Nicolas wrote:

>kernel BUG at mm/slab.c:1631!
>
 That's
      BUG_ON(GET_PAGE_CACHE(page) != cachep);

Someone called kmem_cache_free(cachep, obj), but cachep is for a 
different object type.

>Call Trace:
>[sys_open+120/133] sys_open+0x78/0x85
>
Within sys_open - probably putname().
I have no idea how the bug could be triggered. If you can easily 
reproduce it: can you try the attached patch? It prints additional data.

And please add more details: Which gcc compiler, which filesystems, etc.

--
    Manfred