Revert "NFSv4: Remove incorrect check in can_open_delegated()"

This reverts commit 4e379d36c050b0117b5d10048be63a44f5036115.

This commit opens up a race between the recovery code and the open code.

Reported-by: Olga Kornievskaia <aglo@umich.edu>
Cc: stable@vger.kernel # v4.0+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4proc.c

@@ -1156,6 +1156,8 @@ static int can_open_delegated(struct nfs_delegation *delegation, fmode_t fmode)
 		return 0;
 	if ((delegation->type & fmode) != fmode)
 		return 0;
+	if (test_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags))
+		return 0;
 	if (test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
 		return 0;
 	nfs_mark_delegation_referenced(delegation);