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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@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jan Vorlicek <janvorli@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2016-10-07 17:01:25 -07:00 committed by Linus Torvalds
parent 6d2329f887
commit fb8c41e9ad
1 changed files with 22 additions and 2 deletions
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24
mm/mmap.c
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@ -817,8 +817,28 @@ int vma_adjust(struct vm_area_struct *vma, unsigned long start,
}
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);