1 files changed, 279 insertions, 362 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 4b37f7cea4dd..2f76c4a081a2 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -26,62 +26,38 @@
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/buffer_head.h>
+#include <linux/tracepoint.h>
 #include "internal.h"
 
-#define inode_to_bdi(inode)     ((inode)->i_mapping->backing_dev_info)
-
-/*
- * We don't actually have pdflush, but this one is exported though /proc...
- */
-int nr_pdflush_threads;
-
 /*
  * Passed into wb_writeback(), essentially a subset of writeback_control
  */
-struct wb_writeback_args {
+struct wb_writeback_work {
         long nr_pages;
         struct super_block *sb;
         enum writeback_sync_modes sync_mode;
-        int for_kupdate:1;
-        int range_cyclic:1;
-        int for_background:1;
-};
+        unsigned int for_kupdate:1;
+        unsigned int range_cyclic:1;
+        unsigned int for_background:1;
 
-/*
- * Work items for the bdi_writeback threads
- */
-struct bdi_work {
         struct list_head list;          /* pending work list */
-        struct rcu_head rcu_head;       /* for RCU free/clear of work */
-
-        unsigned long seen;             /* threads that have seen this work */
-        atomic_t pending;               /* number of threads still to do work */
-
-        struct wb_writeback_args args;  /* writeback arguments */
-
-        unsigned long state;            /* flag bits, see WS_* */
-};
-
-enum {
-        WS_USED_B = 0,
-        WS_ONSTACK_B,
+        struct completion *done;        /* set if the caller waits */
 };
 
-#define WS_USED (1 << WS_USED_B)
-#define WS_ONSTACK (1 << WS_ONSTACK_B)
+/*
+ * Include the creation of the trace points after defining the
+ * wb_writeback_work structure so that the definition remains local to this
+ * file.
+ */
+#define CREATE_TRACE_POINTS
+#include <trace/events/writeback.h>
 
-static inline bool bdi_work_on_stack(struct bdi_work *work)
-{
-        return test_bit(WS_ONSTACK_B, &work->state);
-}
+#define inode_to_bdi(inode)     ((inode)->i_mapping->backing_dev_info)
 
-static inline void bdi_work_init(struct bdi_work *work,
-                                 struct wb_writeback_args *args)
-{
-        INIT_RCU_HEAD(&work->rcu_head);
-        work->args = *args;
-        work->state = WS_USED;
-}
+/*
+ * We don't actually have pdflush, but this one is exported though /proc...
+ */
+int nr_pdflush_threads;
 
 /**
  * writeback_in_progress - determine whether there is writeback in progress
@@ -95,183 +71,81 @@ int writeback_in_progress(struct backing_dev_info *bdi)
         return !list_empty(&bdi->work_list);
 }
 
-static void bdi_work_clear(struct bdi_work *work)
-{
-        clear_bit(WS_USED_B, &work->state);
-        smp_mb__after_clear_bit();
-        /*
-         * work can have disappeared at this point. bit waitq functions
-         * should be able to tolerate this, provided bdi_sched_wait does
-         * not dereference it's pointer argument.
-        */
-        wake_up_bit(&work->state, WS_USED_B);
-}
-
-static void bdi_work_free(struct rcu_head *head)
-{
-        struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
-
-        if (!bdi_work_on_stack(work))
-                kfree(work);
-        else
-                bdi_work_clear(work);
-}
-
-static void wb_work_complete(struct bdi_work *work)
-{
-        const enum writeback_sync_modes sync_mode = work->args.sync_mode;
-        int onstack = bdi_work_on_stack(work);
-
-        /*
-         * For allocated work, we can clear the done/seen bit right here.
-         * For on-stack work, we need to postpone both the clear and free
-         * to after the RCU grace period, since the stack could be invalidated
-         * as soon as bdi_work_clear() has done the wakeup.
-         */
-        if (!onstack)
-                bdi_work_clear(work);
-        if (sync_mode == WB_SYNC_NONE || onstack)
-                call_rcu(&work->rcu_head, bdi_work_free);
-}
-
-static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
-{
-        /*
-         * The caller has retrieved the work arguments from this work,
-         * drop our reference. If this is the last ref, delete and free it
-         */
-        if (atomic_dec_and_test(&work->pending)) {
-                struct backing_dev_info *bdi = wb->bdi;
-
-                spin_lock(&bdi->wb_lock);
-                list_del_rcu(&work->list);
-                spin_unlock(&bdi->wb_lock);
-
-                wb_work_complete(work);
-        }
-}
-
-static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
+static void bdi_queue_work(struct backing_dev_info *bdi,
+                struct wb_writeback_work *work)
 {
-        work->seen = bdi->wb_mask;
-        BUG_ON(!work->seen);
-        atomic_set(&work->pending, bdi->wb_cnt);
-        BUG_ON(!bdi->wb_cnt);
+        trace_writeback_queue(bdi, work);
 
