Re: [patch 0/7] improve memcg oom killer robustness v2

[Johannes Weiner <hannes@cmpxchg.org>]

On Mon, Sep 09, 2013 at 03:10:10PM +0200, azurIt wrote:
> >Hi azur,
> >
> >On Wed, Sep 04, 2013 at 10:18:52AM +0200, azurIt wrote:
> >> > CC: "Andrew Morton" <akpm@linux-foundation.org>, "Michal Hocko" <mhocko@suse.cz>, "David Rientjes" <rientjes@google.com>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>, "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org, cgroups@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
> >> >Hello azur,
> >> >
> >> >On Mon, Sep 02, 2013 at 12:38:02PM +0200, azurIt wrote:
> >> >> >>Hi azur,
> >> >> >>
> >> >> >>here is the x86-only rollup of the series for 3.2.
> >> >> >>
> >> >> >>Thanks!
> >> >> >>Johannes
> >> >> >>---
> >> >> >
> >> >> >
> >> >> >Johannes,
> >> >> >
> >> >> >unfortunately, one problem arises: I have (again) cgroup which cannot be deleted :( it's a user who had very high memory usage and was reaching his limit very often. Do you need any info which i can gather now?
> >> >
> >> >Did the OOM killer go off in this group?
> >> >
> >> >Was there a warning in the syslog ("Fixing unhandled memcg OOM
> >> >context")?
> >> 
> >> 
> >> 
> >> Ok, i see this message several times in my syslog logs, one of them is also for this unremovable cgroup (but maybe all of them cannot be removed, should i try?). Example of the log is here (don't know where exactly it starts and ends so here is the full kernel log):
> >> http://watchdog.sk/lkml/oom_syslog.gz
> >There is an unfinished OOM invocation here:
> >
> >  Aug 22 13:15:21 server01 kernel: [1251422.715112] Fixing unhandled memcg OOM context set up from:
> >  Aug 22 13:15:21 server01 kernel: [1251422.715191]  [<ffffffff811105c2>] T.1154+0x622/0x8f0
> >  Aug 22 13:15:21 server01 kernel: [1251422.715274]  [<ffffffff8111153e>] mem_cgroup_cache_charge+0xbe/0xe0
> >  Aug 22 13:15:21 server01 kernel: [1251422.715357]  [<ffffffff810cf31c>] add_to_page_cache_locked+0x4c/0x140
> >  Aug 22 13:15:21 server01 kernel: [1251422.715443]  [<ffffffff810cf432>] add_to_page_cache_lru+0x22/0x50
> >  Aug 22 13:15:21 server01 kernel: [1251422.715526]  [<ffffffff810cfdd3>] find_or_create_page+0x73/0xb0
> >  Aug 22 13:15:21 server01 kernel: [1251422.715608]  [<ffffffff811493ba>] __getblk+0xea/0x2c0
> >  Aug 22 13:15:21 server01 kernel: [1251422.715692]  [<ffffffff8114ca73>] __bread+0x13/0xc0
> >  Aug 22 13:15:21 server01 kernel: [1251422.715774]  [<ffffffff81196968>] ext3_get_branch+0x98/0x140
> >  Aug 22 13:15:21 server01 kernel: [1251422.715859]  [<ffffffff81197557>] ext3_get_blocks_handle+0xd7/0xdc0
> >  Aug 22 13:15:21 server01 kernel: [1251422.715942]  [<ffffffff81198304>] ext3_get_block+0xc4/0x120
> >  Aug 22 13:15:21 server01 kernel: [1251422.716023]  [<ffffffff81155c3a>] do_mpage_readpage+0x38a/0x690
> >  Aug 22 13:15:21 server01 kernel: [1251422.716107]  [<ffffffff81155f8f>] mpage_readpage+0x4f/0x70
> >  Aug 22 13:15:21 server01 kernel: [1251422.716188]  [<ffffffff811973a8>] ext3_readpage+0x28/0x60
> >  Aug 22 13:15:21 server01 kernel: [1251422.716268]  [<ffffffff810cfa48>] filemap_fault+0x308/0x560
> >  Aug 22 13:15:21 server01 kernel: [1251422.716350]  [<ffffffff810ef898>] __do_fault+0x78/0x5a0
> >  Aug 22 13:15:21 server01 kernel: [1251422.716433]  [<ffffffff810f2ab4>] handle_pte_fault+0x84/0x940
> >
> >__getblk() has this weird loop where it tries to instantiate the page,
> >frees memory on failure, then retries.  If the memcg goes OOM, the OOM
> >path might be entered multiple times and each time leak the memcg
> >reference of the respective previous OOM invocation.
> >
> >There are a few more find_or_create() sites that do not propagate an
> >error and it's incredibly hard to find out whether they are even taken
> >during a page fault.  It's not practical to annotate them all with
> >memcg OOM toggles, so let's just catch all OOM contexts at the end of
> >handle_mm_fault() and clear them if !VM_FAULT_OOM instead of treating
> >this like an error.
> >
> >azur, here is a patch on top of your modified 3.2.  Note that Michal
> >might be onto something and we are looking at multiple issues here,
> >but the log excert above suggests this fix is required either way.
> 
> 
> 
> 
> Johannes, is this still up to date? Thank you.

