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Date: Wed, 12 Mar 2014 15:05:20 +0100
From: Michal Hocko <mhocko@...e.cz>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 8/8] memcg: sanitize __mem_cgroup_try_charge() call
protocol
On Wed 12-03-14 15:01:38, Michal Hocko wrote:
> On Tue 11-03-14 21:28:34, Johannes Weiner wrote:
> > Some callsites pass a memcg directly, some callsites pass a mm that
> > first has to be translated to an mm. This makes for a terrible
> > function interface.
> >
> > Just push the mm-to-memcg translation into the respective callsites
> > and always pass a memcg to mem_cgroup_try_charge().
> >
> > Signed-off-by: Johannes Weiner <hannes@...xchg.org>
>
> text data bss dec hex filename
> 39435 5916 4192 49543 c187 mm/memcontrol.o.after
> 40466 5916 4192 50574 c58e mm/memcontrol.o.before
Just to prevent from confusion, .before is before the series is applied
not just this patch.
Before _this_ patch size looks like this:
text data bss dec hex filename
39898 5916 4192 50006 c356 mm/memcontrol.o
> 1K down very nice. But we can shave off additional ~300B if the the
> common mm charging helper as I suggested before:
>
> text data bss dec hex filename
> 39100 5916 4192 49208 c038 mm/memcontrol.o.mm
>
> commit 7aa420bc051849d85dcf5a091f3619c6b8e33cfb
> Author: Michal Hocko <mhocko@...e.cz>
> Date: Wed Mar 12 14:59:06 2014 +0100
>
> add charge mm helper
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2d7aa3e784d9..67e01b27a021 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2757,6 +2757,35 @@ bypass:
> return -EINTR;
> }
>
> +/**
> + * mem_cgroup_try_charge_mm - try charging a mm
> + * @mm: mm_struct to charge
> + * @nr_pages: number of pages to charge
> + * @oom: trigger OOM if reclaim fails
> + *
> + * Returns the charged mem_cgroup associated with the given mm_struct or
> + * NULL the charge failed.
> + */
> +static struct mem_cgroup *mem_cgroup_try_charge_mm(struct mm_struct *mm,
> + gfp_t gfp_mask,
> + unsigned int nr_pages,
> + bool oom)
> +
> +{
> + struct mem_cgroup *memcg;
> + int ret;
> +
> + memcg = get_mem_cgroup_from_mm(mm);
> + ret = mem_cgroup_try_charge(memcg, gfp_mask, nr_pages, oom);
> + css_put(&memcg->css);
> + if (ret == -EINTR)
> + memcg = root_mem_cgroup;
> + else if (ret)
> + memcg = NULL;
> +
> + return memcg;
> +}
> +
> /*
> * Somemtimes we have to undo a charge we got by try_charge().
> * This function is for that and do uncharge, put css's refcnt.
> @@ -3828,7 +3857,6 @@ int mem_cgroup_newpage_charge(struct page *page,
> unsigned int nr_pages = 1;
> struct mem_cgroup *memcg;
> bool oom = true;
> - int ret;
>
> if (mem_cgroup_disabled())
> return 0;
> @@ -3847,13 +3875,9 @@ int mem_cgroup_newpage_charge(struct page *page,
> oom = false;
> }
>
> - memcg = get_mem_cgroup_from_mm(mm);
> - ret = mem_cgroup_try_charge(memcg, gfp_mask, nr_pages, oom);
> - css_put(&memcg->css);
> - if (ret == -EINTR)
> - memcg = root_mem_cgroup;
> - else if (ret)
> - return ret;
> + memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, nr_pages, oom);
> + if (!memcg)
> + return -ENOMEM;
> __mem_cgroup_commit_charge(memcg, page, nr_pages,
> MEM_CGROUP_CHARGE_TYPE_ANON, false);
> return 0;
> @@ -3914,15 +3938,10 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page,
> */
> if (!PageSwapCache(page)) {
> struct mem_cgroup *memcg;
> - int ret;
>
> - memcg = get_mem_cgroup_from_mm(mm);
> - ret = mem_cgroup_try_charge(memcg, gfp_mask, 1, true);
> - css_put(&memcg->css);
> - if (ret == -EINTR)
> - memcg = root_mem_cgroup;
> - else if (ret)
> - return ret;
> + memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, 1, true);
> + if (!memcg)
> + return -ENOMEM;
> *memcgp = memcg;
> return 0;
> }
> @@ -3996,13 +4015,9 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> if (unlikely(!mm))
> memcg = root_mem_cgroup;
> else {
> - memcg = get_mem_cgroup_from_mm(mm);
> - ret = mem_cgroup_try_charge(memcg, gfp_mask, 1, true);
> - css_put(&memcg->css);
> - if (ret == -EINTR)
> - memcg = root_mem_cgroup;
> - else if (ret)
> - return ret;
> + memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, 1, true);
> + if (!memcg)
> + return -ENOMEM;
> }
> __mem_cgroup_commit_charge(memcg, page, 1, type, false);
> return 0;
>
> Anyway to your patch as is. The above can be posted as a separate patch
> or folded in as you prefer.
