Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1262 insertions, 0 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
new file mode 100644
index 000000000..1276e49b3
--- /dev/null
+++ b/mm/oom_kill.c
@@ -0,0 +1,1262 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  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/sched/mm.h>
+#include <linux/sched/coredump.h>
+#include <linux/sched/task.h>
+#include <linux/sched/debug.h>
+#include <linux/swap.h>
+#include <linux/syscalls.h>
+#include <linux/timex.h>
+#include <linux/jiffies.h>
+#include <linux/cpuset.h>
+#include <linux/export.h>
+#include <linux/notifier.h>
+#include <linux/memcontrol.h>
+#include <linux/mempolicy.h>
+#include <linux/security.h>
+#include <linux/ptrace.h>
+#include <linux/freezer.h>
+#include <linux/ftrace.h>
+#include <linux/ratelimit.h>
+#include <linux/kthread.h>
+#include <linux/init.h>
+#include <linux/mmu_notifier.h>
+
+#include <asm/tlb.h>
+#include "internal.h"
+#include "slab.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/oom.h>
+
+static int sysctl_panic_on_oom;
+static int sysctl_oom_kill_allocating_task;
+static int sysctl_oom_dump_tasks = 1;
+
+/*
+ * Serializes oom killer invocations (out_of_memory()) from all contexts to
+ * prevent from over eager oom killing (e.g. when the oom killer is invoked
+ * from different domains).
+ *
+ * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
+ * and mark_oom_victim
+ */
+DEFINE_MUTEX(oom_lock);
+/* Serializes oom_score_adj and oom_score_adj_min updates */
+DEFINE_MUTEX(oom_adj_mutex);
+
+static inline bool is_memcg_oom(struct oom_control *oc)
+{
+	return oc->memcg != NULL;
+}
+
+#ifdef CONFIG_NUMA
+/**
+ * oom_cpuset_eligible() - check task eligibility for kill
+ * @start: task struct of which task to consider
+ * @oc: pointer to struct oom_control
+ *
+ * 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.
+ *
+ * This function is assuming oom-killer context and 'current' has triggered
+ * the oom-killer.
+ */
+static bool oom_cpuset_eligible(struct task_struct *start,
+				struct oom_control *oc)
+{
+	struct task_struct *tsk;
+	bool ret = false;
+	const nodemask_t *mask = oc->nodemask;
+
+	rcu_read_lock();
+	for_each_thread(start, tsk) {
+		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.
+			 */
+			ret = mempolicy_in_oom_domain(tsk, mask);
+		} else {
+			/*
+			 * This is not a mempolicy constrained oom, so only
+			 * check the mems of tsk's cpuset.
+			 */
+			ret = cpuset_mems_allowed_intersects(current, tsk);
+		}
+		if (ret)
+			break;
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+#else
+static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
+{
+	return true;
+}
+#endif /* CONFIG_NUMA */
+
+/*
+ * The process p may have detached its own ->mm while exiting or through
+ * kthread_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;
+
+	rcu_read_lock();
+
+	for_each_thread(p, t) {
+		task_lock(t);
+		if (likely(t->mm))
+			goto found;
+		task_unlock(t);
+	}
+	t = NULL;
+found:
+	rcu_read_unlock();
+
+	return t;
+}
+
+/*
+ * order == -1 means the oom kill is required by sysrq, otherwise only
+ * for display purposes.
+ */
+static inline bool is_sysrq_oom(struct oom_control *oc)
+{
+	return oc->order == -1;
+}
+
+/* return true if the task is not adequate as candidate victim task. */
+static bool oom_unkillable_task(struct task_struct *p)
+{
+	if (is_global_init(p))
+		return true;
+	if (p->flags & PF_KTHREAD)
+		return true;
+	return false;
+}
+
+/*
+ * Check whether unreclaimable slab amount is greater than
+ * all user memory(LRU pages).
+ * dump_unreclaimable_slab() could help in the case that
+ * oom due to too much unreclaimable slab used by kernel.
