1 files changed, 779 insertions, 0 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
new file mode 100644
index 00000000..7c72487c
--- /dev/null
+++ b/mm/oom_kill.c
@@ -0,0 +1,779 @@
+/*
+ *  linux/mm/oom_kill.c
+ * 
+ *  Copyright (C)  1998,2000  Rik van Riel
+ *	Thanks go out to Claus Fischer for some serious inspiration and
+ *	for goading me into coding this file...
+ *  Copyright (C)  2010  Google, Inc.
+ *	Rewritten by David Rientjes
+ *
+ *  The routines in this file are used to kill a process when
+ *  we're seriously out of memory. This gets called from __alloc_pages()
+ *  in mm/page_alloc.c when we really run out of memory.
+ *
+ *  Since we won't call these routines often (on a well-configured
+ *  machine) this file will double as a 'coding guide' and a signpost
+ *  for newbie kernel hackers. It features several pointers to major
+ *  kernel subsystems and hints as to where to find out what things do.
+ */
+
+#include <linux/oom.h>
+#include <linux/mm.h>
+#include <linux/err.h>
+#include <linux/gfp.h>
+#include <linux/sched.h>
+#include <linux/swap.h>
+#include <linux/timex.h>
+#include <linux/jiffies.h>
+#include <linux/cpuset.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/memcontrol.h>
+#include <linux/mempolicy.h>
+#include <linux/security.h>
+#include <linux/ptrace.h>
+
+int sysctl_panic_on_oom;
+int sysctl_oom_kill_allocating_task;
+int sysctl_oom_dump_tasks = 1;
+static DEFINE_SPINLOCK(zone_scan_lock);
+
+/**
+ * test_set_oom_score_adj() - set current's oom_score_adj and return old value
+ * @new_val: new oom_score_adj value
+ *
+ * Sets the oom_score_adj value for current to @new_val with proper
+ * synchronization and returns the old value.  Usually used to temporarily
+ * set a value, save the old value in the caller, and then reinstate it later.
+ */
+int test_set_oom_score_adj(int new_val)
+{
+	struct sighand_struct *sighand = current->sighand;
+	int old_val;
+
+	spin_lock_irq(&sighand->siglock);
+	old_val = current->signal->oom_score_adj;
+	if (new_val != old_val) {
+		if (new_val == OOM_SCORE_ADJ_MIN)
+			atomic_inc(&current->mm->oom_disable_count);
+		else if (old_val == OOM_SCORE_ADJ_MIN)
+			atomic_dec(&current->mm->oom_disable_count);
+		current->signal->oom_score_adj = new_val;
+	}
+	spin_unlock_irq(&sighand->siglock);
+
+	return old_val;
+}
+
+#ifdef CONFIG_NUMA
+/**
+ * has_intersects_mems_allowed() - check task eligiblity for kill
+ * @tsk: task struct of which task to consider
+ * @mask: nodemask passed to page allocator for mempolicy ooms
+ *
+ * Task eligibility is determined by whether or not a candidate task, @tsk,
+ * shares the same mempolicy nodes as current if it is bound by such a policy
+ * and whether or not it has the same set of allowed cpuset nodes.
+ */
+static bool has_intersects_mems_allowed(struct task_struct *tsk,
+					const nodemask_t *mask)
+{
+	struct task_struct *start = tsk;
+
+	do {
+		if (mask) {
+			/*
+			 * If this is a mempolicy constrained oom, tsk's
+			 * cpuset is irrelevant.  Only return true if its
+			 * mempolicy intersects current, otherwise it may be
+			 * needlessly killed.
+			 */
+			if (mempolicy_nodemask_intersects(tsk, mask))
+				return true;
+		} else {
+			/*
+			 * This is not a mempolicy constrained oom, so only
+			 * check the mems of tsk's cpuset.
+			 */
+			if (cpuset_mems_allowed_intersects(current, tsk))
+				return true;
+		}
+	} while_each_thread(start, tsk);
+
+	return false;
+}
+#else
+static bool has_intersects_mems_allowed(struct task_struct *tsk,
+					const nodemask_t *mask)
+{
+	return true;
+}
+#endif /* CONFIG_NUMA */
+
+/*
+ * The process p may have detached its own ->mm while exiting or through
+ * use_mm(), but one or more of its subthreads may still have a valid
+ * pointer.  Return p, or any of its subthreads with a valid ->mm, with
+ * task_lock() held.
