linux-kernel - Re: [PATCH 2/5] block: add request->io_data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200409023857.GB370295@localhost.localdomain>
Date:   Thu, 9 Apr 2020 10:38:57 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...r.kernel.org,
        cgroups@...r.kernel.org, newella@...com, josef@...icpanda.com
Subject: Re: [PATCH 2/5] block: add request->io_data_len

On Wed, Apr 08, 2020 at 10:11:19PM -0400, Tejun Heo wrote:
> On Thu, Apr 09, 2020 at 09:44:06AM +0800, Ming Lei wrote:
> > Almost all __blk_mq_end_request() follow blk_update_request(), so the
> > completed bytes can be passed to __blk_mq_end_request(), then we can
> > avoid to introduce this field.
> 
> But on some drivers blk_update_request() may be called multiple times before
> __blk_mq_end_request() is called and what's needed here is the total number of
> bytes in the whole request, not just in the final completion.

OK.

Another choice might be to record request bytes in rq's payload
when calling .queue_rq() only for these drivers.

> 
> > Also there is just 20 callers of __blk_mq_end_request(), looks this kind
> > of change shouldn't be too big.
> 
> This would work iff we get rid of partial completions and if we get rid of
> partial completions, we might as well stop exposing blk_update_request() and
> __blk_mq_end_request().

Indeed, we can store the completed bytes in request payload, so looks killing
partial completion shouldn't be too hard.

Thanks,
Ming