3 files changed, 133 insertions, 108 deletions
diff --git a/tools/testing/vma/linux/atomic.h b/tools/testing/vma/linux/atomic.h
index 3e1b6adc027b..788c597c4fde 100644
--- a/tools/testing/vma/linux/atomic.h
+++ b/tools/testing/vma/linux/atomic.h
@@ -9,4 +9,9 @@
 #define atomic_set(x, y) uatomic_set(x, y)
 #define U8_MAX UCHAR_MAX
 
+#ifndef atomic_cmpxchg_relaxed
+#define  atomic_cmpxchg_relaxed		uatomic_cmpxchg
+#define  atomic_cmpxchg_release         uatomic_cmpxchg
+#endif /* atomic_cmpxchg_relaxed */
+
 #endif	/* _LINUX_ATOMIC_H */
diff --git a/tools/testing/vma/vma.c b/tools/testing/vma/vma.c
index 04ab45e27fb8..11f761769b5b 100644
--- a/tools/testing/vma/vma.c
+++ b/tools/testing/vma/vma.c
@@ -74,11 +74,23 @@ static struct vm_area_struct *alloc_vma(struct mm_struct *mm,
 	ret->vm_end = end;
 	ret->vm_pgoff = pgoff;
 	ret->__vm_flags = flags;
+	vma_assert_detached(ret);
 
 	return ret;
 }
 
 /* Helper function to allocate a VMA and link it to the tree. */
+static int attach_vma(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	int res;
+
+	res = vma_link(mm, vma);
+	if (!res)
+		vma_assert_attached(vma);
+	return res;
+}
+
+/* Helper function to allocate a VMA and link it to the tree. */
 static struct vm_area_struct *alloc_and_link_vma(struct mm_struct *mm,
 						 unsigned long start,
 						 unsigned long end,
@@ -90,7 +102,7 @@ static struct vm_area_struct *alloc_and_link_vma(struct mm_struct *mm,
 	if (vma == NULL)
 		return NULL;
 
-	if (vma_link(mm, vma)) {
+	if (attach_vma(mm, vma)) {
 		vm_area_free(vma);
 		return NULL;
 	}
@@ -108,6 +120,7 @@ static struct vm_area_struct *alloc_and_link_vma(struct mm_struct *mm,
 /* Helper function which provides a wrapper around a merge new VMA operation. */
 static struct vm_area_struct *merge_new(struct vma_merge_struct *vmg)
 {
+	struct vm_area_struct *vma;
 	/*
 	 * For convenience, get prev and next VMAs. Which the new VMA operation
 	 * requires.
@@ -116,7 +129,11 @@ static struct vm_area_struct *merge_new(struct vma_merge_struct *vmg)
 	vmg->prev = vma_prev(vmg->vmi);
 	vma_iter_next_range(vmg->vmi);
 
-	return vma_merge_new_range(vmg);
+	vma = vma_merge_new_range(vmg);
+	if (vma)
+		vma_assert_attached(vma);
+
+	return vma;
 }
 
 /*
@@ -125,7 +142,12 @@ static struct vm_area_struct *merge_new(struct vma_merge_struct *vmg)
  */
 static struct vm_area_struct *merge_existing(struct vma_merge_struct *vmg)
 {
-	return vma_merge_existing_range(vmg);
+	struct vm_area_struct *vma;
+
+	vma = vma_merge_existing_range(vmg);
+	if (vma)
+		vma_assert_attached(vma);
+	return vma;
 }
 
 /*
@@ -147,13 +169,20 @@ static void vmg_set_range(struct vma_merge_struct *vmg, unsigned long start,
 	vma_iter_set(vmg->vmi, start);
 
 	vmg->prev = NULL;
+	vmg->middle = NULL;
 	vmg->next = NULL;
-	vmg->vma = NULL;
+	vmg->target = NULL;
 
 	vmg->start = start;
 	vmg->end = end;
 	vmg->pgoff = pgoff;
 	vmg->flags = flags;
+
+	vmg->just_expand = false;
+	vmg->__remove_middle = false;
+	vmg->__remove_next = false;
+	vmg->__adjust_middle_start = false;
+	vmg->__adjust_next_start = false;
 }
 
 /*
@@ -253,8 +282,8 @@ static bool test_simple_merge(void)
 		.pgoff = 1,
 	};
 
