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. So I guess we can just remove the condition, but a confirmation for the above would be reassuring :) > > Best Regards, > Huang, Ying > > > - /* > > - * When successful, push dst to LRU immediately: so that if it > > - * turns out to be an mlocked page, remove_migration_ptes() will > > - * automatically build up the correct dst->mlock_count for it. > > - * > > - * We would like to do something similar for the old page, when > > - * unsuccessful, and other cases when a page has been temporarily > > - * isolated from the unevictable LRU: but this case is the easiest. > > - */ > > - folio_add_lru(dst); > > - if (page_was_mapped) > > - lru_add_drain(); > > - > > if (page_was_mapped) > > remove_migration_ptes(src, dst, false); > > > > @@ -1301,9 +1288,16 @@ static int migrate_folio_move(free_page_t put_new_page, unsigned long private, > > /* > > * If migration is successful, decrease refcount of dst, > > * which will not free the page because new page owner increased > > - * refcounter. > > + * refcounter. As well, if it is LRU folio, add the folio to LRU > > + * list in here. Use the old state of the isolated source folio to > > + * determine if we migrated a LRU folio. dst was already unlocked > > + * and possibly modified by its owner - don't rely on the folio > > + * state. > > */ > > - folio_put(dst); > > + if (unlikely(!is_lru)) > > + folio_put(dst); > > + else > > + folio_putback_lru(dst); > > > > /* > > * A folio that has been migrated has all references removed >
