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Commit 544122e5 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
Browse files

memcg: fix LRU accounting for SwapCache 



Now, a page can be deleted from SwapCache while do_swap_page().
memcg-fix-swap-accounting-leak-v3.patch handles that, but, LRU handling is
still broken.  (above behavior broke assumption of memcg-synchronized-lru
patch.)

This patch is a fix for LRU handling (especially for per-zone counters).
At charging SwapCache,
 - Remove page_cgroup from LRU if it's not used.
 - Add page cgroup to LRU if it's not linked to.

Reported-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 54595fe2

mm/memcontrol.c

+50 −9
Original line number Diff line number Diff line
@@ -331,8 +331,12 @@ void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru) 
		return;

	pc = lookup_page_cgroup(page);

	/* can happen while we handle swapcache. */

	if (list_empty(&pc->lru))

	if (list_empty(&pc->lru) || !pc->mem_cgroup)

		return;

	/*

	 * We don't check PCG_USED bit. It's cleared when the "page" is finally

	 * removed from global LRU.

	 */

	mz = page_cgroup_zoneinfo(pc);

	mem = pc->mem_cgroup;

	MEM_CGROUP_ZSTAT(mz, lru) -= 1;
@@ -379,16 +383,44 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru) 
	MEM_CGROUP_ZSTAT(mz, lru) += 1;

	list_add(&pc->lru, &mz->lists[lru]);

}



/*

 * To add swapcache into LRU. Be careful to all this function.

 * zone->lru_lock shouldn't be held and irq must not be disabled.

 * At handling SwapCache, pc->mem_cgroup may be changed while it's linked to

 * lru because the page may.be reused after it's fully uncharged (because of

 * SwapCache behavior).To handle that, unlink page_cgroup from LRU when charge

 * it again. This function is only used to charge SwapCache. It's done under

 * lock_page and expected that zone->lru_lock is never held.

 */

static void mem_cgroup_lru_fixup(struct page *page)

static void mem_cgroup_lru_del_before_commit_swapcache(struct page *page)

{

	if (!isolate_lru_page(page))

		putback_lru_page(page);

	unsigned long flags;

	struct zone *zone = page_zone(page);

	struct page_cgroup *pc = lookup_page_cgroup(page);



	spin_lock_irqsave(&zone->lru_lock, flags);

	/*

	 * Forget old LRU when this page_cgroup is *not* used. This Used bit

	 * is guarded by lock_page() because the page is SwapCache.

	 */

	if (!PageCgroupUsed(pc))

		mem_cgroup_del_lru_list(page, page_lru(page));

	spin_unlock_irqrestore(&zone->lru_lock, flags);

}



static void mem_cgroup_lru_add_after_commit_swapcache(struct page *page)

{

	unsigned long flags;

	struct zone *zone = page_zone(page);

	struct page_cgroup *pc = lookup_page_cgroup(page);



	spin_lock_irqsave(&zone->lru_lock, flags);

	/* link when the page is linked to LRU but page_cgroup isn't */

	if (PageLRU(page) && list_empty(&pc->lru))

		mem_cgroup_add_lru_list(page, page_lru(page));

	spin_unlock_irqrestore(&zone->lru_lock, flags);

}





void mem_cgroup_move_lists(struct page *page,

			   enum lru_list from, enum lru_list to)

{
@@ -1168,8 +1200,11 @@ int mem_cgroup_cache_charge_swapin(struct page *page, 
					mem = NULL; /* charge to current */

			}

		}

		/* SwapCache may be still linked to LRU now. */

		mem_cgroup_lru_del_before_commit_swapcache(page);

		ret = mem_cgroup_charge_common(page, mm, mask,

				MEM_CGROUP_CHARGE_TYPE_SHMEM, mem);

		mem_cgroup_lru_add_after_commit_swapcache(page);

		/* drop extra refcnt from tryget */

		if (mem)

			css_put(&mem->css);
@@ -1185,8 +1220,6 @@ int mem_cgroup_cache_charge_swapin(struct page *page, 
	}

	if (!locked)

		unlock_page(page);

	/* add this page(page_cgroup) to the LRU we want. */

	mem_cgroup_lru_fixup(page);



	return ret;

}
@@ -1201,7 +1234,9 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) 
	if (!ptr)

		return;

	pc = lookup_page_cgroup(page);

	mem_cgroup_lru_del_before_commit_swapcache(page);

	__mem_cgroup_commit_charge(ptr, pc, MEM_CGROUP_CHARGE_TYPE_MAPPED);

	mem_cgroup_lru_add_after_commit_swapcache(page);

	/*

	 * Now swap is on-memory. This means this page may be

	 * counted both as mem and swap....double count.
@@ -1220,7 +1255,7 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) 


	}

	/* add this page(page_cgroup) to the LRU we want. */

	mem_cgroup_lru_fixup(page);



}



void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
@@ -1288,6 +1323,12 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) 


	mem_cgroup_charge_statistics(mem, pc, false);

	ClearPageCgroupUsed(pc);

	/*

	 * pc->mem_cgroup is not cleared here. It will be accessed when it's

	 * freed from LRU. This is safe because uncharged page is expected not

	 * to be reused (freed soon). Exception is SwapCache, it's handled by

	 * special functions.

	 */



	mz = page_cgroup_zoneinfo(pc);

	unlock_page_cgroup(pc);