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Date: Fri, 7 Feb 2014 12:04:25 -0500
From: Johannes Weiner <hannes@...xchg.org>
To: Michal Hocko <mhocko@...e.cz>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [patch 8/8] memcg: sanitize __mem_cgroup_try_charge() call protocol
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>
---
mm/memcontrol.c | 135 +++++++++++++++++++++++---------------------------------
1 file changed, 54 insertions(+), 81 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9eabe4473649..0049081b834d 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
*/
@@ -3864,8 +3830,8 @@ out:
static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
gfp_t gfp_mask, enum charge_type ctype)
{
- struct mem_cgroup *memcg = NULL;
unsigned int nr_pages = 1;
+ struct mem_cgroup *memcg;
bool oom = true;
int ret;
@@ -3879,8 +3845,14 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
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;
+ ret = 0;
+ }
+ if (ret)
return ret;
__mem_cgroup_commit_charge(memcg, page, nr_pages, ctype, false);
return 0;
@@ -3909,7 +3881,7 @@ 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;
@@ -3923,21 +3895,17 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
*/
if (PageCgroupUsed(pc))
return 0;
- if (!do_swap_account)
- goto charge_cur_mm;
- memcg = try_get_mem_cgroup_from_page(page);
+ 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)
+ if (ret == -EINTR) {
+ memcg = root_mem_cgroup;
ret = 0;
+ }
+ *memcgp = memcg;
return ret;
}
@@ -3954,11 +3922,17 @@ 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);
- if (ret == -EINTR)
+ 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;
ret = 0;
+ }
+ *memcgp = memcg;
return ret;
}
return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
@@ -6607,8 +6581,7 @@ 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;
--
1.8.5.3
--
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