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Message-ID: <AANLkTimoSux0Fg6dpiHy24A+4oVW9_74BQ6EC7LhO8Sg@mail.gmail.com>
Date: Fri, 14 Jan 2011 21:28:09 +0900
From: Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>
To: Johannes Weiner <hannes@...xchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
Greg Thelen <gthelen@...gle.com>, aarcange@...hat.com,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/4] [BUGFIX] fix account leak at force_empty, rmdir with THP
2011/1/14 Johannes Weiner <hannes@...xchg.org>:
> On Fri, Jan 14, 2011 at 07:15:35PM +0900, KAMEZAWA Hiroyuki wrote:
>>
>> Now, when THP is enabled, memcg's rmdir() function is broken
>> because move_account() for THP page is not supported.
>>
>> This will cause account leak or -EBUSY issue at rmdir().
>> This patch fixes the issue by supporting move_account() THP pages.
>>
>> And account information will be moved to its parent at rmdir().
>>
>> How to test:
>> 79 mount -t cgroup none /cgroup/memory/ -o memory
>> 80 mkdir /cgroup/A/
>> 81 mkdir /cgroup/memory/A
>> 82 mkdir /cgroup/memory/A/B
>> 83 cgexec -g memory:A/B ./malloc 128 &
>> 84 grep anon /cgroup/memory/A/B/memory.stat
>> 85 grep rss /cgroup/memory/A/B/memory.stat
>> 86 echo 1728 > /cgroup/memory/A/tasks
>> 87 grep rss /cgroup/memory/A/memory.stat
>> 88 rmdir /cgroup/memory/A/B/
>> 89 grep rss /cgroup/memory/A/memory.stat
>>
>> - Create 2 level directory and exec a task calls malloc(big chunk).
>> - Move a task somewhere (its parent cgroup in above)
>> - rmdir /A/B
>> - check memory.stat in /A/B is moved to /A after rmdir. and confirm
>> RSS/LRU information includes usages it was charged against /A/B.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>> ---
>> mm/memcontrol.c | 32 ++++++++++++++++++++++----------
>> 1 file changed, 22 insertions(+), 10 deletions(-)
>>
>> Index: mmotm-0107/mm/memcontrol.c
>> ===================================================================
>> --- mmotm-0107.orig/mm/memcontrol.c
>> +++ mmotm-0107/mm/memcontrol.c
>> @@ -2154,6 +2154,10 @@ void mem_cgroup_split_huge_fixup(struct
>> smp_wmb(); /* see __commit_charge() */
>> SetPageCgroupUsed(tpc);
>> VM_BUG_ON(PageCgroupCache(hpc));
>> + /*
>> + * Note: if dirty ratio etc..are supported,
>> + * other flags may need to be copied.
>> + */
>
> That's a good comment, but it should be in the patch that introduces
> this function and is a bit unrelated in this one.
>
Ok. I'll remove this. This is an alarm for Greg ;)
>> }
>> #endif
>>
>> @@ -2175,8 +2179,11 @@ void mem_cgroup_split_huge_fixup(struct
>> */
>>
>> static void __mem_cgroup_move_account(struct page_cgroup *pc,
>> - struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
>> + struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge,
>> + int charge_size)
>> {
>> + int pagenum = charge_size >> PAGE_SHIFT;
>
> nr_pages?
>
Ok. replace pagenum <-> nr_pages.
>> +
>> VM_BUG_ON(from == to);
>> VM_BUG_ON(PageLRU(pc->page));
>> VM_BUG_ON(!page_is_cgroup_locked(pc));
>> @@ -2190,14 +2197,14 @@ static void __mem_cgroup_move_account(st
>> __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
>> preempt_enable();
>> }
>> - mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -1);
>> + mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -pagenum);
>> if (uncharge)
>> /* This is not "cancel", but cancel_charge does all we need. */
>> - mem_cgroup_cancel_charge(from, PAGE_SIZE);
>> + mem_cgroup_cancel_charge(from, charge_size);
>>
>> /* caller should have done css_get */
>> pc->mem_cgroup = to;
>> - mem_cgroup_charge_statistics(to, PageCgroupCache(pc), 1);
>> + mem_cgroup_charge_statistics(to, PageCgroupCache(pc), pagenum);
>> /*
>> * We charges against "to" which may not have any tasks. Then, "to"
>> * can be under rmdir(). But in current implementation, caller of
>> @@ -2212,7 +2219,8 @@ static void __mem_cgroup_move_account(st
>> * __mem_cgroup_move_account()
>> */
>> static int mem_cgroup_move_account(struct page_cgroup *pc,
>> - struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
>> + struct mem_cgroup *from, struct mem_cgroup *to,
>> + bool uncharge, int charge_size)
>> {
>> int ret = -EINVAL;
>> unsigned long flags;
>> @@ -2220,7 +2228,7 @@ static int mem_cgroup_move_account(struc
>> lock_page_cgroup(pc);
>> if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
>> move_lock_page_cgroup(pc, &flags);
>> - __mem_cgroup_move_account(pc, from, to, uncharge);
>> + __mem_cgroup_move_account(pc, from, to, uncharge, charge_size);
>> move_unlock_page_cgroup(pc, &flags);
>> ret = 0;
>> }
>> @@ -2245,6 +2253,7 @@ static int mem_cgroup_move_parent(struct
>> struct cgroup *cg = child->css.cgroup;
>> struct cgroup *pcg = cg->parent;
>> struct mem_cgroup *parent;
>> + int charge_size = PAGE_SIZE;
>> int ret;
>>
>> /* Is ROOT ? */
>> @@ -2256,16 +2265,19 @@ static int mem_cgroup_move_parent(struct
>> goto out;
>> if (isolate_lru_page(page))
>> goto put;
>> + /* The page is isolated from LRU and we have no race with splitting */
>> + if (PageTransHuge(page))
>> + charge_size = PAGE_SIZE << compound_order(page);
>
> The same as in the previous patch, compound_order() implicitely
> handles order-0 pages and should do the right thing without an extra
> check.
>
Sure.
> The comment is valuable, though!
>
> Nitpicks aside:
> Acked-by: Johannes Weiner <hannes@...xchg.org>
Thank you for quick review!
Updated one will be posted in the next week after some amounts of more tests.
Regards,
-Kame
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