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From: Avi Kivity <avi@scylladb.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-aio@kvack.org,
	Jan Kara <jack@suse.cz>, Steven Whitehouse <swhiteho@redhat.com>,
	xfs@oss.sgi.com
Subject: Re: AIO read returns negative number for bytes read
Date: Tue, 17 Nov 2015 14:52:19 +0200	[thread overview]
Message-ID: <564B2303.7000902@scylladb.com> (raw)
In-Reply-To: <x497flhsq1c.fsf@segfault.boston.devel.redhat.com>



On 11/16/2015 09:27 PM, Jeff Moyer wrote:
> Hi Avi,
>
> Avi Kivity <avi@scylladb.com> writes:
>
>> Due to a bug in my program, I initiated a read beyond
>> eof. Specifically, the file size is 13002 bytes and the read offset is
>> 13312 (0x3400).
>>
>> I would expect such a read to return 0 bytes read, but io_getevents
>> returns -310, which is suspiciously equal to (13002 - 13312).
>>
>> I attach a reproducer.
>>
>> 4.2.5-201.fc22.x86_64
>>
>> Are my expectations incorrect, or is this a bug in aio or xfs?
> Your expectations are correct.  The bug was introduced by commit
> 9fe55eea7e4b4 (Fix race when checking i_size on direct i/o read).  I've
> CC'd the patch author and linux-fsdevel.  I'm not sure what the right
> fix is, given that the size checks were removed from the vfs to fix some
> race condition.  Unfortunately, the commit message doesn't really do a
> good job of explaining the race.  In order to save others time, here is
> a good explanation of the problem that commit is meant to fix, along
> with a reproducer:
>    http://marc.info/?l=linux-fsdevel&m=138641356614458&w=2
>
> Thanks for the great bug report, and sorry I have no solution to
> proffer.
>

Thanks.  I will await a fix with interest.


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WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@scylladb.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: xfs@oss.sgi.com, linux-aio@kvack.org,
	Steven Whitehouse <swhiteho@redhat.com>, Jan Kara <jack@suse.cz>,
	linux-fsdevel@vger.kernel.org
Subject: Re: AIO read returns negative number for bytes read
Date: Tue, 17 Nov 2015 14:52:19 +0200	[thread overview]
Message-ID: <564B2303.7000902@scylladb.com> (raw)
In-Reply-To: <x497flhsq1c.fsf@segfault.boston.devel.redhat.com>



On 11/16/2015 09:27 PM, Jeff Moyer wrote:
> Hi Avi,
>
> Avi Kivity <avi@scylladb.com> writes:
>
>> Due to a bug in my program, I initiated a read beyond
>> eof. Specifically, the file size is 13002 bytes and the read offset is
>> 13312 (0x3400).
>>
>> I would expect such a read to return 0 bytes read, but io_getevents
>> returns -310, which is suspiciously equal to (13002 - 13312).
>>
>> I attach a reproducer.
>>
>> 4.2.5-201.fc22.x86_64
>>
>> Are my expectations incorrect, or is this a bug in aio or xfs?
> Your expectations are correct.  The bug was introduced by commit
> 9fe55eea7e4b4 (Fix race when checking i_size on direct i/o read).  I've
> CC'd the patch author and linux-fsdevel.  I'm not sure what the right
> fix is, given that the size checks were removed from the vfs to fix some
> race condition.  Unfortunately, the commit message doesn't really do a
> good job of explaining the race.  In order to save others time, here is
> a good explanation of the problem that commit is meant to fix, along
> with a reproducer:
>    http://marc.info/?l=linux-fsdevel&m=138641356614458&w=2
>
> Thanks for the great bug report, and sorry I have no solution to
> proffer.
>

Thanks.  I will await a fix with interest.



  reply	other threads:[~2015-11-17 12:52 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-15 13:08 AIO read returns negative number for bytes read Avi Kivity
2015-11-16 15:00 ` Brian Foster
2015-11-16 15:19 ` Alireza Haghdoost
2015-11-16 15:32   ` Avi Kivity
2015-11-16 19:27 ` Jeff Moyer
2015-11-16 19:27   ` Jeff Moyer
2015-11-17 12:52   ` Avi Kivity [this message]
2015-11-17 12:52     ` Avi Kivity
2015-11-19 15:30     ` Jan Kara
2015-11-19 15:30       ` Jan Kara
2015-11-19 15:32       ` Avi Kivity
2015-11-19 15:32         ` Avi Kivity
2015-11-19 15:33       ` Jeff Moyer
2015-11-19 15:33         ` Jeff Moyer

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