Re: block: re-add discard_granularity and alignment checks

From: Ming Lin
Date: Tue Oct 27 2015 - 17:24:06 EST

On Thu, Oct 22, 2015 at 10:03 AM, Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> On Thu, Oct 22 2015 at 12:59pm -0400,
> Ming Lin <mlin@xxxxxxxxxx> wrote:
>> From: Ming Lin <ming.l@xxxxxxxxxxxxxxx>
>> 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@xxxxxx>
>> Tested-by: Christoph Hellwig <hch@xxxxxx>
>> Signed-off-by: Ming Lin <ming.l@xxxxxxxxxxxxxxx>
> Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx>

Hi Jens,

Would you please take this one?

> Thanks!
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