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SubjectRe: [PATCH v5 2/8] mm/lru: replace pgdat lru_lock with lruvec lock
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在 2019/12/10 下午9:41, Matthew Wilcox 写道:
> On Tue, Dec 10, 2019 at 07:46:18PM +0800, Alex Shi wrote:
>> -static void lock_page_lru(struct page *page, int *isolated)
>> +static struct lruvec *lock_page_lru(struct page *page, int *isolated)
>> {
>> - pg_data_t *pgdat = page_pgdat(page);
>> + struct lruvec *lruvec = lock_page_lruvec_irq(page);
>>
>> - spin_lock_irq(&pgdat->lru_lock);
>> 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;
>> } else
>> *isolated = 0;
>> +
>> + return lruvec;
>> }
>
> I still don't understand how this is supposed to work for !PageLRU
> pages. Which lruvec have you locked if this page isn't on an LRU?
>

Good question. We could just fold it under PageLRU and no meaning changes.
Is this better to has this patch?

Thanks
Alex

commit 0f4b66d4a42397d57638352b738c3f9658003e44
Author: Alex Shi <alex.shi@linux.alibaba.com>
Date: Wed Dec 11 11:31:53 2019 +0800

mm/memcg: fold lock in lock_page_lru

According to the calling path of commit_charge, the lrucare is bound
with PageLRU, so we could just fold it under PageLRU. This has no
functional change.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 833df0ce1bc1..4fe2252cf437 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2622,9 +2622,10 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)

static struct lruvec *lock_page_lru(struct page *page, int *isolated)
{
- struct lruvec *lruvec = lock_page_lruvec_irq(page);
+ struct lruvec *lruvec = NULL;

if (PageLRU(page)) {
+ lruvec = lock_page_lruvec_irq(page);

ClearPageLRU(page);
del_page_from_lru_list(page, lruvec, page_lru(page));
@@ -2638,17 +2639,18 @@ static struct lruvec *lock_page_lru(struct page *page, int *isolated)
static void unlock_page_lru(struct page *page, int isolated,
struct lruvec *locked_lruvec)
{
- struct lruvec *lruvec;
+ if (isolated) {
+ struct lruvec *lruvec;

- unlock_page_lruvec_irq(locked_lruvec);
- lruvec = lock_page_lruvec_irq(page);
+ if (locked_lruvec)
+ unlock_page_lruvec_irq(locked_lruvec);
+ lruvec = lock_page_lruvec_irq(page);

- if (isolated) {
VM_BUG_ON_PAGE(PageLRU(page), page);
SetPageLRU(page);
add_page_to_lru_list(page, lruvec, page_lru(page));
+ unlock_page_lruvec_irq(lruvec);
}
- unlock_page_lruvec_irq(lruvec);
}

static void commit_charge(struct page *page, struct mem_cgroup *memcg,
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