On Wed, Oct 10, 2018 at 08:53:27PM +0800, Wei Yang wrote:
> A non-NULL vma returned from find_vma() implies:
>
> vma->vm_start <= start
> Since len != 0, the following condition always hods:
s/hods/holds/
> vma->vm_start < start + len = end
>
> This means the if check would never be true.
Have you considered overflow?
> This patch removes this redundant check and fix two typo in comment.
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> ---
> mm/mmap.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 8d6449e74431..94660ddfa2c1 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -414,7 +414,7 @@ static void vma_gap_update(struct vm_area_struct *vma)
> {
> /*
> * As it turns out, RB_DECLARE_CALLBACKS() already created a callback
> - * function that does exacltly what we want.
> + * function that does exactly what we want.
> */
> vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
> }
> @@ -1621,7 +1621,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
> #endif /* __ARCH_WANT_SYS_OLD_MMAP */
>
> /*
> - * Some shared mappigns will want the pages marked read-only
> + * Some shared mappings will want the pages marked read-only
> * to track write events. If so, we'll downgrade vm_page_prot
> * to the private version (using protection_map[] without the
> * VM_SHARED bit).
> @@ -2705,12 +2705,8 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
> if (!vma)
> return 0;
> prev = vma->vm_prev;
> - /* we have start < vma->vm_end */
> -
> - /* if it doesn't overlap, we have nothing.. */
> + /* we have vma->vm_start <= start < vma->vm_end */
> end = start + len;
> - if (vma->vm_start >= end)
> - return 0;
>
> /*
> * If we need to split any vma, do it now to save pain later.
> --
> 2.15.1
>
--
Kirill A. Shutemov