-        /*
-         * list_add_tail_rcu() contains the necessary barriers to
-         * make sure the above stores are seen before the item is
-         * noticed on the list
-         */
-        spin_lock(&bdi->wb_lock);
-        list_add_tail_rcu(&work->list, &bdi->work_list);
-        spin_unlock(&bdi->wb_lock);
-
-        /*
-         * If the default thread isn't there, make sure we add it. When
-         * it gets created and wakes up, we'll run this work.
-         */
-        if (unlikely(list_empty_careful(&bdi->wb_list)))
+        spin_lock_bh(&bdi->wb_lock);
+        list_add_tail(&work->list, &bdi->work_list);
+        if (bdi->wb.task) {
+                wake_up_process(bdi->wb.task);
+        } else {
+                /*
+                 * The bdi thread isn't there, wake up the forker thread which
+                 * will create and run it.
+                 */
+                trace_writeback_nothread(bdi, work);
                 wake_up_process(default_backing_dev_info.wb.task);
-        else {
-                struct bdi_writeback *wb = &bdi->wb;
-
-                if (wb->task)
-                        wake_up_process(wb->task);
         }
+        spin_unlock_bh(&bdi->wb_lock);
 }
 
-/*
- * Used for on-stack allocated work items. The caller needs to wait until
- * the wb threads have acked the work before it's safe to continue.
- */
-static void bdi_wait_on_work_clear(struct bdi_work *work)
-{
-        wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait,
-                    TASK_UNINTERRUPTIBLE);
-}
-
-static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
-                                 struct wb_writeback_args *args)
+static void
+__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
+                bool range_cyclic, bool for_background)
 {
-        struct bdi_work *work;
+        struct wb_writeback_work *work;
 
         /*
          * This is WB_SYNC_NONE writeback, so if allocation fails just
          * wakeup the thread for old dirty data writeback
          */
-        work = kmalloc(sizeof(*work), GFP_ATOMIC);
-        if (work) {
-                bdi_work_init(work, args);
-                bdi_queue_work(bdi, work);
-        } else {
-                struct bdi_writeback *wb = &bdi->wb;
-
-                if (wb->task)
-                        wake_up_process(wb->task);
+        work = kzalloc(sizeof(*work), GFP_ATOMIC);
+        if (!work) {
+                if (bdi->wb.task) {
+                        trace_writeback_nowork(bdi);
+                        wake_up_process(bdi->wb.task);
+                }
+                return;
         }
+
+        work->sync_mode = WB_SYNC_NONE;
+        work->nr_pages  = nr_pages;
+        work->range_cyclic = range_cyclic;
+        work->for_background = for_background;
+
+        bdi_queue_work(bdi, work);
 }
 
