[PATCH v6 15/20] powerpc/mm: don't use pte_alloc_one_kernel() before slab is available

[Christophe Leroy]

In the same way as PPC64, let's handle pte allocation directly
in kernel_map_page() when slab is not available.

The new function early_pte_alloc_kernel() is put in as inline in
platforms pgalloc.h, this will allow to have different ones later.
It is not an issue because early_pte_alloc_kernel() is called only
once from map_kernel_page() and is inlined anyway.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
 arch/powerpc/include/asm/book3s/32/pgalloc.h | 15 +++++++++++++++
 arch/powerpc/include/asm/nohash/32/pgalloc.h | 15 +++++++++++++++
 arch/powerpc/mm/pgtable_32.c                 | 20 +++++++-------------
 3 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/pgalloc.h b/arch/powerpc/include/asm/book3s/32/pgalloc.h
index 96138ab3ddd6..4ddc7df20381 100644
--- a/arch/powerpc/include/asm/book3s/32/pgalloc.h
+++ b/arch/powerpc/include/asm/book3s/32/pgalloc.h
@@ -4,6 +4,7 @@
 
 #include <linux/threads.h>
 #include <linux/slab.h>
+#include <linux/memblock.h>
 
 /*
  * Functions that deal with pagetables that could be at any level of
@@ -137,4 +138,18 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t table,
 {
 	pgtable_free_tlb(tlb, page_address(table), 0);
 }
+
+static inline pte_t *early_pte_alloc_kernel(pmd_t *pmdp, unsigned long va)
+{
+	if (!pmd_present(*pmdp)) {
+		pte_t *ptep = __va(memblock_alloc(PAGE_SIZE, PAGE_SIZE));
+
+		if (!ptep)
+			return NULL;
+
+		clear_page(ptep);
+		pmd_populate_kernel(&init_mm, pmdp, ptep);
+	}
+	return pte_offset_kernel(pmdp, va);
+}
 #endif /* _ASM_POWERPC_BOOK3S_32_PGALLOC_H */
diff --git a/arch/powerpc/include/asm/nohash/32/pgalloc.h b/arch/powerpc/include/asm/nohash/32/pgalloc.h
index 6fbbb90043c0..da8fdfc76418 100644
--- a/arch/powerpc/include/asm/nohash/32/pgalloc.h
+++ b/arch/powerpc/include/asm/nohash/32/pgalloc.h
@@ -4,6 +4,7 @@
 
 #include <linux/threads.h>
 #include <linux/slab.h>
+#include <linux/memblock.h>
 
 /*
  * Functions that deal with pagetables that could be at any level of
@@ -139,4 +140,18 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t table,
 	tlb_flush_pgtable(tlb, address);
 	pgtable_free_tlb(tlb, page_address(table), 0);
 }
+
+static inline pte_t *early_pte_alloc_kernel(pmd_t *pmdp, unsigned long va)
+{
+	if (!pmd_present(*pmdp)) {
+		pte_t *ptep = __va(memblock_alloc(PAGE_SIZE, PAGE_SIZE));
+
+		if (!ptep)
+			return NULL;
+
+		clear_page(ptep);
+		pmd_populate_kernel(&init_mm, pmdp, ptep);
+	}
+	return pte_offset_kernel(pmdp, va);
+}
 #endif /* _ASM_POWERPC_PGALLOC_32_H */
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 5877f5aa8f5d..ea4442dde0d5 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -43,18 +43,9 @@ EXPORT_SYMBOL(ioremap_bot);	/* aka VMALLOC_END */
 
 extern char etext[], _stext[], _sinittext[], _einittext[];
 
-__ref pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
+pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 {
-	pte_t *pte;
-
-	if (slab_is_available()) {
-		pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
-	} else {
-		pte = __va(memblock_alloc(PAGE_SIZE, PAGE_SIZE));
-		if (pte)
-			clear_page(pte);
-	}
-	return pte;
+	return (pte_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
 }
 
 pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long address)
@@ -222,7 +213,7 @@ void iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(iounmap);
 
-int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
+__ref int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
 {
 	pmd_t *pd;
 	pte_t *pg;
@@ -231,7 +222,10 @@ int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
 	/* Use upper 10 bits of VA to index the first level map */
 	pd = pmd_offset(pud_offset(pgd_offset_k(va), va), va);
 	/* Use middle 10 bits of VA to index the second-level map */
-	pg = pte_alloc_kernel(pd, va);
+	if (slab_is_available())
+		pg = pte_alloc_kernel(pd, va);
+	else
+		pg = early_pte_alloc_kernel(pd, va);
 	if (pg != 0) {
 		err = 0;
 		/* The PTE should never be already set nor present in the
-- 
2.13.3