NFSD: Fix problem of COMMIT and NFS4ERR_DELAY in infinite loop

The following request sequence to the same file causes the NFS client and
server getting into an infinite loop with COMMIT and NFS4ERR_DELAY:

OPEN
REMOVE
WRITE
COMMIT

Problem reported by recall11, recall12, recall14, recall20, recall22,
recall40, recall42, recall48, recall50 of nfstest suite.

This patch restores the handling of race condition in nfsd_file_do_acquire
with unlink to that prior of the regression.

Fixes: ac3a258 ("nfsd: rework refcounting in filecache")
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: daimngo

fs/nfsd/filecache.c

@@ -1099,8 +1099,6 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	 * then unhash.
 	 */
 	if (status != nfs_ok || inode->i_nlink == 0)
-		status = nfserr_jukebox;
-	if (status != nfs_ok)
 		nfsd_file_unhash(nf);
 	clear_and_wake_up_bit(NFSD_FILE_PENDING, &nf->nf_flags);
 	if (status == nfs_ok)