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memcg: sanitize __mem_cgroup_try_charge() call protocol
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Some callsites pass a memcg directly, some callsites pass an mm that
then has to be translated to a memcg.  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().

[mhocko@suse.cz: add charge mm helper]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Johannes Weiner authored and Linus Torvalds committed Apr 7, 2014
1 parent b6b6cc7 commit 6d1fdc4
Showing 1 changed file with 102 additions and 105 deletions.
207 changes: 102 additions & 105 deletions mm/memcontrol.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2575,7 +2575,7 @@ 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 */
Expand Down Expand Up @@ -2648,45 +2648,34 @@ 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)))
Expand All @@ -2695,25 +2684,15 @@ 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;

do {
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);
Expand All @@ -2722,17 +2701,12 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
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;
}
Expand All @@ -2741,19 +2715,43 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
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;
}

/**
* 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.
Expand Down Expand Up @@ -2949,20 +2947,17 @@ 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
Expand All @@ -2972,7 +2967,7 @@ 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
*/
Expand Down Expand Up @@ -3826,10 +3821,9 @@ static int mem_cgroup_move_parent(struct page *page,
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;

if (mem_cgroup_disabled())
return 0;
Expand All @@ -3848,9 +3842,9 @@ 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)
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;
Expand All @@ -3867,7 +3861,7 @@ 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;

Expand All @@ -3880,44 +3874,43 @@ 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
* those cases unuse_pte()'s pte_same() test will fail; but
* there's also a KSM case which does need to charge the page.
*/
if (!PageSwapCache(page)) {
int ret;
struct mem_cgroup *memcg;

ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true);
if (ret == -EINTR)
ret = 0;
return ret;
memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, 1, true);
if (!memcg)
return -ENOMEM;
*memcgp = memcg;
return 0;
}
return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
}
Expand Down Expand Up @@ -3964,32 +3957,37 @@ 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())
return 0;
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 = 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;
}

static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg,
Expand Down Expand Up @@ -6601,8 +6599,7 @@ static int mem_cgroup_do_precharge(unsigned long count)
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;
Expand Down

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