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Message-Id: <36399b6cdc843eb7fe243488ea9b29464f699170.1679468982.git.lstoakes@gmail.com>
Date: Wed, 22 Mar 2023 07:13:02 +0000
From: Lorenzo Stoakes <lstoakes@...il.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
maple-tree@...ts.infradead.org, Vernon Yang <vernon2gm@...il.com>,
Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH v3 2/4] mm/mmap/vma_merge: fold curr, next assignment logic
Use find_vma_intersection() and vma_lookup() to both simplify the logic and
to fold the end == next->vm_start condition into one block.
This groups all of the simple range checks together and establishes the
invariant that, if prev, curr or next are non-NULL then their positions are
as expected.
This has no functional impact.
Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
---
mm/mmap.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index c9834364ac98..dbdbb92493b2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -930,15 +930,14 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
if (vm_flags & VM_SPECIAL)
return NULL;
- curr = find_vma(mm, prev ? prev->vm_end : 0);
- if (curr && curr->vm_end == end) /* cases 6, 7, 8 */
- next = find_vma(mm, curr->vm_end);
- else
- next = curr;
+ /* Does the input range span an existing VMA? (cases 5 - 8) */
+ curr = find_vma_intersection(mm, prev ? prev->vm_end : 0, end);
- /* In cases 1 - 4 there's no CCCC vma */
- if (curr && end <= curr->vm_start)
- curr = NULL;
+ if (!curr || /* cases 1 - 4 */
+ end == curr->vm_end) /* cases 6 - 8, adjacent VMA */
+ next = vma_lookup(mm, end);
+ else
+ next = NULL; /* case 5 */
/* verify some invariant that must be enforced by the caller */
VM_WARN_ON(prev && addr <= prev->vm_start);
@@ -959,11 +958,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
}
}
/* Can we merge the successor? */
- if (next && end == next->vm_start &&
- mpol_equal(policy, vma_policy(next)) &&
- can_vma_merge_before(next, vm_flags,
- anon_vma, file, pgoff+pglen,
- vm_userfaultfd_ctx, anon_name)) {
+ if (next && mpol_equal(policy, vma_policy(next)) &&
+ can_vma_merge_before(next, vm_flags,
+ anon_vma, file, pgoff+pglen,
+ vm_userfaultfd_ctx, anon_name)) {
merge_next = true;
}
--
2.39.2
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