quota: Split dquot_quota_sync() to writeback and cache flushing part

Split off part of dquot_quota_sync() which writes dquots into a quota file
to a separate function. In the next patch we will use the function from
filesystems and we do not want to abuse ->quota_sync quotactl callback more
than necessary.

Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index b97178e..27b5cc7 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -1108,7 +1108,7 @@
 	}
 }
 
-int gfs2_quota_sync(struct super_block *sb, int type, int wait)
+int gfs2_quota_sync(struct super_block *sb, int type)
 {
 	struct gfs2_sbd *sdp = sb->s_fs_info;
 	struct gfs2_quota_data **qda;
@@ -1154,7 +1154,7 @@
 
 static int gfs2_quota_sync_timeo(struct super_block *sb, int type)
 {
-	return gfs2_quota_sync(sb, type, 0);
+	return gfs2_quota_sync(sb, type);
 }
 
 int gfs2_quota_refresh(struct gfs2_sbd *sdp, int user, u32 id)