+*/
+static bool should_dump_unreclaim_slab(void)
+{
+	unsigned long nr_lru;
+
+	nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
+		 global_node_page_state(NR_INACTIVE_ANON) +
+		 global_node_page_state(NR_ACTIVE_FILE) +
+		 global_node_page_state(NR_INACTIVE_FILE) +
+		 global_node_page_state(NR_ISOLATED_ANON) +
+		 global_node_page_state(NR_ISOLATED_FILE) +
+		 global_node_page_state(NR_UNEVICTABLE);
+
+	return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
+}
+
+/**
+ * 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.
+ */
+long oom_badness(struct task_struct *p, unsigned long totalpages)
+{
+	long points;
+	long adj;
+
+	if (oom_unkillable_task(p))
+		return LONG_MIN;
+
+	p = find_lock_task_mm(p);
+	if (!p)
+		return LONG_MIN;
+
+	/*
+	 * Do not even consider tasks which are explicitly marked oom
+	 * unkillable or have been already oom reaped or the are in
+	 * the middle of vfork
+	 */
+	adj = (long)p->signal->oom_score_adj;
+	if (adj == OOM_SCORE_ADJ_MIN ||
+			test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
+			in_vfork(p)) {
+		task_unlock(p);
+		return LONG_MIN;
+	}
+
+	/*
+	 * 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) + get_mm_counter(p->mm, MM_SWAPENTS) +
+		mm_pgtables_bytes(p->mm) / PAGE_SIZE;
+	task_unlock(p);
+
+	/* Normalize to oom_score_adj units */
+	adj *= totalpages / 1000;
+	points += adj;
+
+	return points;
+}
+
+static const char * const oom_constraint_text[] = {
+	[CONSTRAINT_NONE] = "CONSTRAINT_NONE",
+	[CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
+	[CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
+	[CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
+};
+
+/*
+ * Determine the type of allocation constraint.
+ */
+static enum oom_constraint constrained_alloc(struct oom_control *oc)
+{
+	struct zone *zone;
+	struct zoneref *z;
+	enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
+	bool cpuset_limited = false;
+	int nid;
+
+	if (is_memcg_oom(oc)) {
+		oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
+		return CONSTRAINT_MEMCG;
+	}
+
+	/* Default to all available memory */
+	oc->totalpages = totalram_pages() + total_swap_pages;
+
+	if (!IS_ENABLED(CONFIG_NUMA))
+		return CONSTRAINT_NONE;
+
+	if (!oc->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 (oc->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 (oc->nodemask &&
+	    !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
+		oc->totalpages = total_swap_pages;
+		for_each_node_mask(nid, *oc->nodemask)
+			oc->totalpages += node_present_pages(nid);
+		return CONSTRAINT_MEMORY_POLICY;
+	}
+
+	/* Check this allocation failure is caused by cpuset's wall function */
+	for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
+			highest_zoneidx, oc->nodemask)
+		if (!cpuset_zone_allowed(zone, oc->gfp_mask))
+			cpuset_limited = true;
+
+	if (cpuset_limited) {
+		oc->totalpages = total_swap_pages;
+		for_each_node_mask(nid, cpuset_current_mems_allowed)
+			oc->totalpages += node_present_pages(nid);
+		return CONSTRAINT_CPUSET;
+	}
+	return CONSTRAINT_NONE;
+}
+
+static int oom_evaluate_task(struct task_struct *task, void *arg)
+{
+	struct oom_control *oc = arg;
+	long points;
+
+	if (oom_unkillable_task(task))
+		goto next;
+
+	/* p may not have freeable memory in nodemask */
+	if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
+		goto next;
+
+	/*
+	 * This task already has access to memory reserves and is being killed.
+	 * Don't allow any other task to have access to the reserves unless
+	 * the task has MMF_OOM_SKIP because chances that it would release
+	 * any memory is quite low.
+	 */
+	if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
+		if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
+			goto next;
+		goto abort;
+	}
+
+	/*
+	 * If task is allocating a lot of memory and has been marked to be
+	 * killed first if it triggers an oom, then select it.
+	 */
+	if (oom_task_origin(task)) {
+		points = LONG_MAX;
+		goto select;
+	}
+
+	points = oom_badness(task, oc->totalpages);
+	if (points == LONG_MIN || points < oc->chosen_points)
+		goto next;
+
+select:
+	if (oc->chosen)
+		put_task_struct(oc->chosen);
+	get_task_struct(task);
+	oc->chosen = task;
+	oc->chosen_points = points;
+next:
+	return 0;
+abort:
+	if (oc->chosen)
+		put_task_struct(oc->chosen);
+	oc->chosen = (void *)-1UL;
+	return 1;
+}
+
+/*
+ * Simple selection loop. We choose the process with the highest number of
+ * 'points'. In case scan was aborted, oc->chosen is set to -1.
