From: Matthew Wilcox <willy@infradead.org>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-aio@kvack.org, io-uring@vger.kernel.org,
linux-kernel@vger.kernel.org, Kanchan Joshi <joshi.k@samsung.com>,
Javier Gonzalez <javier.gonz@samsung.com>
Subject: Re: [PATCH 0/2] Remove kiocb ki_complete
Date: Thu, 9 Jul 2020 14:43:19 +0100 [thread overview]
Message-ID: <20200709134319.GD12769@casper.infradead.org> (raw)
In-Reply-To: <ffbd272c-32f3-8c8c-6395-5eab47725929@gmail.com>
On Thu, Jul 09, 2020 at 04:37:59PM +0300, Pavel Begunkov wrote:
> On 09/07/2020 16:26, Christoph Hellwig wrote:
> > On Thu, Jul 09, 2020 at 12:10:36PM +0100, Matthew Wilcox wrote:
> >> On Thu, Jul 09, 2020 at 11:17:05AM +0100, Christoph Hellwig wrote:
> >>> I really don't like this series at all. If saves a single pointer
> >>> but introduces a complicated machinery that just doesn't follow any
> >>> natural flow. And there doesn't seem to be any good reason for it to
> >>> start with.
> >>
> >> Jens doesn't want the kiocb to grow beyond a single cacheline, and we
> >> want the ability to set the loff_t in userspace for an appending write,
> >> so the plan was to replace the ki_complete member in kiocb with an
> >> loff_t __user *ki_posp.
> >>
> >> I don't think it's worth worrying about growing kiocb, personally,
> >> but this seemed like the easiest way to make room for a new pointer.
> >
> > The user offset pointer has absolutely no business in the the kiocb
> > itself - it is a io_uring concept which needs to go into the io_kiocb,
> > which has 14 bytes left in the last cache line in my build. It would
> > fit in very well there right next to the result and user pointer.
>
> After getting a valid offset, io_uring shouldn't do anything but
> complete the request. And as io_kiocb implicitly contains a CQE entry,
> not sure we need @append_offset in the first place.
>
> Kanchan, could you take a look if you can hide it in req->cflags?
No, that's not what cflags are for. And besides, there's only 32 bits
there.
next prev parent reply other threads:[~2020-07-09 13:43 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-08 22:26 [PATCH 0/2] Remove kiocb ki_complete Matthew Wilcox (Oracle)
2020-07-08 22:26 ` [PATCH 1/2] fs: Abstract calling the kiocb completion function Matthew Wilcox (Oracle)
2020-07-08 22:37 ` Jens Axboe
2020-07-08 22:40 ` Matthew Wilcox
2020-07-08 22:50 ` Jens Axboe
2020-07-08 22:26 ` [PATCH 2/2] fs: Remove kiocb->ki_complete Matthew Wilcox (Oracle)
2020-07-08 22:38 ` Jens Axboe
2020-07-09 3:25 ` Jens Axboe
2020-07-09 5:23 ` kernel test robot
2020-07-08 22:33 ` [PATCH 0/2] Remove kiocb ki_complete Jens Axboe
2020-07-09 10:17 ` Christoph Hellwig
2020-07-09 11:10 ` Matthew Wilcox
2020-07-09 13:26 ` Christoph Hellwig
2020-07-09 13:32 ` Matthew Wilcox
2020-07-09 13:53 ` Jens Axboe
2020-07-09 13:37 ` Pavel Begunkov
2020-07-09 13:43 ` Matthew Wilcox [this message]
2020-07-09 13:49 ` Pavel Begunkov
2020-07-09 13:53 ` Matthew Wilcox
2020-07-09 13:59 ` Pavel Begunkov
2020-07-09 13:55 ` Jens Axboe
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