[dm-crypt] Does dm-crypt support journaling filesystem transactional guarantees?
arno at wagner.name
Tue Apr 24 10:14:09 CEST 2012
On Tue, Apr 24, 2012 at 09:47:42AM +0200, Milan Broz wrote:
> 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.)
See also FAQ item 2.10, which I just have updated to reflect this
> > 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
> You can also use blktrace to see how are fs requests propagated
> to physical media.
> dm-crypt mailing list
> dm-crypt at saout.de
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
One of the painful things about our time is that those who feel certainty
are stupid, and those with any imagination and understanding are filled
with doubt and indecision. -- Bertrand Russell
More information about the dm-crypt