+ */
+static void select_bad_process(struct oom_control *oc)
+{
+	oc->chosen_points = LONG_MIN;
+
+	if (is_memcg_oom(oc))
+		mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
+	else {
+		struct task_struct *p;
+
+		rcu_read_lock();
+		for_each_process(p)
+			if (oom_evaluate_task(p, oc))
+				break;
+		rcu_read_unlock();
+	}
+}
+
+static int dump_task(struct task_struct *p, void *arg)
+{
+	struct oom_control *oc = arg;
+	struct task_struct *task;
+
+	if (oom_unkillable_task(p))
+		return 0;
+
+	/* p may not have freeable memory in nodemask */
+	if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
+		return 0;
+
+	task = find_lock_task_mm(p);
+	if (!task) {
+		/*
+		 * 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.
+		 */
+		return 0;
+	}
+
+	pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu         %5hd %s\n",
+		task->pid, from_kuid(&init_user_ns, task_uid(task)),
+		task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
+		mm_pgtables_bytes(task->mm),
+		get_mm_counter(task->mm, MM_SWAPENTS),
+		task->signal->oom_score_adj, task->comm);
+	task_unlock(task);
+
+	return 0;
+}
+
+/**
+ * dump_tasks - dump current memory state of all system tasks
+ * @oc: pointer to struct oom_control
+ *
+ * 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,
+ * pgtables_bytes, swapents, oom_score_adj value, and name.
+ */
+static void dump_tasks(struct oom_control *oc)
+{
+	pr_info("Tasks state (memory values in pages):\n");
+	pr_info("[  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name\n");
+
+	if (is_memcg_oom(oc))
+		mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
+	else {
+		struct task_struct *p;
+
+		rcu_read_lock();
+		for_each_process(p)
+			dump_task(p, oc);
+		rcu_read_unlock();
+	}
+}
+
+static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
+{
+	/* one line summary of the oom killer context. */
+	pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
+			oom_constraint_text[oc->constraint],
+			nodemask_pr_args(oc->nodemask));
+	cpuset_print_current_mems_allowed();
+	mem_cgroup_print_oom_context(oc->memcg, victim);
+	pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
+		from_kuid(&init_user_ns, task_uid(victim)));
+}
+
+static void dump_header(struct oom_control *oc, struct task_struct *p)
+{
+	pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
+		current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
+			current->signal->oom_score_adj);
+	if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
+		pr_warn("COMPACTION is disabled!!!\n");
+
+	dump_stack();
+	if (is_memcg_oom(oc))
+		mem_cgroup_print_oom_meminfo(oc->memcg);
+	else {
+		__show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
+		if (should_dump_unreclaim_slab())
+			dump_unreclaimable_slab();
+	}
+	if (sysctl_oom_dump_tasks)
+		dump_tasks(oc);
+	if (p)
+		dump_oom_summary(oc, p);
+}
+
+/*
+ * Number of OOM victims in flight
+ */
+static atomic_t oom_victims = ATOMIC_INIT(0);
+static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
+
+static bool oom_killer_disabled __read_mostly;
+
+#define K(x) ((x) << (PAGE_SHIFT-10))
+
+/*
+ * task->mm can be NULL if the task is the exited group leader.  So to
+ * determine whether the task is using a particular mm, we examine all the
+ * task's threads: if one of those is using this mm then this task was also
+ * using it.
+ */
+bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
+{
+	struct task_struct *t;
+
+	for_each_thread(p, t) {
+		struct mm_struct *t_mm = READ_ONCE(t->mm);
+		if (t_mm)
+			return t_mm == mm;
+	}
+	return false;
+}
+
+#ifdef CONFIG_MMU
+/*
+ * OOM Reaper kernel thread which tries to reap the memory used by the OOM
+ * victim (if that is possible) to help the OOM killer to move on.
