From: Mike Snitzer <snitzer@redhat.com>
To: Sudhakar Panneerselvam <sudhakar.panneerselvam@oracle.com>
Cc: Mike Christie <michael.christie@oracle.com>,
Damien Le Moal <Damien.LeMoal@wdc.com>,
Mikulas Patocka <mpatocka@redhat.com>,
"ssudhakarp@gmail.com" <ssudhakarp@gmail.com>,
"dm-crypt@saout.de" <dm-crypt@saout.de>,
Eric Biggers <ebiggers@kernel.org>,
"dm-devel@redhat.com" <dm-devel@redhat.com>,
Shirley Ma <shirley.ma@oracle.com>,
Martin Petersen <martin.petersen@oracle.com>,
Milan Broz <gmazyland@gmail.com>,
"agk@redhat.com" <agk@redhat.com>,
linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
mst@redhat.com
Subject: Re: [dm-crypt] [RFC PATCH 0/2] dm crypt: Allow unaligned buffer lengths for skcipher devices
Date: Fri, 25 Sep 2020 16:15:12 -0400 [thread overview]
Message-ID: <20200925201512.GA6025@redhat.com> (raw)
In-Reply-To: <MWHPR04MB37588DF8C3FFF4BD0C3CD543E7360@MWHPR04MB3758.namprd04.prod.outlook.com>
On Thu, Sep 24 2020 at 9:09pm -0400,
Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
> On 2020/09/25 4:14, Sudhakar Panneerselvam wrote:
> >>
> >> On Thu, 24 Sep 2020, Sudhakar Panneerselvam wrote:
> >>
> >>>> By copying it to a temporary aligned buffer and issuing I/O on this
> >>>> buffer.
> >>>
> >>> I don't like this idea. Because, you need to allocate additional pages
> >>> for the entire I/O size(for the misaligned case, if you think through
> >>
> >> You can break the I/O to smaller pieces. You can use mempool for
> >> pre-allocation of the pages.
> >
> > Assuming we do this, how is this code simpler(based on your
> > comment below) than the fix in dm-crypt? In fact, this approach
> > would make the code change look bad in vhost, at the same time
> > having performance penalty. By doing this, we are just moving the
> > responsibility to other unrelated component.
>
> Because vhost is at the top of the block-io food chain. Fixing the unaligned
> segments there will ensure that it does not matter what device is under it. It
> will work.
Right, I agree. This should be addressed in vhost-scsi. And vhost-scsi
probably needs to be interfacing through block core to submit IO that
respects the limits of its underlying block device.
So please lift your proposed dm-crypt changes to vhost-scsi:
https://patchwork.kernel.org/patch/11781207/
https://patchwork.kernel.org/patch/11781053/
Maybe work with vhost-scsi maintainers to see about making the code
reusable in block core; so that any future unaligned application IO is
dealt in other drivers using the same common code.
But I'm not interested in taking these changes into dm-crypt:
NAK
> I am still baffled that the unaligned segments go through in the first place...
> Do we have something missing in the BIO code ?
Cc'ing linux-block, could be.
Thanks,
Mike
next prev parent reply other threads:[~2020-09-25 20:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1600281606-1446-1-git-send-email-sudhakar.panneerselvam@oracle.com>
2020-09-23 17:01 ` [dm-crypt] [dm-devel] [RFC PATCH 0/2] dm crypt: Allow unaligned buffer lengths for skcipher devices Sudhakar Panneerselvam
2020-09-24 1:27 ` [dm-crypt] " Mike Snitzer
2020-09-24 5:14 ` [dm-crypt] [dm-devel] " Eric Biggers
2020-09-24 8:15 ` Milan Broz
2020-09-24 16:55 ` Sudhakar Panneerselvam
2020-09-24 16:44 ` Sudhakar Panneerselvam
2020-09-24 17:26 ` Mikulas Patocka
2020-09-24 17:38 ` Sudhakar Panneerselvam
2020-09-24 17:50 ` Mikulas Patocka
2020-09-24 18:11 ` Sudhakar Panneerselvam
2020-09-24 18:44 ` Mikulas Patocka
2020-09-24 19:13 ` Sudhakar Panneerselvam
2020-09-25 1:09 ` Damien Le Moal
2020-09-25 20:15 ` Mike Snitzer [this message]
2020-09-24 12:47 ` [dm-crypt] " Mikulas Patocka
2020-09-24 15:58 ` Sudhakar Panneerselvam
2020-09-24 12:40 ` [dm-crypt] [dm-devel] " Mikulas Patocka
2020-09-24 17:12 ` Sudhakar Panneerselvam
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=20200925201512.GA6025@redhat.com \
--to=snitzer@redhat.com \
--cc=Damien.LeMoal@wdc.com \
--cc=agk@redhat.com \
--cc=dm-crypt@saout.de \
--cc=dm-devel@redhat.com \
--cc=ebiggers@kernel.org \
--cc=gmazyland@gmail.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=michael.christie@oracle.com \
--cc=mpatocka@redhat.com \
--cc=mst@redhat.com \
--cc=shirley.ma@oracle.com \
--cc=ssudhakarp@gmail.com \
--cc=sudhakar.panneerselvam@oracle.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).