Messages in this thread Patch in this message | | | From | Lorenzo Stoakes <> | Subject | [PATCH v3 2/4] mm/mmap/vma_merge: fold curr, next assignment logic | Date | Wed, 22 Mar 2023 07:13:02 +0000 |
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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@gmail.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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