[PATCH v4 43/66] userfaultfd: Use maple tree iterator to iterate VMAs

[Liam Howlett <liam.howlett@oracle.com>]

From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

Don't use the mm_struct linked list or the vma->vm_next in prep for removal

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 fs/userfaultfd.c              | 49 ++++++++++++++++++++++-------------
 include/linux/userfaultfd_k.h |  7 +++--
 mm/mmap.c                     | 12 ++++-----
 3 files changed, 40 insertions(+), 28 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 22bf14ab2d16..2880025598c7 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -606,14 +606,16 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
 	if (release_new_ctx) {
 		struct vm_area_struct *vma;
 		struct mm_struct *mm = release_new_ctx->mm;
+		VMA_ITERATOR(vmi, mm, 0);
 
 		/* the various vma->vm_userfaultfd_ctx still points to it */
 		mmap_write_lock(mm);
-		for (vma = mm->mmap; vma; vma = vma->vm_next)
+		for_each_vma(vmi, vma) {
 			if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
 				vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 				vma->vm_flags &= ~__VM_UFFD_FLAGS;
 			}
+		}
 		mmap_write_unlock(mm);
 
 		userfaultfd_ctx_put(release_new_ctx);
@@ -794,11 +796,13 @@ static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
 	return false;
 }
 
-int userfaultfd_unmap_prep(struct vm_area_struct *vma,
-			   unsigned long start, unsigned long end,
-			   struct list_head *unmaps)
+int userfaultfd_unmap_prep(struct mm_struct *mm, unsigned long start,
+			   unsigned long end, struct list_head *unmaps)
 {
-	for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
+	VMA_ITERATOR(vmi, mm, start);
+	struct vm_area_struct *vma;
+
+	for_each_vma_range(vmi, vma, end) {
 		struct userfaultfd_unmap_ctx *unmap_ctx;
 		struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
 
@@ -848,6 +852,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
 	/* len == 0 means wake all */
 	struct userfaultfd_wake_range range = { .len = 0, };
 	unsigned long new_flags;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
 
 	WRITE_ONCE(ctx->released, true);
 
@@ -864,7 +869,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
 	 */
 	mmap_write_lock(mm);
 	prev = NULL;
-	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+	mas_for_each(&mas, vma, ULONG_MAX) {
 		cond_resched();
 		BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
 		       !!(vma->vm_flags & __VM_UFFD_FLAGS));
@@ -1281,6 +1286,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 	bool found;
 	bool basic_ioctls;
 	unsigned long start, end, vma_end;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
 
 	user_uffdio_register = (struct uffdio_register __user *) arg;
 
@@ -1323,7 +1329,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 		goto out;
 
 	mmap_write_lock(mm);
-	vma = find_vma_prev(mm, start, &prev);
+	mas_set(&mas, start);
+	vma = mas_find(&mas, ULONG_MAX);
 	if (!vma)
 		goto out_unlock;
 
@@ -1348,7 +1355,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 	 */
 	found = false;
 	basic_ioctls = false;
-	for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
+	for (cur = vma; cur; cur = mas_next(&mas, end - 1)) {
 		cond_resched();
 
 		BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
@@ -1408,8 +1415,10 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 	}
 	BUG_ON(!found);
 
-	if (vma->vm_start < start)
-		prev = vma;
+	mas_set(&mas, start);
+	prev = mas_prev(&mas, 0);
+	if (prev != vma)
+		mas_next(&mas, ULONG_MAX);
 
 	ret = 0;
 	do {
@@ -1466,8 +1475,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 	skip:
 		prev = vma;
 		start = vma->vm_end;
-		vma = vma->vm_next;
-	} while (vma && vma->vm_start < end);
+		vma = mas_next(&mas, end - 1);
+	} while (vma);
 out_unlock:
 	mmap_write_unlock(mm);
 	mmput(mm);
@@ -1511,6 +1520,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 	bool found;
 	unsigned long start, end, vma_end;
 	const void __user *buf = (void __user *)arg;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
 
 	ret = -EFAULT;
 	if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
@@ -1529,7 +1539,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 		goto out;
 
 	mmap_write_lock(mm);
-	vma = find_vma_prev(mm, start, &prev);
+	mas_set(&mas, start);
+	vma = mas_find(&mas, ULONG_MAX);
 	if (!vma)
 		goto out_unlock;
 
