ceph: request xattrs if xattr_version is zero

Following sequence of events can happen.
  - Client releases an inode, queues cap release message.
  - A 'lookup' reply brings the same inode back, but the reply
    doesn't contain xattrs because MDS didn't receive the cap release
    message and thought client already has up-to-data xattrs.

The fix is force sending a getattr request to MDS if xattrs_version
is 0. The getattr mask is set to CEPH_STAT_CAP_XATTR, so MDS knows client
does not have xattr.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

fs/ceph/file.c

@@ -826,8 +826,7 @@ again:
 	ceph_put_cap_refs(ci, got);
 
 	if (checkeof && ret >= 0) {
-		int statret = ceph_do_getattr(inode,
-					      CEPH_STAT_CAP_SIZE);
+		int statret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
 
 		/* hit EOF or hole? */
 		if (statret == 0 && iocb->ki_pos < inode->i_size &&
@@ -995,7 +994,7 @@ static loff_t ceph_llseek(struct file *file, loff_t offset, int whence)
 	mutex_lock(&inode->i_mutex);
 
 	if (whence == SEEK_END || whence == SEEK_DATA || whence == SEEK_HOLE) {
-		ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
+		ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
 		if (ret < 0) {
 			offset = ret;
 			goto out;