From: Chris Mason <chris.mason@fusionio.com>
To: Zach Brown <zab@redhat.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 01:11:58 -0400 [thread overview]
Message-ID: <20130531051158.7927.24213@localhost.localdomain> (raw)
In-Reply-To: <20130530223610.GA24721@lenny.home.zabbo.net>
Quoting Zach Brown (2013-05-30 18:36:10)
> 'stable' pages have always been a bit of a fiction. It's easy to
> intentionally modify stable pages under io with some help from page
> references that ignore mappings and page state.
>
> Here's little test that uses O_DIRECT to get the pinned aio ring pages
> under IO and then has event completion stores modify them while they're
> in flight.
>
> It's a nice quick way to test the consequences of stable pages being
> modified. It can be used to burp out ratelimited csum failure kernel
> messages with btrfs, for example.
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?
I do like the small test program though, we should extend it into a test
to make sure crcs are really crcing.
-chris
next prev parent reply other threads:[~2013-05-31 5:12 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 [this message]
2013-05-31 6:24 ` Zach Brown
2013-05-31 13:29 ` Josef Bacik
2013-05-31 13:53 ` Chris Mason
2013-05-31 14:34 ` Josef Bacik
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