linux-kernel - Re: [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write

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Date:	Tue, 13 Oct 2015 10:44:11 -0700
From:	Ming Lin <mlin@...nel.org>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	lkml <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Dongsu Park <dpark@...teo.net>,
	Mike Snitzer <snitzer@...hat.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Ming Lin <ming.l@....samsung.com>,
	linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write_same}

On Tue, Oct 13, 2015 at 4:50 AM, Christoph Hellwig <hch@...radead.org> wrote:
> On Wed, Aug 12, 2015 at 12:07:15AM -0700, Ming Lin wrote:
>> From: Ming Lin <ming.l@....samsung.com>
>>
>> The split code in blkdev_issue_{discard,write_same} can go away
>> now that any driver that cares does the split. We have to make
>> sure bio size doesn't overflow.
>>
>> For discard, we set max discard sectors to (1<<31)>>9 to ensure
>> it doesn't overflow bi_size and hopefully it is of the proper
>> granularity as long as the granularity is a power of two.
>
> This ends up breaking discard on NVMe devices for a me.  An mkfs.xfs
> which does a discard of the whole device now hangs the system.
> Something in here makes it send discard command that the device doesn't
> like and the aborts don't seem to help either, although that might be
> an issue with the abort handling in the driver.
>
> Just a heads up for now, once I get a bit more time I'll try to collect
> a blktrace to figure out how the commands sent to the driver look
> different before and after the patch.

I just did a quick test with a Samsung 900G NVMe device.
mkfs.xfs is OK on 4.3-rc5.

What's your device model? I may find a similar one to try.
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