writeback: Add a 'reason' to wb_writeback_work

This creates a new 'reason' field in a wb_writeback_work
structure, which unambiguously identifies who initiates
writeback activity.  A 'wb_reason' enumeration has been
added to writeback.h, to enumerate the possible reasons.

The 'writeback_work_class' and tracepoint event class and
'writeback_queue_io' tracepoints are updated to include the
symbolic 'reason' in all trace events.

And the 'writeback_inodes_sbXXX' family of routines has had
a wb_stats parameter added to them, so callers can specify
why writeback is being started.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f5be06a..c9ee0e1 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3340,7 +3340,8 @@ static int shrink_delalloc(struct btrfs_trans_handle *trans,
                smp_mb();
                nr_pages = min_t(unsigned long, nr_pages,
                       root->fs_info->delalloc_bytes >> PAGE_CACHE_SHIFT);
-               writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages);
+               writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
+                                               WB_REASON_FS_FREE_SPACE);
 
                spin_lock(&space_info->lock);
                if (reserved > space_info->bytes_reserved)

diff --git a/fs/buffer.c b/fs/buffer.c
index 1a80b04..f5dcee6 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -285,7 +285,7 @@ static void free_more_memory(void)
        struct zone *zone;
        int nid;
 
-       wakeup_flusher_threads(1024);
+       wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
        yield();
 
        for_each_online_node(nid) {

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 986e238..7fa73a3 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2241,7 +2241,7 @@ static int ext4_nonda_switch(struct super_block *sb)
         * start pushing delalloc when 1/2 of free blocks are dirty.
         */
        if (free_blocks < 2 * dirty_blocks)
-               writeback_inodes_sb_if_idle(sb);
+               writeback_inodes_sb_if_idle(sb, WB_REASON_FS_FREE_SPACE);
 
        return 0;
 }

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index c510296..73c3992 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -41,11 +41,23 @@ struct wb_writeback_work {
        unsigned int for_kupdate:1;
        unsigned int range_cyclic:1;
        unsigned int for_background:1;
+       enum wb_reason reason;          /* why was writeback initiated? */
 
        struct list_head list;          /* pending work list */
        struct completion *done;        /* set if the caller waits */
 };
 
+const char *wb_reason_name[] = {
+       [WB_REASON_BACKGROUND]          = "background",
+       [WB_REASON_TRY_TO_FREE_PAGES]   = "try_to_free_pages",
+       [WB_REASON_SYNC]                = "sync",
+       [WB_REASON_PERIODIC]            = "periodic",
+       [WB_REASON_LAPTOP_TIMER]        = "laptop_timer",
+       [WB_REASON_FREE_MORE_MEM]       = "free_more_memory",
+       [WB_REASON_FS_FREE_SPACE]       = "fs_free_space",
+       [WB_REASON_FORKER_THREAD]       = "forker_thread"
+};
+
 /*
  * Include the creation of the trace points after defining the
  * wb_writeback_work structure so that the definition remains local to this
@@ -115,7 +127,7 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
 
 static void
 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
-                     bool range_cyclic)
+                     bool range_cyclic, enum wb_reason reason)
 {
        struct wb_writeback_work *work;
 
@@ -135,6 +147,7 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
        work->sync_mode = WB_SYNC_NONE;
        work->nr_pages  = nr_pages;
        work->range_cyclic = range_cyclic;
+       work->reason    = reason;
 
        bdi_queue_work(bdi, work);
 }
@@ -150,9 +163,10 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
  *   completion. Caller need not hold sb s_umount semaphore.
  *
  */
-void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
+                       enum wb_reason reason)
 {
-       __bdi_start_writeback(bdi, nr_pages, true);
+       __bdi_start_writeback(bdi, nr_pages, true, reason);
 }
 
 /**
@@ -641,12 +655,14 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb,
        return wrote;
 }
 
-long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages)
+long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
+                               enum wb_reason reason)
 {
        struct wb_writeback_work work = {
                .nr_pages       = nr_pages,
                .sync_mode      = WB_SYNC_NONE,
                .range_cyclic   = 1,
+               .reason         = reason,
        };
 
        spin_lock(&wb->list_lock);
@@ -825,6 +841,7 @@ static long wb_check_background_flush(struct bdi_writeback *wb)
                        .sync_mode      = WB_SYNC_NONE,
                        .for_background = 1,
                        .range_cyclic   = 1,
+                       .reason         = WB_REASON_BACKGROUND,
                };
 
                return wb_writeback(wb, &work);
@@ -858,6 +875,7 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
                        .sync_mode      = WB_SYNC_NONE,
                        .for_kupdate    = 1,
                        .range_cyclic   = 1,
+                       .reason         = WB_REASON_PERIODIC,
                };
 
                return wb_writeback(wb, &work);
@@ -976,7 +994,7 @@ int bdi_writeback_thread(void *data)
  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
  * the whole world.
  */
-void wakeup_flusher_threads(long nr_pages)
+void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
 {
        struct backing_dev_info *bdi;
 
