Re: [PATCH] mm: mempolicy: use VM_BUG_ON_VMA in queue_pages_test_walk()

[Yang Shi]

On 1/15/20 4:08 AM, Li Xinhai wrote:
> On 2020-01-15Âat 14:09ÂYang ShiÂwrote:
> > The VM_BUG_ON() is already used by queue_pages_test_walk(), it sounds
> > better to dump more debug information by using VM_BUG_ON_VMA() to help
> > debugging.
> >
> > Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> The .test_walk() is to be called from pagewalk with the rule that 'start'
> and 'end' must within range of vma, in case the rule is broke, we detect
> it. This is not quite relevant to a bug of particular vma.

But when you run into VMA range check failure, isn't it helpful to dump 
the VMA range information to ease debugging? And, VM_BUG_ON is already 
used in the code, I'm supposed the users may prefer more debug 
information dumped for debug kernel.

> > ---
> > mm/mempolicy.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 067cf7d..801d45d 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -621,7 +621,7 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
> > unsigned long flags = qp->flags;
> >
> > /* range check first */
> > -	VM_BUG_ON((vma->vm_start > start) || (vma->vm_end < end));
> > +	VM_BUG_ON_VMA((vma->vm_start > start) || (vma->vm_end < end), vma);
> >
> > if (!qp->first) {
> > qp->first = vma;
> > --
> > 1.8.3.1
> >