Commit 544122e5 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
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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
......@@ -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)
{
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)
{
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);
/* 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);
......
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