 /**
- * bdi_sync_writeback - start and wait for writeback
+ * bdi_start_writeback - start writeback
  * @bdi: the backing device to write from
- * @sb: write inodes from this super_block
+ * @nr_pages: the number of pages to write
  *
  * Description:
- *   This does WB_SYNC_ALL data integrity writeback and waits for the
- *   IO to complete. Callers must hold the sb s_umount semaphore for
- *   reading, to avoid having the super disappear before we are done.
+ *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
+ *   started when this function returns, we make no guarentees on
+ *   completion. Caller need not hold sb s_umount semaphore.
+ *
  */
-static void bdi_sync_writeback(struct backing_dev_info *bdi,
-                               struct super_block *sb)
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
 {
-        struct wb_writeback_args args = {
-                .sb             = sb,
-                .sync_mode      = WB_SYNC_ALL,
-                .nr_pages       = LONG_MAX,
-                .range_cyclic   = 0,
-        };
-        struct bdi_work work;
-
-        bdi_work_init(&work, &args);
-        work.state |= WS_ONSTACK;
-
-        bdi_queue_work(bdi, &work);
-        bdi_wait_on_work_clear(&work);
+        __bdi_start_writeback(bdi, nr_pages, true, false);
 }
 
 /**
- * bdi_start_writeback - start writeback
+ * bdi_start_background_writeback - start background writeback
  * @bdi: the backing device to write from
- * @sb: write inodes from this super_block
- * @nr_pages: the number of pages to write
  *
  * Description:
- *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
+ *   This does WB_SYNC_NONE background writeback. The IO is only
  *   started when this function returns, we make no guarentees on
  *   completion. Caller need not hold sb s_umount semaphore.
- *
  */
-void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
-                         long nr_pages)
+void bdi_start_background_writeback(struct backing_dev_info *bdi)
 {
-        struct wb_writeback_args args = {
-                .sb             = sb,
-                .sync_mode      = WB_SYNC_NONE,
-                .nr_pages       = nr_pages,
-                .range_cyclic   = 1,
-        };
-
-        /*
-         * We treat @nr_pages=0 as the special case to do background writeback,
-         * ie. to sync pages until the background dirty threshold is reached.
-         */
-        if (!nr_pages) {
-                args.nr_pages = LONG_MAX;
-                args.for_background = 1;
-        }
-
-        bdi_alloc_queue_work(bdi, &args);
+        __bdi_start_writeback(bdi, LONG_MAX, true, true);
 }
 
 /*
@@ -398,11 +272,11 @@ static void inode_wait_for_writeback(struct inode *inode)
         wait_queue_head_t *wqh;
 
         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
-        do {
+         while (inode->i_state & I_SYNC) {
                 spin_unlock(&inode_lock);
                 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
                 spin_lock(&inode_lock);
-        } while (inode->i_state & I_SYNC);
+        }
 }
 
 /*
@@ -452,11 +326,9 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 
         BUG_ON(inode->i_state & I_SYNC);
 
-        /* Set I_SYNC, reset I_DIRTY */
-        dirty = inode->i_state & I_DIRTY;
+        /* Set I_SYNC, reset I_DIRTY_PAGES */
         inode->i_state |= I_SYNC;
-        inode->i_state &= ~I_DIRTY;
-
+        inode->i_state &= ~I_DIRTY_PAGES;
         spin_unlock(&inode_lock);
 
         ret = do_writepages(mapping, wbc);
@@ -472,6 +344,15 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
                         ret = err;
         }
 
+        /*
+         * Some filesystems may redirty the inode during the writeback
+         * due to delalloc, clear dirty metadata flags right before
+         * write_inode()
+         */
+        spin_lock(&inode_lock);
+        dirty = inode->i_state & I_DIRTY;
+        inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
+        spin_unlock(&inode_lock);
         /* Don't write the inode if only I_DIRTY_PAGES was set */
         if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
                 int err = write_inode(inode, wbc);
@@ -481,7 +362,7 @@ 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 | I_CLEAR))) {
+        if (!(inode->i_state & I_FREEING)) {
                 if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
                         /*
                          * More pages get dirtied by a fast dirtier.
@@ -554,75 +435,69 @@ select_queue:
         return ret;
 }
 
