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 @@ -817,8 +817,28 @@ 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); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
