powerpc/mm/hash: Don't memset pgd table if not needed

We need to zero-out pgd table only if we share the slab cache with
pud/pmd level caches. With the support of 4PB, we don't share the slab
cache anymore. Instead of removing the code completely hide it within
an #ifdef. We don't need to do this with any other page table level,
because they all allocate table of double the size and we take of
initializing the first half corrrectly during page table zap.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Consolidate multiple #if / #ifdef into one]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/book3s/64/pgalloc.h b/arch/powerpc/include/asm/book3s/64/pgalloc.h
index 4746bc68d446d8e95427e67a86c3493a1d1f1668..558a159600adfbfe675a59d635a496e3ccae8742 100644 (file)
--- a/arch/powerpc/include/asm/book3s/64/pgalloc.h
+++ b/arch/powerpc/include/asm/book3s/64/pgalloc.h
@@ -80,8 +80,18 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm)
 
        pgd = kmem_cache_alloc(PGT_CACHE(PGD_INDEX_SIZE),
                               pgtable_gfp_flags(mm, GFP_KERNEL));
+       /*
+        * With hugetlb, we don't clear the second half of the page table.
+        * If we share the same slab cache with the pmd or pud level table,
+        * we need to make sure we zero out the full table on alloc.
+        * With 4K we don't store slot in the second half. Hence we don't
+        * need to do this for 4k.
+        */
+#if defined(CONFIG_HUGETLB_PAGE) && defined(CONFIG_PPC_64K_PAGES) && \
+       ((H_PGD_INDEX_SIZE == H_PUD_CACHE_INDEX) ||                  \
+        (H_PGD_INDEX_SIZE == H_PMD_CACHE_INDEX))
        memset(pgd, 0, PGD_TABLE_SIZE);
-
+#endif
        return pgd;
 }