-static void unpin_sb_for_writeback(struct super_block *sb)
-{
-        up_read(&sb->s_umount);
-        put_super(sb);
-}
-
-enum sb_pin_state {
-        SB_PINNED,
-        SB_NOT_PINNED,
-        SB_PIN_FAILED
-};
-
 /*
- * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
+ * For background writeback the caller does not have the sb pinned
  * before calling writeback. So make sure that we do pin it, so it doesn't
  * go away while we are writing inodes from it.
  */
-static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
-                                              struct super_block *sb)
+static bool pin_sb_for_writeback(struct super_block *sb)
 {
-        /*
-         * Caller must already hold the ref for this
-         */
-        if (wbc->sync_mode == WB_SYNC_ALL) {
-                WARN_ON(!rwsem_is_locked(&sb->s_umount));
-                return SB_NOT_PINNED;
-        }
         spin_lock(&sb_lock);
+        if (list_empty(&sb->s_instances)) {
+                spin_unlock(&sb_lock);
+                return false;
+        }
+
         sb->s_count++;
+        spin_unlock(&sb_lock);
+
         if (down_read_trylock(&sb->s_umount)) {
-                if (sb->s_root) {
-                        spin_unlock(&sb_lock);
-                        return SB_PINNED;
-                }
-                /*
-                 * umounted, drop rwsem again and fall through to failure
-                 */
+                if (sb->s_root)
+                        return true;
                 up_read(&sb->s_umount);
         }
-        sb->s_count--;
-        spin_unlock(&sb_lock);
-        return SB_PIN_FAILED;
+
+        put_super(sb);
+        return false;
 }
 
 /*
  * Write a portion of b_io inodes which belong to @sb.
- * If @wbc->sb != NULL, then find and write all such
+ *
+ * If @only_this_sb is true, then find and write all such
  * inodes. Otherwise write only ones which go sequentially
  * in reverse order.
+ *
  * Return 1, if the caller writeback routine should be
  * interrupted. Otherwise return 0.
  */
-static int writeback_sb_inodes(struct super_block *sb,
-                               struct bdi_writeback *wb,
-                               struct writeback_control *wbc)
+static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
+                struct writeback_control *wbc, bool only_this_sb)
 {
         while (!list_empty(&wb->b_io)) {
                 long pages_skipped;
                 struct inode *inode = list_entry(wb->b_io.prev,
                                                  struct inode, i_list);
-                if (wbc->sb && sb != inode->i_sb) {
-                        /* super block given and doesn't
-                           match, skip this inode */
-                        redirty_tail(inode);
-                        continue;
-                }
-                if (sb != inode->i_sb)
-                        /* finish with this superblock */
+
+                if (inode->i_sb != sb) {
+                        if (only_this_sb) {
+                                /*
+                                 * We only want to write back data for this
+                                 * superblock, move all inodes not belonging
+                                 * to it back onto the dirty list.
+                                 */
+                                redirty_tail(inode);
+                                continue;
+                        }
+
+                        /*
+                         * The inode belongs to a different superblock.
+                         * Bounce back to the caller to unpin this and
+                         * pin the next superblock.
+                         */
                         return 0;
+                }
+
                 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
                         requeue_io(inode);
                         continue;
@@ -634,7 +509,7 @@ static int writeback_sb_inodes(struct super_block *sb,
                 if (inode_dirtied_after(inode, wbc->wb_start))
                         return 1;
 
-                BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
+                BUG_ON(inode->i_state & I_FREEING);
                 __iget(inode);
                 pages_skipped = wbc->pages_skipped;
                 writeback_single_inode(inode, wbc);
@@ -660,12 +535,13 @@ static int writeback_sb_inodes(struct super_block *sb,
         return 1;
 }
 
-static void writeback_inodes_wb(struct bdi_writeback *wb,
-                                struct writeback_control *wbc)
+void writeback_inodes_wb(struct bdi_writeback *wb,
+                struct writeback_control *wbc)
 {
         int ret = 0;
 
-        wbc->wb_start = jiffies; /* livelock avoidance */
+        if (!wbc->wb_start)
+                wbc->wb_start = jiffies; /* livelock avoidance */
         spin_lock(&inode_lock);
         if (!wbc->for_kupdate || list_empty(&wb->b_io))
                 queue_io(wb, wbc->older_than_this);
@@ -674,24 +550,14 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
                 struct inode *inode = list_entry(wb->b_io.prev,
                                                  struct inode, i_list);
                 struct super_block *sb = inode->i_sb;
-                enum sb_pin_state state;
-
-                if (wbc->sb && sb != wbc->sb) {
-                        /* super block given and doesn't
-                           match, skip this inode */
-                        redirty_tail(inode);
-                        continue;
-                }
-                state = pin_sb_for_writeback(wbc, sb);
 
