NFS: Clean up NFS writeback flush code

The only user of nfs_sync_mapping_range() is nfs_getattr(), which uses it
to flush out the entire inode without sending a commit. We therefore
replace nfs_sync_mapping_range with a more appropriate helper.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 71a49c3..119fefe 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -431,7 +431,7 @@
 
 	/* Flush out writes to the server in order to update c/mtime */
 	if (S_ISREG(inode->i_mode))
-		nfs_sync_mapping_range(inode->i_mapping, 0, 0, FLUSH_NOCOMMIT);
+		nfs_wb_nocommit(inode);
 
 	/*
 	 * We may force a getattr if the user cares about atime.