On Tue, 2016-07-19 at 11:48 -0700, Kees Cook wrote:

On Mon, Jul 18, 2016 at 6:06 PM, Laura Abbott [off-list ref] wrote:

quoted

?
On 07/15/2016 02:44 PM, Kees Cook wrote:
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This doesn't work when copying CMA allocated memory since CMA purposely
allocates larger than a page block size without setting head pages.
Given CMA may be used with drivers doing zero copy buffers, I think it
should be permitted.
?
Something like the following lets it pass (I can clean up and submit
the is_migrate_cma_page APIs as a separate patch for review)

Yeah, this would be great. I'd rather use an accessor to check this
than a direct check for MIGRATE_CMA.

quoted

?????????*/
????????for (; ptr <= end ; ptr += PAGE_SIZE, page = virt_to_head_page(ptr))
{
-???????????????if (!PageReserved(page))
+???????????????if (!PageReserved(page) && !is_migrate_cma_page(page))
????????????????????????return "<spans multiple pages>";
????????}

Yeah, I'll modify this a bit so that which type it starts as is
maintained for all pages (rather than allowing to flip back and forth
-- even though that is likely impossible).
?

Sorry, I completely missed the MIGRATE_CMA bits. Could you clarify if you
caught this in testing/review?

Balbir Singh.