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	Tue, 4 Aug 2015 12:10:54 -0400
From: Jeff Moyer <jmoyer@redhat.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>,
	Andreas Hartmann <andihartmann@freenet.de>,
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	linux-ide@vger.kernel.org
Subject: Re: AMD-Vi IO_PAGE_FAULTs and ata3.00: failed command: READ FPDMA QUEUED errors since Linux 4.0
References: <55B7BEA2.30205@01019freenet.de>
	<20150728175054.GB24782@redhat.com> <55B7D054.4070308@maya.org>
	<20150728192908.GA25264@redhat.com> <55BCD5A7.2080708@maya.org>
	<55BE1D5E.6020709@maya.org>
	<alpine.LRH.2.02.1508021347480.17729@file01.intranet.prod.int.rdu2.redhat.com>
	<55BE65E6.7060901@maya.org> <20150803081249.GF14980@8bytes.org>
	<20150804144711.GB24716@redhat.com>
Date: Tue, 04 Aug 2015 12:10:51 -0400
In-Reply-To: <20150804144711.GB24716@redhat.com> (Mike Snitzer's message of
	"Tue, 4 Aug 2015 10:47:11 -0400")
Message-ID: <x4937zzm3uc.fsf@segfault.boston.devel.redhat.com>
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Mike Snitzer <snitzer@redhat.com> writes:

> On Mon, Aug 03 2015 at  4:12am -0400,
> Joerg Roedel <joro@8bytes.org> wrote:
>
>> On Sun, Aug 02, 2015 at 08:48:06PM +0200, Andreas Hartmann wrote:
>> > >>https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=34b48db66e08ca1c1bc07cf305d672ac940268dc
>> > >>
>> > >>block: remove artifical max_hw_sectors cap
>> 
>> Looking at the patch, it seems to me that it just uncovered a bug
>> elsewhere. It looks like an underlying driver doesn't expect the
>> big io-requests that the patch enables and does not dma-map the whole
>> target buffer, causing the IO_PAGE_FAULTs later.
>
> That patch has caused issues elsewhere too, see this 'Revert "block:
> remove artifical max_hw_sectors cap"' thread (if/when lkml.org
> cooperates): https://lkml.org/lkml/2015/7/20/572
>
> But it could be that there is a need for a horkage fix for this specific
> hardware? something comparable to this?:
> http://git.kernel.org/linus/af34d637637eabaf49406eb35c948cd51ba262a6
>
> We are running out of time to fix these whack-a-mole issues in 4.2
> though.

CC-ing linux-ide.  Original dm-devel posting:
  https://www.redhat.com/archives/dm-devel/2015-July/msg00178.html

Andreas, I would be curious to know what the value of
/sys/block/sdX/queue/max_hw_sectors_kb is for the affected disks.

Cheers,
Jeff