linux-kernel - [PATCH v7 13/70] mm/mmap: Use the maple tree in find

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Date:   Mon, 4 Apr 2022 14:35:37 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v7 13/70] mm/mmap: Use the maple tree in find_vma() instead of
 the rbtree.

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

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@...cle.com>
Acked-by: Vlastimil Babka <vbabka@...e.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