From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from tartarus.angband.pl ([89.206.35.136]:58376 "EHLO tartarus.angband.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbcEGXLZ (ORCPT ); Sat, 7 May 2016 19:11:25 -0400 Date: Sun, 8 May 2016 01:11:18 +0200 From: Adam Borowski To: linux-btrfs@vger.kernel.org, Duncan <1i5t5.duncan@cox.net> Subject: Re: apt taints kernel - btrfs destroys inode Message-ID: <20160507231118.GA19573@angband.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: Duncan wrote: > > btrfs_destroy_inode > That's a known apparent false-positive warning on current 4.6-rc kernel > btrfs. The destroy-inode bit is related to a file deletion happening in > the normal order of things, where this warning code is run, and > apparently triggers even under normal operations. Are you guys reasonably certain it's false-positive? If so, you _really_ want to disable the warning for 4.6, less than a week from now. Any reasonable user of a stable kernel who notices such a warning and stack dumps will assume something is broken, rightfully panic and consider the filesystem unsound. > It's related to some btrfs feature (I think either snapshotting or > quotas, but don't recall which) I don't use here so I don't seem the > warnings, but there's several threads where people have reported the > warnings, so it's apparently quite commonly triggered, but nobody has > reported any further problems even where the warnings are coming in the > hundreds due to their use-case, so as I said, apparently a false-positive > induced by normal operations. A data point: I've been running for a week with this WARN_ON replaced by a printk: --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -9258,7 +9258,8 @@ void btrfs_destroy_inode(struct inode *inode) WARN_ON(BTRFS_I(inode)->outstanding_extents); WARN_ON(BTRFS_I(inode)->reserved_extents); WARN_ON(BTRFS_I(inode)->delalloc_bytes); - WARN_ON(BTRFS_I(inode)->csum_bytes); + if (BTRFS_I(inode)->csum_bytes) + printk("btrfs: btrfs_destroy_inode: WARN csum_bytes\n"); WARN_ON(BTRFS_I(inode)->defrag_bytes); /* and no data loss or anything suspicious so far. This box has a SSD (moderate use) and HDD (light use), no RAID, no quotas, compress=lzo, many subvolumes, 20ish snapshots daily (mostly sbuild for Debian packages). [~]$ dmesg|grep btrfs_destroy_inode|wc -l 50 [~]$ uptime 00:17:47 up 1 day, 18:44, 19 users, load average: 0.23, 0.35, 0.61 [~]$ cat /proc/version Linux version 4.6.0-rc6-debug+ (kilobyte@umbar) (gcc version 6.1.1 20160430 (Debian 6.1.1-1) ) #1 SMP Fri May 6 00:33:44 CEST 2016 > I'd expect the warning to be either fixed to only warn when there's an > actual issue, or be silenced, by 4.6 release. In order to get to 4.6 such a commit would need to hit Linus about right now... Meow! -- How to exploit the Bible for weight loss: Pr28:25: he that putteth his trust in the ʟᴏʀᴅ shall be made fat.