From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:6721 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756529AbbDVFzH convert rfc822-to-8bit (ORCPT ); Wed, 22 Apr 2015 01:55:07 -0400 Message-ID: <553737B9.7010504@cn.fujitsu.com> Date: Wed, 22 Apr 2015 13:55:05 +0800 From: Qu Wenruo MIME-Version: 1.0 To: , David Sterba Subject: Re: [PATCH 0/7] Allow btrfsck to reset csum of all tree blocks, AKA dangerous mode. References: <1423034213-14018-1-git-send-email-quwenruo@cn.fujitsu.com> In-Reply-To: <1423034213-14018-1-git-send-email-quwenruo@cn.fujitsu.com> Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Ping. No new comment nor merged? Thanks, Qu -------- Original Message -------- Subject: [PATCH 0/7] Allow btrfsck to reset csum of all tree blocks, AKA dangerous mode. From: Qu Wenruo To: Date: 2015年02月04日 15:16 > Btrfs's metadata csum is a good mechanism, keeping bit error away from > sensitive kernel. But such mechanism will also be too sensitive, like > bit error in csum bytes or low all zero bits in nodeptr. > It's a trade using "error tolerance" for stable, and is reasonable for > most cases since there is DUP/RAID1/5/6/10 duplication level. > > But in some case, whatever for development purpose or despair user who > can't tolerant all his/her inline data lost, or even crazy QA team > hoping btrfs can survive heavy random bits bombing, there are some guys > want to get rid of the csum protection and face the crucial raw data no > matter what disaster may happen. > > So, introduce the new '--dangerous' (or "destruction"/"debug" if you like) > option for btrfsck to reset all csum of tree blocks. > > The csum reseting have the following features: > 1) Top to down level by level > The csum resetting is done from tree to level 1, and only when all the > csum of nodes in this level is reset and can pass read_tree_block() > check, it will continue to next level. > And all bytenr in nodeptr will be re-aligned, so bit error in the low 12 > bits(4K sector size case) can also be repaired without pain. > With this behavior, error in nodeptr has a chance not affecting its > child. > > 2) No Copy-on-write > COW means we needs to have a valid extent tree, if extent tree is > corrupted COW will only be a BUG_ON blocking us. > So all the r/w in this dangerous mode will use no-cow write. That's why > we export and slightly modified write_tree_block() to do no-cow tree > block write with newly calculated csum. > Since the write is not cowed, if it fails, it will also destroy the last > hope for manual inspection. > > Qu Wenruo (7): > btrfs-progs: Add btrfs_(prev/next)_tree_block() to keep search result > in the same level of path->lowest_level. > btrfs-progs: Introduce btrfs_next_slot() function to iterate to next > slot in given level. > btrfs-progs: Allow btrfs_read_fs_root() to re-read the tree node. > btrfs-progs: Export write_tree_block() and allow it to do nocow write. > btrfs-progs: Introduce new function reset_tree_block_csum() for later > tree block csum reset. > btrfs-progs: Introduce new function reset_(one_root/roots)_csum() to > reset one/all tree's csum in tree root. > btrfs-progs: Introduce "--dangerous" option to reset all tree block > csum. > > cmds-check.c | 284 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- > ctree.c | 18 ++-- > ctree.h | 25 +++++- > disk-io.c | 55 +++++++++--- > disk-io.h | 3 + > 5 files changed, 359 insertions(+), 26 deletions(-) >