powerpc/iommu: Do not call PageTransHuge() on tail pages

commit e889e96e98e8da97bd39e46b7253615eabe14397 upstream.

The CMA pages migration code does not support compound pages at
the moment so it performs few tests before proceeding to actual page
migration.

One of the tests - PageTransHuge() - has VM_BUG_ON_PAGE(PageTail()) as
it is designed to be called on head pages only. Since we also test for
PageCompound(), and it contains PageTail() and PageHead(), we can
simplify the check by leaving just PageCompound() and therefore avoid
possible VM_BUG_ON_PAGE.

Fixes: 2e5bbb5461f1 ("KVM: PPC: Book3S HV: Migrate pinned pages out of CMA")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index 7de7124..fd59680 100644 (file)
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -81,7 +81,7 @@ struct page *new_iommu_non_cma_page(struct page *page, unsigned long private,
        gfp_t gfp_mask = GFP_USER;
        struct page *new_page;
 
-       if (PageHuge(page) || PageTransHuge(page) || PageCompound(page))
+       if (PageCompound(page))
                return NULL;
 
        if (PageHighMem(page))
@@ -100,7 +100,7 @@ static int mm_iommu_move_page_from_cma(struct page *page)
        LIST_HEAD(cma_migrate_pages);
 
        /* Ignore huge pages for now */
-       if (PageHuge(page) || PageTransHuge(page) || PageCompound(page))
+       if (PageCompound(page))
                return -EBUSY;
 
        lru_add_drain();