Hello Milan, > -----Original Message----- > From: Milan Broz [mailto:gmazyland@xxxxxxxxx] > Sent: Thursday, September 24, 2020 2:16 AM > To: Eric Biggers <ebiggers@xxxxxxxxxx>; Mike Snitzer <snitzer@xxxxxxxxxx> > Cc: Sudhakar Panneerselvam <sudhakar.panneerselvam@xxxxxxxxxx>; > Damien.LeMoal@xxxxxxx; ssudhakarp@xxxxxxxxx; Martin Petersen > <martin.petersen@xxxxxxxxxx>; dm-crypt@xxxxxxxx; dm-devel@xxxxxxxxxx; > Shirley Ma <shirley.ma@xxxxxxxxxx>; mpatocka@xxxxxxxxxx; > agk@xxxxxxxxxx > Subject: Re: [RFC PATCH 0/2] dm crypt: Allow unaligned buffer > lengths for skcipher devices > > On 24/09/2020 07:14, Eric Biggers wrote: > > On Wed, Sep 23, 2020 at 09:27:32PM -0400, Mike Snitzer wrote: > >> You've clearly done a nice job with these changes. Looks clean. > >> > >> BUT, I'm struggling to just accept that dm-crypt needs to go to these > >> extra lengths purely because of one bad apple usecase. > >> > >> These alignment constraints aren't new. Are there other portions of > >> Linux's crypto subsystem that needed comparable fixes in order to work > >> with Microsfot OS initiated IO through a guest? > >> > >> You forecast that these same kinds of changes are needed for AEAD and > >> dm-integrity... that's alarming. > >> > >> Are we _certain_ there is no other way forward? > >> (Sorry I don't have suggestions.. I'm in "fact finding mode" ;) > >> > > > > I don't understand why this is needed, since dm-crypt already sets its > > logical_block_size to its crypto sector_size. Isn't it expected that I/O that > > isn't aligned to logical_block_size fails? It's the I/O submitter's > > responsibility to ensure logical_block_size alignment of all I/O segments. > > Exactly how is the misaligned I/O actually being submitted here? > > Thanks for mentioning it - exactly that I asked when reading this patch... > It seems that we are here fixing a problem that is just caused when someone > ignores clearly set restrictions. > > Who is submitting these bioses? Why can it not be fixed there? > > What happens with writes to fs journals, etc., is it still safe if we are > processing such unaligned bios? I don't follow your question regarding fs journals. I am not sure why it is not safe to process unaligned bio segment lengths of fs journals writes. Could you explain with some example on why that would be a problem? Please see my reply to Eric's/Mike's email, in that, I explained why this issue needs to be fixed in dm-crypt. I hope I have answered to your questions there. If not, let me know, I will try to answer. Thanks Sudhakar > > Milan -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