>
> Acked-by: Michal Hocko <mhocko@...e.cz>
>
> > ---
> > mm/memcontrol.c | 184 +++++++++++++++++++++++++-------------------------------
> > 1 file changed, 83 insertions(+), 101 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 4f7192bfa5fa..876598b4505b 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -2609,7 +2609,7 @@ static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
> > }
> >
> >
> > -/* See __mem_cgroup_try_charge() for details */
> > +/* See mem_cgroup_try_charge() for details */
> > enum {
> > CHARGE_OK, /* success */
> > CHARGE_RETRY, /* need to retry but retry is not bad */
> > @@ -2682,45 +2682,34 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
> > return CHARGE_NOMEM;
> > }
> >
> > -/*
> > - * __mem_cgroup_try_charge() does
> > - * 1. detect memcg to be charged against from passed *mm and *ptr,
> > - * 2. update res_counter
> > - * 3. call memory reclaim if necessary.
> > - *
> > - * In some special case, if the task is fatal, fatal_signal_pending() or
> > - * has TIF_MEMDIE, this function returns -EINTR while writing root_mem_cgroup
> > - * to *ptr. There are two reasons for this. 1: fatal threads should quit as soon
> > - * as possible without any hazards. 2: all pages should have a valid
> > - * pc->mem_cgroup. If mm is NULL and the caller doesn't pass a valid memcg
> > - * pointer, that is treated as a charge to root_mem_cgroup.
> > - *
> > - * So __mem_cgroup_try_charge() will return
> > - * 0 ... on success, filling *ptr with a valid memcg pointer.
> > - * -ENOMEM ... charge failure because of resource limits.
> > - * -EINTR ... if thread is fatal. *ptr is filled with root_mem_cgroup.
> > +/**
> > + * mem_cgroup_try_charge - try charging a memcg
> > + * @memcg: memcg to charge
> > + * @nr_pages: number of pages to charge
> > + * @oom: trigger OOM if reclaim fails
> > *
> > - * Unlike the exported interface, an "oom" parameter is added. if oom==true,
> > - * the oom-killer can be invoked.
> > + * Returns 0 if @memcg was charged successfully, -EINTR if the charge
> > + * was bypassed to root_mem_cgroup, and -ENOMEM if the charge failed.
> > */
> > -static int __mem_cgroup_try_charge(struct mm_struct *mm,
> > - gfp_t gfp_mask,
> > - unsigned int nr_pages,
> > - struct mem_cgroup **ptr,
> > - bool oom)
> > +static int mem_cgroup_try_charge(struct mem_cgroup *memcg,
> > + gfp_t gfp_mask,
> > + unsigned int nr_pages,
> > + bool oom)
> > {
> > unsigned int batch = max(CHARGE_BATCH, nr_pages);
> > int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
> > - struct mem_cgroup *memcg = NULL;
> > int ret;
> >
> > + if (mem_cgroup_is_root(memcg))
> > + goto done;
> > /*
> > - * Unlike gloval-vm's OOM-kill, we're not in memory shortage
> > - * in system level. So, allow to go ahead dying process in addition to
> > - * MEMDIE process.
> > + * Unlike in global OOM situations, memcg is not in a physical
> > + * memory shortage. Allow dying and OOM-killed tasks to
> > + * bypass the last charges so that they can exit quickly and
> > + * free their memory.
