writeback: provide a wakeup_flusher_threads_bdi()

Similar to wakeup_flusher_threads(), except that we only wake
up the flusher threads on the specified backing device.

No functional changes in this patch.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Chris Mason <clm@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index fe555bc..9f39829 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1947,6 +1947,33 @@ void wb_workfn(struct work_struct *work)
 }
 
 /*
+ * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
+ * write back the whole world.
+ */
+static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
+                                        long nr_pages, enum wb_reason reason)
+{
+       struct bdi_writeback *wb;
+
+       if (!bdi_has_dirty_io(bdi))
+               return;
+
+       list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
+               wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
+                                       reason);
+}
+
+void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
+                               enum wb_reason reason)
+{
+       long nr_pages = get_nr_dirty_pages();
+
+       rcu_read_lock();
+       __wakeup_flusher_threads_bdi(bdi, nr_pages, reason);
+       rcu_read_unlock();
+}
+
+/*
  * Wakeup the flusher threads to start writeback of all currently dirty pages
  */
 void wakeup_flusher_threads(enum wb_reason reason)
@@ -1963,16 +1990,8 @@ void wakeup_flusher_threads(enum wb_reason reason)
        nr_pages = get_nr_dirty_pages();
 
        rcu_read_lock();
-       list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
-               struct bdi_writeback *wb;
-
-               if (!bdi_has_dirty_io(bdi))
-                       continue;
-
-               list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
-                       wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
-                                               reason);
-       }
+       list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
+               __wakeup_flusher_threads_bdi(bdi, nr_pages, reason);
        rcu_read_unlock();
 }
 

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 1f9c6db..9c00916 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -190,6 +190,8 @@ bool try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
                                   enum wb_reason reason);
 void sync_inodes_sb(struct super_block *);
 void wakeup_flusher_threads(enum wb_reason reason);
+void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
+                               enum wb_reason reason);
 void inode_wait_for_writeback(struct inode *inode);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */