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[70.62.41.24]) by smtp.gmail.com with ESMTPSA id z186-v6sm5041361itd.43.2018.10.16.08.42.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Oct 2018 08:42:52 -0700 (PDT) Subject: Re: CRC mismatch To: Anton Shepelev , linux-btrfs@vger.kernel.org References: <20181016183051.788a79297af47a9798a0c0e3@gmail.com> From: "Austin S. Hemmelgarn" Message-ID: Date: Tue, 16 Oct 2018 11:42:49 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181016183051.788a79297af47a9798a0c0e3@gmail.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 2018-10-16 11:30, Anton Shepelev wrote: > Hello, all > > What may be the reason of a CRC mismatch on a BTRFS file in > a virutal machine: > > csum failed ino 175524 off 1876295680 csum 451760558 > expected csum 1446289185 > > Shall I seek the culprit in the host machine on in the guest > one? Supposing the host machine healty, what operations on > the gueest might have caused a CRC mismatch? > Possible causes include: * On the guest side: - Unclean shutdown of the guest system (not likely even if this did happen). - A kernel bug on in the guest. - Something directly modifying the block device (also not very likely). * On the host side: - Unclean shutdown of the host system without properly flushing data from the guest. Not likely unless you're using an actively unsafe caching mode for the guest's storage back-end. - At-rest data corruption in the storage back-end. - A bug in the host-side storage stack. - A transient error in the host-side storage stack. - A bug in the hypervisor. - Something directly modifying the back-end storage. Of these, the statistically most likely location for the issue is probably the storage stack on the host.