@@ -1554,7 +1565,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 	 */
 	found = false;
 	ret = -EINVAL;
-	for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
+	for (cur = vma; cur; cur = mas_next(&mas, end - 1)) {
 		cond_resched();
 
 		BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
@@ -1574,8 +1585,10 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 	}
 	BUG_ON(!found);
 
-	if (vma->vm_start < start)
-		prev = vma;
+	mas_set(&mas, start);
+	prev = mas_prev(&mas, 0);
+	if (prev != vma)
+		mas_next(&mas, ULONG_MAX);
 
 	ret = 0;
 	do {
@@ -1640,8 +1653,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 	skip:
 		prev = vma;
 		start = vma->vm_end;
-		vma = vma->vm_next;
-	} while (vma && vma->vm_start < end);
+		vma = mas_next(&mas, end - 1);
+	} while (vma);
 out_unlock:
 	mmap_write_unlock(mm);
 	mmput(mm);
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 33cea484d1ad..e0b2ec2c20f2 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -139,9 +139,8 @@ extern bool userfaultfd_remove(struct vm_area_struct *vma,
 			       unsigned long start,
 			       unsigned long end);
 
-extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
-				  unsigned long start, unsigned long end,
-				  struct list_head *uf);
+extern int userfaultfd_unmap_prep(struct mm_struct *mm, unsigned long start,
+				  unsigned long end, struct list_head *uf);
 extern void userfaultfd_unmap_complete(struct mm_struct *mm,
 				       struct list_head *uf);
 
@@ -222,7 +221,7 @@ static inline bool userfaultfd_remove(struct vm_area_struct *vma,
 	return true;
 }
 
-static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
+static inline int userfaultfd_unmap_prep(struct mm_struct *mm,
 					 unsigned long start, unsigned long end,
 					 struct list_head *uf)
 {
diff --git a/mm/mmap.c b/mm/mmap.c
index 79b8494d83c6..dde74e0b195d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2449,7 +2449,7 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 		 * split, despite we could. This is unlikely enough
 		 * failure that it's not worth optimizing it for.
 		 */
-		int error = userfaultfd_unmap_prep(vma, start, end, uf);
+		int error = userfaultfd_unmap_prep(mm, start, end, uf);
 
 		if (error)
 			return error;
@@ -2938,10 +2938,7 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 		goto munmap_full_vma;
 	}
 
-	vma_init(&unmap, mm);
-	unmap.vm_start = newbrk;
-	unmap.vm_end = oldbrk;
-	ret = userfaultfd_unmap_prep(&unmap, newbrk, oldbrk, uf);
+	ret = userfaultfd_unmap_prep(mm, newbrk, oldbrk, uf);
 	if (ret)
 		return ret;
 	ret = 1;
@@ -2954,6 +2951,9 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 	}
 
 	vma->vm_end = newbrk;
+	vma_init(&unmap, mm);
+	unmap.vm_start = newbrk;
+	unmap.vm_end = oldbrk;
 	if (vma_mas_remove(&unmap, mas))
 		goto mas_store_fail;
 
@@ -2963,7 +2963,7 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 	}
 
 	unmap_pages = vma_pages(&unmap);
-	if (unmap.vm_flags & VM_LOCKED) {
+	if (vma->vm_flags & VM_LOCKED) {
 		mm->locked_vm -= unmap_pages;
 		munlock_vma_pages_range(&unmap, newbrk, oldbrk);
 	}
-- 
2.30.2