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

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Message-ID: <CANP1eJHigCfSE-tT_RUfPBY3pg6G5ygx+CKvKkuwGVYgNtR=jw@mail.gmail.com>
Date:	Thu, 26 Mar 2015 22:29:07 -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 3:12 PM, Milosz Tanski <milosz@...in.com> wrote:
> 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.

Okay, It's RWF_DONTWAIT now. I also split it into two RWF_DONTWAIT for
the userspace API and IOCB_DONTWAIT that goes into kiocb->ki_flags.

>
>>
>>
>> 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).

You'll see the patches and the pull request against  viro/for-next
branch tomorrow. The rebase was a bit of work since you guys changed a
fair amount of stuff.

>
>
> --
> Milosz Tanski
> CTO
> 16 East 34th Street, 15th floor
> New York, NY 10016
>
> p: 646-253-9055
> e: milosz@...in.com

P.S: Sorry for the double email / HTML spam. I'm not a my primary
computer and apparently gmail randomly forgets that a thread is plain
text only. Thanks gmail.

-- 
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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