linux-kernel - [PATCH v2 09/70] mm/mmap: Change find_vma

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Date:   Tue, 12 Jan 2021 11:11:39 -0500
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...gle.com>, Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jerome Glisse <jglisse@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v2 09/70] mm/mmap: Change find_vma_prev() to use maple tree

Change the implementation of find_vma_prev to use the new maple tree
data structure.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index ab1cb0efc4c65..f123f9c97dfe8 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2500,23 +2500,30 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
 }
 EXPORT_SYMBOL(find_vma);
 
-/*
- * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
+/**
+ * find_vma_prev() - Find the VMA for a given address, or the next vma and
+ * sets %pprev to the previous VMA, if any.
+ * @mm The mm_struct to check
+ * @addr: The address
+ * @pprev: The pointer to set to the previous VMA
+ *
+ * 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_prev(struct mm_struct *mm, unsigned long addr,
-			struct vm_area_struct **pprev)
+	      struct vm_area_struct **pprev)
 {
 	struct vm_area_struct *vma;
+	MA_STATE(mas, &mm->mm_mt, addr, addr);
 
-	vma = find_vma(mm, addr);
-	if (vma) {
-		*pprev = vma->vm_prev;
-	} else {
-		struct rb_node *rb_node = rb_last(&mm->mm_rb);
+	rcu_read_lock();
+	vma = mas_find(&mas, ULONG_MAX);
+	if (!vma)
+		mas_reset(&mas);
 
-		*pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
-	}
+	*pprev = mas_prev(&mas, 0);
+	rcu_read_unlock();
 	return vma;
 }
 
-- 
2.28.0