-	ASSERT_FALSE(vma_link(&mm, vma_left));
-	ASSERT_FALSE(vma_link(&mm, vma_right));
+	ASSERT_FALSE(attach_vma(&mm, vma_left));
+	ASSERT_FALSE(attach_vma(&mm, vma_right));
 
 	vma = merge_new(&vmg);
 	ASSERT_NE(vma, NULL);
@@ -278,7 +307,7 @@ static bool test_simple_modify(void)
 	struct vm_area_struct *init_vma = alloc_vma(&mm, 0, 0x3000, 0, flags);
 	VMA_ITERATOR(vmi, &mm, 0x1000);
 
-	ASSERT_FALSE(vma_link(&mm, init_vma));
+	ASSERT_FALSE(attach_vma(&mm, init_vma));
 
 	/*
 	 * The flags will not be changed, the vma_modify_flags() function
@@ -338,13 +367,13 @@ static bool test_simple_expand(void)
 	VMA_ITERATOR(vmi, &mm, 0);
 	struct vma_merge_struct vmg = {
 		.vmi = &vmi,
-		.vma = vma,
+		.middle = vma,
 		.start = 0,
 		.end = 0x3000,
 		.pgoff = 0,
 	};
 
-	ASSERT_FALSE(vma_link(&mm, vma));
+	ASSERT_FALSE(attach_vma(&mm, vma));
 
 	ASSERT_FALSE(expand_existing(&vmg));
 
@@ -365,7 +394,7 @@ static bool test_simple_shrink(void)
 	struct vm_area_struct *vma = alloc_vma(&mm, 0, 0x3000, 0, flags);
 	VMA_ITERATOR(vmi, &mm, 0);
 
-	ASSERT_FALSE(vma_link(&mm, vma));
+	ASSERT_FALSE(attach_vma(&mm, vma));
 
 	ASSERT_FALSE(vma_shrink(&vmi, vma, 0, 0x1000, 0));
 
@@ -631,7 +660,7 @@ static bool test_vma_merge_special_flags(void)
 	 */
 	vma = alloc_and_link_vma(&mm, 0x3000, 0x4000, 3, flags);
 	ASSERT_NE(vma, NULL);
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	for (i = 0; i < ARRAY_SIZE(special_flags); i++) {
 		vm_flags_t special_flag = special_flags[i];
@@ -760,7 +789,7 @@ static bool test_vma_merge_with_close(void)
 
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	/*
 	 * The VMA being modified in a way that would otherwise merge should
@@ -787,7 +816,7 @@ static bool test_vma_merge_with_close(void)
 	vma->vm_ops = &vm_ops;
 
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	/*
 	 * Initially this is misapprehended as an out of memory report, as the
@@ -817,7 +846,7 @@ static bool test_vma_merge_with_close(void)
 
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
@@ -843,7 +872,7 @@ static bool test_vma_merge_with_close(void)
 
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -940,7 +969,7 @@ static bool test_merge_existing(void)
 	vma_next = alloc_and_link_vma(&mm, 0x6000, 0x9000, 6, flags);
 	vma_next->vm_ops = &vm_ops; /* This should have no impact. */
 	vmg_set_range(&vmg, 0x3000, 0x6000, 3, flags);
-	vmg.vma = vma;
+	vmg.middle = vma;
 	vmg.prev = vma;
 	vma->anon_vma = &dummy_anon_vma;
 	ASSERT_EQ(merge_existing(&vmg), vma_next);
@@ -973,7 +1002,7 @@ static bool test_merge_existing(void)
 	vma_next = alloc_and_link_vma(&mm, 0x6000, 0x9000, 6, flags);
 	vma_next->vm_ops = &vm_ops; /* This should have no impact. */
 	vmg_set_range(&vmg, 0x2000, 0x6000, 2, flags);
-	vmg.vma = vma;
+	vmg.middle = vma;
 	vma->anon_vma = &dummy_anon_vma;
 	ASSERT_EQ(merge_existing(&vmg), vma_next);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1003,7 +1032,7 @@ static bool test_merge_existing(void)
 	vma->vm_ops = &vm_ops; /* This should have no impact. */
 	vmg_set_range(&vmg, 0x3000, 0x6000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	vma->anon_vma = &dummy_anon_vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
@@ -1037,7 +1066,7 @@ static bool test_merge_existing(void)
 	vma = alloc_and_link_vma(&mm, 0x3000, 0x7000, 3, flags);
 	vmg_set_range(&vmg, 0x3000, 0x7000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	vma->anon_vma = &dummy_anon_vma;
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1067,7 +1096,7 @@ static bool test_merge_existing(void)
 	vma_next = alloc_and_link_vma(&mm, 0x7000, 0x9000, 7, flags);
 	vmg_set_range(&vmg, 0x3000, 0x7000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	vma->anon_vma = &dummy_anon_vma;
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1102,37 +1131,37 @@ static bool test_merge_existing(void)
 
