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 <[email protected]> Signed-off-by: Alex Shi <[email protected]> Acked-by: Hugh Dickins <[email protected]> Acked-by: Johannes Weiner <[email protected]> Cc: Andrew Morton <[email protected]> Cc: [email protected] Cc: [email protected]
Acked-by: Vlastimil Babka <[email protected]>
--- 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); }/**
