powerpc/mm/iommu: allow migration of cma allocated pages during mm_iommu_do_alloc
The current code doesn't do page migration if the page allocated is a compound page. With HugeTLB migration support, we can end up allocating hugetlb pages from CMA region. Also, THP pages can be allocated from CMA region. This patch updates the code to handle compound pages correctly. The patch also switches to a single get_user_pages with the right count, instead of doing one get_user_pages per page. That avoids reading page table multiple times. This is done by using get_user_pages_longterm, because that also takes care of DAX backed pages. DAX pages lifetime is dictated by file system rules and as such, we need to make sure that we free these pages on operations like truncate and punch hole. If we have long term pin on these pages, which are mostly return to userspace with elevated page count, the entity holding the long term pin may not be aware of the fact that file got truncated and the file system blocks possibly got reused. That can result in corruption. The patch also converts the hpas member of mm_iommu_table_group_mem_t to a union. We use the same storage location to store pointers to struct page. We cannot update all the code path use struct page *, because we access hpas in real mode and we can't do that struct page * to pfn conversion in real mode. [aneesh.kumar@linux.ibm.com: address review feedback, update changelog] Link: http://lkml.kernel.org/r/20190227144736.5872-4-aneesh.kumar@linux.ibm.com Link: http://lkml.kernel.org/r/20190114095438.32470-5-aneesh.kumar@linux.ibm.comSigned-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Alexey Kardashevskiy <aik@ozlabs.ru> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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