nfs: fix v4.2 SEEK on files over 2 gigs

We're incorrectly assigning a loff_t return to an int.  If SEEK_HOLE or
SEEK_DATA returns an offset over 2^31 then the application will see a
weird lseek() result (usually -EIO).

Cc: stable@vger.kernel.org
Fixes: bdcc2cd1 "NFSv4.2: handle NFS-specific llseek errors"
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Reviewed-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs42proc.c

@@ -175,10 +175,12 @@ loff_t nfs42_proc_llseek(struct file *filep, loff_t offset, int whence)
 {
 	struct nfs_server *server = NFS_SERVER(file_inode(filep));
 	struct nfs4_exception exception = { };
-	int err;
+	loff_t err;
 
 	do {
 		err = _nfs42_proc_llseek(filep, offset, whence);
+		if (err >= 0)
+			break;
 		if (err == -ENOTSUPP)
 			return -EOPNOTSUPP;
 		err = nfs4_handle_exception(server, err, &exception);