cifs: auto disable 'serverino' in dfs mounts

Different servers have different set of file ids.

After failover, unique IDs will be different so we can't validate
them.
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Paulo Alcantara <palcantara@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/connect.c

@@ -4220,6 +4220,12 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
 	if (rc)
 		goto error;
 
+	/*
+	 * After reconnecting to a different server, unique ids won't
+	 * match anymore, so we disable serverino. This prevents
+	 * dentry revalidation to think the dentry are stale (ESTALE).
+	 */
+	cifs_autodisable_serverino(cifs_sb);
 out:
 	free_xid(xid);
 	return mount_setup_tlink(cifs_sb, ses, tcon);

fs/cifs/inode.c

@@ -730,7 +730,6 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 		    FILE_ALL_INFO *data, struct super_block *sb, int xid,
 		    const struct cifs_fid *fid)
 {
-	bool validinum = false;
 	__u16 srchflgs;
 	int rc = 0, tmprc = ENOSYS;
 	struct cifs_tcon *tcon;
@@ -821,7 +820,6 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 			(FILE_DIRECTORY_INFO *)data, cifs_sb);
 			fattr.cf_uniqueid = le64_to_cpu(
 			((SEARCH_ID_FULL_DIR_INFO *)data)->UniqueId);
-			validinum = true;
 
 			cifs_buf_release(srchinf->ntwrk_buf_start);
 		}
@@ -840,7 +838,6 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	 */
 	if (*inode == NULL) {
 		if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) {
-			if (validinum == false) {
 			if (server->ops->get_srv_inum)
 				tmprc = server->ops->get_srv_inum(xid,
 								  tcon, cifs_sb, full_path,
@@ -859,12 +856,11 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 				fattr.cf_uniqueid =
 					simple_hashstr(tcon->treeName);
 			}
-			}
 		} else
 			fattr.cf_uniqueid = iunique(sb, ROOT_I);
 	} else {
-		if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
-		    validinum == false && server->ops->get_srv_inum) {
+		if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM)
+		    && 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+.

fs/cifs/misc.c

@@ -525,9 +525,17 @@ void
 cifs_autodisable_serverino(struct cifs_sb_info *cifs_sb)
 {
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) {
+		struct cifs_tcon *tcon = NULL;
+
+		if (cifs_sb->master_tlink)
+			tcon = cifs_sb_master_tcon(cifs_sb);
+
 		cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_SERVER_INUM;
-		cifs_dbg(VFS, "Autodisabling the use of server inode numbers on %s. This server doesn't seem to support them properly. Hardlinks will not be recognized on this mount. Consider mounting with the \"noserverino\" option to silence this message.\n",
-			 cifs_sb_master_tcon(cifs_sb)->treeName);
+		cifs_dbg(VFS, "Autodisabling the use of server inode numbers on %s.\n",
+			 tcon ? tcon->treeName : "new server");
+		cifs_dbg(VFS, "The server doesn't seem to support them properly or the files might be on different servers (DFS).\n");
+		cifs_dbg(VFS, "Hardlinks will not be recognized on this mount. Consider mounting with the \"noserverino\" option to silence this message.\n");
+
 	}
 }