No, please use the following on top of 3.2 (i.e. full replacement, not
incremental to what you have):

---

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 5db0490..314fe53 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -842,30 +842,22 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
 }
 
-static noinline int
+static noinline void
 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 	       unsigned long address, unsigned int fault)
 {
-	/*
-	 * Pagefault was interrupted by SIGKILL. We have no reason to
-	 * continue pagefault.
-	 */
-	if (fatal_signal_pending(current)) {
-		if (!(fault & VM_FAULT_RETRY))
-			up_read(&current->mm->mmap_sem);
-		if (!(error_code & PF_USER))
-			no_context(regs, error_code, address);
-		return 1;
+	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
+		up_read(&current->mm->mmap_sem);
+		no_context(regs, error_code, address);
+		return;
 	}
-	if (!(fault & VM_FAULT_ERROR))
-		return 0;
 
 	if (fault & VM_FAULT_OOM) {
 		/* Kernel mode? Handle exceptions or die: */
 		if (!(error_code & PF_USER)) {
 			up_read(&current->mm->mmap_sem);
 			no_context(regs, error_code, address);
-			return 1;
+			return;
 		}
 
 		out_of_memory(regs, error_code, address);
@@ -876,7 +868,6 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 		else
 			BUG();
 	}
-	return 1;
 }
 
 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
@@ -1070,6 +1061,7 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	if (user_mode_vm(regs)) {
 		local_irq_enable();
 		error_code |= PF_USER;
+		flags |= FAULT_FLAG_USER;
 	} else {
 		if (regs->flags & X86_EFLAGS_IF)
 			local_irq_enable();
@@ -1167,9 +1159,17 @@ good_area:
 	 */
 	fault = handle_mm_fault(mm, vma, address, flags);
 
-	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
-		if (mm_fault_error(regs, error_code, address, fault))
-			return;
+	/*
+	 * If we need to retry but a fatal signal is pending, handle the
+	 * signal first. We do not need to release the mmap_sem because it
+	 * would already be released in __lock_page_or_retry in mm/filemap.c.
+	 */
+	if (unlikely((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)))
+		return;
+
+	if (unlikely(fault & VM_FAULT_ERROR)) {
+		mm_fault_error(regs, error_code, address, fault);
+		return;
 	}
 
 	/*
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b87068a..325da07 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -120,6 +120,25 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page);
 extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
 					struct task_struct *p);
 
+static inline void mem_cgroup_enable_oom(void)
+{
+	WARN_ON(current->memcg_oom.may_oom);
+	current->memcg_oom.may_oom = 1;
+}
+
+static inline void mem_cgroup_disable_oom(void)
+{
+	WARN_ON(!current->memcg_oom.may_oom);
+	current->memcg_oom.may_oom = 0;
+}
+
+static inline bool task_in_memcg_oom(struct task_struct *p)
+{
+	return p->memcg_oom.memcg;
+}
+
+bool mem_cgroup_oom_synchronize(bool wait);
+
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 extern int do_swap_account;
 #endif
@@ -333,6 +352,24 @@ mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 {
 }
 
+static inline void mem_cgroup_enable_oom(void)
+{
+}
+
+static inline void mem_cgroup_disable_oom(void)
+{
+}
+
+static inline bool task_in_memcg_oom(struct task_struct *p)
+{
+	return false;
+}
+
+static inline bool mem_cgroup_oom_synchronize(bool wait)
+{
+	return false;
+}
+
 static inline void mem_cgroup_inc_page_stat(struct page *page,
 					    enum mem_cgroup_page_stat_item idx)
 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4baadd1..846b82b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -156,6 +156,7 @@ extern pgprot_t protection_map[16];
 #define FAULT_FLAG_ALLOW_RETRY	0x08	/* Retry fault if blocking */
 #define FAULT_FLAG_RETRY_NOWAIT	0x10	/* Don't drop mmap_sem and wait when retrying */
 #define FAULT_FLAG_KILLABLE	0x20	/* The fault task is in SIGKILL killable region */
+#define FAULT_FLAG_USER		0x40	/* The fault originated in userspace */
 
