Re: 2.4.25 SMP - BUG at page_alloc.c:105

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Wed, Mar 24, 2004 at 12:28:06PM -0800, Andrew Morton wrote:
> Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
> >
> > 
> > The backtrace is odd to me. 
> > 
> > set_page_dirty() does not call __free_pages_ok() directly or indirectly.
> > 
> 
> I'd suspect that's just gunk on the stack and that zap_pte_range() freed an
> anonymous page which had a non-null ->mapping.  It could be a hardware bug.
> Without seeing the actual value of page->mapping it's hard to know.
> 
> It would be good to backport the bad_page() debug code so we get a bit more
> info when this sort of thing happens.

This should work. Matthias, please apply and try to reproduce.

--- mm/page_alloc.c.orig	2004-03-24 18:42:53.693251224 -0300
+++ mm/page_alloc.c	2004-03-24 18:47:52.484828000 -0300
@@ -81,6 +81,20 @@
  * -- wli
  */
 
+static void bad_page(const char *function, struct page *page)
+{
+        printk("Bad page state at %s\n", function);
+        printk("flags:0x%08lx mapping:%p buffers:%p count:%d\n",
+                page->flags, page->mapping,
+		page->buffers, page_count(page));
+        printk("Backtrace:\n");
+        dump_stack();
+	printk("bad_page: Trying to fix it up.\n");
+        set_page_count(page, 0);
+        page->mapping = NULL;
+}
+
+
 static void FASTCALL(__free_pages_ok (struct page *page, unsigned int order));
 static void __free_pages_ok (struct page *page, unsigned int order)
 {
@@ -101,8 +115,8 @@
 
 	if (page->buffers)
 		BUG();
-	if (page->mapping)
-		BUG();
+	if (page->mapping) 
+		bad_page(page);
 	if (!VALID_PAGE(page))
 		BUG();
 	if (PageLocked(page))