From: Milan Broz <mbroz@redhat.com>
To: Yang Zhang <yanghatespam@gmail.com>
Cc: dm-crypt@saout.de
Subject: Re: [dm-crypt] Does dm-crypt support journaling filesystem transactional guarantees?
Date: Tue, 24 Apr 2012 09:47:42 +0200 [thread overview]
Message-ID: <4F965A9E.7090804@redhat.com> (raw)
In-Reply-To: <CAKxBDU9Ctqh9xSYwsbQQ3ZY68SgAf3Ft=2Js9z4sCDMvWLKY8w@mail.gmail.com>
On 04/24/2012 08:45 AM, Yang Zhang wrote:
> I'm considering using ext4 on encrypted LVM (which uses LUKS and
> dm-crypt). Will the transactional guarantees in ext4's journaling be
> preserved?
yes. dm-crypt operates in block layer, so it is filesystem responsibility
to properly set needed bits for IO (flush cache, FUA - force unit access)
and dmcrypt (device-mapper in general and block layer) must process them.
(read http://lwn.net/Articles/400541/ for more info).
In short, ext4, xfs, btrfs and similar filesystems supports
all features over dmcrypt.
(Except very old kernels, but most of stable distros backports patches.)
> Bonus: where may I find authoritative information on this (besides the source)?
The source is your best friend :-)
basically this is the first commit introducing real barrier
(later replaced with FUA) support
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=647c7db14ef9cacc4ccb3683e206b61f0de6dc2b
You can also use blktrace to see how are fs requests propagated
to physical media.
Milan
next prev parent reply other threads:[~2012-04-24 7:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-24 6:45 [dm-crypt] Does dm-crypt support journaling filesystem transactional guarantees? Yang Zhang
2012-04-24 7:47 ` Milan Broz [this message]
2012-04-24 8:14 ` Arno Wagner
2012-04-24 8:16 ` Yang Zhang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4F965A9E.7090804@redhat.com \
--to=mbroz@redhat.com \
--cc=dm-crypt@saout.de \
--cc=yanghatespam@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.