Re: block: re-add discard_granularity and alignment checks

[Jens Axboe <axboe@kernel.dk>]

On 10/28/2015 06:23 AM, Ming Lin wrote:
> On Thu, Oct 22, 2015 at 10:03 AM, Mike Snitzer <snitzer@redhat.com> wrote:
>> On Thu, Oct 22 2015 at 12:59pm -0400,
>> Ming Lin <mlin@kernel.org> wrote:
>>
>>> From: Ming Lin <ming.l@ssi.samsung.com>
>>>
>>> In commit b49a087("block: remove split code in
>>> blkdev_issue_{discard,write_same}"), discard_granularity and alignment
>>> checks were removed. Ideally, with bio late splitting, the upper layers
>>> shouldn't need to depend on device's limits.
>>>
>>> Christoph reported a discard regression on the HGST Ultrastar SN100 NVMe
>>> device when mkfs.xfs. We have not found the root cause yet.
>>>
>>> This patch re-adds discard_granularity and alignment checks by reverting
>>> the related changes in commit b49a087. The good thing is now we can
>>> remove the 2G discard size cap and just use UINT_MAX to avoid bi_size
>>> overflow.
>>>
>>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>>> Tested-by: Christoph Hellwig <hch@lst.de>
>>> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
>>
>> Reviewed-by: Mike Snitzer <snitzer@redhat.com>
>
> Hi Jens,
>
> Would you please take this one?

I was going to add it for 4.3, but hch just pointed out that it's a 
regression in this series. I'll send it in for 4.3.

-- 
Jens Axboe