+ */
+struct task_struct *find_lock_task_mm(struct task_struct *p)
+{
+	struct task_struct *t = p;
+
+	do {
+		task_lock(t);
+		if (likely(t->mm))
+			return t;
+		task_unlock(t);
+	} while_each_thread(p, t);
+
+	return NULL;
+}
+
+/* return true if the task is not adequate as candidate victim task. */
+static bool oom_unkillable_task(struct task_struct *p,
+		const struct mem_cgroup *mem, const nodemask_t *nodemask)
+{
+	if (is_global_init(p))
+		return true;
+	if (p->flags & PF_KTHREAD)
+		return true;
+
+	/* When mem_cgroup_out_of_memory() and p is not member of the group */
+	if (mem && !task_in_mem_cgroup(p, mem))
+		return true;
+
+	/* p may not have freeable memory in nodemask */
+	if (!has_intersects_mems_allowed(p, nodemask))
+		return true;
+
+	return false;
+}
+
+/**
+ * oom_badness - heuristic function to determine which candidate task to kill
+ * @p: task struct of which task we should calculate
+ * @totalpages: total present RAM allowed for page allocation
+ *
+ * The heuristic for determining which task to kill is made to be as simple and
+ * predictable as possible.  The goal is to return the highest value for the
+ * task consuming the most memory to avoid subsequent oom failures.
+ */
+unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
+		      const nodemask_t *nodemask, unsigned long totalpages)
+{
+	long points;
+
+	if (oom_unkillable_task(p, mem, nodemask))
+		return 0;
+
+	p = find_lock_task_mm(p);
+	if (!p)
+		return 0;
+
+	/*
+	 * Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN
+	 * so the entire heuristic doesn't need to be executed for something
+	 * that cannot be killed.
+	 */
+	if (atomic_read(&p->mm->oom_disable_count)) {
+		task_unlock(p);
+		return 0;
+	}
+
+	/*
+	 * The memory controller may have a limit of 0 bytes, so avoid a divide
+	 * by zero, if necessary.
+	 */
+	if (!totalpages)
+		totalpages = 1;
+
+	/*
+	 * The baseline for the badness score is the proportion of RAM that each
+	 * task's rss, pagetable and swap space use.
+	 */
+	points = get_mm_rss(p->mm) + p->mm->nr_ptes;
+	points += get_mm_counter(p->mm, MM_SWAPENTS);
+
+	points *= 1000;
+	points /= totalpages;
+	task_unlock(p);
+
+	/*
+	 * Root processes get 3% bonus, just like the __vm_enough_memory()
+	 * implementation used by LSMs.
+	 */
+	if (has_capability_noaudit(p, CAP_SYS_ADMIN))
+		points -= 30;
+
+	/*
+	 * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
+	 * either completely disable oom killing or always prefer a certain
+	 * task.
+	 */
+	points += p->signal->oom_score_adj;
+
+	/*
+	 * Never return 0 for an eligible task that may be killed since it's
+	 * possible that no single user task uses more than 0.1% of memory and
+	 * no single admin tasks uses more than 3.0%.
+	 */
+	if (points <= 0)
+		return 1;
+	return (points < 1000) ? points : 1000;
+}
+
+/*
+ * Determine the type of allocation constraint.
+ */
+#ifdef CONFIG_NUMA
+static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
+				gfp_t gfp_mask, nodemask_t *nodemask,
+				unsigned long *totalpages)
+{
+	struct zone *zone;
+	struct zoneref *z;
+	enum zone_type high_zoneidx = gfp_zone(gfp_mask);
+	bool cpuset_limited = false;
+	int nid;
+
+	/* Default to all available memory */
+	*totalpages = totalram_pages + total_swap_pages;
+
+	if (!zonelist)
+		return CONSTRAINT_NONE;
+	/*
+	 * Reach here only when __GFP_NOFAIL is used. So, we should avoid
+	 * to kill current.We have to random task kill in this case.
