From: Josef Bacik <jbacik@fusionio.com>
To: Zach Brown <zab@redhat.com>
Cc: Chris Mason <clmason@fusionio.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: testing stable pages being modified
Date: Fri, 31 May 2013 09:29:07 -0400 [thread overview]
Message-ID: <20130531132907.GF9829@localhost.localdomain> (raw)
In-Reply-To: <20130531062430.GB24721@lenny.home.zabbo.net>
On Fri, May 31, 2013 at 12:24:30AM -0600, Zach Brown wrote:
> > Changing O_DIRECT in flight has always been a deep dark corner case, and
> > crc errors are the expected result. Have you found anyone doing this in
> > real life?
>
> Agreed; and no, I haven't heard of people accidentally modifying stable
> pages.
>
Windows does this, it also will send down the same page for different offsets
which is why we have that special check in check_direct_IO for reads because
that would cause lots of csum errors too. I tried to fix the modified in flight
problem by checking the csums of the pages in the io completion handler and
re-submitting the IO if the pages had changed, but this of course dramatically
reduced performance for all of those well behaved O_DIRECT applications, so in
the end I just set nodatasum for that vm image and carried on. I'm not sure
what the solution is for this problem. Thanks,
Josef
next prev parent reply other threads:[~2013-05-31 13:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-30 22:36 testing stable pages being modified Zach Brown
2013-05-31 5:11 ` Chris Mason
2013-05-31 6:24 ` Zach Brown
2013-05-31 13:29 ` Josef Bacik [this message]
2013-05-31 13:53 ` Chris Mason
2013-05-31 14:34 ` Josef Bacik
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