On Tue, Apr 24, 2012 at 1:14 AM, Arno Wagner <arno@xxxxxxxxxxx> wrote: > 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 > information ;-) At first I was confused what this was referring to - for posterity, turns out this is the (very useful) cryptsetup FAQ at http://code.google.com/p/cryptsetup/wiki/FrequentlyAskedQuestions Thanks! > > Arno > > > >> > 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 >> _______________________________________________ >> dm-crypt mailing list >> dm-crypt@xxxxxxxx >> http://www.saout.de/mailman/listinfo/dm-crypt >> > > -- > Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@xxxxxxxxxxx > 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 > _______________________________________________ > dm-crypt mailing list > dm-crypt@xxxxxxxx > http://www.saout.de/mailman/listinfo/dm-crypt -- Yang Zhang http://yz.mit.edu/ _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
