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mm/mmap/vma_merge: fold curr, next assignment logic

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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.

Link: https://lkml.kernel.org/r/c6d960641b4ba58fa6ad3d07bf68c27d847963c8.1679516210.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vernon Yang <vernon2gm@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2023-03-22 20:18:58 +00:00
committed by Andrew Morton
parent fcfccd9184
commit 00cd00a6a2
1 changed files with 11 additions and 13 deletions
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24
mm/mmap.c
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@@ -917,15 +917,14 @@ 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);
@@ -946,11 +945,10 @@ 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;
}