From: Sergei Trofimovich <slyfox@gentoo.org>
To: gentoo-dev@lists.gentoo.org
Cc: ryao@gentoo.org,
Kernel development list <linux-kernel@vger.kernel.org>,
kernel@gentoo.org, gentooligan@gmail.com
Subject: Re: [gentoo-dev] dm-crypt reordering BIOs across barriers?
Date: Sat, 8 Jun 2013 09:11:14 +0300 [thread overview]
Message-ID: <20130608091114.441c5f17@sf> (raw)
In-Reply-To: <51B2A955.4010906@gentoo.org>
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On Fri, 07 Jun 2013 23:47:33 -0400
Richard Yao <ryao@gentoo.org> wrote:
> When you use dm-crypt, block IO requests to a dm-* device will invoke
> dm_request_fn() -> map_request() -> crypt_map(). If a BIO is a write
> barrier, crypt_map() will return DM_MAPIO_REMAPPED to map_request(),
> which will immediately queue it to the device.
>
> If a few dozen IOs are queued in rapid succession with multiple write
> barriers, all write barriers will be executed before any actual write
> BIOs occur because the write IOs will be processed asynchronously in a
> work queue. Since the barriers will be long gone by the time the write
> IOs are queued, they can be queued in any order.
>
> Am I misunderstanding this or is dm-crypt ignoring proper write barrier
> semantics?
>
http://www.saout.de/pipermail/dm-crypt/2012-April/002441.html
http://lwn.net/Articles/400541/
--
Sergei
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next prev parent reply other threads:[~2013-06-08 6:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-08 3:47 dm-crypt reordering BIOs across barriers? Richard Yao
2013-06-08 6:11 ` Sergei Trofimovich [this message]
2013-06-08 9:17 ` [gentoo-dev] " Richard Yao
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