Merge branch 'akpm' (patches from Andrew)

Mergr misc fixes from Andrew Morton:
"11 fixes"

Mostly VM fixes, one psi polling fix, and one parisc build fix.

* emailed patches from Andrew Morton <[e-mail]>:
mm/kasan: fix false positive invalid-free reports with CONFIG_KASAN_SW_TAGS=y
mm/zsmalloc.c: fix race condition in zs_destroy_pool
mm/zsmalloc.c: migration can leave pages in ZS_EMPTY indefinitely
mm, page_owner: handle THP splits correctly
userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx
psi: get poll_work to run when calling poll syscall next time
mm: memcontrol: flush percpu vmevents before releasing memcg
mm: memcontrol: flush percpu vmstats before releasing memcg
parisc: fix compilation errrors
mm, page_alloc: move_freepages should not examine struct page of reserved memory
mm/z3fold.c: fix race between migration and destruction

arch/parisc/include/asm/pgtable.h

···
 #ifndef _PARISC_PGTABLE_H
 #define _PARISC_PGTABLE_H
 
+#include <asm/page.h>
 #include <asm-generic/4level-fixup.h>
 
 #include <asm/fixmap.h>
···
 	} while (0)
 
 #endif /* !__ASSEMBLY__ */
-
-#include <asm/page.h>
 
 #define pte_ERROR(e) \
 	printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))

fs/userfaultfd.c

···
 	/* len == 0 means wake all */
 	struct userfaultfd_wake_range range = { .len = 0, };
 	unsigned long new_flags;
+	bool still_valid;
 
 	WRITE_ONCE(ctx->released, true);
 
···
 	 * taking the mmap_sem for writing.
 	 */
 	down_write(&mm->mmap_sem);
-	if (!mmget_still_valid(mm))
-		goto skip_mm;
+	still_valid = mmget_still_valid(mm);
 	prev = NULL;
 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
 		cond_resched();
···
 			continue;
 		}
 		new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
-		prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
-				 new_flags, vma->anon_vma,
-				 vma->vm_file, vma->vm_pgoff,
-				 vma_policy(vma),
-				 NULL_VM_UFFD_CTX);
-		if (prev)
-			vma = prev;
-		else
-			prev = vma;
+		if (still_valid) {
+			prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
+					 new_flags, vma->anon_vma,
+					 vma->vm_file, vma->vm_pgoff,
+					 vma_policy(vma),
+					 NULL_VM_UFFD_CTX);
+			if (prev)
+				vma = prev;
+			else
+				prev = vma;
+		}
 		vma->vm_flags = new_flags;
 		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 	}
-skip_mm:
 	up_write(&mm->mmap_sem);
 	mmput(mm);
 wakeup:

kernel/sched/psi.c

···
 	 * deadlock while waiting for psi_poll_work to acquire trigger_lock
 	 */
 	if (kworker_to_destroy) {
+		/*
+		 * After the RCU grace period has expired, the worker
+		 * can no longer be found through group->poll_kworker.
+		 * But it might have been already scheduled before
+		 * that - deschedule it cleanly before destroying it.
+		 */
 		kthread_cancel_delayed_work_sync(&group->poll_work);
+		atomic_set(&group->poll_scheduled, 0);
+
 		kthread_destroy_worker(kworker_to_destroy);
 	}
 	kfree(t);

mm/huge_memory.c

···
 #include <linux/shmem_fs.h>
 #include <linux/oom.h>
 #include <linux/numa.h>
+#include <linux/page_owner.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
···
 	}
 
 	ClearPageCompound(head);
+
+	split_page_owner(head, HPAGE_PMD_ORDER);
+
 	/* See comment in __split_huge_page_tail() */
 	if (PageAnon(head)) {
 		/* Additional pin to swap cache */

mm/kasan/common.c

···
 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
 		return shadow_byte < 0 ||
 			shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
-	else
-		return tag != (u8)shadow_byte;
+
+	/* else CONFIG_KASAN_SW_TAGS: */
+	if ((u8)shadow_byte == KASAN_TAG_INVALID)
+		return true;
+	if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte))
+		return true;
+
+	return false;
 }
 
