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mm/mmap/vma_merge: use the proper vma pointers in cases 1 and 6 

Case 1 is now shown in the comment as next vma being merged with prev, so
use 'next' instead of 'mid'.  In case 1 they both point to the same vma.

As a consequence, in case 6, the dup_anon_vma() is now tried first on
'next' and then on 'mid', before it was the opposite order.  This is not a
functional change, as those two vma's cannnot have a different anon_vma,
as that would have prevented the merging in the first place.

Link: https://lkml.kernel.org/r/20230309111258.24079-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2023-03-09 12:12:51 +01:00 committed by Andrew Morton
parent 097d70c627
commit 5ff783f151
1 changed files with 6 additions and 5 deletions
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11
mm/mmap.c
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@ -605,7 +605,7 @@ again:
/*
* In mprotect's case 6 (see comments on vma_merge),
* we must remove the one after next as well.
* we are removing both mid and next vmas
*/
if (vp->remove2) {
vp->remove = vp->remove2;
@ -948,13 +948,14 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
/* Can we merge both the predecessor and the successor? */
if (merge_prev && merge_next &&
is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) {
remove = mid; /* case 1 */
remove = next; /* case 1 */
vma_end = next->vm_end;
err = dup_anon_vma(prev, mid);
err = dup_anon_vma(prev, next);
if (mid != next) { /* case 6 */
remove = mid;
remove2 = next;
if (!mid->anon_vma)
err = dup_anon_vma(prev, next);
if (!next->anon_vma)
err = dup_anon_vma(prev, mid);
}
} else if (merge_prev) {
err = 0; /* case 2 */