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.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
mm/mmap.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 57b1eaf..bf2dc6b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -915,8 +915,28 @@ 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);
--
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