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From: Jeff Moyer <jmoyer@redhat.com>
To: Milosz Tanski <milosz@adfin.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	linux-aio@kvack.org, Mel Gorman <mgorman@suse.de>,
	Volker Lendecke <Volker.Lendecke@sernet.de>,
	Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 4/7] O_NONBLOCK flag for readv2/preadv2
Date: Tue, 16 Sep 2014 15:53:56 -0400	[thread overview]
Message-ID: <x49ppevwdd7.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <CANP1eJEiGxQ0fZMkOY1utmkUOkGC4gOHYrXt+yO-9+tnzA24hw@mail.gmail.com> (Milosz Tanski's message of "Tue, 16 Sep 2014 15:44:13 -0400")

Milosz Tanski <milosz@adfin.com> writes:

>> Why did you put the wouldblock label inside the loop?  That should be
>> pushed down to just above out, and then you can get rid of the goto.
>
> When I put the code outside the loop it actually looked worse (imo):
>
> }
>
> goto out;
>
> would_block:
> error = -EAGAIN;
>
> out:
> ...
>

We don't exit the loop without a return or a goto, so you wouldn't need
that 'goto out' just below the end of the loop.  It would look like:

	}

would_block:
	error = -EAGAIN;
out:
...

> Point taken and I can fix this for the next version further up the
> stack. A longer term question is how the flags the file is open with
> interact with the read/write flags ... since I imagine folks will want
> to add other flags (like force a SYNC write).

I think we'll have to address those one at a time.  I do like the idea
of the SYNC flag for a write, though you'll probably have several
variants of that (equivalents of SYNC and DSYNC at least).  Another fun
write flag to consider is O_ATOMIC.  :)

Cheers,
Jeff

WARNING: multiple messages have this Message-ID (diff)
From: Jeff Moyer <jmoyer@redhat.com>
To: Milosz Tanski <milosz@adfin.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	linux-aio@kvack.org, Mel Gorman <mgorman@suse.de>,
	Volker Lendecke <Volker.Lendecke@sernet.de>,
	Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 4/7] O_NONBLOCK flag for readv2/preadv2
Date: Tue, 16 Sep 2014 15:53:56 -0400	[thread overview]
Message-ID: <x49ppevwdd7.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <CANP1eJEiGxQ0fZMkOY1utmkUOkGC4gOHYrXt+yO-9+tnzA24hw@mail.gmail.com> (Milosz Tanski's message of "Tue, 16 Sep 2014 15:44:13 -0400")

Milosz Tanski <milosz@adfin.com> writes:

>> Why did you put the wouldblock label inside the loop?  That should be
>> pushed down to just above out, and then you can get rid of the goto.
>
> When I put the code outside the loop it actually looked worse (imo):
>
> }
>
> goto out;
>
> would_block:
> error = -EAGAIN;
>
> out:
> ...
>

We don't exit the loop without a return or a goto, so you wouldn't need
that 'goto out' just below the end of the loop.  It would look like:

	}

would_block:
	error = -EAGAIN;
out:
...

> Point taken and I can fix this for the next version further up the
> stack. A longer term question is how the flags the file is open with
> interact with the read/write flags ... since I imagine folks will want
> to add other flags (like force a SYNC write).

I think we'll have to address those one at a time.  I do like the idea
of the SYNC flag for a write, though you'll probably have several
variants of that (equivalents of SYNC and DSYNC at least).  Another fun
write flag to consider is O_ATOMIC.  :)

Cheers,
Jeff

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  reply	other threads:[~2014-09-16 19:54 UTC|newest]

