ARM/kirkwood: v3.12-rc6: kernel BUG at mm/util.c:390!

Hi Russell,

On Sun, Oct 27, 2013 at 01:53:44PM +0000, Russell King - ARM Linux wrote:

On Sun, Oct 27, 2013 at 09:16:53PM +0800, Ming Lei wrote:

quoted

On Sun, Oct 27, 2013 at 8:50 PM, Aaro Koskinen [off-list ref] wrote:

quoted

So...

flush_kernel_dcache_page() is expected to take a struct page pointer.
This struct page pointer is part of the kernel's array of struct pages
which identifies every single physical page under the control of the
kernel.

Arguably, it should not crash if passed a page which has been allocated
to the slab cache; as this is not a page cache page,
flush_kernel_dcache_page() should merely ignore the call to it and
simply return on these.  So this makes total sense:

In this respect, flush_kernel_dcache_page() is following
flush_dcache_page(). For example in crypto/scatterwalk.c:

static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
                                 unsigned int more)
{
        if (out) {
                struct page *page;

                page = sg_page(walk->sg) + ((walk->offset - 1) >>
PAGE_SHIFT);
                if (!PageSlab(page))
                        flush_dcache_page(page);
        }
... 


or in drivers/ata/libata-sff.c:

...
        if (!do_write && !PageSlab(page))
                flush_dcache_page(page);
...


(Probably, both cases should have used
flush_kernel_dcache_page() in the first place). If we say that this
check belongs in flush_kernel_dcache_page() we should also put it
into flush_dcache_page(), no?

- Simon