Re: [PATCH 1/3] compound page: use page[1].lru

[Andrew Morton]

Hugh Dickins <hugh@xxxxxxxxxxx> wrote:
>
> On Sun, 12 Feb 2006, Andrew Morton wrote:
> > 
> > I'm scratching my head over flush_dcache_page() on, say, sparc64.  For
> > example, the one in fs/direct-io.c.  With this patch, we'll call
> > flush_dcache_page_impl(), which at least won't crash.  Before the patch I
> > think we'd just do random stuff.
> 
> A head-scratching business indeed.  I think your description is right.
> 
> I haven't looked up the intersection of the set of arches which have
> hugetlb with the set of arches which do something in flush_dcache_page,
> but maybe you have, and found sparc64 the only or most significant.

We have a page which has no ->mapping, but lo, it's mmapped by userspace
and can be MAP_SHARED between different CPUs and processes.

Yes, I suspect it'll do the wrong thing in unpleasantly subtle ways.

(cc's davem and runs away).

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