+	 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
+	 */
+	if (gfp_mask & __GFP_THISNODE)
+		return CONSTRAINT_NONE;
+
+	/*
+	 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in
+	 * the page allocator means a mempolicy is in effect.  Cpuset policy
+	 * is enforced in get_page_from_freelist().
+	 */
+	if (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
+		*totalpages = total_swap_pages;
+		for_each_node_mask(nid, *nodemask)
+			*totalpages += node_spanned_pages(nid);
+		return CONSTRAINT_MEMORY_POLICY;
+	}
+
+	/* Check this allocation failure is caused by cpuset's wall function */
+	for_each_zone_zonelist_nodemask(zone, z, zonelist,
+			high_zoneidx, nodemask)
+		if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
+			cpuset_limited = true;
+
+	if (cpuset_limited) {
+		*totalpages = total_swap_pages;
+		for_each_node_mask(nid, cpuset_current_mems_allowed)
+			*totalpages += node_spanned_pages(nid);
+		return CONSTRAINT_CPUSET;
+	}
+	return CONSTRAINT_NONE;
+}
+#else
+static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
+				gfp_t gfp_mask, nodemask_t *nodemask,
+				unsigned long *totalpages)
+{
+	*totalpages = totalram_pages + total_swap_pages;
+	return CONSTRAINT_NONE;
+}
+#endif
+
+/*
+ * Simple selection loop. We chose the process with the highest
+ * number of 'points'. We expect the caller will lock the tasklist.
+ *
+ * (not docbooked, we don't want this one cluttering up the manual)
+ */
+static struct task_struct *select_bad_process(unsigned int *ppoints,
+		unsigned long totalpages, struct mem_cgroup *mem,
+		const nodemask_t *nodemask)
+{
+	struct task_struct *g, *p;
+	struct task_struct *chosen = NULL;
+	*ppoints = 0;
+
+	do_each_thread(g, p) {
+		unsigned int points;
+
+		if (p->exit_state)
+			continue;
+		if (oom_unkillable_task(p, mem, nodemask))
+			continue;
+
+		/*
+		 * This task already has access to memory reserves and is
+		 * being killed. Don't allow any other task access to the
+		 * memory reserve.
+		 *
+		 * Note: this may have a chance of deadlock if it gets
+		 * blocked waiting for another task which itself is waiting
+		 * for memory. Is there a better alternative?
+		 */
+		if (test_tsk_thread_flag(p, TIF_MEMDIE))
+			return ERR_PTR(-1UL);
+		if (!p->mm)
+			continue;
+
+		if (p->flags & PF_EXITING) {
+			/*
+			 * If p is the current task and is in the process of
+			 * releasing memory, we allow the "kill" to set
+			 * TIF_MEMDIE, which will allow it to gain access to
+			 * memory reserves.  Otherwise, it may stall forever.
+			 *
+			 * The loop isn't broken here, however, in case other
+			 * threads are found to have already been oom killed.
+			 */
+			if (p == current) {
+				chosen = p;
+				*ppoints = 1000;
+			} else {
+				/*
+				 * If this task is not being ptraced on exit,
+				 * then wait for it to finish before killing
+				 * some other task unnecessarily.
+				 */
+				if (!(task_ptrace(p->group_leader) &
+							PT_TRACE_EXIT))
+					return ERR_PTR(-1UL);
+			}
+		}
+
+		points = oom_badness(p, mem, nodemask, totalpages);
+		if (points > *ppoints) {
+			chosen = p;
+			*ppoints = points;
+		}
+	} while_each_thread(g, p);
+
+	return chosen;
+}
+
+/**
+ * dump_tasks - dump current memory state of all system tasks
+ * @mem: current's memory controller, if constrained
+ * @nodemask: nodemask passed to page allocator for mempolicy ooms
+ *
+ * Dumps the current memory state of all eligible tasks.  Tasks not in the same
+ * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
+ * are not shown.
+ * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
+ * value, oom_score_adj value, and name.
+ *
+ * Call with tasklist_lock read-locked.
