On 27.07.23 13:02, Ryan Roberts wrote:
> The recent change to batch-zap anonymous ptes did not take into account
> that for platforms where MMU_GATHER_NO_GATHER is enabled (e.g. s390),
> __tlb_remove_page() drops a reference to the page. This means that the
> folio reference count can drop to zero while still in use (i.e. before
> folio_remove_rmap_range() is called). This does not happen on other
> platforms because the actual page freeing is deferred.
>
> Solve this by appropriately getting/putting the folio to guarrantee it
> does not get freed early.
>
> Given the new need to get/put the folio in the batch path, let's stick
> to the non-batched path if the folio is not large. In this case batching
> is not helpful since the batch size is 1.
>
> Signed-off-by: Ryan Roberts <[email protected]>
> Fixes: 904d9713b3b0 ("mm: batch-zap large anonymous folio PTE mappings")
> Reported-by: Nathan Chancellor <[email protected]>
> Link: https://lore.kernel.org/linux-mm/[email protected]/
> ---
>
> Hi Andrew,
>
> This fixes patch 3 in the series at [1], which is currently in mm-unstable. I'm
> not sure whether you want to take the fix or whether I should re-post the entire
> series?
>
Please repost the complete thing, you're touching some sensible places
that really need decent review.
--
Cheers,
David / dhildenb
Ryan,
David Hildenbrand <[email protected]> writes:
> On 27.07.23 13:02, Ryan Roberts wrote:
>> The recent change to batch-zap anonymous ptes did not take into account
>> that for platforms where MMU_GATHER_NO_GATHER is enabled (e.g. s390),
>> __tlb_remove_page() drops a reference to the page. This means that the
>> folio reference count can drop to zero while still in use (i.e. before
>> folio_remove_rmap_range() is called). This does not happen on other
>> platforms because the actual page freeing is deferred.
>> Solve this by appropriately getting/putting the folio to guarrantee
>> it
>> does not get freed early.
>> Given the new need to get/put the folio in the batch path, let's
>> stick
>> to the non-batched path if the folio is not large. In this case batching
>> is not helpful since the batch size is 1.
>> Signed-off-by: Ryan Roberts <[email protected]>
>> Fixes: 904d9713b3b0 ("mm: batch-zap large anonymous folio PTE mappings")
>> Reported-by: Nathan Chancellor <[email protected]>
>> Link: https://lore.kernel.org/linux-mm/[email protected]/
>> ---
>> Hi Andrew,
>> This fixes patch 3 in the series at [1], which is currently in
>> mm-unstable. I'm
>> not sure whether you want to take the fix or whether I should re-post the entire
>> series?
>>
>
> Please repost the complete thing, you're touching some sensible places
> that really need decent review.
Please also add:
Alexander Gordeev <[email protected]>
Gerald Schaefer <[email protected]>
when reposting. Thanks!