-                if (state == SB_PIN_FAILED) {
+                if (!pin_sb_for_writeback(sb)) {
                         requeue_io(inode);
                         continue;
                 }
-                ret = writeback_sb_inodes(sb, wb, wbc);
+                ret = writeback_sb_inodes(sb, wb, wbc, false);
+                drop_super(sb);
 
-                if (state == SB_PINNED)
-                        unpin_sb_for_writeback(sb);
                 if (ret)
                         break;
         }
@@ -699,11 +565,16 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
         /* Leave any unwritten inodes on b_io */
 }
 
-void writeback_inodes_wbc(struct writeback_control *wbc)
+static void __writeback_inodes_sb(struct super_block *sb,
+                struct bdi_writeback *wb, struct writeback_control *wbc)
 {
-        struct backing_dev_info *bdi = wbc->bdi;
+        WARN_ON(!rwsem_is_locked(&sb->s_umount));
 
-        writeback_inodes_wb(&bdi->wb, wbc);
+        spin_lock(&inode_lock);
+        if (!wbc->for_kupdate || list_empty(&wb->b_io))
+                queue_io(wb, wbc->older_than_this);
+        writeback_sb_inodes(sb, wb, wbc, true);
+        spin_unlock(&inode_lock);
 }
 
 /*
@@ -741,16 +612,14 @@ static inline bool over_bground_thresh(void)
  * all dirty pages if they are all attached to "old" mappings.
  */
 static long wb_writeback(struct bdi_writeback *wb,
-                         struct wb_writeback_args *args)
+                         struct wb_writeback_work *work)
 {
         struct writeback_control wbc = {
-                .bdi                    = wb->bdi,
-                .sb                     = args->sb,
-                .sync_mode              = args->sync_mode,
+                .sync_mode              = work->sync_mode,
                 .older_than_this        = NULL,
-                .for_kupdate            = args->for_kupdate,
-                .for_background         = args->for_background,
-                .range_cyclic           = args->range_cyclic,
+                .for_kupdate            = work->for_kupdate,
+                .for_background         = work->for_background,
+                .range_cyclic           = work->range_cyclic,
         };
         unsigned long oldest_jif;
         long wrote = 0;
@@ -766,25 +635,33 @@ static long wb_writeback(struct bdi_writeback *wb,
                 wbc.range_end = LLONG_MAX;
         }
 
+        wbc.wb_start = jiffies; /* livelock avoidance */
         for (;;) {
                 /*
                  * Stop writeback when nr_pages has been consumed
                  */
-                if (args->nr_pages <= 0)
+                if (work->nr_pages <= 0)
                         break;
 
                 /*
                  * For background writeout, stop when we are below the
                  * background dirty threshold
                  */
-                if (args->for_background && !over_bground_thresh())
+                if (work->for_background && !over_bground_thresh())
                         break;
 
                 wbc.more_io = 0;
                 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
                 wbc.pages_skipped = 0;
-                writeback_inodes_wb(wb, &wbc);
-                args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+
+                trace_wbc_writeback_start(&wbc, wb->bdi);
+                if (work->sb)
+                        __writeback_inodes_sb(work->sb, wb, &wbc);
+                else
+                        writeback_inodes_wb(wb, &wbc);
+                trace_wbc_writeback_written(&wbc, wb->bdi);
+
+                work->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
                 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
 
                 /*
@@ -811,6 +688,7 @@ static long wb_writeback(struct bdi_writeback *wb,
                 if (!list_empty(&wb->b_more_io))  {
                         inode = list_entry(wb->b_more_io.prev,
                                                 struct inode, i_list);
+                        trace_wbc_writeback_wait(&wbc, wb->bdi);
                         inode_wait_for_writeback(inode);
                 }
                 spin_unlock(&inode_lock);
@@ -820,31 +698,21 @@ static long wb_writeback(struct bdi_writeback *wb,
 }
 
