From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:46331 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932356AbdJaUXd (ORCPT ); Tue, 31 Oct 2017 16:23:33 -0400 Subject: Re: [PATCH] Btrfs: bail out gracefully rather than BUG_ON To: Liu Bo , linux-btrfs@vger.kernel.org References: <20171030171440.27044-1-bo.li.liu@oracle.com> From: Nikolay Borisov Message-ID: Date: Tue, 31 Oct 2017 22:23:30 +0200 MIME-Version: 1.0 In-Reply-To: <20171030171440.27044-1-bo.li.liu@oracle.com> Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 30.10.2017 19:14, Liu Bo wrote: > If a file's DIR_ITEM key is invalid (due to memory errors) and gets > written to disk, a future lookup_path can end up with kernel panic due > to BUG_ON(). > > This gets rid of the BUG_ON(), meanwhile output the corrupted key and > return ENOENT if it's invalid. > > Signed-off-by: Liu Bo > --- > The diff doesn't show the logic well, 'goto out_err' will return with > assigning 0 to location->objectid, and the caller already has a check > for (location->objectid == 0) to return -ENOENT. > > fs/btrfs/inode.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index d94e3f6..916cdc9 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -5500,6 +5500,14 @@ static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry, > goto out_err; > > btrfs_dir_item_key_to_cpu(path->nodes[0], di, location); > + if (location->type != BTRFS_INODE_ITEM_KEY && > + location->type != BTRFS_ROOT_ITEM_KEY) { > + btrfs_warn(root->fs_info, > + "%s gets something invalid in DIR_ITEM (name %s, directory ino %llu, location(%llu %u %llu))", > + __func__, name, btrfs_ino(BTRFS_I(dir)), > + location->objectid, location->type, location->offset); > + goto out_err; If this situation happens it's possible that ret is still 0 so the error handling in btrfs_lookup_dentry might not trigger. How about just setting -EUCLEAN if we execute the if branch? > + } > out: > btrfs_free_path(path); > return ret; > @@ -5816,8 +5824,6 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry) > return inode; > } > > - BUG_ON(location.type != BTRFS_ROOT_ITEM_KEY); > - > index = srcu_read_lock(&fs_info->subvol_srcu); > ret = fixup_tree_root_location(fs_info, dir, dentry, > &location, &sub_root); >