The patch titled
Subject: mm: vma_adjust: remove superfluous confusing update in remove_next == 1 case
has been added to the -mm tree. Its filename is
mm-vma_adjust-remove-superfluous-confusing-update-in-remove_next-==-1-case.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-vma_adjust-remove-superfluous-confusing-update-in-remove_next-%3D%3D-1-case.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-vma_adjust-remove-superfluous-confusing-update-in-remove_next-%3D%3D-1-case.patch
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------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: mm: vma_adjust: remove superfluous confusing update in remove_next == 1 case
mm->highest_vm_end doesn't need any update.
After finally removing the oddness from vma_merge case 8 that was causing:
1) constant risk of trouble whenever anybody would check vma fields
from rmap_walks, like it happened when page migration was
introduced and it read the vma->vm_page_prot from a rmap_walk
2) the callers of vma_merge to re-initialize any value different from
the current vma, instead of vma_merge() more reliably returning a
vma that already matches all fields passed as parameter
... it is also worth to take the opportunity of cleaning up
superfluous code in vma_adjust(), that if not removed adds up to the
hard readability of the function.
Link: http://lkml.kernel.org/r/1474492522-2261-5-git-send-email-aarcange@xxxxxxxxxx
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Jan Vorlicek <janvorli@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff -puN mm/mmap.c~mm-vma_adjust-remove-superfluous-confusing-update-in-remove_next-==-1-case mm/mmap.c
--- a/mm/mmap.c~mm-vma_adjust-remove-superfluous-confusing-update-in-remove_next-==-1-case
+++ a/mm/mmap.c
@@ -812,8 +812,28 @@ again:
}
else if (next)
vma_gap_update(next);
- else
- mm->highest_vm_end = end;
+ else {
+ /*
+ * If remove_next == 2 we obviously can't
+ * reach this path.
+ *
+ * If remove_next == 3 we can't reach this
+ * path because pre-swap() next is always not
+ * NULL. pre-swap() "next" is not being
+ * removed and its next->vm_end is not altered
+ * (and furthermore "end" already matches
+ * next->vm_end in remove_next == 3).
+ *
+ * We reach this only in the remove_next == 1
+ * case if the "next" vma that was removed was
+ * the highest vma of the mm. However in such
+ * case next->vm_end == "end" and the extended
+ * "vma" has vma->vm_end == next->vm_end so
+ * mm->highest_vm_end doesn't need any update
+ * in remove_next == 1 case.
+ */
+ VM_WARN_ON(mm->highest_vm_end != end);
+ }
}
if (insert && file)
uprobe_mmap(insert);
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
mm-vm_page_prot-update-with-write_once-read_once.patch
mm-vma_adjust-remove-superfluous-confusing-update-in-remove_next-==-1-case.patch
mm-vma_merge-fix-vm_page_prot-smp-race-condition-against-rmap_walk.patch
mm-vma_adjust-remove-superfluous-check-for-next-not-null.patch
mm-vma_adjust-minor-comment-correction.patch
mm-vma_merge-correct-false-positive-from-__vma_unlink-validate_mm_rb.patch
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