[PATCH 1/3] x86 e820: Check for exactmap appearance when parsing first memmap option

[Thomas Renninger]

From: Yinghai Lu <yinghai at kernel.org>

memmap=exactmap will throw away all original, but also until then
user defined (through other provided memmap= parameters) areas.
That means all memmap= boot parameters passed before a memmap=exactmap
parameter are not recognized.
Without this fix:
memmap=x at y memmap=exactmap memmap=i#k
only i#k would get recognized.

This is wrong, this fix will only throw away all original e820 areas once
when memmap=exactmap is found in the whole boot command line and before
any other memmap= option is parsed.

Signed-off-by: Yinghai Lu <yinghai at kernel.org>
Reviewed-by: Thomas Renninger <trenn at suse.de>
---
 arch/x86/kernel/e820.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

Index: linux-2.6/arch/x86/kernel/e820.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/e820.c
+++ linux-2.6/arch/x86/kernel/e820.c
@@ -835,6 +835,8 @@ static int __init parse_memopt(char *p)
 }
 early_param("mem", parse_memopt);
 
+static bool __initdata exactmap_parsed;
+
 static int __init parse_memmap_one(char *p)
 {
 	char *oldp;
@@ -844,6 +846,10 @@ static int __init parse_memmap_one(char
 		return -EINVAL;
 
 	if (!strncmp(p, "exactmap", 8)) {
+		if (exactmap_parsed)
+			return 0;
+
+		exactmap_parsed = true;
 #ifdef CONFIG_CRASH_DUMP
 		/*
 		 * If we are doing a crash dump, we still need to know
@@ -879,6 +885,12 @@ static int __init parse_memmap_one(char
 }
 static int __init parse_memmap_opt(char *str)
 {
+	char *p = boot_command_line;
+
+	p = strstr(p, "exactmap");
+	if (p)
+		parse_memmap_one("exactmap");
+
 	while (str) {
 		char *k = strchr(str, ',');