+ */
+static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
+{
+	struct task_struct *p;
+	struct task_struct *task;
+
+	pr_info("[ pid ]   uid  tgid total_vm      rss cpu oom_adj oom_score_adj name\n");
+	for_each_process(p) {
+		if (oom_unkillable_task(p, mem, nodemask))
+			continue;
+
+		task = find_lock_task_mm(p);
+		if (!task) {
+			/*
+			 * This is a kthread or all of p's threads have already
+			 * detached their mm's.  There's no need to report
+			 * them; they can't be oom killed anyway.
+			 */
+			continue;
+		}
+
+		pr_info("[%5d] %5d %5d %8lu %8lu %3u     %3d         %5d %s\n",
+			task->pid, task_uid(task), task->tgid,
+			task->mm->total_vm, get_mm_rss(task->mm),
+			task_cpu(task), task->signal->oom_adj,
+			task->signal->oom_score_adj, task->comm);
+		task_unlock(task);
+	}
+}
+
+static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
+			struct mem_cgroup *mem, const nodemask_t *nodemask)
+{
+	task_lock(current);
+	pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
+		"oom_adj=%d, oom_score_adj=%d\n",
+		current->comm, gfp_mask, order, current->signal->oom_adj,
+		current->signal->oom_score_adj);
+	cpuset_print_task_mems_allowed(current);
+	task_unlock(current);
+	dump_stack();
+	mem_cgroup_print_oom_info(mem, p);
+	show_mem(SHOW_MEM_FILTER_NODES);
+	if (sysctl_oom_dump_tasks)
+		dump_tasks(mem, nodemask);
+}
+
+#define K(x) ((x) << (PAGE_SHIFT-10))
+static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
+{
+	struct task_struct *q;
+	struct mm_struct *mm;
+
+	p = find_lock_task_mm(p);
+	if (!p)
+		return 1;
+
+	/* mm cannot be safely dereferenced after task_unlock(p) */
+	mm = p->mm;
+
+	pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
+		task_pid_nr(p), p->comm, K(p->mm->total_vm),
+		K(get_mm_counter(p->mm, MM_ANONPAGES)),
+		K(get_mm_counter(p->mm, MM_FILEPAGES)));
+	task_unlock(p);
+
+	/*
+	 * Kill all processes sharing p->mm in other thread groups, if any.
+	 * They don't get access to memory reserves or a higher scheduler
+	 * priority, though, to avoid depletion of all memory or task
+	 * starvation.  This prevents mm->mmap_sem livelock when an oom killed
+	 * task cannot exit because it requires the semaphore and its contended
+	 * by another thread trying to allocate memory itself.  That thread will
+	 * now get access to memory reserves since it has a pending fatal
+	 * signal.
+	 */
+	for_each_process(q)
+		if (q->mm == mm && !same_thread_group(q, p)) {
+			task_lock(q);	/* Protect ->comm from prctl() */
+			pr_err("Kill process %d (%s) sharing same memory\n",
+				task_pid_nr(q), q->comm);
+			task_unlock(q);
+			force_sig(SIGKILL, q);
+		}
+
+	set_tsk_thread_flag(p, TIF_MEMDIE);
+	force_sig(SIGKILL, p);
+
+	return 0;
+}
+#undef K
+
+static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
+			    unsigned int points, unsigned long totalpages,
+			    struct mem_cgroup *mem, nodemask_t *nodemask,
+			    const char *message)
+{
+	struct task_struct *victim = p;
+	struct task_struct *child;
+	struct task_struct *t = p;
+	unsigned int victim_points = 0;
+
+	if (printk_ratelimit())
+		dump_header(p, gfp_mask, order, mem, nodemask);
+
+	/*
+	 * If the task is already exiting, don't alarm the sysadmin or kill
+	 * its children or threads, just set TIF_MEMDIE so it can die quickly
+	 */
+	if (p->flags & PF_EXITING) {
+		set_tsk_thread_flag(p, TIF_MEMDIE);
+		return 0;
+	}
+
+	task_lock(p);
+	pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
+		message, task_pid_nr(p), p->comm, points);
+	task_unlock(p);
+
+	/*
+	 * If any of p's children has a different mm and is eligible for kill,
+	 * the one with the highest badness() score is sacrificed for its
+	 * parent.  This attempts to lose the minimal amount of work done while
+	 * still freeing memory.
