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([2620:10d:c091:480::1:c550]) by smtp.gmail.com with ESMTPSA id f7sm4018640qkk.88.2020.06.04.06.17.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Jun 2020 06:17:05 -0700 (PDT) Subject: Re: [PATCH v7 2/2] btrfs: Introduce new mount option to skip block group items scan To: Qu Wenruo , linux-btrfs@vger.kernel.org References: <20200604071807.61345-1-wqu@suse.com> <20200604071807.61345-3-wqu@suse.com> From: Josef Bacik Message-ID: <8303441a-d192-7c7c-bd22-fdce2bb894bc@toxicpanda.com> Date: Thu, 4 Jun 2020 09:17:03 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 MIME-Version: 1.0 In-Reply-To: <20200604071807.61345-3-wqu@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 6/4/20 3:18 AM, Qu Wenruo wrote: > [PROBLEM] > There are some reports of corrupted fs which can't be mounted due to > corrupted extent tree. > > However under such situation, it's more likely the fs/subvolume trees > are still fine. > > For such case we normally go btrfs-restore and salvage as much as we > can. However btrfs-restore can't list subvolumes as "btrfs subv list", > making it harder to restore a fs. > > [ENHANCEMENT] > This patch will introduce a new mount option "rescue=skipbg" to skip > the mount time block group scan, and use chunk info solely to populate > fake block group cache. > > The mount option has the following dependency: > - RO mount > Obviously. > > - No dirty log. > Either there is no log, or use rescue=nologreplay mount option. > > - No way to remoutn RW > Similar to rescue=nologreplay option. > > This allow kernel to accept all extent tree corruption, even when the > whole extent tree is corrupted, and allow user to salvage data and > subvolume info. > > Signed-off-by: Qu Wenruo Reviewed-by: Josef Bacik Thanks, Josef