[PATCH v3 1/3] mm, powerpc: use vma_kernel_pagesize() in vma_mmu_pagesize()

[Dan Williams <dan.j.williams@intel.com>]

The current powerpc definition of vma_mmu_pagesize() open codes looking
up the page size via hstate. It is identical to the generic
vma_kernel_pagesize() implementation.

Now, vma_kernel_pagesize() is growing support for determining the
page size of Device-DAX vmas in addition to the existing Hugetlbfs page
size determination.

Ideally, if the powerpc vma_mmu_pagesize() used vma_kernel_pagesize() it
would automatically benefit from any new vma-type support that is added
to vma_kernel_pagesize(). However, the powerpc vma_mmu_pagesize() is
prevented from calling vma_kernel_pagesize() due to a circular header
dependency that requires vma_mmu_pagesize() to be defined before
including <linux/hugetlb.h>.

Break this circular dependency by defining the default
vma_mmu_pagesize() as a __weak symbol to be overridden by the powerpc
version.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 arch/powerpc/include/asm/hugetlb.h |    6 ------
 arch/powerpc/mm/hugetlbpage.c      |    5 +----
 mm/hugetlb.c                       |    8 +++-----
 3 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
index 1a4847f67ea8..6f6751d3eba9 100644
--- a/arch/powerpc/include/asm/hugetlb.h
+++ b/arch/powerpc/include/asm/hugetlb.h
@@ -118,12 +118,6 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
 			    unsigned long ceiling);
 
 /*
- * The version of vma_mmu_pagesize() in arch/powerpc/mm/hugetlbpage.c needs
- * to override the version in mm/hugetlb.c
- */
-#define vma_mmu_pagesize vma_mmu_pagesize
-
-/*
  * If the arch doesn't supply something else, assume that hugepage
  * size aligned regions are ok without further preparation.
  */
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 876da2bc1796..3a08d211d2ee 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -568,10 +568,7 @@ unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
 	if (!radix_enabled())
 		return 1UL << mmu_psize_to_shift(psize);
 #endif
-	if (!is_vm_hugetlb_page(vma))
-		return PAGE_SIZE;
-
-	return huge_page_size(hstate_vma(vma));
+	return vma_kernel_pagesize(vma);
 }
 
 static inline bool is_power_of_4(unsigned long x)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7c204e3d132b..f9c4ea42b04a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -650,15 +650,13 @@ EXPORT_SYMBOL_GPL(vma_kernel_pagesize);
 /*
  * Return the page size being used by the MMU to back a VMA. In the majority
  * of cases, the page size used by the kernel matches the MMU size. On
- * architectures where it differs, an architecture-specific version of this
- * function is required.
+ * architectures where it differs, an architecture-specific 'strong'
+ * version of this symbol is required.
  */
-#ifndef vma_mmu_pagesize
-unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
+__weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
 {
 	return vma_kernel_pagesize(vma);
 }
-#endif
 
 /*
  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom

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