From: Andrei Borzenkov <arvidjaar@gmail.com>
To: Tomasz Melcer <liori@exroot.org>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: Force recalculation of a data block checksum
Date: Sun, 24 Jul 2016 08:07:50 +0300 [thread overview]
Message-ID: <818f5843-20ad-2a9e-9b88-a16689739c80@gmail.com> (raw)
In-Reply-To: <6699a315-17f4-9298-fb6b-64358c497be0@exroot.org>
24.07.2016 07:32, Tomasz Melcer пишет:
> On 24.07.2016 04:16, Chris Murphy wrote:
>> On Sat, Jul 23, 2016 at 8:03 PM, Tomasz Melcer <liori@exroot.org> wrote:
>>> How can I ask btrfs to recompute the checksum of a data block as it is
>>> stored on the drive?
>>
>> Since btrfs-progs 3.17 'btrfs check --init-csum-tree' will create a
>> whole new csum tree.
>
> I can't make this command recalculate only checksum of that single file?
>
>
Rewriting single block in question should do it. As you can read from
raw device and have both physical and logical block address something like
dd if=/dev/sdd1 skip=222940168 count=8 | dd of=/path/to/dysk/dysk.bin
seek=189669768 conv=notrunc count=8
If you have possibility to verify file content(s), this technique can be
used to read over unreadable parts of file by combining multiple dd's
from file and device.
It probably makes sense to create (read-only) snapshot to make sure you
have old content available.
next prev parent reply other threads:[~2016-07-24 5:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-24 2:03 Force recalculation of a data block checksum Tomasz Melcer
2016-07-24 2:16 ` Chris Murphy
2016-07-24 4:32 ` Tomasz Melcer
2016-07-24 5:07 ` Andrei Borzenkov [this message]
2016-07-26 1:50 ` Tomasz Melcer
2016-07-24 5:57 ` Chris Murphy
2016-07-24 2:36 ` Duncan
2016-07-24 2:51 ` Chris Murphy
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