Re: [PATCH] mm: rmap: use VM_BUG_ON() in __page_check_anon_rmap()

[Yang Shi]

On 11/6/19 12:28 AM, Kirill A. Shutemov wrote:
> On Wed, Nov 06, 2019 at 01:03:36AM +0800, Yang Shi wrote:
> > The __page_check_anon_rmap() just calls two BUG_ON()s protected by
> > CONFIG_DEBUG_VM, the #ifdef could be eliminated by using VM_BUG_ON().
> >
> > Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> > ---
> >   mm/rmap.c | 6 ++----
> >   1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/rmap.c b/mm/rmap.c
> > index d17cbf3..39178eb 100644
> > --- a/mm/rmap.c
> > +++ b/mm/rmap.c
> > @@ -1055,7 +1055,6 @@ static void __page_set_anon_rmap(struct page *page,
> >   static void __page_check_anon_rmap(struct page *page,
> >   	struct vm_area_struct *vma, unsigned long address)
> >   {
> > -#ifdef CONFIG_DEBUG_VM
> >   	/*
> >   	 * The page's anon-rmap details (mapping and index) are guaranteed to
> >   	 * be set up correctly at this point.
> > @@ -1068,9 +1067,8 @@ static void __page_check_anon_rmap(struct page *page,
> >   	 * are initially only visible via the pagetables, and the pte is locked
> >   	 * over the call to page_add_new_anon_rmap.
> >   	 */
> > -	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
> > -	BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
> > -#endif
> > +	VM_BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
> > +	VM_BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
> Why not VM_BUG_ON_PAGE()?

Because I was not intended to change the behavior, just cleanup. We 
definitely could use VM_BUG_ON_PAGE() if that is preferred.

>