[POWERPC] Don't use SLAB/SLUB for PTE pages

The SLUB allocator relies on struct page fields first_page and slab,
overwritten by ptl when SPLIT_PTLOCK: so the SLUB allocator cannot then
be used for the lowest level of pagetable pages.  This was obstructing
SLUB on PowerPC, which uses kmem_caches for its pagetables.  So convert
its pte level to use normal gfp pages (whereas pmd, pud and 64k-page pgd
want partpages, so continue to use kmem_caches for pmd, pud and pgd).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 19 insertions, 42 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ecd459dd1baf..ccc5410af996 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -120,19 +120,6 @@ config GENERIC_BUG
 config SYS_SUPPORTS_APM_EMULATION
         bool
 
-#
-# Powerpc uses the slab allocator to manage its ptes and the
-# page structs of ptes are used for splitting the page table
-# lock for configurations supporting more than SPLIT_PTLOCK_CPUS.
-#
-# In that special configuration the page structs of slabs are modified.
-# This setting disables the selection of SLUB as a slab allocator.
-#
-config ARCH_USES_SLAB_PAGE_STRUCT
-        bool
-        default y
-        depends on SPLIT_PTLOCK_CPUS <= NR_CPUS
-
 config DEFAULT_UIMAGE
         bool
         help
diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index fe1fe852181a..7312a265545f 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -146,21 +146,16 @@ static void zero_ctor(void *addr, struct kmem_cache *cache, unsigned long flags)
         memset(addr, 0, kmem_cache_size(cache));
 }
 
-#ifdef CONFIG_PPC_64K_PAGES
-static const unsigned int pgtable_cache_size[3] = {
-        PTE_TABLE_SIZE, PMD_TABLE_SIZE, PGD_TABLE_SIZE
-};
-static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
-        "pte_pmd_cache", "pmd_cache", "pgd_cache",
-};
-#else
 static const unsigned int pgtable_cache_size[2] = {
-        PTE_TABLE_SIZE, PMD_TABLE_SIZE
+        PGD_TABLE_SIZE, PMD_TABLE_SIZE
 };
 static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
-        "pgd_pte_cache", "pud_pmd_cache",
-};
+#ifdef CONFIG_PPC_64K_PAGES
+        "pgd_cache", "pmd_cache",
+#else
+        "pgd_cache", "pud_pmd_cache",
 #endif /* CONFIG_PPC_64K_PAGES */
+};
 
 #ifdef CONFIG_HUGETLB_PAGE
 /* Hugepages need one extra cache, initialized in hugetlbpage.c.  We
diff --git a/include/asm-powerpc/pgalloc-64.h b/include/asm-powerpc/pgalloc-64.h
index 30b50cf56e2c..d9a3a8ca58a1 100644
--- a/include/asm-powerpc/pgalloc-64.h
+++ b/include/asm-powerpc/pgalloc-64.h
@@ -14,18 +14,11 @@
 
 extern struct kmem_cache *pgtable_cache[];
 
-#ifdef CONFIG_PPC_64K_PAGES
-#define PTE_CACHE_NUM   0
-#define PMD_CACHE_NUM   1
-#define PGD_CACHE_NUM   2
-#define HUGEPTE_CACHE_NUM 3
-#else
-#define PTE_CACHE_NUM   0
-#define PMD_CACHE_NUM   1
-#define PUD_CACHE_NUM   1
-#define PGD_CACHE_NUM   0
-#define HUGEPTE_CACHE_NUM 2
-#endif
+#define PGD_CACHE_NUM           0
+#define PUD_CACHE_NUM           1
+#define PMD_CACHE_NUM           1
+#define HUGEPTE_CACHE_NUM       2
+#define PTE_NONCACHE_NUM        3  /* from GFP rather than kmem_cache */
 
 static inline pgd_t *pgd_alloc(struct mm_struct *mm)
 {
@@ -91,8 +84,7 @@ static inline void pmd_free(pmd_t *pmd)
 static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,
                                           unsigned long address)
 {
-        return kmem_cache_alloc(pgtable_cache[PTE_CACHE_NUM],
-                                GFP_KERNEL|__GFP_REPEAT);
+        return (pte_t *)__get_free_page(GFP_KERNEL | __GFP_REPEAT | __GFP_ZERO);
 }
 
 static inline struct page *pte_alloc_one(struct mm_struct *mm,
@@ -103,12 +95,12 @@ static inline struct page *pte_alloc_one(struct mm_struct *mm,
 
 static inline void pte_free_kernel(pte_t *pte)
 {
-        kmem_cache_free(pgtable_cache[PTE_CACHE_NUM], pte);
+        free_page((unsigned long)pte);
 }
 
 static inline void pte_free(struct page *ptepage)
 {
-        pte_free_kernel(page_address(ptepage));
+        __free_page(ptepage);
 }
 
 #define PGF_CACHENUM_MASK       0x3
@@ -130,14 +122,17 @@ static inline void pgtable_free(pgtable_free_t pgf)
         void *p = (void *)(pgf.val & ~PGF_CACHENUM_MASK);
         int cachenum = pgf.val & PGF_CACHENUM_MASK;
 
-        kmem_cache_free(pgtable_cache[cachenum], p);
+        if (cachenum == PTE_NONCACHE_NUM)
+                free_page((unsigned long)p);
+        else
+                kmem_cache_free(pgtable_cache[cachenum], p);
 }
 
 extern void pgtable_free_tlb(struct mmu_gather *tlb, pgtable_free_t pgf);
 
 #define __pte_free_tlb(tlb, ptepage)    \
         pgtable_free_tlb(tlb, pgtable_free_cache(page_address(ptepage), \
-                PTE_CACHE_NUM, PTE_TABLE_SIZE-1))
+                PTE_NONCACHE_NUM, PTE_TABLE_SIZE-1))
 #define __pmd_free_tlb(tlb, pmd)        \
         pgtable_free_tlb(tlb, pgtable_free_cache(pmd, \
                 PMD_CACHE_NUM, PMD_TABLE_SIZE-1))