 /*
- * Return the next bdi_work struct that hasn't been processed by this
- * wb thread yet. ->seen is initially set for each thread that exists
- * for this device, when a thread first notices a piece of work it
- * clears its bit. Depending on writeback type, the thread will notify
- * completion on either receiving the work (WB_SYNC_NONE) or after
- * it is done (WB_SYNC_ALL).
+ * Return the next wb_writeback_work struct that hasn't been processed yet.
  */
-static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
-                                           struct bdi_writeback *wb)
+static struct wb_writeback_work *
+get_next_work_item(struct backing_dev_info *bdi)
 {
-        struct bdi_work *work, *ret = NULL;
-
-        rcu_read_lock();
-
-        list_for_each_entry_rcu(work, &bdi->work_list, list) {
-                if (!test_bit(wb->nr, &work->seen))
-                        continue;
-                clear_bit(wb->nr, &work->seen);
+        struct wb_writeback_work *work = NULL;
 
-                ret = work;
-                break;
+        spin_lock_bh(&bdi->wb_lock);
+        if (!list_empty(&bdi->work_list)) {
+                work = list_entry(bdi->work_list.next,
+                                  struct wb_writeback_work, list);
+                list_del_init(&work->list);
         }
-
-        rcu_read_unlock();
-        return ret;
+        spin_unlock_bh(&bdi->wb_lock);
+        return work;
 }
 
 static long wb_check_old_data_flush(struct bdi_writeback *wb)
@@ -852,6 +720,12 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
         unsigned long expired;
         long nr_pages;
 
+        /*
+         * When set to zero, disable periodic writeback
+         */
+        if (!dirty_writeback_interval)
+                return 0;
+
         expired = wb->last_old_flush +
                         msecs_to_jiffies(dirty_writeback_interval * 10);
         if (time_before(jiffies, expired))
@@ -863,14 +737,14 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
                         (inodes_stat.nr_inodes - inodes_stat.nr_unused);
 
         if (nr_pages) {
-                struct wb_writeback_args args = {
+                struct wb_writeback_work work = {
                         .nr_pages       = nr_pages,
                         .sync_mode      = WB_SYNC_NONE,
                         .for_kupdate    = 1,
                         .range_cyclic   = 1,
                 };
 
-                return wb_writeback(wb, &args);
+                return wb_writeback(wb, &work);
         }
 
         return 0;
@@ -882,33 +756,29 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
 {
         struct backing_dev_info *bdi = wb->bdi;
-        struct bdi_work *work;
+        struct wb_writeback_work *work;
         long wrote = 0;
 
-        while ((work = get_next_work_item(bdi, wb)) != NULL) {
-                struct wb_writeback_args args = work->args;
-
+        while ((work = get_next_work_item(bdi)) != NULL) {
                 /*
                  * Override sync mode, in case we must wait for completion
+                 * because this thread is exiting now.
                  */
                 if (force_wait)
-                        work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
+                        work->sync_mode = WB_SYNC_ALL;
 
-                /*
-                 * If this isn't a data integrity operation, just notify
-                 * that we have seen this work and we are now starting it.
-                 */
-                if (args.sync_mode == WB_SYNC_NONE)
-                        wb_clear_pending(wb, work);
+                trace_writeback_exec(bdi, work);
 
-                wrote += wb_writeback(wb, &args);
+                wrote += wb_writeback(wb, work);
 
                 /*
-                 * This is a data integrity writeback, so only do the
-                 * notification when we have completed the work.
+                 * Notify the caller of completion if this is a synchronous
+                 * work item, otherwise just free it.
                  */
-                if (args.sync_mode == WB_SYNC_ALL)
-                        wb_clear_pending(wb, work);
+                if (work->done)
+                        complete(work->done);
+                else
+                        kfree(work);
         }
 
         /*
@@ -923,75 +793,88 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
  * Handle writeback of dirty data for the device backed by this bdi. Also
  * wakes up periodically and does kupdated style flushing.
  */
-int bdi_writeback_task(struct bdi_writeback *wb)
+int bdi_writeback_thread(void *data)
 {
-        unsigned long last_active = jiffies;
-        unsigned long wait_jiffies = -1UL;
+        struct bdi_writeback *wb = data;
+        struct backing_dev_info *bdi = wb->bdi;
         long pages_written;
 
