On Sun, Oct 27, 2013 at 02:18:17PM +0000, Simon Baatz wrote:
> 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:
> > > On Sun, Oct 27, 2013 at 8:50 PM, Aaro Koskinen <aaro.koskinen@xxxxxx> wrote:
> > > >
> > 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?
According to cachetlb.txt, flush_dcache_page() is only called on page
cache pages, so this excludes the PageSlab() check.
For flush_kernel_dcache_page() it says "when the kernel modifies and
user page" and my reading is that this applies to either page cache
or anonymous pages but not slab pages, so I would add such check to the
caller.
--
Catalin
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