 /*
  * This interface is used by x86 PAT code to identify a pfn mapping that is
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1c4f3e9..fb1f145 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1568,6 +1568,11 @@ struct task_struct {
 		unsigned long nr_pages;	/* uncharged usage */
 		unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
 	} memcg_batch;
+	struct memcg_oom_info {
+		struct mem_cgroup *memcg;
+		gfp_t gfp_mask;
+		unsigned int may_oom:1;
+	} memcg_oom;
 #endif
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 	atomic_t ptrace_bp_refcnt;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b63f5f7..56643fe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1743,16 +1743,19 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_memcg,
 	return total;
 }
 
+static DEFINE_SPINLOCK(memcg_oom_lock);
+
 /*
  * Check OOM-Killer is already running under our hierarchy.
  * If someone is running, return false.
- * Has to be called with memcg_oom_lock
  */
-static bool mem_cgroup_oom_lock(struct mem_cgroup *memcg)
+static bool mem_cgroup_oom_trylock(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup *iter, *failed = NULL;
 	bool cond = true;
 
+	spin_lock(&memcg_oom_lock);
+
 	for_each_mem_cgroup_tree_cond(iter, memcg, cond) {
 		if (iter->oom_lock) {
 			/*
@@ -1765,34 +1768,34 @@ static bool mem_cgroup_oom_lock(struct mem_cgroup *memcg)
 			iter->oom_lock = true;
 	}
 
-	if (!failed)
-		return true;
-
-	/*
-	 * OK, we failed to lock the whole subtree so we have to clean up
-	 * what we set up to the failing subtree
-	 */
-	cond = true;
-	for_each_mem_cgroup_tree_cond(iter, memcg, cond) {
-		if (iter == failed) {
-			cond = false;
-			continue;
+	if (failed) {
+		/*
+		 * OK, we failed to lock the whole subtree so we have
+		 * to clean up what we set up to the failing subtree
+		 */
+		cond = true;
+		for_each_mem_cgroup_tree_cond(iter, memcg, cond) {
+			if (iter == failed) {
+				cond = false;
+				continue;
+			}
+			iter->oom_lock = false;
 		}
-		iter->oom_lock = false;
 	}
-	return false;
+
+	spin_unlock(&memcg_oom_lock);
+
+	return !failed;
 }
 
-/*
- * Has to be called with memcg_oom_lock
- */
-static int mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
+static void mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup *iter;
 
+	spin_lock(&memcg_oom_lock);
 	for_each_mem_cgroup_tree(iter, memcg)
 		iter->oom_lock = false;
-	return 0;
+	spin_unlock(&memcg_oom_lock);
 }
 
 static void mem_cgroup_mark_under_oom(struct mem_cgroup *memcg)
@@ -1816,7 +1819,6 @@ static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg)
 		atomic_add_unless(&iter->under_oom, -1, 0);
 }
 
-static DEFINE_SPINLOCK(memcg_oom_lock);
 static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
 
 struct oom_wait_info {
@@ -1856,56 +1858,106 @@ static void memcg_oom_recover(struct mem_cgroup *memcg)
 		memcg_wakeup_oom(memcg);
 }
 
-/*
- * try to call OOM killer. returns false if we should exit memory-reclaim loop.
+static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask)
+{
+	if (!current->memcg_oom.may_oom)
+		return;
+	/*
+	 * We are in the middle of the charge context here, so we
+	 * don't want to block when potentially sitting on a callstack
+	 * that holds all kinds of filesystem and mm locks.
+	 *
+	 * Also, the caller may handle a failed allocation gracefully
+	 * (like optional page cache readahead) and so an OOM killer
+	 * invocation might not even be necessary.
+	 *
+	 * That's why we don't do anything here except remember the
+	 * OOM context and then deal with it at the end of the page
+	 * fault when the stack is unwound, the locks are released,
+	 * and when we know whether the fault was overall successful.
+	 */
+	css_get(&memcg->css);
+	current->memcg_oom.memcg = memcg;
+	current->memcg_oom.gfp_mask = mask;
+}
+
+/**
+ * mem_cgroup_oom_synchronize - complete memcg OOM handling
+ * @handle: actually kill/wait or just clean up the OOM state
+ *
+ * This has to be called at the end of a page fault if the memcg OOM
+ * handler was enabled.
+ *
+ * Memcg supports userspace OOM handling where failed allocations must
+ * sleep on a waitqueue until the userspace task resolves the
+ * situation.  Sleeping directly in the charge context with all kinds
+ * of locks held is not a good idea, instead we remember an OOM state
+ * in the task and mem_cgroup_oom_synchronize() has to be called at
+ * the end of the page fault to complete the OOM handling.
+ *
+ * Returns %true if an ongoing memcg OOM situation was detected and
+ * completed, %false otherwise.
  */
-bool mem_cgroup_handle_oom(struct mem_cgroup *memcg, gfp_t mask)
+bool mem_cgroup_oom_synchronize(bool handle)
 {
+	struct mem_cgroup *memcg = current->memcg_oom.memcg;
 	struct oom_wait_info owait;
-	bool locked, need_to_kill;
+	bool locked;
+
+	/* OOM is global, do not handle */
+	if (!memcg)
+		return false;
+
+	if (!handle)
+		goto cleanup;
 