> > */
> > - if (unlikely(test_thread_flag(TIF_MEMDIE)
> > - || fatal_signal_pending(current)))
> > + if (unlikely(test_thread_flag(TIF_MEMDIE) ||
> > + fatal_signal_pending(current)))
> > goto bypass;
> >
> > if (unlikely(task_in_memcg_oom(current)))
> > @@ -2729,14 +2718,6 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
> > if (gfp_mask & __GFP_NOFAIL)
> > oom = false;
> > again:
> > - if (*ptr) { /* css should be a valid one */
> > - memcg = *ptr;
> > - css_get(&memcg->css);
> > - } else {
> > - memcg = get_mem_cgroup_from_mm(mm);
> > - }
> > - if (mem_cgroup_is_root(memcg))
> > - goto done;
> > if (consume_stock(memcg, nr_pages))
> > goto done;
> >
> > @@ -2744,10 +2725,8 @@ again:
> > bool invoke_oom = oom && !nr_oom_retries;
> >
> > /* If killed, bypass charge */
> > - if (fatal_signal_pending(current)) {
> > - css_put(&memcg->css);
> > + if (fatal_signal_pending(current))
> > goto bypass;
> > - }
> >
> > ret = mem_cgroup_do_charge(memcg, gfp_mask, batch,
> > nr_pages, invoke_oom);
> > @@ -2756,17 +2735,12 @@ again:
> > break;
> > case CHARGE_RETRY: /* not in OOM situation but retry */
> > batch = nr_pages;
> > - css_put(&memcg->css);
> > - memcg = NULL;
> > goto again;
> > case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
> > - css_put(&memcg->css);
> > goto nomem;
> > case CHARGE_NOMEM: /* OOM routine works */
> > - if (!oom || invoke_oom) {
> > - css_put(&memcg->css);
> > + if (!oom || invoke_oom)
> > goto nomem;
> > - }
> > nr_oom_retries--;
> > break;
> > }
> > @@ -2775,16 +2749,11 @@ again:
> > if (batch > nr_pages)
> > refill_stock(memcg, batch - nr_pages);
> > done:
> > - css_put(&memcg->css);
> > - *ptr = memcg;
> > return 0;
> > nomem:
> > - if (!(gfp_mask & __GFP_NOFAIL)) {
> > - *ptr = NULL;
> > + if (!(gfp_mask & __GFP_NOFAIL))
> > return -ENOMEM;
> > - }
> > bypass:
> > - *ptr = root_mem_cgroup;
> > return -EINTR;
> > }
> >
> > @@ -2983,20 +2952,17 @@ static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)
> > static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
> > {
> > struct res_counter *fail_res;
> > - struct mem_cgroup *_memcg;
> > int ret = 0;
> >
> > ret = res_counter_charge(&memcg->kmem, size, &fail_res);
> > if (ret)
> > return ret;
> >
> > - _memcg = memcg;
> > - ret = __mem_cgroup_try_charge(NULL, gfp, size >> PAGE_SHIFT,
> > - &_memcg, oom_gfp_allowed(gfp));
> > -
> > + ret = mem_cgroup_try_charge(memcg, gfp, size >> PAGE_SHIFT,
> > + oom_gfp_allowed(gfp));
> > if (ret == -EINTR) {
> > /*
> > - * __mem_cgroup_try_charge() chosed to bypass to root due to
> > + * mem_cgroup_try_charge() chosed to bypass to root due to
> > * OOM kill or fatal signal. Since our only options are to
> > * either fail the allocation or charge it to this cgroup, do
> > * it as a temporary condition. But we can't fail. From a
> > @@ -3006,7 +2972,7 @@ static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
> > *
> > * This condition will only trigger if the task entered
> > * memcg_charge_kmem in a sane state, but was OOM-killed during
> > - * __mem_cgroup_try_charge() above. Tasks that were already
> > + * mem_cgroup_try_charge() above. Tasks that were already
> > * dying when the allocation triggers should have been already
> > * directed to the root cgroup in memcontrol.h
> > */
> > @@ -3858,8 +3824,8 @@ out:
> > int mem_cgroup_newpage_charge(struct page *page,
> > struct mm_struct *mm, gfp_t gfp_mask)
> > {
> > - struct mem_cgroup *memcg = NULL;
> > unsigned int nr_pages = 1;
> > + struct mem_cgroup *memcg;
> > bool oom = true;
> > int ret;
> >
> > @@ -3880,8 +3846,12 @@ int mem_cgroup_newpage_charge(struct page *page,
> > oom = false;
> > }
> >
> > - ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom);
> > - if (ret == -ENOMEM)
> > + memcg = get_mem_cgroup_from_mm(mm);
> > + ret = mem_cgroup_try_charge(memcg, gfp_mask, nr_pages, oom);
> > + css_put(&memcg->css);
> > + if (ret == -EINTR)
> > + memcg = root_mem_cgroup;
> > + else if (ret)
> > return ret;
> > __mem_cgroup_commit_charge(memcg, page, nr_pages,
> > MEM_CGROUP_CHARGE_TYPE_ANON, false);
> > @@ -3899,7 +3869,7 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
> > gfp_t mask,
> > struct mem_cgroup **memcgp)
> > {
> > - struct mem_cgroup *memcg;
> > + struct mem_cgroup *memcg = NULL;
> > struct page_cgroup *pc;
> > int ret;
> >
> > @@ -3912,31 +3882,29 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
> > * in turn serializes uncharging.