 	vmg_set_range(&vmg, 0x4000, 0x5000, 4, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
 
 	vmg_set_range(&vmg, 0x5000, 0x6000, 5, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
 
 	vmg_set_range(&vmg, 0x6000, 0x7000, 6, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
 
 	vmg_set_range(&vmg, 0x4000, 0x7000, 4, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
 
 	vmg_set_range(&vmg, 0x4000, 0x6000, 4, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
 
 	vmg_set_range(&vmg, 0x5000, 0x6000, 5, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 	ASSERT_EQ(merge_existing(&vmg), NULL);
 	ASSERT_EQ(vmg.state, VMA_MERGE_NOMERGE);
 
@@ -1197,7 +1226,7 @@ static bool test_anon_vma_non_mergeable(void)
 
 	vmg_set_range(&vmg, 0x3000, 0x7000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1277,7 +1306,7 @@ static bool test_dup_anon_vma(void)
 	vma_next->anon_vma = &dummy_anon_vma;
 
 	vmg_set_range(&vmg, 0, 0x5000, 0, flags);
-	vmg.vma = vma_prev;
+	vmg.middle = vma_prev;
 	vmg.next = vma_next;
 
 	ASSERT_EQ(expand_existing(&vmg), 0);
@@ -1309,7 +1338,7 @@ static bool test_dup_anon_vma(void)
 	vma_next->anon_vma = &dummy_anon_vma;
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1338,7 +1367,7 @@ static bool test_dup_anon_vma(void)
 	vma->anon_vma = &dummy_anon_vma;
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1366,7 +1395,7 @@ static bool test_dup_anon_vma(void)
 	vma->anon_vma = &dummy_anon_vma;
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_prev);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1394,7 +1423,7 @@ static bool test_dup_anon_vma(void)
 	vma->anon_vma = &dummy_anon_vma;
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	ASSERT_EQ(merge_existing(&vmg), vma_next);
 	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
@@ -1432,7 +1461,7 @@ static bool test_vmi_prealloc_fail(void)
 
 	vmg_set_range(&vmg, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.vma = vma;
+	vmg.middle = vma;
 
 	fail_prealloc = true;
 
@@ -1458,7 +1487,7 @@ static bool test_vmi_prealloc_fail(void)
 	vma->anon_vma = &dummy_anon_vma;
 
 	vmg_set_range(&vmg, 0, 0x5000, 3, flags);
-	vmg.vma = vma_prev;
+	vmg.middle = vma_prev;
 	vmg.next = vma;
 
 	fail_prealloc = true;
@@ -1515,11 +1544,11 @@ static bool test_copy_vma(void)
 
 	vma = alloc_and_link_vma(&mm, 0x3000, 0x5000, 3, flags);
 	vma_new = copy_vma(&vma, 0, 0x2000, 0, &need_locks);
-
 	ASSERT_NE(vma_new, vma);
 	ASSERT_EQ(vma_new->vm_start, 0);
 	ASSERT_EQ(vma_new->vm_end, 0x2000);
 	ASSERT_EQ(vma_new->vm_pgoff, 0);
+	vma_assert_attached(vma_new);
 
 	cleanup_mm(&mm, &vmi);
 
@@ -1528,6 +1557,7 @@ static bool test_copy_vma(void)
 	vma = alloc_and_link_vma(&mm, 0, 0x2000, 0, flags);
 	vma_next = alloc_and_link_vma(&mm, 0x6000, 0x8000, 6, flags);
 	vma_new = copy_vma(&vma, 0x4000, 0x2000, 4, &need_locks);
+	vma_assert_attached(vma_new);
 
 	ASSERT_EQ(vma_new, vma_next);
 
@@ -1546,7 +1576,7 @@ static bool test_expand_only_mode(void)
 	/*
 	 * Place a VMA prior to the one we're expanding so we assert that we do
 	 * not erroneously try to traverse to the previous VMA even though we
-	 * have, through the use of VMG_FLAG_JUST_EXPAND, indicated we do not
+	 * have, through the use of the just_expand flag, indicated we do not
 	 * need to do so.
 	 */
 	alloc_and_link_vma(&mm, 0, 0x2000, 0, flags);
@@ -1558,7 +1588,7 @@ static bool test_expand_only_mode(void)
 	vma_iter_set(&vmi, 0x3000);
 	vma_prev = alloc_and_link_vma(&mm, 0x3000, 0x5000, 3, flags);
 	vmg.prev = vma_prev;
-	vmg.merge_flags = VMG_FLAG_JUST_EXPAND;
+	vmg.just_expand = true;
 