 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,

mm/memcontrol.c

···
 	}
 }
 
+static void memcg_flush_percpu_vmstats(struct mem_cgroup *memcg)
+{
+	unsigned long stat[MEMCG_NR_STAT];
+	struct mem_cgroup *mi;
+	int node, cpu, i;
+
+	for (i = 0; i < MEMCG_NR_STAT; i++)
+		stat[i] = 0;
+
+	for_each_online_cpu(cpu)
+		for (i = 0; i < MEMCG_NR_STAT; i++)
+			stat[i] += raw_cpu_read(memcg->vmstats_percpu->stat[i]);
+
+	for (mi = memcg; mi; mi = parent_mem_cgroup(mi))
+		for (i = 0; i < MEMCG_NR_STAT; i++)
+			atomic_long_add(stat[i], &mi->vmstats[i]);
+
+	for_each_node(node) {
+		struct mem_cgroup_per_node *pn = memcg->nodeinfo[node];
+		struct mem_cgroup_per_node *pi;
+
+		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
+			stat[i] = 0;
+
+		for_each_online_cpu(cpu)
+			for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
+				stat[i] += raw_cpu_read(
+					pn->lruvec_stat_cpu->count[i]);
+
+		for (pi = pn; pi; pi = parent_nodeinfo(pi, node))
+			for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
+				atomic_long_add(stat[i], &pi->lruvec_stat[i]);
+	}
+}
+
+static void memcg_flush_percpu_vmevents(struct mem_cgroup *memcg)
+{
+	unsigned long events[NR_VM_EVENT_ITEMS];
+	struct mem_cgroup *mi;
+	int cpu, i;
+
+	for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
+		events[i] = 0;
+
+	for_each_online_cpu(cpu)
+		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
+			events[i] += raw_cpu_read(
+				memcg->vmstats_percpu->events[i]);
+
+	for (mi = memcg; mi; mi = parent_mem_cgroup(mi))
+		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
+			atomic_long_add(events[i], &mi->vmevents[i]);
+}
+
 #ifdef CONFIG_MEMCG_KMEM
 static int memcg_online_kmem(struct mem_cgroup *memcg)
 {
···
 {
 	int node;
 
+	/*
+	 * Flush percpu vmstats and vmevents to guarantee the value correctness
+	 * on parent's and all ancestor levels.
+	 */
+	memcg_flush_percpu_vmstats(memcg);
+	memcg_flush_percpu_vmevents(memcg);
 	for_each_node(node)
 		free_mem_cgroup_per_node_info(memcg, node);
 	free_percpu(memcg->vmstats_percpu);

mm/page_alloc.c

···
 	unsigned int order;
 	int pages_moved = 0;
 
-#ifndef CONFIG_HOLES_IN_ZONE
-	/*
-	 * page_zone is not safe to call in this context when
-	 * CONFIG_HOLES_IN_ZONE is set. This bug check is probably redundant
-	 * anyway as we check zone boundaries in move_freepages_block().
-	 * Remove at a later date when no bug reports exist related to
-	 * grouping pages by mobility
-	 */
-	VM_BUG_ON(pfn_valid(page_to_pfn(start_page)) &&
-	          pfn_valid(page_to_pfn(end_page)) &&
-	          page_zone(start_page) != page_zone(end_page));
-#endif
 	for (page = start_page; page <= end_page;) {
 		if (!pfn_valid_within(page_to_pfn(page))) {
 			page++;
 			continue;
 		}
-
-		/* Make sure we are not inadvertently changing nodes */
-		VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
 
 		if (!PageBuddy(page)) {
 			/*
···
 			page++;
 			continue;
 		}
+
+		/* Make sure we are not inadvertently changing nodes */
+		VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
+		VM_BUG_ON_PAGE(page_zone(page) != zone, page);
 
 		order = page_order(page);
 		move_to_free_area(page, &zone->free_area[order], migratetype);

mm/z3fold.c

···
 #include <linux/workqueue.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/wait.h>
 #include <linux/zpool.h>
 #include <linux/magic.h>
 
···
  * @release_wq:	workqueue for safe page release
  * @work:	work_struct for safe page release
  * @inode:	inode for z3fold pseudo filesystem
+ * @destroying: bool to stop migration once we start destruction
+ * @isolated: int to count the number of pages currently in isolation
  *
  * This structure is allocated at pool creation time and maintains metadata
  * pertaining to a particular z3fold pool.
···
 	const struct zpool_ops *zpool_ops;
 	struct workqueue_struct *compact_wq;
 	struct workqueue_struct *release_wq;
+	struct wait_queue_head isolate_wait;
 	struct work_struct work;
 	struct inode *inode;
+	bool destroying;
+	int isolated;
 };
 
