On Mon, Jun 19, 2023 at 12:58 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 19.06.23 09:56, David Hildenbrand wrote: > > On 19.06.23 05:59, Yosry Ahmed wrote: > >> On Sun, Jun 18, 2023 at 7:00 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: > >>> > >>> Hi, Yosry, > >>> > >>> Yosry Ahmed <yosryahmed@xxxxxxxxxx> writes: > >>> > >>>> This reverts commit c3096e6782b733158bf34f6bbb4567808d4e0740. > >>>> > >>>> That commit made sure we immediately add the new page to the LRU before > >>>> remove_migration_ptes() is called in migrate_move_folio() (used to be > >>>> __unmap_and_move() back then), such that the rmap walk will rebuild the > >>>> correct mlock_count for the page again. This was needed because the > >>>> mlock_count was lost when the page is isolated. This is no longer the > >>>> case since mlock_count no longer overlays page->lru. > >>>> > >>>> Revert the commit (the code was foliated afterward the commit, so the > >>>> revert is updated as such). > >>>> > >>>> Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > >>>> --- > >>>> mm/migrate.c | 24 +++++++++--------------- > >>>> 1 file changed, 9 insertions(+), 15 deletions(-) > >>>> > >>>> diff --git a/mm/migrate.c b/mm/migrate.c > >>>> index 01cac26a3127..68f693731865 100644 > >>>> --- a/mm/migrate.c > >>>> +++ b/mm/migrate.c > >>>> @@ -1279,19 +1279,6 @@ static int migrate_folio_move(free_page_t put_new_page, unsigned long private, > >>>> if (unlikely(!is_lru)) > >>>> goto out_unlock_both; > >>> > >>> The patch itself looks good to me! Thanks! > >>> > >>> Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx> > >> > >> Thanks for taking a look! > >> > >>> > >>> And, it seems that we can remove the above 2 lines and "out_unlock_both" > >>> label now. That can make the code simpler a little. Right? > >> > >> I am not familiar with this code. If we remove the above condition > >> then pages that have is_lru == 0 (i.e __PageMovable(src) is true) and > >> page_was_mapped == 1 will call remove_migration_ptes(). This wouldn't > >> happen without removing the above 2 lines. If this combination is > >> impossible (is_lru == 0 && page_was_mapped == 1), then yeah we can > >> remove the above condition. > >> > >> It looks like __SetPageMovable() is only called by zsmalloc, z3fold, > >> and balloon_page_insert(). The former 2 will never have those pages > >> mapped into userspace. I am not familiar with balloon_page_insert(), > >> but my gut feeling is that those are pages used by the driver and are > >> also not mapped into userspace. > > > > On XEN, there is xen_alloc_ballooned_pages(), which ends up mapping > > balloon-inflated pages into user space (for something like MMIO IIRC). > > But the XEN balloon does not use the balloon compaction framework, so > > __SetPageMovable() does not apply. > > > > The other balloon_page_insert() users (VMware balloon, CMM, > > virtio-balloon) shouldn't be doing something like that. > > Ah, and I remember they even can't, because in balloon_page_insert() we > also do a __SetPageOffline(). And such typed pages cannot be mapped into > user space (because the type overlays the mapcount). Thanks David, good to know! I will remove the condition as Ying suggested in the next version then! > > -- > Cheers, > > David / dhildenb >
