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 should be called on head pages. Since we also test for PageCompound(),
and it contains PageTail(), we can simply move PageCompound() in front
of PageTransHuge() and therefore avoid possible VM_BUG_ON_PAGE.
Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
---
Some of actual POWER8 systems do crash on that BUG_ON.
---
arch/powerpc/mm/mmu_context_iommu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/mmu_context_iommu.c
b/arch/powerpc/mm/mmu_context_iommu.c
index 497130c5c742..ba7fccf993b3 100644
--- 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) || PageHuge(page) || PageTransHuge(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) || PageHuge(page) || PageTransHuge(page))
return -EBUSY;
lru_add_drain();
--
2.11.0