 	owait.mem = memcg;
 	owait.wait.flags = 0;
 	owait.wait.func = memcg_oom_wake_function;
 	owait.wait.private = current;
 	INIT_LIST_HEAD(&owait.wait.task_list);
-	need_to_kill = true;
-	mem_cgroup_mark_under_oom(memcg);
 
-	/* At first, try to OOM lock hierarchy under memcg.*/
-	spin_lock(&memcg_oom_lock);
-	locked = mem_cgroup_oom_lock(memcg);
 	/*
+	 * As with any blocking lock, a contender needs to start
+	 * listening for wakeups before attempting the trylock,
+	 * otherwise it can miss the wakeup from the unlock and sleep
+	 * indefinitely.  This is just open-coded because our locking
+	 * is so particular to memcg hierarchies.
+	 *
 	 * Even if signal_pending(), we can't quit charge() loop without
 	 * accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
 	 * under OOM is always welcomed, use TASK_KILLABLE here.
 	 */
 	prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
-	if (!locked || memcg->oom_kill_disable)
-		need_to_kill = false;
+	mem_cgroup_mark_under_oom(memcg);
+
+	locked = mem_cgroup_oom_trylock(memcg);
+
 	if (locked)
 		mem_cgroup_oom_notify(memcg);
-	spin_unlock(&memcg_oom_lock);
 
-	if (need_to_kill) {
+	if (locked && !memcg->oom_kill_disable) {
+		mem_cgroup_unmark_under_oom(memcg);
 		finish_wait(&memcg_oom_waitq, &owait.wait);
-		mem_cgroup_out_of_memory(memcg, mask);
+		mem_cgroup_out_of_memory(memcg, current->memcg_oom.gfp_mask);
 	} else {
 		schedule();
+		mem_cgroup_unmark_under_oom(memcg);
 		finish_wait(&memcg_oom_waitq, &owait.wait);
 	}
-	spin_lock(&memcg_oom_lock);
-	if (locked)
-		mem_cgroup_oom_unlock(memcg);
-	memcg_wakeup_oom(memcg);
-	spin_unlock(&memcg_oom_lock);
-
-	mem_cgroup_unmark_under_oom(memcg);
 
-	if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
-		return false;
-	/* Give chance to dying process */
-	schedule_timeout_uninterruptible(1);
+	if (locked) {
+		mem_cgroup_oom_unlock(memcg);
+		/*
+		 * There is no guarantee that an OOM-lock contender
+		 * sees the wakeups triggered by the OOM kill
+		 * uncharges.  Wake any sleepers explicitely.
+		 */
+		memcg_oom_recover(memcg);
+	}
+cleanup:
+	current->memcg_oom.memcg = NULL;
+	css_put(&memcg->css);
 	return true;
 }
 
@@ -2195,11 +2247,10 @@ enum {
 	CHARGE_RETRY,		/* need to retry but retry is not bad */
 	CHARGE_NOMEM,		/* we can't do more. return -ENOMEM */
 	CHARGE_WOULDBLOCK,	/* GFP_WAIT wasn't set and no enough res. */
-	CHARGE_OOM_DIE,		/* the current is killed because of OOM */
 };
 
 static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
-				unsigned int nr_pages, bool oom_check)
+				unsigned int nr_pages, bool invoke_oom)
 {
 	unsigned long csize = nr_pages * PAGE_SIZE;
 	struct mem_cgroup *mem_over_limit;
@@ -2257,14 +2308,10 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	if (mem_cgroup_wait_acct_move(mem_over_limit))
 		return CHARGE_RETRY;
 
