linux-kernel - [PATCH v3 21/66] mm/mmap: Convert count_vma_pages_range() to use ma

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Date:   Tue, 5 Oct 2021 01:30:45 +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>,
        David Hildenbrand <david@...hat.com>,
        Douglas Gilbert <dgilbert@...erlog.com>
CC:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        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 v3 21/66] mm/mmap: Convert count_vma_pages_range() to use
 ma_state

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

mmap_region() uses a maple state to do all the work so convert the
static inline count_vma_pages_range() to use the same structure.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 54838406518d..ec3eac307a25 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -500,30 +500,41 @@ static inline struct vm_area_struct *vma_next(struct mm_struct *mm,
 	return vma->vm_next;
 }
 
-static unsigned long count_vma_pages_range(struct mm_struct *mm,
-		unsigned long addr, unsigned long end)
+/*
+ * count_vma_pages_range() - Count the number of pages in a range.
+ * @mas: The maple state
+ *
+ * The start and end address are in the @mas
+ * @mas must be locked.
+ */
+static unsigned long count_vma_pages_range(struct ma_state *mas)
 {
 	unsigned long nr_pages = 0;
 	struct vm_area_struct *vma;
 	unsigned long vm_start, vm_end;
-	MA_STATE(mas, &mm->mm_mt, addr, addr);
+	unsigned long end = mas->last;
+	unsigned long addr = mas->index;
+	struct ma_state ma_count = *mas;
 
+	rcu_read_lock();
 	/* Find first overlapping mapping */
-	vma = mas_find(&mas, end - 1);
+	vma = mas_find(&ma_count, end);
 	if (!vma)
-		return 0;
+		goto unlock;
 
 	vm_start = vma->vm_start;
 	vm_end = vma->vm_end;
-	nr_pages = (min(end, vm_end) - max(addr, vm_start)) >> PAGE_SHIFT;
+	nr_pages = (min(end + 1, vm_end) - max(addr, vm_start)) >> PAGE_SHIFT;
 
 	/* Iterate over the rest of the overlaps */
-	mas_for_each(&mas, vma, end) {
+	mas_for_each(&ma_count, vma, end) {
 		vm_start = vma->vm_start;
 		vm_end = vma->vm_end;
 		nr_pages += (min(end, vm_end) - vm_start) >> PAGE_SHIFT;
 	}
 
+unlock:
+	rcu_read_unlock();
 	return nr_pages;
 }
 
@@ -2599,7 +2610,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		 * MAP_FIXED may remove pages of mappings that intersects with
 		 * requested mapping. Account for the pages it would unmap.
 		 */
-		nr_pages = count_vma_pages_range(mm, addr, end);
+		nr_pages = count_vma_pages_range(&mas);
 
 		if (!may_expand_vm(mm, vm_flags,
 					(len >> PAGE_SHIFT) - nr_pages))
-- 
2.30.2