[RFC PATCH v4 8/9] fs: export wait_sb_inodes()

[Chengguang Xu <cgxu519@mykernel.net>]

In order to wait syncing upper inodes we need to call wait_sb_inodes()
in overlayfs' ->sync_fs.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
 fs/fs-writeback.c         | 3 ++-
 include/linux/writeback.h | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 149227160ff0..55dafdc72661 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2365,7 +2365,7 @@ EXPORT_SYMBOL(__mark_inode_dirty);
  * completed by the time we have gained the lock and waited for all IO that is
  * in progress regardless of the order callers are granted the lock.
  */
-static void wait_sb_inodes(struct super_block *sb)
+void wait_sb_inodes(struct super_block *sb)
 {
 	LIST_HEAD(sync_list);
 
@@ -2449,6 +2449,7 @@ static void wait_sb_inodes(struct super_block *sb)
 	rcu_read_unlock();
 	mutex_unlock(&sb->s_sync_lock);
 }
+EXPORT_SYMBOL(wait_sb_inodes);
 
 static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
 				     enum wb_reason reason, bool skip_if_busy)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 8e5c5bb16e2d..53e826af33b6 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -198,6 +198,7 @@ void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
 				enum wb_reason reason);
 void inode_wait_for_writeback(struct inode *inode);
 void inode_io_list_del(struct inode *inode);
+void wait_sb_inodes(struct super_block *sb);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */
 static inline void wait_on_inode(struct inode *inode)
-- 
2.26.2