1 files changed, 143 insertions, 112 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index d5be1693ac93..7d9d06ba184b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -26,15 +26,9 @@
 #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
  */
@@ -50,6 +44,21 @@ struct wb_writeback_work {
         struct completion *done;        /* set if the caller waits */
 };
 
+/*
+ * 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>
+
+#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;
+
 /**
  * writeback_in_progress - determine whether there is writeback in progress
  * @bdi: the device's backing_dev_info structure.
@@ -59,28 +68,27 @@ struct wb_writeback_work {
  */
 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,
                 struct wb_writeback_work *work)
 {
-        spin_lock(&bdi->wb_lock);
-        list_add_tail(&work->list, &bdi->work_list);
-        spin_unlock(&bdi->wb_lock);
+        trace_writeback_queue(bdi, work);
 
-        /*
-         * 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);
 }
 
 static void
@@ -95,8 +103,10 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
          */
         work = kzalloc(sizeof(*work), GFP_ATOMIC);
         if (!work) {
-                if (bdi->wb.task)
+                if (bdi->wb.task) {
+                        trace_writeback_nowork(bdi);
                         wake_up_process(bdi->wb.task);
+                }
                 return;
         }
 
@@ -239,10 +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);
 }
 
@@ -352,63 +370,36 @@ 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_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 (!(inode->i_state & I_FREEING)) {
+                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.
-                         */
-                        /*
-                         * 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.
+                         * sometimes bales out without doing anything.
                          */
-                        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
@@ -499,7 +490,7 @@ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
                 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);
@@ -530,7 +521,8 @@ void writeback_inodes_wb(struct bdi_writeback *wb,
 {
         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);
@@ -559,7 +551,6 @@ static void __writeback_inodes_sb(struct super_block *sb,
 {
         WARN_ON(!rwsem_is_locked(&sb->s_umount));
 
-        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);
@@ -580,7 +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);
@@ -625,6 +616,7 @@ 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
@@ -642,10 +634,14 @@ static long wb_writeback(struct bdi_writeback *wb,
                 wbc.more_io = 0;
                 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
                 wbc.pages_skipped = 0;
+
+                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;
 
@@ -673,6 +669,7 @@ 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);
@@ -685,17 +682,17 @@ static long wb_writeback(struct bdi_writeback *wb,
  * Return the next wb_writeback_work struct that hasn't been processed yet.
  */
 static struct wb_writeback_work *
-get_next_work_item(struct backing_dev_info *bdi, struct bdi_writeback *wb)
+get_next_work_item(struct backing_dev_info *bdi)
 {
         struct wb_writeback_work *work = NULL;
 
-        spin_lock(&bdi->wb_lock);
+        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);
         }
-        spin_unlock(&bdi->wb_lock);
+        spin_unlock_bh(&bdi->wb_lock);
         return work;
 }
 
@@ -743,7 +740,8 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
         struct wb_writeback_work *work;
         long wrote = 0;
 
-        while ((work = get_next_work_item(bdi, wb)) != NULL) {
+        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
                  * because this thread is exiting now.
@@ -751,6 +749,8 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
                 if (force_wait)
                         work->sync_mode = WB_SYNC_ALL;
 
+                trace_writeback_exec(bdi, work);
+
                 wrote += wb_writeback(wb, work);
 
                 /*
@@ -767,6 +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;
 }
@@ -775,47 +776,66 @@ 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;
 
-                        /*
-                         * Longest period of inactivity that we tolerate. If we
-                         * see dirty data again later, the task will get
-                         * recreated automatically.
-                         */
-                        max_idle = max(5UL * 60 * HZ, wait_jiffies);
-                        if (time_after(jiffies, max_idle + last_active))
-                                break;
+                set_current_state(TASK_INTERRUPTIBLE);
+                if (!list_empty(&bdi->work_list)) {
+                        __set_current_state(TASK_RUNNING);
+                        continue;
                 }
 
-                if (dirty_writeback_interval) {
-                        wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
-                        schedule_timeout_interruptible(wait_jiffies);
-                } else {
-                        set_current_state(TASK_INTERRUPTIBLE);
-                        if (list_empty_careful(&wb->bdi->work_list) &&
-                            !kthread_should_stop())
-                                schedule();
-                        __set_current_state(TASK_RUNNING);
+                if (wb_has_dirty_io(wb) && dirty_writeback_interval)
+                        schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
+                else {
+                        /*
+                         * 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.
+                         */
+                        schedule();
                 }
 
                 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;
 }
 
+
 /*
  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
  * the whole world.
@@ -890,6 +910,8 @@ 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
@@ -935,7 +957,7 @@ 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;
 
                 /*
@@ -943,22 +965,31 @@ 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);
 
@@ -1001,7 +1032,7 @@ 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)