Re: [PATCH] mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE

[Sasha Levin]

On 12/27/2013 05:38 AM, Kirill A. Shutemov wrote:
> On Thu, Dec 26, 2013 at 10:20:52PM -0500, Sasha Levin wrote:
> > Most of the VM_BUG_ON assertions are performed on a page. Usually, when
> > one of these assertions fails we'll get a BUG_ON with a call stack and
> > the registers.
> >
> > I've recently noticed based on the requests to add a small piece of code
> > that dumps the page to various VM_BUG_ON sites that the page dump is quite
> > useful to people debugging issues in mm.
> >
> > This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what
> > VM_BUG_ON() does, also dumps the page before executing the actual BUG_ON.
> >
> > Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
>
> I like the idea. One thing I've noticed you have a lot of page flag based
> asserts, like:
>
> 	VM_BUG_ON_PAGE(PageLRU(page), page);
> 	VM_BUG_ON_PAGE(!PageLocked(page), page);
>
> What about adding per-page-flag assert macros, like:
>
> 	PageNotLRU_assert(page);
> 	PageLocked_assert(page);
>
> ? This way we will always dump right page on bug.

Sure, sounds good.

I'll send another patch on top of this one.


Thanks,
Sasha
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