linux-kernel - [PATCH v4 11/20] powerpc/mm: don't use pte_alloc_one

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Message-Id: <9f7d38d6928b00f53f61717884305ac30278237b.1537288312.git.christophe.leroy@c-s.fr>
Date:   Tue, 18 Sep 2018 16:57:24 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        aneesh.kumar@...ux.vnet.ibm.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v4 11/20] powerpc/mm: don't use pte_alloc_one_kernel() before
 slab is available

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

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/mm/pgtable_32.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 5877f5aa8f5d..6c8a07624773 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 +213,21 @@ void iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(iounmap);
 
-int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
+static __init 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);
+}
+
+__ref int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
 {
 	pmd_t *pd;
 	pte_t *pg;
@@ -231,7 +236,10 @@ 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