Re: [Qemu-devel] [PATCH v9 07/17] blockdev: adds bdrv_parse_aio to use io_uring

From: Stefan Hajnoczi <stefanha@gmail.com>
To: Julia Suvorova <jusual@mail.ru>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <fam@euphon.net>,
	Stefan Hajnoczi <stefan@redhat.com>,
	Sergio Lopez <slp@redhat.com>,
	qemu-block@nongnu.org, qemu-devel@nongnu.org,
	Markus Armbruster <armbru@redhat.com>,
	Maxim Levitsky <mlevitsk@redhat.com>,
	saket.sinha89@gmail.com, Stefan Hajnoczi <stefanha@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Max Reitz <mreitz@redhat.com>,
	Aarushi Mehta <mehta.aaru20@gmail.com>
Subject: Re: [Qemu-devel] [PATCH v9 07/17] blockdev: adds bdrv_parse_aio to use io_uring
Date: Fri, 4 Oct 2019 16:06:01 +0100	[thread overview]
Message-ID: <20191004150601.GA11748@stefanha-x1.localdomain> (raw)
In-Reply-To: <CAMDeoFW6PBWhfkdB0=wDmW_oDkgDPcygkKDu44qD=8dWDZwW=g@mail.gmail.com>

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On Wed, Aug 07, 2019 at 02:49:51PM +0200, Julia Suvorova via Qemu-devel wrote:
> On Wed, Aug 7, 2019 at 2:06 PM Aarushi Mehta <mehta.aaru20@gmail.com> wrote:
> >
> >
> >
> > On Wed, 7 Aug, 2019, 17:15 Julia Suvorova, <jusual@mail.ru> wrote:
> >>
> >> On Fri, Aug 2, 2019 at 1:41 AM Aarushi Mehta <mehta.aaru20@gmail.com> wrote:
> >> > +int bdrv_parse_aio(const char *mode, int *flags)
> >> > +{
> >> > +    if (!strcmp(mode, "threads")) {
> >> > +        /* do nothing, default */
> >> > +    } else if (!strcmp(mode, "native")) {
> >> > +        *flags |= BDRV_O_NATIVE_AIO;
> >>
> >> This 'if' should be covered with CONFIG_LINUX_AIO.
> >
> >
> > The aio=native definition is shared with Windows hosts' native aio and will break if it was covered.
> >
> > file-posix handles the case.
> 
> Fair enough. Then you can remove all ifdefs for io_uring from
> raw_open_common in file-posix.c as this case was already checked here.

This is not possible since the BLOCKDEV_AIO_OPTIONS_IO_URING enum
constant is conditional in the QAPI schema:

  { 'enum': 'BlockdevAioOptions',
    'data': [ 'threads', 'native',
              { 'name': 'io_uring', 'if': 'defined(CONFIG_LINUX_IO_URING)' } ] }

The code can only use BLOCKDEV_AIO_OPTIONS_IO_URING if
CONFIG_LINUX_IO_URING was defined, so we cannot drop the #ifdefs in
raw_open_common().

Stefan

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