 	vma = vma_merge_new_range(&vmg);
 	ASSERT_NE(vma, NULL);
@@ -1569,6 +1599,7 @@ static bool test_expand_only_mode(void)
 	ASSERT_EQ(vma->vm_pgoff, 3);
 	ASSERT_TRUE(vma_write_started(vma));
 	ASSERT_EQ(vma_iter_addr(&vmi), 0x3000);
+	vma_assert_attached(vma);
 
 	cleanup_mm(&mm, &vmi);
 	return true;
diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
index 1eae23039854..572ab2cea763 100644
--- a/tools/testing/vma/vma_internal.h
+++ b/tools/testing/vma/vma_internal.h
@@ -25,7 +25,7 @@
 #include <linux/maple_tree.h>
 #include <linux/mm.h>
 #include <linux/rbtree.h>
-#include <linux/rwsem.h>
+#include <linux/refcount.h>
 
 extern unsigned long stack_guard_gap;
 #ifdef CONFIG_MMU
@@ -135,10 +135,6 @@ typedef __bitwise unsigned int vm_fault_t;
  */
 #define pr_warn_once pr_err
 
-typedef struct refcount_struct {
-	atomic_t refs;
-} refcount_t;
-
 struct kref {
 	refcount_t refcount;
 };
@@ -233,15 +229,12 @@ struct mm_struct {
 	unsigned long flags; /* Must use atomic bitops to access */
 };
 
-struct vma_lock {
-	struct rw_semaphore lock;
-};
-
-
 struct file {
 	struct address_space	*f_mapping;
 };
 
+#define VMA_LOCK_OFFSET	0x40000000
+
 struct vm_area_struct {
 	/* The first cache line has the info for VMA tree walking. */
 
@@ -269,16 +262,13 @@ struct vm_area_struct {
 	};
 
 #ifdef CONFIG_PER_VMA_LOCK
-	/* Flag to indicate areas detached from the mm->mm_mt tree */
-	bool detached;
-
 	/*
 	 * Can only be written (using WRITE_ONCE()) while holding both:
 	 *  - mmap_lock (in write mode)
-	 *  - vm_lock->lock (in write mode)
+	 *  - vm_refcnt bit at VMA_LOCK_OFFSET is set
 	 * Can be read reliably while holding one of:
 	 *  - mmap_lock (in read or write mode)
-	 *  - vm_lock->lock (in read or write mode)
+	 *  - vm_refcnt bit at VMA_LOCK_OFFSET is set or vm_refcnt > 1
 	 * Can be read unreliably (using READ_ONCE()) for pessimistic bailout
 	 * while holding nothing (except RCU to keep the VMA struct allocated).
 	 *
@@ -287,20 +277,9 @@ struct vm_area_struct {
 	 * slowpath.
 	 */
 	unsigned int vm_lock_seq;
-	struct vma_lock *vm_lock;
 #endif
 
 	/*
-	 * For areas with an address space and backing store,
-	 * linkage into the address_space->i_mmap interval tree.
-	 *
-	 */
-	struct {
-		struct rb_node rb;
-		unsigned long rb_subtree_last;
-	} shared;
-
-	/*
 	 * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
 	 * list, after a COW of one of the file pages.	A MAP_SHARED vma
 	 * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
@@ -319,14 +298,6 @@ struct vm_area_struct {
 	struct file * vm_file;		/* File we map to (can be NULL). */
 	void * vm_private_data;		/* was vm_pte (shared mem) */
 
-#ifdef CONFIG_ANON_VMA_NAME
-	/*
-	 * For private and shared anonymous mappings, a pointer to a null
-	 * terminated string containing the name given to the vma, or NULL if
-	 * unnamed. Serialized by mmap_lock. Use anon_vma_name to access.
-	 */
-	struct anon_vma_name *anon_name;
-#endif
 #ifdef CONFIG_SWAP
 	atomic_long_t swap_readahead_info;
 #endif
@@ -339,6 +310,27 @@ struct vm_area_struct {
 #ifdef CONFIG_NUMA_BALANCING
 	struct vma_numab_state *numab_state;	/* NUMA Balancing state */
 #endif
+#ifdef CONFIG_PER_VMA_LOCK
+	/* Unstable RCU readers are allowed to read this. */
+	refcount_t vm_refcnt;
+#endif
+	/*
+	 * For areas with an address space and backing store,
+	 * linkage into the address_space->i_mmap interval tree.
+	 *
+	 */
+	struct {
+		struct rb_node rb;
+		unsigned long rb_subtree_last;
+	} shared;
+#ifdef CONFIG_ANON_VMA_NAME
+	/*
+	 * For private and shared anonymous mappings, a pointer to a null
+	 * terminated string containing the name given to the vma, or NULL if
+	 * unnamed. Serialized by mmap_lock. Use anon_vma_name to access.
+	 */
+	struct anon_vma_name *anon_name;
+#endif
 	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 } __randomize_layout;
 
