From: Milan Broz <mbroz@redhat.com>
To: dm-crypt@saout.de
Subject: Re: [dm-crypt] FYI: how to (really) cleanly shutdown the system when root is on multiple stacked block devices
Date: Sat, 26 Jun 2010 21:24:27 +0200 [thread overview]
Message-ID: <4C2653EB.2090606@redhat.com> (raw)
In-Reply-To: <20100626183632.GA30731@tansi.org>
On 06/26/2010 08:36 PM, Arno Wagner wrote:
> On Sat, Jun 26, 2010 at 04:21:52PM +0200, Christoph Anton Mitterer wrote:
>> And I'm not even sure if flushing alone is enough,... or where one needs
>> something like barriers...
>
> Barriesrs are a filesystem concept and play no role here.
Nope, "IO barriers" here are block level functionality.
See Documentation/block/barrier.txt in kernel
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/block/barrier.txt;hb=HEAD
(yes, it is confusing:-)
> Flushing ("fdatasync" or "fsunc") is not enough in some cases,
> hence the ro-remount, which is.
fsycn currently in kerenl issues barrier in block layer and then waits for it.
But if because ever reads can cause some metadata updates (last access on file stamp),
remounting read-only is there.
Milan
next prev parent reply other threads:[~2010-06-26 19:24 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-26 11:59 [dm-crypt] FYI: how to (really) cleanly shutdown the system when root is on multiple stacked block devices Christoph Anton Mitterer
2010-06-26 12:52 ` Arno Wagner
2010-06-26 14:21 ` Christoph Anton Mitterer
2010-06-26 18:36 ` Arno Wagner
2010-06-26 19:24 ` Milan Broz [this message]
2010-06-26 23:13 ` Christoph Anton Mitterer
2010-06-26 23:34 ` Arno Wagner
2010-06-27 0:20 ` markus reichelt
2010-06-27 8:35 ` Milan Broz
2010-06-27 12:03 ` Christoph Anton Mitterer
2010-07-02 18:48 ` markus reichelt
2010-07-02 19:29 ` Christoph Anton Mitterer
2010-06-27 2:28 ` Christoph Anton Mitterer
2010-06-27 2:53 ` Arno Wagner
2010-06-27 11:57 ` Christoph Anton Mitterer
2010-06-26 23:30 ` Arno Wagner
2010-06-27 2:31 ` Christoph Anton Mitterer
2010-06-27 2:39 ` Christoph Anton Mitterer
2010-06-27 2:56 ` Arno Wagner
2010-06-27 12:21 ` Christoph Anton Mitterer
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