Re: nvme discard issue

[Jens Axboe <axboe@kernel.dk>]

On 11/18/25 8:34 AM, Keith Busch wrote:
> On Tue, Nov 18, 2025 at 08:28:16AM -0700, Jens Axboe wrote:
>> On 11/18/25 8:22 AM, Keith Busch wrote:
>>> On Tue, Nov 18, 2025 at 07:24:59AM -0700, Jens Axboe wrote:
>>>> commit 2516c246d01c23a5f5310e9ac78d9f8aad9b1d0e
>>>> Author: Keith Busch <kbusch@kernel.org>
>>>> Date:   Fri Nov 14 10:31:45 2025 -0800
>>>>
>>>>     block: consider discard merge last
>>>>
>>>> This was just doing an allmodconfig build, using XFS as per the trace
>>>> above. The fs is mounted:
>>>
>>> Huh, xfs was the only filesystem I tested, but obviously not enough. So
>>> the segment accounting is off now, I'll take a look.
>>
>> It's all very strange - reverted the above commit, and ran into other
>> issues. So may be something else entirely and your commit is fine. My
>> for-6.19/block branch seems fine (?!?), but merged into master it's not.
> 
> Interesting, I'll keep testing futher back too.

Thanks!

> But I do see a non-trivial problem with my patch, so I think you should
> either drop or revert it at this time. For the discard back merge case,
> ideally we'd just adjust the bio's bi_size and drop the second bio
> completely.
> 
> Anyway, sorry, that was my mistake. I was trying to get nvme to hit a
> previous bug from merging data-less bio's that nvme had dodged.

OK, I'll revert it for now. Done.

-- 
Jens Axboe