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[70.62.41.24]) by smtp.gmail.com with ESMTPSA id q205-v6sm832769itc.2.2018.10.18.05.35.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Oct 2018 05:35:00 -0700 (PDT) Subject: Re: CRC mismatch To: Anton Shepelev , linux-btrfs@vger.kernel.org References: <20181016183051.788a79297af47a9798a0c0e3@gmail.com> <20181018150228.16680172c2551c06038d5344@gmail.com> From: "Austin S. Hemmelgarn" Message-ID: <42f3ecf9-9e43-62ca-80b6-720ba23ba230@gmail.com> Date: Thu, 18 Oct 2018 08:34:59 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181018150228.16680172c2551c06038d5344@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 18/10/2018 08.02, Anton Shepelev wrote: > I wrote: > >> 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? > > Thank you, Austin and Chris, for your replies. While > describing the problem for the client, I tried again to copy > the corrupt file and this time it was copied without error, > which is of course scary because errors that miraculously > disappear may suddenly reappear in the same manner. > If The filesystem was running some profile that supports repairs (pretty much, anything except single or raid0 profiles), then BTRFS will have fixed that particular block for you automatically. Of course, the other possibility is that it was a transient error in the block layer that caused it tor return bogus data when the data that was on-disk was in fact correct.