Messages in this thread | | | Subject | Re: [PATCH v21 16/19] mm/swap.c: serialize memcg changes in pagevec_lru_move_fn | From | Vlastimil Babka <> | Date | Wed, 11 Nov 2020 19:00:10 +0100 |
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On 11/5/20 9:55 AM, Alex Shi wrote: > Hugh Dickins' found a memcg change bug on original version: > If we want to change the pgdat->lru_lock to memcg's lruvec lock, we have > to serialize mem_cgroup_move_account during pagevec_lru_move_fn. The > possible bad scenario would like: > > cpu 0 cpu 1 > lruvec = mem_cgroup_page_lruvec() > if (!isolate_lru_page()) > mem_cgroup_move_account > > spin_lock_irqsave(&lruvec->lru_lock <== wrong lock. > > So we need TestClearPageLRU to block isolate_lru_page(), that serializes > the memcg change. and then removing the PageLRU check in move_fn callee > as the consequence. > > __pagevec_lru_add_fn() is different from the others, because the pages > it deals with are, by definition, not yet on the lru. TestClearPageLRU > is not needed and would not work, so __pagevec_lru_add() goes its own > way. > > Reported-by: Hugh Dickins <hughd@google.com> > Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> > Acked-by: Hugh Dickins <hughd@google.com> > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> --- > mm/swap.c | 44 +++++++++++++++++++++++++++++++++++--------- > 1 file changed, 35 insertions(+), 9 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 2681d9023998..1838a9535703 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -222,8 +222,14 @@ static void pagevec_lru_move_fn(struct pagevec *pvec, > spin_lock_irqsave(&pgdat->lru_lock, flags); > } > > + /* block memcg migration during page moving between lru */ > + if (!TestClearPageLRU(page)) > + continue; > + > lruvec = mem_cgroup_page_lruvec(page, pgdat); > (*move_fn)(page, lruvec); > + > + SetPageLRU(page); > } > if (pgdat) > spin_unlock_irqrestore(&pgdat->lru_lock, flags); > @@ -233,7 +239,7 @@ static void pagevec_lru_move_fn(struct pagevec *pvec, > > static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec) > { > - if (PageLRU(page) && !PageUnevictable(page)) { > + if (!PageUnevictable(page)) { > del_page_from_lru_list(page, lruvec, page_lru(page)); > ClearPageActive(page); > add_page_to_lru_list_tail(page, lruvec, page_lru(page)); > @@ -306,7 +312,7 @@ void lru_note_cost_page(struct page *page) > > static void __activate_page(struct page *page, struct lruvec *lruvec) > { > - if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { > + if (!PageActive(page) && !PageUnevictable(page)) { > int lru = page_lru_base_type(page); > int nr_pages = thp_nr_pages(page); > > @@ -362,7 +368,8 @@ static void activate_page(struct page *page) > > page = compound_head(page); > spin_lock_irq(&pgdat->lru_lock); > - __activate_page(page, mem_cgroup_page_lruvec(page, pgdat)); > + if (PageLRU(page)) > + __activate_page(page, mem_cgroup_page_lruvec(page, pgdat)); > spin_unlock_irq(&pgdat->lru_lock); > } > #endif > @@ -519,9 +526,6 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec) > bool active; > int nr_pages = thp_nr_pages(page); > > - if (!PageLRU(page)) > - return; > - > if (PageUnevictable(page)) > return; > > @@ -562,7 +566,7 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec) > > static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec) > { > - if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) { > + if (PageActive(page) && !PageUnevictable(page)) { > int lru = page_lru_base_type(page); > int nr_pages = thp_nr_pages(page); > > @@ -579,7 +583,7 @@ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec) > > static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec) > { > - if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) && > + if (PageAnon(page) && PageSwapBacked(page) && > !PageSwapCache(page) && !PageUnevictable(page)) { > bool active = PageActive(page); > int nr_pages = thp_nr_pages(page); > @@ -1021,7 +1025,29 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec) > */ > void __pagevec_lru_add(struct pagevec *pvec) > { > - pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn); > + int i; > + struct pglist_data *pgdat = NULL; > + struct lruvec *lruvec; > + unsigned long flags = 0; > + > + for (i = 0; i < pagevec_count(pvec); i++) { > + struct page *page = pvec->pages[i]; > + struct pglist_data *pagepgdat = page_pgdat(page); > + > + if (pagepgdat != pgdat) { > + if (pgdat) > + spin_unlock_irqrestore(&pgdat->lru_lock, flags); > + pgdat = pagepgdat; > + spin_lock_irqsave(&pgdat->lru_lock, flags); > + } > + > + lruvec = mem_cgroup_page_lruvec(page, pgdat); > + __pagevec_lru_add_fn(page, lruvec); > + } > + if (pgdat) > + spin_unlock_irqrestore(&pgdat->lru_lock, flags); > + release_pages(pvec->pages, pvec->nr); > + pagevec_reinit(pvec); > } > > /** >
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