+	 */
+	do {
+		list_for_each_entry(child, &t->children, sibling) {
+			unsigned int child_points;
+
+			if (child->mm == p->mm)
+				continue;
+			/*
+			 * oom_badness() returns 0 if the thread is unkillable
+			 */
+			child_points = oom_badness(child, mem, nodemask,
+								totalpages);
+			if (child_points > victim_points) {
+				victim = child;
+				victim_points = child_points;
+			}
+		}
+	} while_each_thread(p, t);
+
+	return oom_kill_task(victim, mem);
+}
+
+/*
+ * Determines whether the kernel must panic because of the panic_on_oom sysctl.
+ */
+static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
+				int order, const nodemask_t *nodemask)
+{
+	if (likely(!sysctl_panic_on_oom))
+		return;
+	if (sysctl_panic_on_oom != 2) {
+		/*
+		 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
+		 * does not panic for cpuset, mempolicy, or memcg allocation
+		 * failures.
+		 */
+		if (constraint != CONSTRAINT_NONE)
+			return;
+	}
+	read_lock(&tasklist_lock);
+	dump_header(NULL, gfp_mask, order, NULL, nodemask);
+	read_unlock(&tasklist_lock);
+	panic("Out of memory: %s panic_on_oom is enabled\n",
+		sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
+}
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
+{
+	unsigned long limit;
+	unsigned int points = 0;
+	struct task_struct *p;
+
+	/*
+	 * If current has a pending SIGKILL, then automatically select it.  The
+	 * goal is to allow it to allocate so that it may quickly exit and free
+	 * its memory.
+	 */
+	if (fatal_signal_pending(current)) {
+		set_thread_flag(TIF_MEMDIE);
+		return;
+	}
+
+	check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
+	limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT;
+	read_lock(&tasklist_lock);
+retry:
+	p = select_bad_process(&points, limit, mem, NULL);
+	if (!p || PTR_ERR(p) == -1UL)
+		goto out;
+
+	if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
+				"Memory cgroup out of memory"))
+		goto retry;
+out:
+	read_unlock(&tasklist_lock);
+}
+#endif
+
+static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
+
+int register_oom_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&oom_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_oom_notifier);
+
+int unregister_oom_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&oom_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_oom_notifier);
+
+/*
+ * Try to acquire the OOM killer lock for the zones in zonelist.  Returns zero
+ * if a parallel OOM killing is already taking place that includes a zone in
+ * the zonelist.  Otherwise, locks all zones in the zonelist and returns 1.
+ */
+int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+{
+	struct zoneref *z;
+	struct zone *zone;
+	int ret = 1;
+
+	spin_lock(&zone_scan_lock);
+	for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+		if (zone_is_oom_locked(zone)) {
+			ret = 0;
+			goto out;
+		}
+	}
+
+	for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+		/*
+		 * Lock each zone in the zonelist under zone_scan_lock so a
+		 * parallel invocation of try_set_zonelist_oom() doesn't succeed
+		 * when it shouldn't.
+		 */
+		zone_set_flag(zone, ZONE_OOM_LOCKED);
+	}
+
+out:
+	spin_unlock(&zone_scan_lock);
+	return ret;
+}
+
+/*
+ * Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
+ * allocation attempts with zonelists containing them may now recall the OOM
+ * killer, if necessary.
+ */
+void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+{
+	struct zoneref *z;
+	struct zone *zone;
+
+	spin_lock(&zone_scan_lock);
+	for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+		zone_clear_flag(zone, ZONE_OOM_LOCKED);
+	}
+	spin_unlock(&zone_scan_lock);
+}
+
+/*
+ * Try to acquire the oom killer lock for all system zones.  Returns zero if a
+ * parallel oom killing is taking place, otherwise locks all zones and returns
+ * non-zero.
