Re: mm: kernel BUG at include/linux/swapops.h:131!

[Joonsoo Kim]

On Mon, Dec 23, 2013 at 10:01:10PM -0500, Sasha Levin wrote:
> On 12/23/2013 09:51 PM, Joonsoo Kim wrote:
> >On Mon, Dec 23, 2013 at 12:24:02PM -0500, Sasha Levin wrote:
> >>>Ping?
> >>>
> >>>I've also Cc'ed the "this page shouldn't be locked at all" team.
> >Hello,
> >
> >I can't find the reason of this problem.
> >If it is reproducible, how about bisecting?
> 
> While it reproduces under fuzzing it's pretty hard to bisect it with
> the amount of issues uncovered by trinity recently.
> 
> I can add any debug code to the site of the BUG if that helps.

Good!
It will be helpful to add dump_page() in migration_entry_to_page().

Thanks.

--------8<------
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index c0f7526..f695abc 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -3,6 +3,7 @@
 
 #include <linux/radix-tree.h>
 #include <linux/bug.h>
+#include <linux/mm.h>
 
 /*
  * swapcache pages are stored in the swapper_space radix tree.  We want to
@@ -128,6 +129,8 @@ static inline struct page *migration_entry_to_page(swp_entry_t entry)
         * Any use of migration entries may only occur while the
         * corresponding page is locked
         */
+       if (!PageLocked(p))
+               dump_page(p);
        BUG_ON(!PageLocked(p));
        return p;
 }

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