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

From: Sasha Levin
Date: Fri Dec 27 2013 - 18:19:39 EST

On 12/26/2013 10:20 PM, 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.

Somewhat related to that, I've tried adding a VM_BUG_ON_PAGE in SetPageXXX()
and ClearPageXXX macros to catch cases where page flags are being set or
cleared twice.

There seems to be a lot of those...

Is that a valid use? Or should it be fixed?

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