Commit e4f67422 authored Jun 04, 2014 by Dave Hansen Committed by Linus Torvalds Jun 04, 2014

mm: pass VM_BUG_ON() reason to dump_page()



I recently added a patch to let folks pass a "reason" string dump_page()
which gets dumped out along with the page's data.  This essentially
saves the bug-reader a trip in to the source to figure out why we
BUG_ON()'d.

The new VM_BUG_ON_PAGE() passes in NULL for "reason".  It seems like we
might as well pass the BUG_ON() condition if we have it.  This will
bloat kernels a bit with ~160 new strings, but this is all under a
debugging option anyway.

	page:ffffea0008560280 count:1 mapcount:0 mapping:(null) index:0x0
	page flags: 0xbfffc0000000001(locked)
	page dumped because: VM_BUG_ON_PAGE(PageLocked(page))
	------------[ cut here ]------------
	kernel BUG at /home/davehans/linux.git/mm/filemap.c:464!
	invalid opcode: 0000 [#1] SMP
	CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.14.0+ #251
	Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
	...

[akpm@linux-foundation.org: include stringify.h]
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 3dae7fec

include/linux/mmdebug.h

+9 −2

Original line number	Diff line number	Diff line
		#ifndef LINUX_MM_DEBUG_H
		#define LINUX_MM_DEBUG_H 1

		#include <linux/stringify.h>

		struct page;

		extern void dump_page(struct page page, const char reason);
		@@ -10,7 +12,12 @@ extern void dump_page_badflags(struct page page, const char reason,
		#ifdef CONFIG_DEBUG_VM
		#define VM_BUG_ON(cond) BUG_ON(cond)
		#define VM_BUG_ON_PAGE(cond, page) \
		do { if (unlikely(cond)) { dump_page(page, NULL); BUG(); } } while (0)
		do { \
		if (unlikely(cond)) { \
		dump_page(page, "VM_BUG_ON_PAGE(" __stringify(cond)")");\
		BUG(); \
		} \
		} while (0)
		#define VM_WARN_ON(cond) WARN_ON(cond)
		#define VM_WARN_ON_ONCE(cond) WARN_ON_ONCE(cond)
		#else

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