Re: [PATCH 1/3] mm: generalize VM_BUG_ON() macros

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

Andrew Morton wrote:
> On Wed,  1 Oct 2014 14:31:59 +0300 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:
> 
> > This patch makes VM_BUG_ON() to accept one to three arguments after the
> > condition. Any of these arguments can be page, vma or mm. VM_BUG_ON()
> > will dump info about the argument using appropriate dump_* function.
> > 
> > It's intended to replace separate VM_BUG_ON_PAGE(), VM_BUG_ON_VMA(),
> > VM_BUG_ON_MM() and allows additional use-cases like:
> > 
> >   VM_BUG_ON(cond, vma, page);
> >   VM_BUG_ON(cond, vma, src_page, dst_page);
> >   VM_BUG_ON(cond, mm, src_vma, dst_vma);
> >   ...
> 
> I can't say I'm a fan of this.  We don't do this sort of thing anywhere
> else in the kernel and passing different types to the same thing in
> different places is unusual and exceptional.  We gain very little from
> this so why bother?

We had bug like this: lkml.kernel.org/r/53F487EB.7070703@oracle.com where
it's useful to see more than one structure dumped: vma + page in this
case.

We can keep inventing new macros: VM_BUG_ON_PAGE_AND_VM() for the case.
But why not have one to rule them all? ;)

-- 
 Kirill A. Shutemov

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