Re: [PATCH 0/2] don't use mapcount() to check large folio sharing

Yin, Fengwei
2023-08-08T00:02:52Z

Hi Andrew,

On 8/8/2023 12:43 AM, Andrew Morton wrote:
> On Fri, 4 Aug 2023 15:14:53 +0800 "Yin, Fengwei" <fengwei.yin@intel.com> wrote:
>
>> Hi Andrew,
>>
>> On 8/2/2023 8:39 PM, Yin, Fengwei wrote:
>>> Hi Andrew,
>>>
>>> On 7/29/2023 1:24 AM, Andrew Morton wrote:
>>>> On Sat, 29 Jul 2023 00:13:54 +0800 Yin Fengwei <fengwei.yin@intel.com> wrote:
>>>>
>>>>> In madvise_cold_or_pageout_pte_range() and madvise_free_pte_range(),
>>>>> folio_mapcount() is used to check whether the folio is shared. But it's
>>>>> not correct as folio_mapcount() returns total mapcount of large folio.
>>>>>
>>>>> Use folio_estimated_sharers() here as the estimated number is enough.
>>>>
>>>> What are the user-visible runtime effects of these changes?
>>>>
>>>> (and please try to avoid using the same Subject: for different patches)
>>>>
>>>
>>> Can you hold on these patches to mm-unstable? I think we need to wait for
>>> David's work on folio_maybe_mapped_shared() and redo the fix base on that.
>>> Thanks and sorry for the noise.
>> Sorry for bothering you again for this patchset.
>>
>> Let me explain the situation here:
>> - The reason to hold on the patches to mm-unstable is that I don't want to
>> promote the fix in this patch (using folio_estimated_sharers()). The
>> correct way is waiting for folio_maybe_mapped_shared() from David.
>>
>> Merging these patches motivate using folio_estimated_sharers() in other
>> places. So once folio_maybe_mapped_shared() is ready, we need to replace
>> folio_estimated_sharers() with folio_maybe_mapped_shared().
>>
>> - For this specific patches, if they are suitable for stable, we may want to
>> merge it (special for stable branch. I assume folio_maybe_mapped_shared()
>> may not be back ported to stable branch).
>>
>> So how do we deal with this situation? Thanks in advance.
>>
>
> I think I'll stage them for 6.5, with a cc:stable.
>
> I'll drop the current three patches. Please resend with
Thanks. Will resend the patches.

Regards
Yin, Fengwei

>
> a) different Subject:s for all patches and
>
> b) changelogs which fully describe the user-visible effects of the change.
>
> Thanks.