+ */
+static struct task_struct *oom_reaper_th;
+static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
+static struct task_struct *oom_reaper_list;
+static DEFINE_SPINLOCK(oom_reaper_lock);
+
+static bool __oom_reap_task_mm(struct mm_struct *mm)
+{
+	struct vm_area_struct *vma;
+	bool ret = true;
+	VMA_ITERATOR(vmi, mm, 0);
+
+	/*
+	 * Tell all users of get_user/copy_from_user etc... that the content
+	 * is no longer stable. No barriers really needed because unmapping
+	 * should imply barriers already and the reader would hit a page fault
+	 * if it stumbled over a reaped memory.
+	 */
+	set_bit(MMF_UNSTABLE, &mm->flags);
+
+	for_each_vma(vmi, vma) {
+		if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
+			continue;
+
+		/*
+		 * Only anonymous pages have a good chance to be dropped
+		 * without additional steps which we cannot afford as we
+		 * are OOM already.
+		 *
+		 * We do not even care about fs backed pages because all
+		 * which are reclaimable have already been reclaimed and
+		 * we do not want to block exit_mmap by keeping mm ref
+		 * count elevated without a good reason.
+		 */
+		if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
+			struct mmu_notifier_range range;
+			struct mmu_gather tlb;
+
+			mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
+						vma, mm, vma->vm_start,
+						vma->vm_end);
+			tlb_gather_mmu(&tlb, mm);
+			if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
+				tlb_finish_mmu(&tlb);
+				ret = false;
+				continue;
+			}
+			unmap_page_range(&tlb, vma, range.start, range.end, NULL);
+			mmu_notifier_invalidate_range_end(&range);
+			tlb_finish_mmu(&tlb);
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * Reaps the address space of the give task.
+ *
+ * Returns true on success and false if none or part of the address space
+ * has been reclaimed and the caller should retry later.
+ */
+static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
+{
+	bool ret = true;
+
+	if (!mmap_read_trylock(mm)) {
+		trace_skip_task_reaping(tsk->pid);
+		return false;
+	}
+
+	/*
+	 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
+	 * work on the mm anymore. The check for MMF_OOM_SKIP must run
+	 * under mmap_lock for reading because it serializes against the
+	 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
+	 */
+	if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
+		trace_skip_task_reaping(tsk->pid);
+		goto out_unlock;
+	}
+
+	trace_start_task_reaping(tsk->pid);
+
+	/* failed to reap part of the address space. Try again later */
+	ret = __oom_reap_task_mm(mm);
+	if (!ret)
+		goto out_finish;
+
+	pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
+			task_pid_nr(tsk), tsk->comm,
+			K(get_mm_counter(mm, MM_ANONPAGES)),
+			K(get_mm_counter(mm, MM_FILEPAGES)),
+			K(get_mm_counter(mm, MM_SHMEMPAGES)));
+out_finish:
+	trace_finish_task_reaping(tsk->pid);
+out_unlock:
+	mmap_read_unlock(mm);
+
+	return ret;
+}
+
+#define MAX_OOM_REAP_RETRIES 10
+static void oom_reap_task(struct task_struct *tsk)
+{
+	int attempts = 0;
+	struct mm_struct *mm = tsk->signal->oom_mm;
+
+	/* Retry the mmap_read_trylock(mm) a few times */
+	while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
+		schedule_timeout_idle(HZ/10);
+
+	if (attempts <= MAX_OOM_REAP_RETRIES ||
+	    test_bit(MMF_OOM_SKIP, &mm->flags))
+		goto done;
+
+	pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
+		task_pid_nr(tsk), tsk->comm);
+	sched_show_task(tsk);
+	debug_show_all_locks();
+
+done:
+	tsk->oom_reaper_list = NULL;
+
+	/*
+	 * Hide this mm from OOM killer because it has been either reaped or
+	 * somebody can't call mmap_write_unlock(mm).