@@ -989,7 +1007,7 @@ void wakeup_flusher_threads(long nr_pages)
        list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
                if (!bdi_has_dirty_io(bdi))
                        continue;
-               __bdi_start_writeback(bdi, nr_pages, false);
+               __bdi_start_writeback(bdi, nr_pages, false, reason);
        }
        rcu_read_unlock();
 }
@@ -1210,7 +1228,9 @@ static void wait_sb_inodes(struct super_block *sb)
  * on how many (if any) will be written, and this function does not wait
  * for IO completion of submitted IO.
  */
-void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
+void writeback_inodes_sb_nr(struct super_block *sb,
+                           unsigned long nr,
+                           enum wb_reason reason)
 {
        DECLARE_COMPLETION_ONSTACK(done);
        struct wb_writeback_work work = {
@@ -1219,6 +1239,7 @@ void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
                .tagged_writepages      = 1,
                .done                   = &done,
                .nr_pages               = nr,
+               .reason                 = reason,
        };
 
        WARN_ON(!rwsem_is_locked(&sb->s_umount));
@@ -1235,9 +1256,9 @@ EXPORT_SYMBOL(writeback_inodes_sb_nr);
  * on how many (if any) will be written, and this function does not wait
  * for IO completion of submitted IO.
  */
-void writeback_inodes_sb(struct super_block *sb)
+void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
 {
-       return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
+       return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
 }
 EXPORT_SYMBOL(writeback_inodes_sb);
 
@@ -1248,11 +1269,11 @@ EXPORT_SYMBOL(writeback_inodes_sb);
  * Invoke writeback_inodes_sb if no writeback is currently underway.
  * Returns 1 if writeback was started, 0 if not.
  */
-int writeback_inodes_sb_if_idle(struct super_block *sb)
+int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
 {
        if (!writeback_in_progress(sb->s_bdi)) {
                down_read(&sb->s_umount);
-               writeback_inodes_sb(sb);
+               writeback_inodes_sb(sb, reason);
                up_read(&sb->s_umount);
                return 1;
        } else
@@ -1269,11 +1290,12 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
  * Returns 1 if writeback was started, 0 if not.
  */
 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
-                                  unsigned long nr)
+                                  unsigned long nr,
+                                  enum wb_reason reason)
 {
        if (!writeback_in_progress(sb->s_bdi)) {
                down_read(&sb->s_umount);
-               writeback_inodes_sb_nr(sb, nr);
+               writeback_inodes_sb_nr(sb, nr, reason);
                up_read(&sb->s_umount);
                return 1;
        } else
@@ -1297,6 +1319,7 @@ void sync_inodes_sb(struct super_block *sb)
                .nr_pages       = LONG_MAX,
                .range_cyclic   = 0,
                .done           = &done,
+               .reason         = WB_REASON_SYNC,
        };
 
        WARN_ON(!rwsem_is_locked(&sb->s_umount));

diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 10b6be3..4bae57f 100644 (file)
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -286,7 +286,7 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id,
                /* caller already holds s_umount */
                if (sb->s_flags & MS_RDONLY)
                        return -EROFS;
-               writeback_inodes_sb(sb);
+               writeback_inodes_sb(sb, WB_REASON_SYNC);
                return 0;
        default:
                return -EINVAL;

diff --git a/fs/sync.c b/fs/sync.c
index c98a747..101b8ef 100644 (file)
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -43,7 +43,7 @@ static int __sync_filesystem(struct super_block *sb, int wait)
        if (wait)
                sync_inodes_sb(sb);
        else
-               writeback_inodes_sb(sb);
+               writeback_inodes_sb(sb, WB_REASON_SYNC);
 
        if (sb->s_op->sync_fs)
                sb->s_op->sync_fs(sb, wait);
@@ -98,7 +98,7 @@ static void sync_filesystems(int wait)
  */
 SYSCALL_DEFINE0(sync)
 {
-       wakeup_flusher_threads(0);
+       wakeup_flusher_threads(0, WB_REASON_SYNC);
        sync_filesystems(0);
        sync_filesystems(1);
        if (unlikely(laptop_mode))

diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index 315de66..bc4f94b 100644 (file)
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -63,7 +63,7 @@
 static void shrink_liability(struct ubifs_info *c, int nr_to_write)
 {
        down_read(&c->vfs_sb->s_umount);
-       writeback_inodes_sb(c->vfs_sb);
+       writeback_inodes_sb(c->vfs_sb, WB_REASON_FS_FREE_SPACE);
        up_read(&c->vfs_sb->s_umount);
 }
 

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index c3b9201..b1038bd 100644 (file)
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -118,7 +118,8 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
 void bdi_unregister(struct backing_dev_info *bdi);
 int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
-void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages);
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
+                       enum wb_reason reason);
 void bdi_start_background_writeback(struct backing_dev_info *bdi);
 int bdi_writeback_thread(void *data);
 int bdi_has_dirty_io(struct backing_dev_info *bdi);