+        current->flags |= PF_FLUSHER | PF_SWAPWRITE;
+        set_freezable();
+        wb->last_active = jiffies;
+
+        /*
+         * Our parent may run at a different priority, just set us to normal
+         */
+        set_user_nice(current, 0);
+
+        trace_writeback_thread_start(bdi);
+
         while (!kthread_should_stop()) {
+                /*
+                 * Remove own delayed wake-up timer, since we are already awake
+                 * and we'll take care of the preriodic write-back.
+                 */
+                del_timer(&wb->wakeup_timer);
+
                 pages_written = wb_do_writeback(wb, 0);
 
+                trace_writeback_pages_written(pages_written);
+
                 if (pages_written)
-                        last_active = jiffies;
-                else if (wait_jiffies != -1UL) {
-                        unsigned long max_idle;
+                        wb->last_active = jiffies;
+
+                set_current_state(TASK_INTERRUPTIBLE);
+                if (!list_empty(&bdi->work_list)) {
+                        __set_current_state(TASK_RUNNING);
+                        continue;
+                }
 
+                if (wb_has_dirty_io(wb) && dirty_writeback_interval)
+                        schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
+                else {
                         /*
-                         * Longest period of inactivity that we tolerate. If we
-                         * see dirty data again later, the task will get
-                         * recreated automatically.
+                         * We have nothing to do, so can go sleep without any
+                         * timeout and save power. When a work is queued or
+                         * something is made dirty - we will be woken up.
                          */
-                        max_idle = max(5UL * 60 * HZ, wait_jiffies);
-                        if (time_after(jiffies, max_idle + last_active))
-                                break;
+                        schedule();
                 }
 
-                wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
-                schedule_timeout_interruptible(wait_jiffies);
                 try_to_freeze();
         }
 
+        /* Flush any work that raced with us exiting */
+        if (!list_empty(&bdi->work_list))
+                wb_do_writeback(wb, 1);
+
+        trace_writeback_thread_stop(bdi);
         return 0;
 }
 
+
 /*
- * Schedule writeback for all backing devices. This does WB_SYNC_NONE
- * writeback, for integrity writeback see bdi_sync_writeback().
+ * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
+ * the whole world.
  */
-static void bdi_writeback_all(struct super_block *sb, long nr_pages)
+void wakeup_flusher_threads(long nr_pages)
 {
-        struct wb_writeback_args args = {
-                .sb             = sb,
-                .nr_pages       = nr_pages,
-                .sync_mode      = WB_SYNC_NONE,
-        };
         struct backing_dev_info *bdi;
 
-        rcu_read_lock();
+        if (!nr_pages) {
+                nr_pages = global_page_state(NR_FILE_DIRTY) +
+                                global_page_state(NR_UNSTABLE_NFS);
+        }
 
+        rcu_read_lock();
         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
                 if (!bdi_has_dirty_io(bdi))
                         continue;
-
-                bdi_alloc_queue_work(bdi, &args);
+                __bdi_start_writeback(bdi, nr_pages, false, false);
         }
-
         rcu_read_unlock();
 }
 
-/*
- * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
- * the whole world.
- */
-void wakeup_flusher_threads(long nr_pages)
-{
-        if (nr_pages == 0)
-                nr_pages = global_page_state(NR_FILE_DIRTY) +
-                                global_page_state(NR_UNSTABLE_NFS);
-        bdi_writeback_all(NULL, nr_pages);
-}
-
 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
 {
         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
@@ -1044,6 +927,8 @@ static noinline void block_dump___mark_inode_dirty(struct inode *inode)
 void __mark_inode_dirty(struct inode *inode, int flags)
 {
         struct super_block *sb = inode->i_sb;
+        struct backing_dev_info *bdi = NULL;
+        bool wakeup_bdi = false;
 
