nfsd4: fix break_lease flags on nfsd open

Thanks to Casey Bodley for pointing out that on a read open we pass 0,
instead of O_RDONLY, to break_lease, with the result that a read open is
treated like a write open for the purposes of lease breaking!
Reported-by: Casey Bodley <cbodley@citi.umich.edu>
Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/vfs.c

@@ -696,7 +696,15 @@ nfsd_access(struct svc_rqst *rqstp, struct svc_fh *fhp, u32 *access, u32 *suppor
 }
 #endif /* CONFIG_NFSD_V3 */
 
+static int nfsd_open_break_lease(struct inode *inode, int access)
+{
+	unsigned int mode;
 
+	if (access & NFSD_MAY_NOT_BREAK_LEASE)
+		return 0;
+	mode = (access & NFSD_MAY_WRITE) ? O_WRONLY : O_RDONLY;
+	return break_lease(inode, mode | O_NONBLOCK);
+}
 
 /*
  * Open an existing file or directory.
@@ -744,12 +752,7 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 	if (!inode->i_fop)
 		goto out;
 
-	/*
-	 * Check to see if there are any leases on this file.
-	 * This may block while leases are broken.
-	 */
-	if (!(access & NFSD_MAY_NOT_BREAK_LEASE))
-		host_err = break_lease(inode, O_NONBLOCK | ((access & NFSD_MAY_WRITE) ? O_WRONLY : 0));
+	host_err = nfsd_open_break_lease(inode, access);
 	if (host_err) /* NOMEM or WOULDBLOCK */
 		goto out_nfserr;