On 24/11/2023 17:40, David Hildenbrand wrote:
> On 22.11.23 17:29, Ryan Roberts wrote:
>> In preparation for supporting anonymous small-sized THP, improve
>> folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be
>> passed to it. In this case, all contained pages are accounted using the
>> order-0 folio (or base page) scheme.
>>
>> Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx>
>> Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
>> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
>> ---
>> mm/rmap.c | 28 ++++++++++++++++++++--------
>> 1 file changed, 20 insertions(+), 8 deletions(-)
>>
>> diff --git a/mm/rmap.c b/mm/rmap.c
>> index 49e4d86a4f70..b086dc957b0c 100644
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -1305,32 +1305,44 @@ void page_add_anon_rmap(struct page *page, struct
>> vm_area_struct *vma,
>> * This means the inc-and-test can be bypassed.
>> * The folio does not have to be locked.
>> *
>> - * If the folio is large, it is accounted as a THP. As the folio
>> + * If the folio is pmd-mappable, it is accounted as a THP. As the folio
>> * is new, it's assumed to be mapped exclusively by a single process.
>> */
>> void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
>> unsigned long address)
>> {
>> - int nr;
>> + int nr = folio_nr_pages(folio);
>>
>> - VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
>> + VM_BUG_ON_VMA(address < vma->vm_start ||
>> + address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
>> __folio_set_swapbacked(folio);
>> + __folio_set_anon(folio, vma, address, true);
>
> Likely the changed order doesn't matter.
Yes; the reason I moved __folio_set_anon() up here is because
SetPageAnonExclusive() asserts that the page is anon, and SetPageAnonExclusive()
has to be called differently for the 3 cases. I couldn't see any reason why it
wouldn't be safe to call __folio_set_anon() before setting up the mapcounts.
>
> LGTM
>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
>
Thanks!