+	 */
+	set_bit(MMF_OOM_SKIP, &mm->flags);
+
+	/* Drop a reference taken by queue_oom_reaper */
+	put_task_struct(tsk);
+}
+
+static int oom_reaper(void *unused)
+{
+	set_freezable();
+
+	while (true) {
+		struct task_struct *tsk = NULL;
+
+		wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
+		spin_lock_irq(&oom_reaper_lock);
+		if (oom_reaper_list != NULL) {
+			tsk = oom_reaper_list;
+			oom_reaper_list = tsk->oom_reaper_list;
+		}
+		spin_unlock_irq(&oom_reaper_lock);
+
+		if (tsk)
+			oom_reap_task(tsk);
+	}
+
+	return 0;
+}
+
+static void wake_oom_reaper(struct timer_list *timer)
+{
+	struct task_struct *tsk = container_of(timer, struct task_struct,
+			oom_reaper_timer);
+	struct mm_struct *mm = tsk->signal->oom_mm;
+	unsigned long flags;
+
+	/* The victim managed to terminate on its own - see exit_mmap */
+	if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
+		put_task_struct(tsk);
+		return;
+	}
+
+	spin_lock_irqsave(&oom_reaper_lock, flags);
+	tsk->oom_reaper_list = oom_reaper_list;
+	oom_reaper_list = tsk;
+	spin_unlock_irqrestore(&oom_reaper_lock, flags);
+	trace_wake_reaper(tsk->pid);
+	wake_up(&oom_reaper_wait);
+}
+
+/*
+ * Give the OOM victim time to exit naturally before invoking the oom_reaping.
+ * The timers timeout is arbitrary... the longer it is, the longer the worst
+ * case scenario for the OOM can take. If it is too small, the oom_reaper can
+ * get in the way and release resources needed by the process exit path.
+ * e.g. The futex robust list can sit in Anon|Private memory that gets reaped
+ * before the exit path is able to wake the futex waiters.
+ */
+#define OOM_REAPER_DELAY (2*HZ)
+static void queue_oom_reaper(struct task_struct *tsk)
+{
+	/* mm is already queued? */
+	if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
+		return;
+
+	get_task_struct(tsk);
+	timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
+	tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
+	add_timer(&tsk->oom_reaper_timer);
+}
+
+#ifdef CONFIG_SYSCTL
+static struct ctl_table vm_oom_kill_table[] = {
+	{
+		.procname	= "panic_on_oom",
+		.data		= &sysctl_panic_on_oom,
+		.maxlen		= sizeof(sysctl_panic_on_oom),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
+	{
+		.procname	= "oom_kill_allocating_task",
+		.data		= &sysctl_oom_kill_allocating_task,
+		.maxlen		= sizeof(sysctl_oom_kill_allocating_task),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "oom_dump_tasks",
+		.data		= &sysctl_oom_dump_tasks,
+		.maxlen		= sizeof(sysctl_oom_dump_tasks),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{}
+};
+#endif
+
+static int __init oom_init(void)
+{
+	oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
+#ifdef CONFIG_SYSCTL
+	register_sysctl_init("vm", vm_oom_kill_table);
+#endif
+	return 0;
+}
+subsys_initcall(oom_init)
+#else
+static inline void queue_oom_reaper(struct task_struct *tsk)
+{
+}
+#endif /* CONFIG_MMU */
+
+/**
+ * mark_oom_victim - mark the given task as OOM victim
+ * @tsk: task to mark
+ *
+ * Has to be called with oom_lock held and never after
+ * oom has been disabled already.
+ *
+ * tsk->mm has to be non NULL and caller has to guarantee it is stable (either
+ * under task_lock or operate on the current).
+ */
+static void mark_oom_victim(struct task_struct *tsk)
+{
+	struct mm_struct *mm = tsk->mm;
+
+	WARN_ON(oom_killer_disabled);
+	/* OOM killer might race with memcg OOM */
+	if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
+		return;
+
+	/* oom_mm is bound to the signal struct life time. */
+	if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
+		mmgrab(tsk->signal->oom_mm);
+
+	/*
+	 * Make sure that the task is woken up from uninterruptible sleep
+	 * if it is frozen because OOM killer wouldn't be able to free
+	 * any memory and livelock. freezing_slow_path will tell the freezer
+	 * that TIF_MEMDIE tasks should be ignored.
+	 */
+	__thaw_task(tsk);
+	atomic_inc(&oom_victims);
+	trace_mark_victim(tsk->pid);
+}
+
+/**
+ * exit_oom_victim - note the exit of an OOM victim
+ */
+void exit_oom_victim(void)
+{
+	clear_thread_flag(TIF_MEMDIE);
+
+	if (!atomic_dec_return(&oom_victims))
+		wake_up_all(&oom_victims_wait);
+}
+
+/**
+ * oom_killer_enable - enable OOM killer
+ */
+void oom_killer_enable(void)
+{
+	oom_killer_disabled = false;
+	pr_info("OOM killer enabled.\n");
+}
+
+/**
+ * oom_killer_disable - disable OOM killer
+ * @timeout: maximum timeout to wait for oom victims in jiffies
+ *
+ * Forces all page allocations to fail rather than trigger OOM killer.
