linux-kernel - [PATCH v2 16/61] mm: Use maple tree operations for find_vma_intersection() and find

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Message-ID: <20210817154651.1570984-17-Liam.Howlett@oracle.com>
Date:   Tue, 17 Aug 2021 15:47:13 +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>
CC:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.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>,
        Michel Lespinasse <walken.cr@...il.com>,
        Liam Howlett <liam.howlett@...cle.com>
Subject: [PATCH v2 16/61] mm: Use maple tree operations for
 find_vma_intersection() and find_vma()

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

Move find_vma_intersection() to mmap.c and change implementation to
maple tree.

When searching for a vma within a range, it is easier to use the maple
tree interface.  This means the find_vma() call changes to a special
case of the find_vma_intersection().

Exported for kvm module.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 include/linux/mm.h | 25 ++++++-------------------
 mm/mmap.c          | 38 ++++++++++++++++++++++++++++----------
 2 files changed, 34 insertions(+), 29 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a3086474d8d2..10763bd6fccb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2774,26 +2774,13 @@ extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long add
 extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,
 					     struct vm_area_struct **pprev);
 
-/**
- * find_vma_intersection() - Look up the first VMA which intersects the interval
- * @mm: The process address space.
- * @start_addr: The inclusive start user address.
- * @end_addr: The exclusive end user address.
- *
- * Returns: The first VMA within the provided range, %NULL otherwise.  Assumes
- * start_addr < end_addr.
+/*
+ * Look up the first VMA which intersects the interval [start_addr, end_addr)
+ * NULL if none.  Assume start_addr < end_addr.
  */
-static inline
-struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
-					     unsigned long start_addr,
-					     unsigned long end_addr)
-{
-	struct vm_area_struct *vma = find_vma(mm, start_addr);
-
-	if (vma && end_addr <= vma->vm_start)
-		vma = NULL;
-	return vma;
-}
+extern struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
+						    unsigned long start_addr,
+						    unsigned long end_addr);
 
 /**
  * vma_lookup() - Find a VMA at a specific address
diff --git a/mm/mmap.c b/mm/mmap.c
index 3d88fc87c289..9b86f47f7387 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2052,32 +2052,50 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
 EXPORT_SYMBOL(get_unmapped_area);
 
 /**
- * find_vma() - Find the VMA for a given address, or the next vma.
- * @mm: The mm_struct to check
- * @addr: The address
+ * find_vma_intersection() - Look up the first VMA which intersects the interval
+ * @mm: The process address space.
+ * @start_addr: The inclusive start user address.
+ * @end_addr: The exclusive end user address.
  *
- * Returns: The VMA associated with addr, or the next vma.
- * May return %NULL in the case of no vma at addr or above.
+ * Returns: The first VMA within the provided range, %NULL otherwise.  Assumes
+ * start_addr < end_addr.
  */
-struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
+					     unsigned long start_addr,
+					     unsigned long end_addr)
 {
 	struct vm_area_struct *vma;
-	MA_STATE(mas, &mm->mm_mt, addr, addr);
+	MA_STATE(mas, &mm->mm_mt, start_addr, start_addr);
 
 	mmap_assert_locked(mm);
 	/* Check the cache first. */
-	vma = vmacache_find(mm, addr);
+	vma = vmacache_find(mm, start_addr);
 	if (likely(vma))
 		return vma;
 
 	rcu_read_lock();
-	vma = mas_find(&mas, -1);
+	vma = mas_find(&mas, end_addr - 1);
 	rcu_read_unlock();
 	if (vma)
-		vmacache_update(addr, vma);
+		vmacache_update(mas.index, vma);
 
 	return vma;
 }
+EXPORT_SYMBOL(find_vma_intersection);
+
+/**
+ * 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.
+ */
+inline struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+{
+	// Note find_vma_intersection will decrease 0 to underflow to ULONG_MAX
+	return find_vma_intersection(mm, addr, 0);
+}
 EXPORT_SYMBOL(find_vma);
 
 /**
-- 
2.30.2