1 files changed, 32 insertions, 49 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2f76c4a081a..7d9d06ba184 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -68,7 +68,7 @@ int nr_pdflush_threads;
  */
 int writeback_in_progress(struct backing_dev_info *bdi)
 {
-        return !list_empty(&bdi->work_list);
+        return test_bit(BDI_writeback_running, &bdi->state);
 }
 
 static void bdi_queue_work(struct backing_dev_info *bdi,
@@ -249,10 +249,18 @@ static void move_expired_inodes(struct list_head *delaying_queue,
 
 /*
  * Queue all expired dirty inodes for io, eldest first.
+ * Before
+ *         newly dirtied     b_dirty    b_io    b_more_io
+ *         =============>    gf         edc     BA
+ * After
+ *         newly dirtied     b_dirty    b_io    b_more_io
+ *         =============>    g          fBAedc
+ *                                           |
+ *                                           +--> dequeue for IO
  */
 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
 {
-        list_splice_init(&wb->b_more_io, wb->b_io.prev);
+        list_splice_init(&wb->b_more_io, &wb->b_io);
         move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
 }
 
@@ -363,62 +371,35 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
         spin_lock(&inode_lock);
         inode->i_state &= ~I_SYNC;
         if (!(inode->i_state & I_FREEING)) {
-                if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
-                        /*
-                         * More pages get dirtied by a fast dirtier.
-                         */
-                        goto select_queue;
-                } else if (inode->i_state & I_DIRTY) {
-                        /*
-                         * At least XFS will redirty the inode during the
-                         * writeback (delalloc) and on io completion (isize).
-                         */
-                        redirty_tail(inode);
-                } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+                if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
                         /*
                          * We didn't write back all the pages.  nfs_writepages()
-                         * sometimes bales out without doing anything. Redirty
-                         * the inode; Move it from b_io onto b_more_io/b_dirty.
+                         * sometimes bales out without doing anything.
                          */
-                        /*
-                         * akpm: if the caller was the kupdate function we put
-                         * this inode at the head of b_dirty so it gets first
-                         * consideration.  Otherwise, move it to the tail, for
-                         * the reasons described there.  I'm not really sure
-                         * how much sense this makes.  Presumably I had a good
-                         * reasons for doing it this way, and I'd rather not
-                         * muck with it at present.
-                         */
-                        if (wbc->for_kupdate) {
+                        inode->i_state |= I_DIRTY_PAGES;
+                        if (wbc->nr_to_write <= 0) {
                                 /*
-                                 * For the kupdate function we move the inode
-                                 * to b_more_io so it will get more writeout as
-                                 * soon as the queue becomes uncongested.
+                                 * slice used up: queue for next turn
                                  */
-                                inode->i_state |= I_DIRTY_PAGES;
-select_queue:
-                                if (wbc->nr_to_write <= 0) {
-                                        /*
-                                         * slice used up: queue for next turn
-                                         */
-                                        requeue_io(inode);
-                                } else {
-                                        /*
-                                         * somehow blocked: retry later
-                                         */
-                                        redirty_tail(inode);
-                                }
+                                requeue_io(inode);
                         } else {
                                 /*
-                                 * Otherwise fully redirty the inode so that
-                                 * other inodes on this superblock will get some
-                                 * writeout.  Otherwise heavy writing to one
-                                 * file would indefinitely suspend writeout of
-                                 * all the other files.
+                                 * Writeback blocked by something other than
+                                 * congestion. Delay the inode for some time to
+                                 * avoid spinning on the CPU (100% iowait)
+                                 * retrying writeback of the dirty page/inode
+                                 * that cannot be performed immediately.
                                  */
-                                inode->i_state |= I_DIRTY_PAGES;
                                 redirty_tail(inode);
                         }
+                } else if (inode->i_state & I_DIRTY) {
+                        /*
+                         * Filesystems can dirty the inode during writeback
+                         * operations, such as delayed allocation during
+                         * submission or metadata updates after data IO
+                         * completion.
+                         */
+                        redirty_tail(inode);
                 } else if (atomic_read(&inode->i_count)) {
                         /*
                          * The inode is clean, inuse
@@ -590,7 +571,7 @@ static inline bool over_bground_thresh(void)
 {
         unsigned long background_thresh, dirty_thresh;
 
-        get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
+        global_dirty_limits(&background_thresh, &dirty_thresh);
 
         return (global_page_state(NR_FILE_DIRTY) +
                 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
@@ -759,6 +740,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
         struct wb_writeback_work *work;
         long wrote = 0;
 
+        set_bit(BDI_writeback_running, &wb->bdi->state);
         while ((work = get_next_work_item(bdi)) != NULL) {
                 /*
                  * Override sync mode, in case we must wait for completion
@@ -785,6 +767,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
          * Check for periodic writeback, kupdated() style
          */
         wrote += wb_check_old_data_flush(wb);
+        clear_bit(BDI_writeback_running, &wb->bdi->state);
 
         return wrote;
 }