 /*
···
 		goto out_c;
 	spin_lock_init(&pool->lock);
 	spin_lock_init(&pool->stale_lock);
+	init_waitqueue_head(&pool->isolate_wait);
 	pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
 	if (!pool->unbuddied)
 		goto out_pool;
···
 	return NULL;
 }
 
+static bool pool_isolated_are_drained(struct z3fold_pool *pool)
+{
+	bool ret;
+
+	spin_lock(&pool->lock);
+	ret = pool->isolated == 0;
+	spin_unlock(&pool->lock);
+	return ret;
+}
 /**
  * z3fold_destroy_pool() - destroys an existing z3fold pool
  * @pool:	the z3fold pool to be destroyed
···
 static void z3fold_destroy_pool(struct z3fold_pool *pool)
 {
 	kmem_cache_destroy(pool->c_handle);
+	/*
+	 * We set pool-> destroying under lock to ensure that
+	 * z3fold_page_isolate() sees any changes to destroying. This way we
+	 * avoid the need for any memory barriers.
+	 */
+
+	spin_lock(&pool->lock);
+	pool->destroying = true;
+	spin_unlock(&pool->lock);
+
+	/*
+	 * We need to ensure that no pages are being migrated while we destroy
+	 * these workqueues, as migration can queue work on either of the
+	 * workqueues.
+	 */
+	wait_event(pool->isolate_wait, !pool_isolated_are_drained(pool));
 
 	/*
 	 * We need to destroy pool->compact_wq before pool->release_wq,
···
 	return atomic64_read(&pool->pages_nr);
 }
 
+/*
+ * z3fold_dec_isolated() expects to be called while pool->lock is held.
+ */
+static void z3fold_dec_isolated(struct z3fold_pool *pool)
+{
+	assert_spin_locked(&pool->lock);
+	VM_BUG_ON(pool->isolated <= 0);
+	pool->isolated--;
+
+	/*
+	 * If we have no more isolated pages, we have to see if
+	 * z3fold_destroy_pool() is waiting for a signal.
+	 */
+	if (pool->isolated == 0 && waitqueue_active(&pool->isolate_wait))
+		wake_up_all(&pool->isolate_wait);
+}
+
+static void z3fold_inc_isolated(struct z3fold_pool *pool)
+{
+	pool->isolated++;
+}
+
 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
 {
 	struct z3fold_header *zhdr;
···
 		spin_lock(&pool->lock);
 		if (!list_empty(&page->lru))
 			list_del(&page->lru);
+		/*
+		 * We need to check for destruction while holding pool->lock, as
+		 * otherwise destruction could see 0 isolated pages, and
+		 * proceed.
+		 */
+		if (unlikely(pool->destroying)) {
+			spin_unlock(&pool->lock);
+			/*
+			 * If this page isn't stale, somebody else holds a
+			 * reference to it. Let't drop our refcount so that they
+			 * can call the release logic.
+			 */
+			if (unlikely(kref_put(&zhdr->refcount,
+					      release_z3fold_page_locked))) {
+				/*
+				 * If we get here we have kref problems, so we
+				 * should freak out.
+				 */
+				WARN(1, "Z3fold is experiencing kref problems\n");
+				return false;
+			}
+			z3fold_page_unlock(zhdr);
+			return false;
+		}
+
+
+		z3fold_inc_isolated(pool);
 		spin_unlock(&pool->lock);
 		z3fold_page_unlock(zhdr);
 		return true;
···
 
 	queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
 
+	spin_lock(&pool->lock);
+	z3fold_dec_isolated(pool);
+	spin_unlock(&pool->lock);
+
 	page_mapcount_reset(page);
 	put_page(page);
 	return 0;
···
 	INIT_LIST_HEAD(&page->lru);
 	if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 		atomic64_dec(&pool->pages_nr);
+		spin_lock(&pool->lock);
+		z3fold_dec_isolated(pool);
+		spin_unlock(&pool->lock);
 		return;
 	}
 	spin_lock(&pool->lock);
 	list_add(&page->lru, &pool->lru);
+	z3fold_dec_isolated(pool);
 	spin_unlock(&pool->lock);
 	z3fold_page_unlock(zhdr);
 }

mm/zsmalloc.c

···
 #include <linux/mount.h>
 #include <linux/pseudo_fs.h>
 #include <linux/migrate.h>
+#include <linux/wait.h>
 #include <linux/pagemap.h>
 #include <linux/fs.h>
 
