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" <a...@linux-foundation.org>, "Michal Hocko" 
> >> > <mho...@suse.cz>, "David Rientjes" <rient...@google.com>, "KAMEZAWA 
> >> > Hiroyuki" <kamezawa.hir...@jp.fujitsu.com>, "KOSAKI Motohiro" 
> >> > <kosaki.motoh...@jp.fujitsu.com>, linux...@kvack.org, 
> >> > cgro...@vger.kernel.org, x...@kernel.org, linux-a...@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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