| Message ID | 20200818184704.3625199-2-yuzhao@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/3] mm: remove activate_page() from unuse_pte() | expand |
On Tue, Aug 18, 2020 at 11:47 AM Yu Zhao <yuzhao@google.com> wrote: > > To activate a page, mark_page_accessed() always holds a reference > on it. It either gets a new reference when adding a page to > lru_pvecs.activate_page or reuses an existing one it previously > got when it added a page to lru_pvecs.lru_add. So it doesn't call > SetPageActive() on a page that doesn't have any reference left. > Therefore, the race is impossible these days (I didn't brother to > dig into its history). > > For other paths, namely reclaim and migration, a reference count is > always held while calling SetPageActive() on a page. > > SetPageSlabPfmemalloc() also uses SetPageActive(), but it's irrelevant > to LRU pages. Seems fine to me. Reviewed-by: Yang Shi <shy828301@gmail.com> > > Signed-off-by: Yu Zhao <yuzhao@google.com> > --- > mm/memremap.c | 2 -- > mm/swap.c | 2 -- > 2 files changed, 4 deletions(-) > > diff --git a/mm/memremap.c b/mm/memremap.c > index 03e38b7a38f1..3a06eb91cb59 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -451,8 +451,6 @@ void free_devmap_managed_page(struct page *page) > return; > } > > - /* Clear Active bit in case of parallel mark_page_accessed */ > - __ClearPageActive(page); > __ClearPageWaiters(page); > > mem_cgroup_uncharge(page); > diff --git a/mm/swap.c b/mm/swap.c > index 25c4043491b3..999a84dbe12c 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -900,8 +900,6 @@ void release_pages(struct page **pages, int nr) > del_page_from_lru_list(page, lruvec, page_off_lru(page)); > } > > - /* Clear Active bit in case of parallel mark_page_accessed */ > - __ClearPageActive(page); > __ClearPageWaiters(page); > > list_add(&page->lru, &pages_to_free); > -- > 2.28.0.220.ged08abb693-goog > >
diff --git a/mm/memremap.c b/mm/memremap.c index 03e38b7a38f1..3a06eb91cb59 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -451,8 +451,6 @@ void free_devmap_managed_page(struct page *page) return; } - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); __ClearPageWaiters(page); mem_cgroup_uncharge(page); diff --git a/mm/swap.c b/mm/swap.c index 25c4043491b3..999a84dbe12c 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -900,8 +900,6 @@ void release_pages(struct page **pages, int nr) del_page_from_lru_list(page, lruvec, page_off_lru(page)); } - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); __ClearPageWaiters(page); list_add(&page->lru, &pages_to_free);
To activate a page, mark_page_accessed() always holds a reference on it. It either gets a new reference when adding a page to lru_pvecs.activate_page or reuses an existing one it previously got when it added a page to lru_pvecs.lru_add. So it doesn't call SetPageActive() on a page that doesn't have any reference left. Therefore, the race is impossible these days (I didn't brother to dig into its history). For other paths, namely reclaim and migration, a reference count is always held while calling SetPageActive() on a page. SetPageSlabPfmemalloc() also uses SetPageActive(), but it's irrelevant to LRU pages. Signed-off-by: Yu Zhao <yuzhao@google.com> --- mm/memremap.c | 2 -- mm/swap.c | 2 -- 2 files changed, 4 deletions(-)