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@xxxxxxxxxx>
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
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);
}
/**