Thread overview: 167+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-15 20:20 [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-09-15 20:20 ` Milosz Tanski
2014-09-15 20:20 ` [PATCH 1/7] Prepare for adding a new readv/writev with user flags Milosz Tanski
2014-09-15 20:20   ` Milosz Tanski
2014-09-15 20:28   ` Al Viro
2014-09-15 21:15     ` Christoph Hellwig
2014-09-15 21:15       ` Christoph Hellwig
2014-09-15 21:44       ` Milosz Tanski
2014-09-15 21:44         ` Milosz Tanski
2014-09-15 20:20 ` [PATCH 2/7] Define new syscalls readv2,preadv2,writev2,pwritev2 Milosz Tanski
2014-09-15 20:20   ` Milosz Tanski
2014-09-16 19:20   ` Jeff Moyer
2014-09-16 19:20     ` Jeff Moyer
2014-09-16 19:54     ` Milosz Tanski
2014-09-16 19:54       ` Milosz Tanski
2014-09-16 21:03     ` Christoph Hellwig
2014-09-16 21:03       ` Christoph Hellwig
2014-09-17 15:43   ` Theodore Ts'o
2014-09-17 15:43     ` Theodore Ts'o
2014-09-17 16:05     ` Milosz Tanski
2014-09-17 16:05       ` Milosz Tanski
2014-09-17 16:59       ` Theodore Ts'o
2014-09-17 16:59         ` Theodore Ts'o
2014-09-17 17:24         ` Zach Brown
2014-09-17 17:24           ` Zach Brown
2014-09-15 20:20 ` [PATCH 3/7] Export new vector IO (with flags) to userland Milosz Tanski
2014-09-15 20:20   ` Milosz Tanski
2014-09-15 20:21 ` [PATCH 4/7] O_NONBLOCK flag for readv2/preadv2 Milosz Tanski
2014-09-15 20:21   ` Milosz Tanski
2014-09-16 19:19   ` Jeff Moyer
2014-09-16 19:19     ` Jeff Moyer
2014-09-16 19:44     ` Milosz Tanski
2014-09-16 19:44       ` Milosz Tanski
2014-09-16 19:53       ` Jeff Moyer [this message]
2014-09-16 19:53         ` Jeff Moyer
2014-09-15 20:21 ` [PATCH 5/7] documentation updates Christoph Hellwig
2014-09-15 20:21   ` Christoph Hellwig
2014-09-15 20:21 ` [PATCH 6/7] move flags enforcement to vfs_preadv/vfs_pwritev Christoph Hellwig
2014-09-15 21:15   ` Christoph Hellwig
2014-09-15 21:15     ` Christoph Hellwig
2014-09-15 21:45     ` Milosz Tanski
2014-09-15 21:45       ` Milosz Tanski
2014-09-15 20:22 ` [PATCH 7/7] check for O_NONBLOCK in all read_iter instances Christoph Hellwig
2014-09-15 20:22   ` Christoph Hellwig
2014-09-16 19:27   ` Jeff Moyer
2014-09-16 19:27     ` Jeff Moyer
2014-09-16 19:45     ` Milosz Tanski
2014-09-16 19:45       ` Milosz Tanski
2014-09-16 21:42       ` Dave Chinner
2014-09-16 21:42         ` Dave Chinner
2014-09-17 12:24         ` Benjamin LaHaise
2014-09-17 12:24           ` Benjamin LaHaise
2014-09-17 13:47           ` Theodore Ts'o
2014-09-17 13:47             ` Theodore Ts'o
2014-09-17 13:56             ` Benjamin LaHaise
2014-09-17 13:56               ` Benjamin LaHaise
2014-09-17 15:33               ` Milosz Tanski
2014-09-17 15:33                 ` Milosz Tanski
2014-09-17 15:49                 ` Theodore Ts'o
2014-09-17 15:49                   ` Theodore Ts'o
2014-09-17 15:52               ` Zach Brown
2014-09-17 15:52                 ` Zach Brown
2014-09-16 21:04     ` Christoph Hellwig
2014-09-16 21:04       ` Christoph Hellwig
2014-09-16 21:24       ` Jeff Moyer
2014-09-16 21:24         ` Jeff Moyer
2014-09-15 20:27 ` [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-09-15 20:27   ` Milosz Tanski
2014-09-15 21:33 ` Andreas Dilger
2014-09-15 22:13   ` Milosz Tanski
2014-09-15 22:13     ` Milosz Tanski
2014-09-15 22:36   ` Elliott, Robert (Server Storage)
2014-09-15 22:36     ` Elliott, Robert (Server Storage)
2014-09-16 18:24     ` Zach Brown
2014-09-16 18:24       ` Zach Brown
2014-09-19 11:21     ` Christoph Hellwig
2014-09-19 11:21       ` Christoph Hellwig
2014-09-22 15:48       ` Jeff Moyer
2014-09-22 15:48         ` Jeff Moyer
2014-09-22 16:32         ` Milosz Tanski
2014-09-22 16:32           ` Milosz Tanski
2014-09-22 16:42           ` Christoph Hellwig
2014-09-22 17:02             ` Milosz Tanski
2014-09-22 17:02               ` Milosz Tanski
2014-09-22 16:25       ` Elliott, Robert (Server Storage)
2014-09-15 21:58 ` Jeff Moyer
2014-09-15 21:58   ` Jeff Moyer
