linux-kernel - Re: [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only)

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Message-ID: <CANP1eJGpgXUv626KQb6kduJgMaOzU5hH9GLGBM-QSVUBagoG8w@mail.gmail.com>
Date:	Thu, 26 Mar 2015 15:12:32 -0400
From:	Milosz Tanski <milosz@...in.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-aio@...ck.org" <linux-aio@...ck.org>,
	Mel Gorman <mgorman@...e.de>,
	Volker Lendecke <Volker.Lendecke@...net.de>,
	Tejun Heo <tj@...nel.org>, Jeff Moyer <jmoyer@...hat.com>,
	"Theodore Ts'o" <tytso@....edu>, Al Viro <viro@...iv.linux.org.uk>,
	Linux API <linux-api@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-arch@...r.kernel.org, Dave Chinner <david@...morbit.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only)

On Thu, Mar 26, 2015 at 7:55 AM, Christoph Hellwig <hch@...radead.org> wrote:
>
> On Mon, Mar 16, 2015 at 02:27:10PM -0400, Milosz Tanski wrote:
> > This patchset introduces two new syscalls preadv2 and pwritev2. They are the
> > same syscalls as preadv and pwrite but with a flag argument. Additionally,
> > preadv2 implements an extra RWF_NONBLOCK flag.
>
> There was some arugment that we just don't wait and don't have the
> classic unix "blocking" semantics.  Maybe it's time to bite the bullet
> and rename it to RWF_DONTWAIT? (I personally dont really care).


Sure. It is in line with the MSG_DONTWAIT flag for sendmsg() which
this whole idea is based on anyways.

>
>
> Second this probably needs to be on top of Al's for-next tree:
>
>         https://git.kernel.org/cgit/linux/kernel/git/viro/vfs.git/log/?h=for-next
>
> Note that this has a flags field in struct kiocb, so we could just use
> that for the flags.


Okay I started rebasing the patches on-top of that. I did see that
there is a new flags field "ki_flags". I see that there's already a
IOCB_EVENTFD flag.

Did you see you Andres' question about making the flags a enum? I
usually wouldn't do that, because C++ is stronger when it comes enums,
you can't combine them then assignment them to an enum without a cast.
But in the kernel this doesn't matter.

>
>
> Otherwise this version look fine to me, let's get it merged!
>
> Al, are yo ready to pick this up?  I'd hate to miss another merge
> window.


Just got back from vacation today, I'll try to get this out before the
end of the week. I also have to make some adjustments to xfs-tests (to
push preadv2 into xfs_io).


-- 
Milosz Tanski
CTO
16 East 34th Street, 15th floor
New York, NY 10016

p: 646-253-9055
e: milosz@...in.com
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