Export sync_filesystem() for modular ->remount_fs() use

This patch changes sync_filesystem() to be EXPORT_SYMBOL().

The reason this is needed is that starting with 3.15 kernel, due to
Theodore Ts'o's commit 02b9984d64 ("fs: push sync_filesystem() down to
the file system's remount_fs()"), all file systems that have dirty data
to be written out need to call sync_filesystem() from their
->remount_fs() method when remounting read-only.

As this is now a generically required function rather than an internal
only function it should be EXPORT_SYMBOL() so that all file systems can
call it.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/sync.c

@@ -65,7 +65,7 @@ int sync_filesystem(struct super_block *sb)
 		return ret;
 	return __sync_filesystem(sb, 1);
 }
-EXPORT_SYMBOL_GPL(sync_filesystem);
+EXPORT_SYMBOL(sync_filesystem);
 
 static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 {