@@ -464,26 +456,40 @@ static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi)
 	return mas_find(&vmi->mas, ULONG_MAX);
 }
 
-static inline bool vma_lock_alloc(struct vm_area_struct *vma)
+/*
+ * WARNING: to avoid racing with vma_mark_attached()/vma_mark_detached(), these
+ * assertions should be made either under mmap_write_lock or when the object
+ * has been isolated under mmap_write_lock, ensuring no competing writers.
+ */
+static inline void vma_assert_attached(struct vm_area_struct *vma)
 {
-	vma->vm_lock = calloc(1, sizeof(struct vma_lock));
-
-	if (!vma->vm_lock)
-		return false;
-
-	init_rwsem(&vma->vm_lock->lock);
-	vma->vm_lock_seq = UINT_MAX;
+	WARN_ON_ONCE(!refcount_read(&vma->vm_refcnt));
+}
 
-	return true;
+static inline void vma_assert_detached(struct vm_area_struct *vma)
+{
+	WARN_ON_ONCE(refcount_read(&vma->vm_refcnt));
 }
 
 static inline void vma_assert_write_locked(struct vm_area_struct *);
-static inline void vma_mark_detached(struct vm_area_struct *vma, bool detached)
+static inline void vma_mark_attached(struct vm_area_struct *vma)
 {
-	/* When detaching vma should be write-locked */
-	if (detached)
-		vma_assert_write_locked(vma);
-	vma->detached = detached;
+	vma_assert_write_locked(vma);
+	vma_assert_detached(vma);
+	refcount_set_release(&vma->vm_refcnt, 1);
+}
+
+static inline void vma_mark_detached(struct vm_area_struct *vma)
+{
+	vma_assert_write_locked(vma);
+	vma_assert_attached(vma);
+	/* We are the only writer, so no need to use vma_refcount_put(). */
+	if (unlikely(!refcount_dec_and_test(&vma->vm_refcnt))) {
+		/*
+		 * Reader must have temporarily raised vm_refcnt but it will
+		 * drop it without using the vma since vma is write-locked.
+		 */
+	}
 }
 
 extern const struct vm_operations_struct vma_dummy_vm_ops;
@@ -496,7 +502,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 	vma->vm_mm = mm;
 	vma->vm_ops = &vma_dummy_vm_ops;
 	INIT_LIST_HEAD(&vma->anon_vma_chain);
-	vma_mark_detached(vma, false);
+	vma->vm_lock_seq = UINT_MAX;
 }
 
 static inline struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
@@ -507,10 +513,6 @@ static inline struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
 		return NULL;
 
 	vma_init(vma, mm);
-	if (!vma_lock_alloc(vma)) {
-		free(vma);
-		return NULL;
-	}
 
 	return vma;
 }
@@ -523,10 +525,8 @@ static inline struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 		return NULL;
 
 	memcpy(new, orig, sizeof(*new));
-	if (!vma_lock_alloc(new)) {
-		free(new);
-		return NULL;
-	}
+	refcount_set(&new->vm_refcnt, 0);
+	new->vm_lock_seq = UINT_MAX;
 	INIT_LIST_HEAD(&new->anon_vma_chain);
 
 	return new;
@@ -696,20 +696,9 @@ static inline void mpol_put(struct mempolicy *)
 {
 }
 
-static inline void vma_lock_free(struct vm_area_struct *vma)
-{
-	free(vma->vm_lock);
-}
-
-static inline void __vm_area_free(struct vm_area_struct *vma)
-{
-	vma_lock_free(vma);
-	free(vma);
-}
-
 static inline void vm_area_free(struct vm_area_struct *vma)
 {
-	__vm_area_free(vma);
+	free(vma);
 }
 
 static inline void lru_add_drain(void)
@@ -796,12 +785,12 @@ static inline void vma_start_write(struct vm_area_struct *vma)
 static inline void vma_adjust_trans_huge(struct vm_area_struct *vma,
 					 unsigned long start,
 					 unsigned long end,
-					 long adjust_next)
+					 struct vm_area_struct *next)
 {
 	(void)vma;
 	(void)start;
 	(void)end;
-	(void)adjust_next;
+	(void)next;
 }
 
 static inline void vma_iter_free(struct vma_iterator *vmi)