Merge branch 'akpm' (patches from Andrew)

Merge misc updates from Andrew Morton:

 - large KASAN update to use arm's "software tag-based mode"

 - a few misc things

 - sh updates

 - ocfs2 updates

 - just about all of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (167 commits)
  kernel/fork.c: mark 'stack_vm_area' with __maybe_unused
  memcg, oom: notify on oom killer invocation from the charge path
  mm, swap: fix swapoff with KSM pages
  include/linux/gfp.h: fix typo
  mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm
  hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race
  hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization
  memory_hotplug: add missing newlines to debugging output
  mm: remove __hugepage_set_anon_rmap()
  include/linux/vmstat.h: remove unused page state adjustment macro
  mm/page_alloc.c: allow error injection
  mm: migrate: drop unused argument of migrate_page_move_mapping()
  blkdev: avoid migration stalls for blkdev pages
  mm: migrate: provide buffer_migrate_page_norefs()
  mm: migrate: move migrate_page_lock_buffers()
  mm: migrate: lock buffers before migrate_page_move_mapping()
  mm: migration: factor out code to compute expected number of page references
  mm, page_alloc: enable pcpu_drain with zone capability
  kmemleak: add config to select auto scan
  mm/page_alloc.c: don't call kasan_free_pages() at deferred mem init
  ...

1 files changed, 14 insertions, 7 deletions

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 59dc28047030..89800fc7dc9d 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -53,7 +53,7 @@ struct userfaultfd_ctx {
 	/* a refile sequence protected by fault_pending_wqh lock */
 	struct seqcount refile_seq;
 	/* pseudo fd refcounting */
-	atomic_t refcount;
+	refcount_t refcount;
 	/* userfaultfd syscall flags */
 	unsigned int flags;
 	/* features requested from the userspace */
@@ -140,8 +140,7 @@ out:
  */
 static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
 {
-	if (!atomic_inc_not_zero(&ctx->refcount))
-		BUG();
+	refcount_inc(&ctx->refcount);
 }
 
 /**
@@ -154,7 +153,7 @@ static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
  */
 static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
 {
-	if (atomic_dec_and_test(&ctx->refcount)) {
+	if (refcount_dec_and_test(&ctx->refcount)) {
 		VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
 		VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
 		VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
@@ -686,7 +685,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
 			return -ENOMEM;
 		}
 
-		atomic_set(&ctx->refcount, 1);
+		refcount_set(&ctx->refcount, 1);
 		ctx->flags = octx->flags;
 		ctx->state = UFFD_STATE_RUNNING;
 		ctx->features = octx->features;
@@ -736,10 +735,18 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,
 	struct userfaultfd_ctx *ctx;
 
 	ctx = vma->vm_userfaultfd_ctx.ctx;
-	if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {
+
+	if (!ctx)
+		return;
+
+	if (ctx->features & UFFD_FEATURE_EVENT_REMAP) {
 		vm_ctx->ctx = ctx;
 		userfaultfd_ctx_get(ctx);
 		WRITE_ONCE(ctx->mmap_changing, true);
+	} else {
+		/* Drop uffd context if remap feature not enabled */
+		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
+		vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
 	}
 }
 
@@ -1927,7 +1934,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
 	if (!ctx)
 		return -ENOMEM;
 
-	atomic_set(&ctx->refcount, 1);
+	refcount_set(&ctx->refcount, 1);
 	ctx->flags = flags;
 	ctx->features = 0;
 	ctx->state = UFFD_STATE_WAIT_API;