Re: [PATCH] lib/raid6: Replace custom zero page with ZERO_PAGE

[Andrew Morton]

On Sun, 16 Mar 2025 13:51:50 +0800 Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:

> > Is there any possibility that the MD drivers will point DMA hardware at
> > the global zero page, thereby invalidating that page from CPU caches in
> > some manner?
> 
> The only spots that can hand this off to DMA are:

Cool, thanks for checking.

> crypto/async_tx/async_pq.c:                     srcs[i] = (void*)raid6_empty_zero_page;
> crypto/async_tx/async_raid6_recov.c:                            ptrs[i] = (void *) raid6_empty_zero_page;
> crypto/async_tx/async_raid6_recov.c:                            ptrs[i] = (void*)raid6_empty_zero_page;
> 
> But they all turn out to be synchronous fallback code paths that
> do not involve DMA at all.

And all three cast a pointer to a void* ;)