From: Kent Overstreet <kent.overstreet@gmail.com>
To: Marc MERLIN <marc@merlins.org>
Cc: ching <lsching17@gmail.com>,
Eric Wheeler <bcache@lists.ewheeler.net>,
linux-bcache@vger.kernel.org
Subject: Re: scrub backing device
Date: Fri, 13 May 2016 14:21:33 -0800 [thread overview]
Message-ID: <20160513222133.GA3784@kmo-pixel> (raw)
In-Reply-To: <20160511235748.GR18290@merlins.org>
On Wed, May 11, 2016 at 04:57:48PM -0700, Marc MERLIN wrote:
> On Thu, May 12, 2016 at 07:34:26AM +0800, ching wrote:
> > for example https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs-scrub
>
> btrfs scrub is designed to make sure all the blocks and checksums are
> consistent.
> Ching makes a good point that it would be helpful to have a way to
> access the underlying backing device directly to ensure it is
> consistent.
>
> I think currently you can use dmsetup with an offset to get the real
> filesystem past the bcache header, mount that read only somewhere and
> scrub that.
> Not ideal because scrub will not be able to fix issues that are fixable,
> but at least it should report errors.
Look at the verify code in drivers/md/bcache/debug.c, there's a
CONFIG_BCACHE_DEBUG mode where every time it reads clean cached data it reads
the data from the backing device and compares.
But for a scrub though you really want to walk all the _cached_ data, so it'd
take a bit more code than that.
next prev parent reply other threads:[~2016-05-13 22:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-29 2:13 scrub backing device ching lu
2016-05-11 1:15 ` Eric Wheeler
2016-05-11 1:36 ` ching lu
2016-05-11 19:13 ` Eric Wheeler
2016-05-11 23:34 ` ching
2016-05-11 23:57 ` Marc MERLIN
2016-05-12 10:25 ` ching
2016-05-13 22:10 ` Marc MERLIN
2016-05-13 22:21 ` Kent Overstreet [this message]
2016-05-15 23:56 ` ching
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