         /*
          * Don't do this for I_DIRTY_PAGES - that doesn't actually
@@ -1089,7 +974,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
                         if (hlist_unhashed(&inode->i_hash))
                                 goto out;
                 }
-                if (inode->i_state & (I_FREEING|I_CLEAR))
+                if (inode->i_state & I_FREEING)
                         goto out;
 
                 /*
@@ -1097,22 +982,31 @@ void __mark_inode_dirty(struct inode *inode, int flags)
                  * reposition it (that would break b_dirty time-ordering).
                  */
                 if (!was_dirty) {
-                        struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
-                        struct backing_dev_info *bdi = wb->bdi;
-
-                        if (bdi_cap_writeback_dirty(bdi) &&
-                            !test_bit(BDI_registered, &bdi->state)) {
-                                WARN_ON(1);
-                                printk(KERN_ERR "bdi-%s not registered\n",
-                                                                bdi->name);
+                        bdi = inode_to_bdi(inode);
+
+                        if (bdi_cap_writeback_dirty(bdi)) {
+                                WARN(!test_bit(BDI_registered, &bdi->state),
+                                     "bdi-%s not registered\n", bdi->name);
+
+                                /*
+                                 * If this is the first dirty inode for this
+                                 * bdi, we have to wake-up the corresponding
+                                 * bdi thread to make sure background
+                                 * write-back happens later.
+                                 */
+                                if (!wb_has_dirty_io(&bdi->wb))
+                                        wakeup_bdi = true;
                         }
 
                         inode->dirtied_when = jiffies;
-                        list_move(&inode->i_list, &wb->b_dirty);
+                        list_move(&inode->i_list, &bdi->wb.b_dirty);
                 }
         }
 out:
         spin_unlock(&inode_lock);
+
+        if (wakeup_bdi)
+                bdi_wakeup_thread_delayed(bdi);
 }
 EXPORT_SYMBOL(__mark_inode_dirty);
 
@@ -1155,7 +1049,7 @@ static void wait_sb_inodes(struct super_block *sb)
         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
                 struct address_space *mapping;
 
-                if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
+                if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
                         continue;
                 mapping = inode->i_mapping;
                 if (mapping->nrpages == 0)
@@ -1196,12 +1090,20 @@ void writeback_inodes_sb(struct super_block *sb)
 {
         unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
         unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
-        long nr_to_write;
+        DECLARE_COMPLETION_ONSTACK(done);
+        struct wb_writeback_work work = {
+                .sb             = sb,
+                .sync_mode      = WB_SYNC_NONE,
+                .done           = &done,
+        };
+
+        WARN_ON(!rwsem_is_locked(&sb->s_umount));
 
-        nr_to_write = nr_dirty + nr_unstable +
+        work.nr_pages = nr_dirty + nr_unstable +
                         (inodes_stat.nr_inodes - inodes_stat.nr_unused);
 
-        bdi_start_writeback(sb->s_bdi, sb, nr_to_write);
+        bdi_queue_work(sb->s_bdi, &work);
+        wait_for_completion(&done);
 }
 EXPORT_SYMBOL(writeback_inodes_sb);
 
@@ -1215,7 +1117,9 @@ EXPORT_SYMBOL(writeback_inodes_sb);
 int writeback_inodes_sb_if_idle(struct super_block *sb)
 {
         if (!writeback_in_progress(sb->s_bdi)) {
+                down_read(&sb->s_umount);
                 writeback_inodes_sb(sb);
+                up_read(&sb->s_umount);
                 return 1;
         } else
                 return 0;
@@ -1231,7 +1135,20 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
  */
 void sync_inodes_sb(struct super_block *sb)
 {
-        bdi_sync_writeback(sb->s_bdi, sb);
+        DECLARE_COMPLETION_ONSTACK(done);
+        struct wb_writeback_work work = {
+                .sb             = sb,
+                .sync_mode      = WB_SYNC_ALL,
+                .nr_pages       = LONG_MAX,
+                .range_cyclic   = 0,
+                .done           = &done,
+        };
+
+        WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
+        bdi_queue_work(sb->s_bdi, &work);
+        wait_for_completion(&done);
+
         wait_sb_inodes(sb);
 }
 EXPORT_SYMBOL(sync_inodes_sb);