Commit fb8c41e9 authored Oct 07, 2016 by Andrea Arcangeli Committed by Linus Torvalds Oct 07, 2016

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>

parent 6d2329f8

mm/mmap.c

+22 −2

Original line number	Diff line number	Diff line
		@@ -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);