linux-kernel - Re: scsi-mq V2

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Date:	Thu, 10 Jul 2014 16:05:02 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	Benjamin LaHaise <bcrl@...ck.org>,
	"Elliott\, Robert \(Server Storage\)" <Elliott@...com>,
	Christoph Hellwig <hch@...radead.org>,
	"dgilbert\@interlog.com" <dgilbert@...erlog.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Bart Van Assche <bvanassche@...ionio.com>,
	"linux-scsi\@vger.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: scsi-mq V2

Jens Axboe <axboe@...nel.dk> writes:

> On 2014-07-10 17:11, Jeff Moyer wrote:
>> Benjamin LaHaise <bcrl@...ck.org> writes:
>>
>>>>
>>>> [  186.339064] ioctx_alloc: nr_events=-2 aio_max_nr=65536
>>>> [  186.339065] ioctx_alloc: nr_events=-2 aio_max_nr=65536
>>>> [  186.339067] ioctx_alloc: nr_events=-2 aio_max_nr=65536
>>>> [  186.339068] ioctx_alloc: nr_events=-2 aio_max_nr=65536
>>>> [  186.339069] ioctx_alloc: nr_events=-2 aio_max_nr=65536
>>>
>>> Something is horribly wrong here.  There is no way that value for nr_events
>>> should be passed in to ioctx_alloc().  This implies that userland is calling
>>> io_setup() with an impossibly large value for nr_events.  Can you post the
>>> actual diff for your fs/aio.c relative to linus' tree?
>>>
>>
>> fio does exactly this!  it passes INT_MAX.
>
> That's correct, I had actually forgotten about this. It was a change
> made a few years back, in correlation with the aio optimizations
> posted then, basically telling aio to ignore that silly (and broken)
> user ring.

I still don't see how you accomplish that.  Making it bigger doesn't get
rid of it.  ;-)

Cheers,
Jeff
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