[PATCH v10 11/69] mm/mmap: use the maple tree in find_vma() instead of the rbtree.

[Liam Howlett]

From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>

Using the maple tree interface mt_find() will handle the RCU locking and
will start searching at the address up to the limit, ULONG_MAX in this
case.

Add kernel documentation to this API.

Link: https://lkml.kernel.org/r/20220504010716.661115-13-Liam.Howlett@xxxxxxxxxx
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 mm/mmap.c | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index d7e6baa2f40f..fdb61252448f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2486,11 +2486,18 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
 
 EXPORT_SYMBOL(get_unmapped_area);
 
-/* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
+/**
+ * find_vma() - Find the VMA for a given address, or the next vma.
+ * @mm: The mm_struct to check
+ * @addr: The address
+ *
+ * Returns: The VMA associated with addr, or the next vma.
+ * May return %NULL in the case of no vma at addr or above.
+ */
 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 {
-	struct rb_node *rb_node;
 	struct vm_area_struct *vma;
+	unsigned long index = addr;
 
 	mmap_assert_locked(mm);
 	/* Check the cache first. */
@@ -2498,22 +2505,7 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 	if (likely(vma))
 		return vma;
 
-	rb_node = mm->mm_rb.rb_node;
-
-	while (rb_node) {
-		struct vm_area_struct *tmp;
-
-		tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
-
-		if (tmp->vm_end > addr) {
-			vma = tmp;
-			if (tmp->vm_start <= addr)
-				break;
-			rb_node = rb_node->rb_left;
-		} else
-			rb_node = rb_node->rb_right;
-	}
-
+	vma = mt_find(&mm->mm_mt, &index, ULONG_MAX);
 	if (vma)
 		vmacache_update(addr, vma);
 	return vma;
-- 
2.35.1