> > */
> > if (PageCgroupUsed(pc))
> > - return 0;
> > - if (!do_swap_account)
> > - goto charge_cur_mm;
> > - memcg = try_get_mem_cgroup_from_page(page);
> > + goto out;
> > + if (do_swap_account)
> > + memcg = try_get_mem_cgroup_from_page(page);
> > if (!memcg)
> > - goto charge_cur_mm;
> > - *memcgp = memcg;
> > - ret = __mem_cgroup_try_charge(NULL, mask, 1, memcgp, true);
> > + memcg = get_mem_cgroup_from_mm(mm);
> > + ret = mem_cgroup_try_charge(memcg, mask, 1, true);
> > css_put(&memcg->css);
> > if (ret == -EINTR)
> > - ret = 0;
> > - return ret;
> > -charge_cur_mm:
> > - ret = __mem_cgroup_try_charge(mm, mask, 1, memcgp, true);
> > - if (ret == -EINTR)
> > - ret = 0;
> > - return ret;
> > + memcg = root_mem_cgroup;
> > + else if (ret)
> > + return ret;
> > +out:
> > + *memcgp = memcg;
> > + return 0;
> > }
> >
> > int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page,
> > gfp_t gfp_mask, struct mem_cgroup **memcgp)
> > {
> > - *memcgp = NULL;
> > - if (mem_cgroup_disabled())
> > + if (mem_cgroup_disabled()) {
> > + *memcgp = NULL;
> > return 0;
> > + }
> > /*
> > * A racing thread's fault, or swapoff, may have already
> > * updated the pte, and even removed page from swap cache: in
> > @@ -3944,12 +3912,18 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page,
> > * there's also a KSM case which does need to charge the page.
> > */
> > if (!PageSwapCache(page)) {
> > + struct mem_cgroup *memcg;
> > int ret;
> >
> > - ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true);
> > + memcg = get_mem_cgroup_from_mm(mm);
> > + ret = mem_cgroup_try_charge(memcg, gfp_mask, 1, true);
> > + css_put(&memcg->css);
> > if (ret == -EINTR)
> > - ret = 0;
> > - return ret;
> > + memcg = root_mem_cgroup;
> > + else if (ret)
> > + return ret;
> > + *memcgp = memcg;
> > + return 0;
> > }
> > return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
> > }
> > @@ -3996,8 +3970,8 @@ void mem_cgroup_commit_charge_swapin(struct page *page,
> > int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> > gfp_t gfp_mask)
> > {
> > - struct mem_cgroup *memcg = NULL;
> > enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
> > + struct mem_cgroup *memcg;
> > int ret;
> >
> > if (mem_cgroup_disabled())
> > @@ -4005,23 +3979,32 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> > if (PageCompound(page))
> > return 0;
> >
> > - if (!PageSwapCache(page)) {
> > - /*
> > - * Page cache insertions can happen without an actual
> > - * task context, e.g. during disk probing on boot.
> > - */
> > - if (!mm)
> > - memcg = root_mem_cgroup;
> > - ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &memcg, true);
> > - if (ret != -ENOMEM)
> > - __mem_cgroup_commit_charge(memcg, page, 1, type, false);
> > - } else { /* page is swapcache/shmem */
> > + if (PageSwapCache(page)) { /* shmem */
> > ret = __mem_cgroup_try_charge_swapin(mm, page,
> > gfp_mask, &memcg);
> > - if (!ret)
> > - __mem_cgroup_commit_charge_swapin(page, memcg, type);
> > + if (ret)
> > + return ret;
> > + __mem_cgroup_commit_charge_swapin(page, memcg, type);
> > + return 0;
> > }
> > - return ret;
> > +
> > + /*
> > + * Page cache insertions can happen without an actual mm
> > + * context, e.g. during disk probing on boot.
> > + */
> > + if (unlikely(!mm))
> > + memcg = root_mem_cgroup;
> > + else {
> > + memcg = get_mem_cgroup_from_mm(mm);
> > + ret = mem_cgroup_try_charge(memcg, gfp_mask, 1, true);
> > + css_put(&memcg->css);
> > + if (ret == -EINTR)
> > + memcg = root_mem_cgroup;
> > + else if (ret)
> > + return ret;
> > + }
> > + __mem_cgroup_commit_charge(memcg, page, 1, type, false);
> > + return 0;
> > }
> >
> > static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg,
> > @@ -6635,8 +6618,7 @@ one_by_one:
> > batch_count = PRECHARGE_COUNT_AT_ONCE;
> > cond_resched();
> > }
> > - ret = __mem_cgroup_try_charge(NULL,
> > - GFP_KERNEL, 1, &memcg, false);
> > + ret = mem_cgroup_try_charge(memcg, GFP_KERNEL, 1, false);
> > if (ret)
> > /* mem_cgroup_clear_mc() will do uncharge later */
> > return ret;
> > --
> > 1.9.0
> >
>
> --
> Michal Hocko
> SUSE Labs
> --
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--
Michal Hocko
SUSE Labs
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