Re: [PATCH 2/2] ubifs: Allow O_DIRECT

From	Richard Weinberger <richard@nod.at>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] ubifs: Allow O_DIRECT
Date	2015-08-20 08:50 +0200
Message-ID	<pZrPI-5tD-9@gated-at.bofh.it> (permalink)
References	<pZijn-8mM-15@gated-at.bofh.it> <pZijn-8mM-13@gated-at.bofh.it> <pZooN-tt-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Yang, (Sorry if I've used your last name lately)

Am 20.08.2015 um 05:00 schrieb Dongsheng Yang:
> On 08/20/2015 04:35 AM, Richard Weinberger wrote:
>> Currently UBIFS does not support direct IO, but some applications
>> blindly use the O_DIRECT flag.
>> Instead of failing upon open() we can do better and fall back
>> to buffered IO.
> 
> Hmmmm, to be honest, I am not sure we have to do it as Dave
> suggested. I think that's just a work-around for current fstests.
> 
> IMHO, perform a buffered IO when user request direct IO without
> any warning sounds not a good idea. Maybe adding a warning would
> make it better.

Well, how would you inform the user?
A printk() to dmesg is useless are the vast majority of open()
callers do not check dmesg... :)

Major filesystems implement ->direct_IO these days and having
a "return 0"-stub seems to be legit.
For example exofs does too. So, I really don't consider it a work around.

> I think we need more discussion about AIO&DIO in ubifs, and actually
> I have a plan for it. But I have not listed the all cons and pros of
> it so far.

Sure, having a real ->direct_IO would be be best solution.
My patch won't block this.

Thanks,
//richard
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Thread

[PATCH 2/2] ubifs: Allow O_DIRECT Richard Weinberger <richard@nod.at> - 2015-08-19 22:40 +0200
  Re: [PATCH 2/2] ubifs: Allow O_DIRECT Dongsheng Yang <yangds.fnst@cn.fujitsu.com> - 2015-08-20 05:10 +0200
    Re: [PATCH 2/2] ubifs: Allow O_DIRECT Richard Weinberger <richard@nod.at> - 2015-08-20 08:50 +0200
      Re: [PATCH 2/2] ubifs: Allow O_DIRECT Dongsheng Yang <yangds.fnst@cn.fujitsu.com> - 2015-08-20 09:30 +0200
    Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-20 13:40 +0200
      Re: [PATCH 2/2] ubifs: Allow O_DIRECT Richard Weinberger <richard@nod.at> - 2015-08-20 13:50 +0200
        Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-20 14:40 +0200
          Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-24 09:20 +0200
            Re: [PATCH 2/2] ubifs: Allow O_DIRECT Dongsheng Yang <yangds.fnst@cn.fujitsu.com> - 2015-08-24 09:30 +0200
            Re: [PATCH 2/2] ubifs: Allow O_DIRECT Dongsheng Yang <yangds.fnst@cn.fujitsu.com> - 2015-08-24 09:30 +0200
              Re: [PATCH 2/2] ubifs: Allow O_DIRECT Christoph Hellwig <hch@infradead.org> - 2015-08-24 10:10 +0200
        Re: [PATCH 2/2] ubifs: Allow O_DIRECT Brian Norris <computersforpeace@gmail.com> - 2015-08-20 23:00 +0200
          Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-24 09:20 +0200
            Re: [PATCH 2/2] ubifs: Allow O_DIRECT Christoph Hellwig <hch@infradead.org> - 2015-08-24 10:00 +0200
              Re: [PATCH 2/2] ubifs: Allow O_DIRECT Christoph Hellwig <hch@infradead.org> - 2015-08-24 10:10 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Dongsheng Yang <yangds.fnst@cn.fujitsu.com> - 2015-08-24 10:10 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Richard Weinberger <richard@nod.at> - 2015-08-24 11:40 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-24 11:40 +0200
              Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-24 10:10 +0200
            Re: [PATCH 2/2] ubifs: Allow O_DIRECT Brian Norris <computersforpeace@gmail.com> - 2015-08-24 18:20 +0200
              Re: [PATCH 2/2] ubifs: Allow O_DIRECT Jeff Moyer <jmoyer@redhat.com> - 2015-08-24 19:20 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Dave Chinner <david@fromorbit.com> - 2015-08-25 01:50 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Chris Mason <clm@fb.com> - 2015-08-25 03:30 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-25 17:50 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Jeff Moyer <jmoyer@redhat.com> - 2015-08-25 16:10 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Jeff Moyer <jmoyer@redhat.com> - 2015-08-25 16:20 +0200
                Re: [PATCH 2/2] ubifs: Allow O_DIRECT Chris Mason <clm@fb.com> - 2015-08-25 16:20 +0200
  Re: [PATCH 2/2] ubifs: Allow O_DIRECT Artem Bityutskiy <dedekind1@gmail.com> - 2015-08-20 13:30 +0200

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