2014-09-15 22:27   ` Milosz Tanski
2014-09-15 22:27     ` Milosz Tanski
2014-09-16 13:44     ` Jeff Moyer
2014-09-16 13:44       ` Jeff Moyer
2014-09-19 11:23   ` Christoph Hellwig
2014-09-19 11:23     ` Christoph Hellwig
2014-09-16 19:30 ` Jeff Moyer
2014-09-16 19:30   ` Jeff Moyer
2014-09-16 20:34   ` Milosz Tanski
2014-09-16 20:34     ` Milosz Tanski
2014-09-16 20:49     ` Jeff Moyer
2014-09-16 20:49       ` Jeff Moyer
2014-09-17 14:49 ` [RFC 1/2] aio: async readahead Benjamin LaHaise
2014-09-17 14:49   ` Benjamin LaHaise
2014-09-17 15:26   ` [RFC 2/2] ext4: async readpage for indirect style inodes Benjamin LaHaise
2014-09-17 15:26     ` Benjamin LaHaise
2014-09-19 11:26   ` [RFC 1/2] aio: async readahead Christoph Hellwig
2014-09-19 11:26     ` Christoph Hellwig
2014-09-19 16:01     ` Benjamin LaHaise
2014-09-19 16:01       ` Benjamin LaHaise
2014-09-17 22:20 ` [RFC v2 0/5] Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-09-17 22:20   ` Milosz Tanski
2014-09-17 22:20   ` [RFC v2 1/5] Prepare for adding a new readv/writev with user flags Milosz Tanski
2014-09-17 22:20     ` Milosz Tanski
2014-09-17 22:20   ` [RFC v2 2/5] Define new syscalls readv2,preadv2,writev2,pwritev2 Milosz Tanski
2014-09-17 22:20     ` Milosz Tanski
2014-09-18 18:48     ` Darrick J. Wong
2014-09-18 18:48       ` Darrick J. Wong
2014-09-19 10:52       ` Christoph Hellwig
2014-09-19 10:52         ` Christoph Hellwig
2014-09-20  0:19         ` Darrick J. Wong
2014-09-20  0:19           ` Darrick J. Wong
2014-09-17 22:20   ` [RFC v2 3/5] Export new vector IO (with flags) to userland Milosz Tanski
2014-09-17 22:20     ` Milosz Tanski
2014-09-17 22:20   ` [RFC v2 4/5] O_NONBLOCK flag for readv2/preadv2 Milosz Tanski
2014-09-17 22:20     ` Milosz Tanski
2014-09-19 11:27     ` Christoph Hellwig
2014-09-19 11:27       ` Christoph Hellwig
2014-09-19 11:59       ` Milosz Tanski
2014-09-19 11:59         ` Milosz Tanski
2014-09-22 17:12     ` Jeff Moyer
2014-09-22 17:12       ` Jeff Moyer
2014-09-17 22:20   ` [RFC v2 5/5] Check for O_NONBLOCK in all read_iter instances Milosz Tanski
2014-09-17 22:20     ` Milosz Tanski
2014-09-19 11:26     ` Christoph Hellwig
2014-09-19 11:26       ` Christoph Hellwig
2014-09-19 14:42   ` [RFC v2 0/5] Non-blockling buffered fs read (page cache only) Jonathan Corbet
2014-09-19 14:42     ` Jonathan Corbet
2014-09-19 16:13     ` Volker Lendecke
2014-09-19 16:13       ` Volker Lendecke
2014-09-19 17:19     ` Milosz Tanski
2014-09-19 17:19       ` Milosz Tanski
2014-09-19 17:33     ` Milosz Tanski
2014-09-19 17:33       ` Milosz Tanski
2014-09-22 14:12       ` Jonathan Corbet
2014-09-22 14:12         ` Jonathan Corbet
2014-09-22 14:24         ` Jeff Moyer
2014-09-22 14:24           ` Jeff Moyer
2014-09-22 14:25         ` Christoph Hellwig
2014-09-22 14:25           ` Christoph Hellwig
2014-09-22 14:30         ` Milosz Tanski
2014-09-22 14:30           ` Milosz Tanski
2014-09-24 21:46 ` [RFC v3 0/4] vfs: " Milosz Tanski
2014-09-24 21:46   ` Milosz Tanski
2014-09-24 21:46   ` [RFC v3 1/4] vfs: Prepare for adding a new preadv/pwritev with user flags Milosz Tanski
2014-09-24 21:46     ` Milosz Tanski
2014-09-24 21:46   ` [RFC v3 2/4] vfs: Define new syscalls preadv2,pwritev2 Milosz Tanski
2014-09-24 21:46     ` Milosz Tanski
2014-09-24 21:46   ` [RFC v3 3/4] vfs: Export new vector IO syscalls (with flags) to userland Milosz Tanski
2014-09-24 21:46     ` Milosz Tanski
2014-09-24 21:46   ` [RFC v3 4/4] vfs: RWF_NONBLOCK flag for preadv2 Milosz Tanski
2014-09-24 21:46     ` Milosz Tanski
2014-09-25  4:06   ` [RFC v3 0/4] vfs: Non-blockling buffered fs read (page cache only) Michael Kerrisk
2014-09-25  4:06     ` Michael Kerrisk
2014-09-25 11:16     ` Jan Kara
2014-09-25 11:16       ` Jan Kara
2014-09-25 15:48     ` Milosz Tanski
2014-09-25 15:48       ` Milosz Tanski
2014-10-08  2:53   ` Milosz Tanski
2014-10-08  2:53     ` Milosz Tanski

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