mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE

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.

[akpm@linux-foundation.org: fix up includes]
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 580bd58..5042c03 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -1,10 +1,19 @@
 #ifndef LINUX_MM_DEBUG_H
 #define LINUX_MM_DEBUG_H 1
 
+struct page;
+
+extern void dump_page(struct page *page, char *reason);
+extern void dump_page_badflags(struct page *page, char *reason,
+			       unsigned long badflags);
+
 #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)
 #else
 #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
+#define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
 #endif
 
 #ifdef CONFIG_DEBUG_VIRTUAL