cifs: Check uniqueid for SMB2+ and return -ESTALE if necessary

Commit 7196ac11 ("Fix to check Unique id and FileType when client
refer file directly.") checks whether the uniqueid of an inode has
changed when getting the inode info, but only when using the UNIX
extensions. Add a similar check for SMB2+, since this can be done
without an extra network roundtrip.
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/inode.c

@@ -814,8 +814,21 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 			}
 		} else
 			fattr.cf_uniqueid = iunique(sb, ROOT_I);
-	} else
-		fattr.cf_uniqueid = CIFS_I(*inode)->uniqueid;
+	} else {
+		if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
+		    validinum == false && server->ops->get_srv_inum) {
+			/*
+			 * Pass a NULL tcon to ensure we don't make a round
+			 * trip to the server. This only works for SMB2+.
+			 */
+			tmprc = server->ops->get_srv_inum(xid,
+				NULL, cifs_sb, full_path,
+				&fattr.cf_uniqueid, data);
+			if (tmprc)
+				fattr.cf_uniqueid = CIFS_I(*inode)->uniqueid;
+		} else
+			fattr.cf_uniqueid = CIFS_I(*inode)->uniqueid;
+	}
 
 	/* query for SFU type info if supported and needed */
 	if (fattr.cf_cifsattrs & ATTR_SYSTEM &&
@@ -856,6 +869,13 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	} else {
 		/* we already have inode, update it */
 
+		/* if uniqueid is different, return error */
+		if (unlikely(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM &&
+		    CIFS_I(*inode)->uniqueid != fattr.cf_uniqueid)) {
+			rc = -ESTALE;
+			goto cgii_exit;
+		}
+
 		/* if filetype is different, return error */
 		if (unlikely(((*inode)->i_mode & S_IFMT) !=
 		    (fattr.cf_mode & S_IFMT))) {