[PATCHv10 4/9] block: allow ability to limit partition write hints

[Bart Van Assche]

On 10/30/24 1:11 PM, Keith Busch wrote:
> On Wed, Oct 30, 2024 at 05:46:58AM +0100, Christoph Hellwig wrote:
>> On Tue, Oct 29, 2024 at 10:25:11AM -0700, Bart Van Assche wrote:
>>>> +}
>>>
>>> bitmap_copy() is not atomic. Shouldn't the bitmap_copy() call be
>>> serialized against the code that tests bits in bdev->write_hint_mask?
>>
>> It needs something.  I actually pointed that out last round, but forgot
>> about it again this time :)
> 
> I disagree. Whether we serialize it or not, writes in flight will either
> think it can write or it won't. There's no point adding any overhead to
> the IO path for this as you can't stop ending up with inflight writes
> using the tag you're trying to turn off.

Shouldn't the request queue be frozen while this write_hint_mask bitmap
is modified, just like the request queue is frozen while queue limits
are updated? This change wouldn't add any additional overhead to the I/O
path.

Thanks,

Bart.