+ * Will block and wait until all OOM victims are killed or the given
+ * timeout expires.
+ *
+ * The function cannot be called when there are runnable user tasks because
+ * the userspace would see unexpected allocation failures as a result. Any
+ * new usage of this function should be consulted with MM people.
+ *
+ * Returns true if successful and false if the OOM killer cannot be
+ * disabled.
+ */
+bool oom_killer_disable(signed long timeout)
+{
+	signed long ret;
+
+	/*
+	 * Make sure to not race with an ongoing OOM killer. Check that the
+	 * current is not killed (possibly due to sharing the victim's memory).
+	 */
+	if (mutex_lock_killable(&oom_lock))
+		return false;
+	oom_killer_disabled = true;
+	mutex_unlock(&oom_lock);
+
+	ret = wait_event_interruptible_timeout(oom_victims_wait,
+			!atomic_read(&oom_victims), timeout);
+	if (ret <= 0) {
+		oom_killer_enable();
+		return false;
+	}
+	pr_info("OOM killer disabled.\n");
+
+	return true;
+}
+
+static inline bool __task_will_free_mem(struct task_struct *task)
+{
+	struct signal_struct *sig = task->signal;
+
+	/*
+	 * A coredumping process may sleep for an extended period in
+	 * coredump_task_exit(), so the oom killer cannot assume that
+	 * the process will promptly exit and release memory.
+	 */
+	if (sig->core_state)
+		return false;
+
+	if (sig->flags & SIGNAL_GROUP_EXIT)
+		return true;
+
+	if (thread_group_empty(task) && (task->flags & PF_EXITING))
+		return true;
+
+	return false;
+}
+
+/*
+ * Checks whether the given task is dying or exiting and likely to
+ * release its address space. This means that all threads and processes
+ * sharing the same mm have to be killed or exiting.
+ * Caller has to make sure that task->mm is stable (hold task_lock or
+ * it operates on the current).
+ */
+static bool task_will_free_mem(struct task_struct *task)
+{
+	struct mm_struct *mm = task->mm;
+	struct task_struct *p;
+	bool ret = true;
+
+	/*
+	 * Skip tasks without mm because it might have passed its exit_mm and
+	 * exit_oom_victim. oom_reaper could have rescued that but do not rely
+	 * on that for now. We can consider find_lock_task_mm in future.
+	 */
+	if (!mm)
+		return false;
+
+	if (!__task_will_free_mem(task))
+		return false;
+
+	/*
+	 * This task has already been drained by the oom reaper so there are
+	 * only small chances it will free some more
+	 */
+	if (test_bit(MMF_OOM_SKIP, &mm->flags))
+		return false;
+
+	if (atomic_read(&mm->mm_users) <= 1)
+		return true;
+
+	/*
+	 * Make sure that all tasks which share the mm with the given tasks
+	 * are dying as well to make sure that a) nobody pins its mm and
+	 * b) the task is also reapable by the oom reaper.
+	 */
+	rcu_read_lock();
+	for_each_process(p) {
+		if (!process_shares_mm(p, mm))
+			continue;
+		if (same_thread_group(task, p))
+			continue;
+		ret = __task_will_free_mem(p);
+		if (!ret)
+			break;
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static void __oom_kill_process(struct task_struct *victim, const char *message)
+{
+	struct task_struct *p;
+	struct mm_struct *mm;
+	bool can_oom_reap = true;
+
+	p = find_lock_task_mm(victim);
+	if (!p) {
+		pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
+			message, task_pid_nr(victim), victim->comm);
+		put_task_struct(victim);
+		return;
+	} else if (victim != p) {
+		get_task_struct(p);
+		put_task_struct(victim);
+		victim = p;
+	}
+
+	/* Get a reference to safely compare mm after task_unlock(victim) */
+	mm = victim->mm;
+	mmgrab(mm);
+
+	/* Raise event before sending signal: task reaper must see this */
+	count_vm_event(OOM_KILL);
+	memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
+
+	/*
+	 * We should send SIGKILL before granting access to memory reserves
+	 * in order to prevent the OOM victim from depleting the memory
+	 * reserves from the user space under its control.
