[PATCH v7 13/70] mm/mmap: Use the maple tree in find_vma() instead of the rbtree.

Liam Howlett
2022-04-04T14:37:44Z

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.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/mmap.c | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 3b4351f384b5..4b1f0e95375e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2424,11 +2424,18 @@ 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. */
@@ -2436,22 +2443,7 @@ 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;
--
2.34.1