-	/* If we don't need to call oom-killer at el, return immediately */
-	if (!oom_check)
-		return CHARGE_NOMEM;
-	/* check OOM */
-	if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask))
-		return CHARGE_OOM_DIE;
+	if (invoke_oom)
+		mem_cgroup_oom(mem_over_limit, gfp_mask);
 
-	return CHARGE_RETRY;
+	return CHARGE_NOMEM;
 }
 
 /*
@@ -2292,6 +2339,12 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
 		goto bypass;
 
 	/*
+	 * Task already OOMed, just get out of here.
+	 */
+	if (unlikely(current->memcg_oom.memcg))
+		goto nomem;
+
+	/*
 	 * We always charge the cgroup the mm_struct belongs to.
 	 * The mm_struct's mem_cgroup changes on task migration if the
 	 * thread group leader migrates. It's possible that mm is not
@@ -2349,7 +2402,7 @@ again:
 	}
 
 	do {
-		bool oom_check;
+		bool invoke_oom = oom && !nr_oom_retries;
 
 		/* If killed, bypass charge */
 		if (fatal_signal_pending(current)) {
@@ -2357,13 +2410,7 @@ again:
 			goto bypass;
 		}
 
-		oom_check = false;
-		if (oom && !nr_oom_retries) {
-			oom_check = true;
-			nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
-		}
-
-		ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, oom_check);
+		ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, invoke_oom);
 		switch (ret) {
 		case CHARGE_OK:
 			break;
@@ -2376,16 +2423,12 @@ again:
 			css_put(&memcg->css);
 			goto nomem;
 		case CHARGE_NOMEM: /* OOM routine works */
-			if (!oom) {
+			if (!oom || invoke_oom) {
 				css_put(&memcg->css);
 				goto nomem;
 			}
-			/* If oom, we never return -ENOMEM */
 			nr_oom_retries--;
 			break;
-		case CHARGE_OOM_DIE: /* Killed by OOM Killer */
-			css_put(&memcg->css);
-			goto bypass;
 		}
 	} while (ret != CHARGE_OK);
 
diff --git a/mm/memory.c b/mm/memory.c
index 829d437..20c43a0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3439,22 +3439,14 @@ unlock:
 /*
  * By the time we get here, we already hold the mm semaphore
  */
-int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
-		unsigned long address, unsigned int flags)
+static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+			     unsigned long address, unsigned int flags)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 
-	__set_current_state(TASK_RUNNING);
-
-	count_vm_event(PGFAULT);
-	mem_cgroup_count_vm_event(mm, PGFAULT);
-
-	/* do counter updates before entering really critical section. */
-	check_sync_rss_stat(current);
-
 	if (unlikely(is_vm_hugetlb_page(vma)))
 		return hugetlb_fault(mm, vma, address, flags);
 
@@ -3503,6 +3495,43 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
 }
 
+int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+		    unsigned long address, unsigned int flags)
+{
+	int ret;
+
+	__set_current_state(TASK_RUNNING);
+
+	count_vm_event(PGFAULT);
+	mem_cgroup_count_vm_event(mm, PGFAULT);
+
+	/* do counter updates before entering really critical section. */
+	check_sync_rss_stat(current);
+
+	/*
+	 * Enable the memcg OOM handling for faults triggered in user
+	 * space.  Kernel faults are handled more gracefully.
+	 */
+	if (flags & FAULT_FLAG_USER)
+		mem_cgroup_enable_oom();
+
+	ret = __handle_mm_fault(mm, vma, address, flags);
+
+	if (flags & FAULT_FLAG_USER) {
+		mem_cgroup_disable_oom();
+		/*
+		 * The task may have entered a memcg OOM situation but
+		 * if the allocation error was handled gracefully (no
+		 * VM_FAULT_OOM), there is no need to kill anything.
+		 * Just clean up the OOM state peacefully.
+		 */
+		if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
+			mem_cgroup_oom_synchronize(false);
+	}
+
+	return ret;
+}
+
 #ifndef __PAGETABLE_PUD_FOLDED
 /*
  * Allocate page upper directory.
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 069b64e..3bf664c 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -785,6 +785,8 @@ out:
  */
 void pagefault_out_of_memory(void)
 {
+	if (mem_cgroup_oom_synchronize(true))
+		return;
 	if (try_set_system_oom()) {
 		out_of_memory(NULL, 0, 0, NULL);
 		clear_system_oom();

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