+	 */
+	do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
+	mark_oom_victim(victim);
+	pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n",
+		message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
+		K(get_mm_counter(mm, MM_ANONPAGES)),
+		K(get_mm_counter(mm, MM_FILEPAGES)),
+		K(get_mm_counter(mm, MM_SHMEMPAGES)),
+		from_kuid(&init_user_ns, task_uid(victim)),
+		mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
+	task_unlock(victim);
+
+	/*
+	 * Kill all user processes sharing victim->mm in other thread groups, if
+	 * any.  They don't get access to memory reserves, though, to avoid
+	 * depletion of all memory.  This prevents mm->mmap_lock livelock when an
+	 * oom killed thread 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.
+	 */
+	rcu_read_lock();
+	for_each_process(p) {
+		if (!process_shares_mm(p, mm))
+			continue;
+		if (same_thread_group(p, victim))
+			continue;
+		if (is_global_init(p)) {
+			can_oom_reap = false;
+			set_bit(MMF_OOM_SKIP, &mm->flags);
+			pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
+					task_pid_nr(victim), victim->comm,
+					task_pid_nr(p), p->comm);
+			continue;
+		}
+		/*
+		 * No kthread_use_mm() user needs to read from the userspace so
+		 * we are ok to reap it.
+		 */
+		if (unlikely(p->flags & PF_KTHREAD))
+			continue;
+		do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
+	}
+	rcu_read_unlock();
+
+	if (can_oom_reap)
+		queue_oom_reaper(victim);
+
+	mmdrop(mm);
+	put_task_struct(victim);
+}
+#undef K
+
+/*
+ * Kill provided task unless it's secured by setting
+ * oom_score_adj to OOM_SCORE_ADJ_MIN.
+ */
+static int oom_kill_memcg_member(struct task_struct *task, void *message)
+{
+	if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
+	    !is_global_init(task)) {
+		get_task_struct(task);
+		__oom_kill_process(task, message);
+	}
+	return 0;
+}
+
+static void oom_kill_process(struct oom_control *oc, const char *message)
+{
+	struct task_struct *victim = oc->chosen;
+	struct mem_cgroup *oom_group;
+	static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
+					      DEFAULT_RATELIMIT_BURST);
+
+	/*
+	 * If the task is already exiting, don't alarm the sysadmin or kill
+	 * its children or threads, just give it access to memory reserves
+	 * so it can die quickly
+	 */
+	task_lock(victim);
+	if (task_will_free_mem(victim)) {
+		mark_oom_victim(victim);
+		queue_oom_reaper(victim);
+		task_unlock(victim);
+		put_task_struct(victim);
+		return;
+	}
+	task_unlock(victim);
+
+	if (__ratelimit(&oom_rs))
+		dump_header(oc, victim);
+
+	/*
+	 * Do we need to kill the entire memory cgroup?
+	 * Or even one of the ancestor memory cgroups?
+	 * Check this out before killing the victim task.
+	 */
+	oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
+
+	__oom_kill_process(victim, message);
+
+	/*
+	 * If necessary, kill all tasks in the selected memory cgroup.
+	 */
+	if (oom_group) {
+		memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
+		mem_cgroup_print_oom_group(oom_group);
+		mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
+				      (void *)message);
+		mem_cgroup_put(oom_group);
+	}
+}
+
+/*
+ * Determines whether the kernel must panic because of the panic_on_oom sysctl.
+ */
+static void check_panic_on_oom(struct oom_control *oc)
+{
+	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 (oc->constraint != CONSTRAINT_NONE)
+			return;
+	}
+	/* Do not panic for oom kills triggered by sysrq */
+	if (is_sysrq_oom(oc))
+		return;
+	dump_header(oc, NULL);
+	panic("Out of memory: %s panic_on_oom is enabled\n",
+		sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
+}
+
+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);
+
+/**
+ * out_of_memory - kill the "best" process when we run out of memory
+ * @oc: pointer to struct oom_control
+ *
+ * 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.
