1 files changed, 52 insertions, 16 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index aed881a76b22..3d06ccc953aa 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -707,6 +707,17 @@ get_next_work_item(struct backing_dev_info *bdi)
         return work;
 }
 
+/*
+ * Add in the number of potentially dirty inodes, because each inode
+ * write can dirty pagecache in the underlying blockdev.
+ */
+static unsigned long get_nr_dirty_pages(void)
+{
+        return global_page_state(NR_FILE_DIRTY) +
+                global_page_state(NR_UNSTABLE_NFS) +
+                get_nr_dirty_inodes();
+}
+
 static long wb_check_old_data_flush(struct bdi_writeback *wb)
 {
         unsigned long expired;
@@ -724,13 +735,7 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
                 return 0;
 
         wb->last_old_flush = jiffies;
-        /*
-         * Add in the number of potentially dirty inodes, because each inode
-         * write can dirty pagecache in the underlying blockdev.
-         */
-        nr_pages = global_page_state(NR_FILE_DIRTY) +
-                        global_page_state(NR_UNSTABLE_NFS) +
-                        get_nr_dirty_inodes();
+        nr_pages = get_nr_dirty_pages();
 
         if (nr_pages) {
                 struct wb_writeback_work work = {
@@ -1076,32 +1081,42 @@ static void wait_sb_inodes(struct super_block *sb)
 }
 
 /**
- * writeback_inodes_sb  -       writeback dirty inodes from given super_block
+ * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
  * @sb: the superblock
+ * @nr: the number of pages to write
  *
  * Start writeback on some inodes on this super_block. No guarantees are made
  * on how many (if any) will be written, and this function does not wait
- * for IO completion of submitted IO. The number of pages submitted is
- * returned.
+ * for IO completion of submitted IO.
  */
-void writeback_inodes_sb(struct super_block *sb)
+void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
 {
-        unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
-        unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
         DECLARE_COMPLETION_ONSTACK(done);
         struct wb_writeback_work work = {
                 .sb             = sb,
                 .sync_mode      = WB_SYNC_NONE,
                 .done           = &done,
+                .nr_pages       = nr,
         };
 
         WARN_ON(!rwsem_is_locked(&sb->s_umount));
-
-        work.nr_pages = nr_dirty + nr_unstable + get_nr_dirty_inodes();
-
         bdi_queue_work(sb->s_bdi, &work);
         wait_for_completion(&done);
 }
+EXPORT_SYMBOL(writeback_inodes_sb_nr);
+
+/**
+ * writeback_inodes_sb  -       writeback dirty inodes from given super_block
+ * @sb: the superblock
+ *
+ * Start writeback on some inodes on this super_block. No guarantees are made
+ * 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)
+{
+        return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
+}
 EXPORT_SYMBOL(writeback_inodes_sb);
 
 /**
@@ -1124,6 +1139,27 @@ int writeback_inodes_sb_if_idle(struct super_block *sb)
 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
 
 /**
+ * writeback_inodes_sb_if_idle  -       start writeback if none underway
+ * @sb: the superblock
+ * @nr: the number of pages to write
+ *
+ * Invoke writeback_inodes_sb if no writeback is currently underway.
+ * Returns 1 if writeback was started, 0 if not.
+ */
+int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
+                                   unsigned long nr)
+{
+        if (!writeback_in_progress(sb->s_bdi)) {
+                down_read(&sb->s_umount);
+                writeback_inodes_sb_nr(sb, nr);
+                up_read(&sb->s_umount);
+                return 1;
+        } else
+                return 0;
+}
+EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
+
+/**
  * sync_inodes_sb       -       sync sb inode pages
  * @sb: the superblock
  *