_buf_zone;
@@ -395,7 +396,7 @@ _xfs_buf_lookup_pages(
 
                         XFS_STATS_INC(xb_page_retries);
                         xfsbufd_wakeup(0, gfp_mask);
-                        blk_congestion_wait(WRITE, HZ/50);
+                        congestion_wait(WRITE, HZ/50);
                         goto retry;
                 }
 
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;
diff --git a/mm/Makefile b/mm/Makefile
index 12b3a4eee88d..f3c077eb0b8e 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -10,7 +10,8 @@ mmu-$(CONFIG_MMU)	:= fremap.o highmem.o madvise.o memory.o mincore.o \
 obj-y                   := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
                            page_alloc.o page-writeback.o pdflush.o \
                            readahead.o swap.o truncate.o vmscan.o \
-                           prio_tree.o util.o mmzone.o vmstat.o $(mmu-y)
+                           prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
+                           $(mmu-y)
 
 ifeq ($(CONFIG_MMU)$(CONFIG_BLOCK),yy)
 obj-y                   += bounce.o
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
new file mode 100644
index 000000000000..f50a2811f9dc
--- /dev/null
+++ b/mm/backing-dev.c
@@ -0,0 +1,69 @@
+
+#include <linux/wait.h>
+#include <linux/backing-dev.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+
+static wait_queue_head_t congestion_wqh[2] = {
+                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
+                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
+        };
+
+
+void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
+{
+        enum bdi_state bit;
+        wait_queue_head_t *wqh = &congestion_wqh[rw];
+
+        bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
+        clear_bit(bit, &bdi->state);
+        smp_mb__after_clear_bit();
+        if (waitqueue_active(wqh))
+                wake_up(wqh);
+}
+EXPORT_SYMBOL(clear_bdi_congested);
+
+void set_bdi_congested(struct backing_dev_info *bdi, int rw)
+{
+        enum bdi_state bit;
+
+        bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
+        set_bit(bit, &bdi->state);
+}
+EXPORT_SYMBOL(set_bdi_congested);
+
+/**
+ * congestion_wait - wait for a backing_dev to become uncongested
+ * @rw: READ or WRITE
+ * @timeout: timeout in jiffies
+ *
+ * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
+ * write congestion.  If no backing_devs are congested then just wait for the
+ * next write to be completed.
+ */
+long congestion_wait(int rw, long timeout)
+{
+        long ret;
+        DEFINE_WAIT(wait);
+        wait_queue_head_t *wqh = &congestion_wqh[rw];
+
+        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
+        ret = io_schedule_timeout(timeout);
+        finish_wait(wqh, &wait);
+        return ret;
+}
+EXPORT_SYMBOL(congestion_wait);
+
+/**
+ * congestion_end - wake up sleepers on a congested backing_dev_info
+ * @rw: READ or WRITE
+ */
+void congestion_end(int rw)
+{
+        wait_queue_head_t *wqh = &congestion_wqh[rw];
+
+        if (waitqueue_active(wqh))
+                wake_up(wqh);
+}
+EXPORT_SYMBOL(congestion_end);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index a0f339057449..8d9b19f239c3 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -222,7 +222,7 @@ static void balance_dirty_pages(struct address_space *mapping)
                         if (pages_written >= write_chunk)
                                 break;          /* We've done our duty */
                 }
-                blk_congestion_wait(WRITE, HZ/10);
+                congestion_wait(WRITE, HZ/10);
         }
 
         if (nr_reclaimable + global_page_state(NR_WRITEBACK)
@@ -314,7 +314,7 @@ void throttle_vm_writeout(void)
                 if (global_page_state(NR_UNSTABLE_NFS) +
                         global_page_state(NR_WRITEBACK) <= dirty_thresh)
                                 break;
-                blk_congestion_wait(WRITE, HZ/10);
+                congestion_wait(WRITE, HZ/10);
         }
 }
 
@@ -351,7 +351,7 @@ static void background_writeout(unsigned long _min_pages)
                 min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
                 if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
                         /* Wrote less than expected */
-                        blk_congestion_wait(WRITE, HZ/10);
+                        congestion_wait(WRITE, HZ/10);
                         if (!wbc.encountered_congestion)
                                 break;
                 }
@@ -422,7 +422,7 @@ static void wb_kupdate(unsigned long arg)
                 writeback_inodes(&wbc);
                 if (wbc.nr_to_write > 0) {
                         if (wbc.encountered_congestion)
-                                blk_congestion_wait(WRITE, HZ/10);
+                                congestion_wait(WRITE, HZ/10);
                         else
                                 break;  /* All the old data is written */
                 }
@@ -956,15 +956,6 @@ int test_set_page_writeback(struct page *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.
  */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 40db96a655d0..afee38f04d84 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -39,6 +39,7 @@
 #include <linux/stop_machine.h>
 #include <linux/sort.h>
 #include <linux/pfn.h>
+#include <linux/backing-dev.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -1050,7 +1051,7 @@ nofail_alloc:
                         if (page)
                                 goto got_pg;
                         if (gfp_mask & __GFP_NOFAIL) {
-                                blk_congestion_wait(WRITE, HZ/50);
+                                congestion_wait(WRITE, HZ/50);
                                 goto nofail_alloc;
                         }
                 }
@@ -1113,7 +1114,7 @@ rebalance:
                         do_retry = 1;
         }
         if (do_retry) {
-                blk_congestion_wait(WRITE, HZ/50);
+                congestion_wait(WRITE, HZ/50);
                 goto rebalance;
         }
 
diff --git a/mm/shmem.c b/mm/shmem.c
index b378f66cf2f9..4959535fc14c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -48,6 +48,7 @@
 #include <linux/ctype.h>
 #include <linux/migrate.h>
 #include <linux/highmem.h>
+#include <linux/backing-dev.h>
 
 #include <asm/uaccess.h>
 #include <asm/div64.h>
@@ -1131,7 +1132,7 @@ repeat:
                         page_cache_release(swappage);
                         if (error == -ENOMEM) {
                                 /* let kswapd refresh zone for GFP_ATOMICs */
-                                blk_congestion_wait(WRITE, HZ/50);
+                                congestion_wait(WRITE, HZ/50);
                         }
                         goto repeat;
                 }
diff --git a/mm/vmscan.c b/mm/vmscan.c
index af73c14f9d88..f05527bf792b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1059,7 +1059,7 @@ unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
 
                 /* Take a nap, wait for some writeback to complete */
                 if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
-                        blk_congestion_wait(WRITE, HZ/10);
+                        congestion_wait(WRITE, HZ/10);
         }
         /* top priority shrink_caches still had more to do? don't OOM, then */
         if (!sc.all_unreclaimable)
@@ -1214,7 +1214,7 @@ scan:
                  * another pass across the zones.
                  */
                 if (total_scanned && priority < DEF_PRIORITY - 2)
-                        blk_congestion_wait(WRITE, HZ/10);
+                        congestion_wait(WRITE, HZ/10);
 
                 /*
                  * We do this so kswapd doesn't build up large priorities for
@@ -1458,7 +1458,7 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
                                 goto out;
 
                         if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
-                                blk_congestion_wait(WRITE, HZ / 10);
+                                congestion_wait(WRITE, HZ / 10);
                 }
 
                 lru_pages = 0;