+ */
+bool out_of_memory(struct oom_control *oc)
+{
+	unsigned long freed = 0;
+
+	if (oom_killer_disabled)
+		return false;
+
+	if (!is_memcg_oom(oc)) {
+		blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
+		if (freed > 0 && !is_sysrq_oom(oc))
+			/* Got some memory back in the last second. */
+			return true;
+	}
+
+	/*
+	 * If current has a pending SIGKILL or is exiting, then automatically
+	 * select it.  The goal is to allow it to allocate so that it may
+	 * quickly exit and free its memory.
+	 */
+	if (task_will_free_mem(current)) {
+		mark_oom_victim(current);
+		queue_oom_reaper(current);
+		return true;
+	}
+
+	/*
+	 * The OOM killer does not compensate for IO-less reclaim.
+	 * pagefault_out_of_memory lost its gfp context so we have to
+	 * make sure exclude 0 mask - all other users should have at least
+	 * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to
+	 * invoke the OOM killer even if it is a GFP_NOFS allocation.
+	 */
+	if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
+		return true;
+
+	/*
+	 * Check if there were limitations on the allocation (only relevant for
+	 * NUMA and memcg) that may require different handling.
+	 */
+	oc->constraint = constrained_alloc(oc);
+	if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
+		oc->nodemask = NULL;
+	check_panic_on_oom(oc);
+
+	if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
+	    current->mm && !oom_unkillable_task(current) &&
+	    oom_cpuset_eligible(current, oc) &&
+	    current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
+		get_task_struct(current);
+		oc->chosen = current;
+		oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
+		return true;
+	}
+
+	select_bad_process(oc);
+	/* Found nothing?!?! */
+	if (!oc->chosen) {
+		dump_header(oc, NULL);
+		pr_warn("Out of memory and no killable processes...\n");
+		/*
+		 * If we got here due to an actual allocation at the
+		 * system level, we cannot survive this and will enter
+		 * an endless loop in the allocator. Bail out now.
+		 */
+		if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
+			panic("System is deadlocked on memory\n");
+	}
+	if (oc->chosen && oc->chosen != (void *)-1UL)
+		oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
+				 "Memory cgroup out of memory");
+	return !!oc->chosen;
+}
+
+/*
+ * The pagefault handler calls here because some allocation has failed. We have
+ * to take care of the memcg OOM here because this is the only safe context without
+ * any locks held but let the oom killer triggered from the allocation context care
+ * about the global OOM.
+ */
+void pagefault_out_of_memory(void)
+{
+	static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+
+	if (mem_cgroup_oom_synchronize(true))
+		return;
+
+	if (fatal_signal_pending(current))
+		return;
+
+	if (__ratelimit(&pfoom_rs))
+		pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
+}
+
+SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
+{
+#ifdef CONFIG_MMU
+	struct mm_struct *mm = NULL;
+	struct task_struct *task;
+	struct task_struct *p;
+	unsigned int f_flags;
+	bool reap = false;
+	long ret = 0;
+
+	if (flags)
+		return -EINVAL;
+
+	task = pidfd_get_task(pidfd, &f_flags);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+
+	/*
+	 * Make sure to choose a thread which still has a reference to mm
+	 * during the group exit
+	 */
+	p = find_lock_task_mm(task);
+	if (!p) {
+		ret = -ESRCH;
+		goto put_task;
+	}
+
+	mm = p->mm;
+	mmgrab(mm);
+
+	if (task_will_free_mem(p))
+		reap = true;
+	else {
+		/* Error only if the work has not been done already */
+		if (!test_bit(MMF_OOM_SKIP, &mm->flags))
+			ret = -EINVAL;
+	}
+	task_unlock(p);
+
+	if (!reap)
+		goto drop_mm;
+
+	if (mmap_read_lock_killable(mm)) {
+		ret = -EINTR;
+		goto drop_mm;
+	}
+	/*
+	 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
+	 * possible change in exit_mmap is seen
+	 */
+	if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
+		ret = -EAGAIN;
+	mmap_read_unlock(mm);
+
+drop_mm:
+	mmdrop(mm);
+put_task:
+	put_task_struct(task);
+	return ret;
+#else
+	return -ENOSYS;
+#endif /* CONFIG_MMU */
+}