···
 #ifdef CONFIG_COMPACTION
 	struct inode *inode;
 	struct work_struct free_work;
+	/* A wait queue for when migration races with async_free_zspage() */
+	struct wait_queue_head migration_wait;
+	atomic_long_t isolated_pages;
+	bool destroying;
 #endif
 };
 
···
 	zspage->isolated--;
 }
 
+static void putback_zspage_deferred(struct zs_pool *pool,
+				    struct size_class *class,
+				    struct zspage *zspage)
+{
+	enum fullness_group fg;
+
+	fg = putback_zspage(class, zspage);
+	if (fg == ZS_EMPTY)
+		schedule_work(&pool->free_work);
+
+}
+
+static inline void zs_pool_dec_isolated(struct zs_pool *pool)
+{
+	VM_BUG_ON(atomic_long_read(&pool->isolated_pages) <= 0);
+	atomic_long_dec(&pool->isolated_pages);
+	/*
+	 * There's no possibility of racing, since wait_for_isolated_drain()
+	 * checks the isolated count under &class->lock after enqueuing
+	 * on migration_wait.
+	 */
+	if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying)
+		wake_up_all(&pool->migration_wait);
+}
+
 static void replace_sub_page(struct size_class *class, struct zspage *zspage,
 				struct page *newpage, struct page *oldpage)
 {
···
 	 */
 	if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
 		get_zspage_mapping(zspage, &class_idx, &fullness);
+		atomic_long_inc(&pool->isolated_pages);
 		remove_zspage(class, zspage, fullness);
 	}
 
···
 	 * Page migration is done so let's putback isolated zspage to
 	 * the list if @page is final isolated subpage in the zspage.
 	 */
-	if (!is_zspage_isolated(zspage))
-		putback_zspage(class, zspage);
+	if (!is_zspage_isolated(zspage)) {
+		/*
+		 * We cannot race with zs_destroy_pool() here because we wait
+		 * for isolation to hit zero before we start destroying.
+		 * Also, we ensure that everyone can see pool->destroying before
+		 * we start waiting.
+		 */
+		putback_zspage_deferred(pool, class, zspage);
+		zs_pool_dec_isolated(pool);
+	}
 
 	reset_page(page);
 	put_page(page);
···
 	spin_lock(&class->lock);
 	dec_zspage_isolation(zspage);
 	if (!is_zspage_isolated(zspage)) {
-		fg = putback_zspage(class, zspage);
 		/*
 		 * Due to page_lock, we cannot free zspage immediately
 		 * so let's defer.
 		 */
-		if (fg == ZS_EMPTY)
-			schedule_work(&pool->free_work);
+		putback_zspage_deferred(pool, class, zspage);
+		zs_pool_dec_isolated(pool);
 	}
 	spin_unlock(&class->lock);
 }
···
 	return 0;
 }
 
+static bool pool_isolated_are_drained(struct zs_pool *pool)
+{
+	return atomic_long_read(&pool->isolated_pages) == 0;
+}
+
+/* Function for resolving migration */
+static void wait_for_isolated_drain(struct zs_pool *pool)
+{
+
+	/*
+	 * We're in the process of destroying the pool, so there are no
+	 * active allocations. zs_page_isolate() fails for completely free
+	 * zspages, so we need only wait for the zs_pool's isolated
+	 * count to hit zero.
+	 */
+	wait_event(pool->migration_wait,
+		   pool_isolated_are_drained(pool));
+}
+
 static void zs_unregister_migration(struct zs_pool *pool)
 {
+	pool->destroying = true;
+	/*
+	 * We need a memory barrier here to ensure global visibility of
+	 * pool->destroying. Thus pool->isolated pages will either be 0 in which
+	 * case we don't care, or it will be > 0 and pool->destroying will
+	 * ensure that we wake up once isolation hits 0.
+	 */
+	smp_mb();
+	wait_for_isolated_drain(pool); /* This can block */
 	flush_work(&pool->free_work);
 	iput(pool->inode);
 }
···
 	pool->name = kstrdup(name, GFP_KERNEL);
 	if (!pool->name)
 		goto err;
+
+	init_waitqueue_head(&pool->migration_wait);
 
 	if (create_cache(pool))
 		goto err;