On 20/08/2019 12.48, Alex Shi wrote:
Now we repeatly assign the lruvec->pgdat in memcg. Will remove the
assignment in lruvec getting function after very points are protected.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/memcontrol.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e8a1b0d95ba8..19fd911e8098 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2550,12 +2550,12 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
static void lock_page_lru(struct page *page, int *isolated)
{
pg_data_t *pgdat = page_pgdat(page);
+ struct lruvec *lruvec = mem_cgroup_page_lruvec(page, pgdat);
What protects lruvec from freeing at this point?
After reading resolving lruvec page could be moved and cgroup deleted.
In this old patches I've used RCU for that: https://lkml.org/lkml/2012/2/20/276
Pointer to lruvec should be resolved under disabled irq.
Not sure this works these days.
- spin_lock_irq(&pgdat->lruvec.lru_lock);
+ spin_lock_irq(&lruvec->lru_lock);
+ sync_lruvec_pgdat(lruvec, pgdat);
if (PageLRU(page)) {
- struct lruvec *lruvec;
- lruvec = mem_cgroup_page_lruvec(page, pgdat);
ClearPageLRU(page);
del_page_from_lru_list(page, lruvec, page_lru(page));
*isolated = 1;
@@ -2566,16 +2566,14 @@ static void lock_page_lru(struct page *page, int *isolated)
static void unlock_page_lru(struct page *page, int isolated)
{
pg_data_t *pgdat = page_pgdat(page);
+ struct lruvec *lruvec = mem_cgroup_page_lruvec(page, pgdat);
if (isolated) {
- struct lruvec *lruvec;
-
- lruvec = mem_cgroup_page_lruvec(page, pgdat);
VM_BUG_ON_PAGE(PageLRU(page), page);
SetPageLRU(page);
add_page_to_lru_list(page, lruvec, page_lru(page));
}
- spin_unlock_irq(&pgdat->lruvec.lru_lock);
+ spin_unlock_irq(&lruvec->lru_lock);
}
static void commit_charge(struct page *page, struct mem_cgroup *memcg,
