NFS: Block new writes while syncing data in nfs_getattr()

Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/inode.c

···
 	trace_nfs_getattr_enter(inode);
 	/* Flush out writes to the server in order to update c/mtime.  */
 	if (S_ISREG(inode->i_mode)) {
+		mutex_lock(&inode->i_mutex);
 		err = nfs_sync_inode(inode);
+		mutex_unlock(&inode->i_mutex);
 		if (err)
 			goto out;
 	}