* Yajun Deng <yajun.deng@xxxxxxxxx> [240129 02:53]:
> There are vma_merge() and do_brk_flags() pass mm to vma_complete(), others
> would pass the vma->vm_mm. The following explains that the mm is the
> vma->vm_mm in vma_merge() and do_brk_flags().
>
> All vma will point to the same mm struct if the vma_merge() is successful.
> So the mm and the vma->mm are the same.
Absolutely, they must be the same. I don't think vma_merge() checks
this, but it is true.
>
> vm_brk_flags() and brk syscall will initialize vmi with current->mm,
> so the vma->vm_mm and the current->mm are the same if vma exists in
> do_brk_flags().
>
> Remove the mm parameter in vma_complete() and get mm from the vma in vp.
You have added a dereference to the two paths that don't need it to
reduce the argument list from 3 to 2. It's the same number of lines as
well. vma_shrink() is only used on process creation, but brk is more
common. Note that this function is marked as inline.
I'm not sure this change is worth making.
>
> Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
> ---
> mm/mmap.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e97b9144c61a..9b968d1edf55 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -509,11 +509,11 @@ static inline void vma_prepare(struct vma_prepare *vp)
> *
> * @vp: The vma_prepare struct
> * @vmi: The vma iterator
> - * @mm: The mm_struct
> */
> -static inline void vma_complete(struct vma_prepare *vp,
> - struct vma_iterator *vmi, struct mm_struct *mm)
> +static inline void vma_complete(struct vma_prepare *vp, struct vma_iterator *vmi)
> {
> + struct mm_struct *mm = vp->vma->vm_mm;
> +
> if (vp->file) {
> if (vp->adj_next)
> vma_interval_tree_insert(vp->adj_next,
> @@ -666,7 +666,7 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
> vma_set_range(vma, start, end, pgoff);
> vma_iter_store(vmi, vma);
>
> - vma_complete(&vp, vmi, vma->vm_mm);
> + vma_complete(&vp, vmi);
> return 0;
>
> nomem:
> @@ -707,7 +707,7 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
>
> vma_iter_clear(vmi);
> vma_set_range(vma, start, end, pgoff);
> - vma_complete(&vp, vmi, vma->vm_mm);
> + vma_complete(&vp, vmi);
> return 0;
> }
>
> @@ -1030,7 +1030,7 @@ static struct vm_area_struct
> }
> }
>
> - vma_complete(&vp, vmi, mm);
> + vma_complete(&vp, vmi);
> khugepaged_enter_vma(res, vm_flags);
> return res;
>
> @@ -2377,7 +2377,7 @@ static int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
> }
>
> /* vma_complete stores the new vma */
> - vma_complete(&vp, vmi, vma->vm_mm);
> + vma_complete(&vp, vmi);
>
> /* Success. */
> if (new_below)
> @@ -3145,7 +3145,7 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
> vm_flags_set(vma, VM_SOFTDIRTY);
> vma_iter_store(vmi, vma);
>
> - vma_complete(&vp, vmi, mm);
> + vma_complete(&vp, vmi);
> khugepaged_enter_vma(vma, flags);
> goto out;
> }
> --
> 2.25.1
>
>
