atmel-mci causes kernel panic when CONFIG_DEBUG_VM is set

On 5/19/2011 10:04 AM, Barry Song wrote:

2011/5/19 Ludovic Desroches[off-list ref]:

quoted

Hello,

There is a bug with the atmel-mci driver when the debug feature
CONFIG_DEBUG_VM is set.

Into the atmci_read_data_pio function we use flush_dcache_page (do we really
need it?) which call the page_mapping function where we can find
VM_BUG_ON(PageSlab(Page)). Then a kernel panic happens.

I don't understand the purpose of the VM_BUG_ON(PageSlab(Page)) (the page
comes from a scatter list). How could I correct this problem?

linux/include/linux/mmdebug.h:

#ifdef CONFIG_DEBUG_VM
#define VM_BUG_ON(cond) BUG_ON(cond)
#else
#define VM_BUG_ON(cond) do { (void)(cond); } while (0)
#endif

it is something like "assert" in kernel.

Thanks for your answer but I know that. My question is more focused on 
why there is this check.

Is flushing a page taken from a slab forbidden ? Is it risky ? Is it no 
sense ?


Regards,

Ludovic