+ */
+static int try_set_system_oom(void)
+{
+	struct zone *zone;
+	int ret = 1;
+
+	spin_lock(&zone_scan_lock);
+	for_each_populated_zone(zone)
+		if (zone_is_oom_locked(zone)) {
+			ret = 0;
+			goto out;
+		}
+	for_each_populated_zone(zone)
+		zone_set_flag(zone, ZONE_OOM_LOCKED);
+out:
+	spin_unlock(&zone_scan_lock);
+	return ret;
+}
+
+/*
+ * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
+ * attempts or page faults may now recall the oom killer, if necessary.
+ */
+static void clear_system_oom(void)
+{
+	struct zone *zone;
+
+	spin_lock(&zone_scan_lock);
+	for_each_populated_zone(zone)
+		zone_clear_flag(zone, ZONE_OOM_LOCKED);
+	spin_unlock(&zone_scan_lock);
+}
+
+/**
+ * out_of_memory - kill the "best" process when we run out of memory
+ * @zonelist: zonelist pointer
+ * @gfp_mask: memory allocation flags
+ * @order: amount of memory being requested as a power of 2
+ * @nodemask: nodemask passed to page allocator
+ *
+ * If we run out of memory, we have the choice between either
+ * killing a random task (bad), letting the system crash (worse)
+ * OR try to be smart about which process to kill. Note that we
+ * don't have to be perfect here, we just have to be good.
+ */
+void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
+		int order, nodemask_t *nodemask)
+{
+	const nodemask_t *mpol_mask;
+	struct task_struct *p;
+	unsigned long totalpages;
+	unsigned long freed = 0;
+	unsigned int points;
+	enum oom_constraint constraint = CONSTRAINT_NONE;
+	int killed = 0;
+
+	blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
+	if (freed > 0)
+		/* Got some memory back in the last second. */
+		return;
+
+	/*
+	 * If current has a pending SIGKILL, then automatically select it.  The
+	 * goal is to allow it to allocate so that it may quickly exit and free
+	 * its memory.
+	 */
+	if (fatal_signal_pending(current)) {
+		set_thread_flag(TIF_MEMDIE);
+		return;
+	}
+
+	/*
+	 * Check if there were limitations on the allocation (only relevant for
+	 * NUMA) that may require different handling.
+	 */
+	constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
+						&totalpages);
+	mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
+	check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
+
+	read_lock(&tasklist_lock);
+	if (sysctl_oom_kill_allocating_task &&
+	    !oom_unkillable_task(current, NULL, nodemask) &&
+	    current->mm && !atomic_read(&current->mm->oom_disable_count)) {
+		/*
+		 * oom_kill_process() needs tasklist_lock held.  If it returns
+		 * non-zero, current could not be killed so we must fallback to
+		 * the tasklist scan.
+		 */
+		if (!oom_kill_process(current, gfp_mask, order, 0, totalpages,
+				NULL, nodemask,
+				"Out of memory (oom_kill_allocating_task)"))
+			goto out;
+	}
+
+retry:
+	p = select_bad_process(&points, totalpages, NULL, mpol_mask);
+	if (PTR_ERR(p) == -1UL)
+		goto out;
+
+	/* Found nothing?!?! Either we hang forever, or we panic. */
+	if (!p) {
+		dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
+		read_unlock(&tasklist_lock);
+		panic("Out of memory and no killable processes...\n");
+	}
+
+	if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
+				nodemask, "Out of memory"))
+		goto retry;
+	killed = 1;
+out:
+	read_unlock(&tasklist_lock);
+
+	/*
+	 * Give "p" a good chance of killing itself before we
+	 * retry to allocate memory unless "p" is current
+	 */
+	if (killed && !test_thread_flag(TIF_MEMDIE))
+		schedule_timeout_uninterruptible(1);
+}
+
+/*
+ * The pagefault handler calls here because it is out of memory, so kill a
+ * memory-hogging task.  If a populated zone has ZONE_OOM_LOCKED set, a parallel
+ * oom killing is already in progress so do nothing.  If a task is found with
+ * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
+ */
+void pagefault_out_of_memory(void)
+{
+	if (try_set_system_oom()) {
+		out_of_memory(NULL, 0, 0, NULL);
+		clear_system_oom();
+	}
+	if (!test_thread_flag(TIF_MEMDIE))
+		schedule_timeout_uninterruptible(1);
+}