linux-kernel - [PATCH 2/3] x86, mm: Don't clear page table if next range is ram

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Date:	Sat,  6 Oct 2012 00:44:28 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Tejun Heo <tj@...nel.org>
Cc:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>
Subject: [PATCH 2/3] x86, mm: Don't clear page table if next range is ram

During adding code from BRK to map buffer for final page table,

It should be safe to remove early_memmap for page table accessing.

But get panic after that.

It turns out we clear the initial page table wrongly for next range
that is separated by holes.
And it only happens when we are trying to map range one by one range.

After checking before clearing the related page table to fix the problem.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
---
 arch/x86/mm/init_64.c |   39 +++++++++++++++++++--------------------
 1 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5375cf0..0348a02 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -367,20 +367,21 @@ static unsigned long __meminit
 phys_pte_init(pte_t *pte_page, unsigned long addr, unsigned long end,
 	      pgprot_t prot)
 {
-	unsigned pages = 0;
+	unsigned long pages = 0, next;
 	unsigned long last_map_addr = end;
 	int i;
 
 	pte_t *pte = pte_page + pte_index(addr);
 
-	for(i = pte_index(addr); i < PTRS_PER_PTE; i++, addr += PAGE_SIZE, pte++) {
+	for (i = pte_index(addr); i < PTRS_PER_PTE; i++, addr = next, pte++) {
 
+		next = (addr & PAGE_MASK) + PAGE_SIZE;
 		if (addr >= end) {
-			if (!after_bootmem) {
-				for(; i < PTRS_PER_PTE; i++, pte++)
-					set_pte(pte, __pte(0));
-			}
-			break;
+			if (!after_bootmem &&
+			    addr < (2UL<<30) &&
+			    !e820_any_mapped(addr & PAGE_MASK, next, 0))
+				set_pte(pte, __pte(0));
+			continue;
 		}
 
 		/*
@@ -422,16 +423,15 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long address, unsigned long end,
 		pte_t *pte;
 		pgprot_t new_prot = prot;
 
+		next = (address & PMD_MASK) + PMD_SIZE;
 		if (address >= end) {
-			if (!after_bootmem) {
-				for (; i < PTRS_PER_PMD; i++, pmd++)
-					set_pmd(pmd, __pmd(0));
-			}
-			break;
+			if (!after_bootmem &&
+			    address < (2UL<<30) &&
+			    !e820_any_mapped(address & PMD_MASK, next, 0))
+				set_pmd(pmd, __pmd(0));
+			continue;
 		}
 
-		next = (address & PMD_MASK) + PMD_SIZE;
-
 		if (pmd_val(*pmd)) {
 			if (!pmd_large(*pmd)) {
 				spin_lock(&init_mm.page_table_lock);
@@ -498,13 +498,12 @@ phys_pud_init(pud_t *pud_page, unsigned long addr, unsigned long end,
 		pmd_t *pmd;
 		pgprot_t prot = PAGE_KERNEL;
 
-		if (addr >= end)
-			break;
-
 		next = (addr & PUD_MASK) + PUD_SIZE;
-
-		if (!after_bootmem && !e820_any_mapped(addr, next, 0)) {
-			set_pud(pud, __pud(0));
+		if (addr >= end) {
+			if (!after_bootmem &&
+			    addr < (2UL<<30) &&
+			    !e820_any_mapped(addr & PUD_MASK, next, 0))
+				set_pud(pud, __pud(0));
 			continue;
 		}
 
-- 
1.7.7

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