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mm/swap.c: serialize memcg changes in pagevec_lru_move_fn 

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>
This commit is contained in:
Peng Hao 2021-09-03 10:03:54 +08:00 committed by kaixuxiakx
parent f784a238c7
commit 4e9dc3310b
1 changed files with 34 additions and 10 deletions
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44
mm/swap.c
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@ -205,9 +205,13 @@ static void pagevec_lru_move_fn(struct pagevec *pvec,
pgdat = pagepgdat;
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);
@ -217,7 +221,7 @@ 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));
@ -259,7 +263,7 @@ static void update_page_reclaim_stat(struct lruvec *lruvec,
static void __activate_page(struct page *page, struct lruvec *lruvec)
{
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
if (!PageActive(page) && !PageUnevictable(page)) {
int file = page_is_file_cache(page);
int lru = page_lru_base_type(page);
@ -312,7 +316,8 @@ 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
@ -482,9 +487,6 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec)
int lru, file;
bool active;
if (!PageLRU(page))
return;
if (PageUnevictable(page))
return;
@ -524,7 +526,7 @@ 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 file = page_is_file_cache(page);
int lru = page_lru_base_type(page);
@ -540,7 +542,7 @@ 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);
@ -934,7 +936,29 @@ 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);
}
EXPORT_SYMBOL(__pagevec_lru_add);