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index ddb4652..a378c29 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -38,6 +38,23 @@ enum writeback_sync_modes {
        WB_SYNC_ALL,    /* Wait on every mapping */
 };
 
+/*
+ * why some writeback work was initiated
+ */
+enum wb_reason {
+       WB_REASON_BACKGROUND,
+       WB_REASON_TRY_TO_FREE_PAGES,
+       WB_REASON_SYNC,
+       WB_REASON_PERIODIC,
+       WB_REASON_LAPTOP_TIMER,
+       WB_REASON_FREE_MORE_MEM,
+       WB_REASON_FS_FREE_SPACE,
+       WB_REASON_FORKER_THREAD,
+
+       WB_REASON_MAX,
+};
+extern const char *wb_reason_name[];
+
 /*
  * A control structure which tells the writeback code what to do.  These are
  * always on the stack, and hence need no locking.  They are always initialised
@@ -69,14 +86,17 @@ struct writeback_control {
  */    
 struct bdi_writeback;
 int inode_wait(void *);
-void writeback_inodes_sb(struct super_block *);
-void writeback_inodes_sb_nr(struct super_block *, unsigned long nr);
-int writeback_inodes_sb_if_idle(struct super_block *);
-int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr);
+void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
+void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
+                                                       enum wb_reason reason);
+int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
+int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
+                                                       enum wb_reason reason);
 void sync_inodes_sb(struct super_block *);
-long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages);
+long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
+                               enum wb_reason reason);
 long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
-void wakeup_flusher_threads(long nr_pages);
+void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */
 static inline void wait_on_inode(struct inode *inode)

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 1261db3..b99caa8 100644 (file)
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -34,6 +34,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
                __field(int, for_kupdate)
                __field(int, range_cyclic)
                __field(int, for_background)
+               __field(int, reason)
        ),
        TP_fast_assign(
                strncpy(__entry->name, dev_name(bdi->dev), 32);
@@ -43,16 +44,18 @@ DECLARE_EVENT_CLASS(writeback_work_class,
                __entry->for_kupdate = work->for_kupdate;
                __entry->range_cyclic = work->range_cyclic;
                __entry->for_background = work->for_background;
+               __entry->reason = work->reason;
        ),
        TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d "
-                 "kupdate=%d range_cyclic=%d background=%d",
+                 "kupdate=%d range_cyclic=%d background=%d reason=%s",
                  __entry->name,
                  MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev),
                  __entry->nr_pages,
                  __entry->sync_mode,
                  __entry->for_kupdate,
                  __entry->range_cyclic,
-                 __entry->for_background
+                 __entry->for_background,
+                 wb_reason_name[__entry->reason]
        )
 );
 #define DEFINE_WRITEBACK_WORK_EVENT(name) \
@@ -165,6 +168,7 @@ TRACE_EVENT(writeback_queue_io,
                __field(unsigned long,  older)
                __field(long,           age)
                __field(int,            moved)
+               __field(int,            reason)
        ),
        TP_fast_assign(
                unsigned long *older_than_this = work->older_than_this;
@@ -173,12 +177,14 @@ TRACE_EVENT(writeback_queue_io,
                __entry->age    = older_than_this ?
                                  (jiffies - *older_than_this) * 1000 / HZ : -1;
                __entry->moved  = moved;
+               __entry->reason = work->reason;
        ),
-       TP_printk("bdi %s: older=%lu age=%ld enqueue=%d",
+       TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s",
                __entry->name,
                __entry->older, /* older_than_this in jiffies */
                __entry->age,   /* older_than_this in relative milliseconds */
-               __entry->moved)
+               __entry->moved,
+               wb_reason_name[__entry->reason])
 );
 
 TRACE_EVENT(global_dirty_state,

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 5dcaa3c..dd8916f 100644 (file)
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -476,7 +476,8 @@ static int bdi_forker_thread(void *ptr)
                                 * the bdi from the thread. Hopefully 1024 is
                                 * large enough for efficient IO.
                                 */
-                               writeback_inodes_wb(&bdi->wb, 1024);
+                               writeback_inodes_wb(&bdi->wb, 1024,
+                                                   WB_REASON_FORKER_THREAD);
                        } else {
                                /*
                                 * The spinlock makes sure we do not lose

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 45d36f7..650846b 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1301,7 +1301,8 @@ void laptop_mode_timer_fn(unsigned long data)
         * threshold
         */
        if (bdi_has_dirty_io(&q->backing_dev_info))
-               bdi_start_writeback(&q->backing_dev_info, nr_pages);
+               bdi_start_writeback(&q->backing_dev_info, nr_pages,
+                                       WB_REASON_LAPTOP_TIMER);
 }
 
 /*

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b55699c..c735bd7 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2181,7 +2181,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                 */
                writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
                if (total_scanned > writeback_threshold) {
-                       wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
+                       wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
+                                               WB_REASON_TRY_TO_FREE_PAGES);
                        sc->may_writepage = 1;
                }