[PATCH -v2] x86, memblock: Fix crashkernel allocation

Cai Qian found crashkernel is broken with x86 memblock changes
1. crashkernel=128M@32M always reported that range is used, even first kernel is small
   no one use that range
2. always get following report when using "kexec -p"
	Could not find a free area of memory of a000 bytes...
	locate_hole failed

The root cause is that generic memblock_find_in_range() will try to get range from top_down.
But crashkernel do need from low and specified range.

Let's limit the target range with rash_base + crash_size to make sure that
We get range from bottom.

-v2: don't limit it with 0xffffffff, in case kexec will use bzImage 64bit entry or vmlinux,
     and try to allocate huge area for crashkernel.

Reported-and-Bisected-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/setup.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -516,19 +516,28 @@ static void __init reserve_crashkernel(v
 
 	/* 0 means: find the address automatically */
 	if (crash_base <= 0) {
+		unsigned long long start = 0;
 		const unsigned long long alignment = 16<<20;	/* 16M */
 
-		crash_base = memblock_find_in_range(alignment, ULONG_MAX, crash_size,
-				 alignment);
-		if (crash_base == MEMBLOCK_ERROR) {
+		crash_base = alignment;
+		while ((crash_base + crash_size) <= total_mem) {
+			start = memblock_find_in_range(crash_base,
+				crash_base + crash_size, crash_size, alignment);
+
+			if (start == crash_base)
+				break;
+
+			crash_base += alignment;
+		}
+		if (start != crash_base) {
 			pr_info("crashkernel reservation failed - No suitable area found.\n");
 			return;
 		}
 	} else {
 		unsigned long long start;
 
-		start = memblock_find_in_range(crash_base, ULONG_MAX, crash_size,
-				 1<<20);
+		start = memblock_find_in_range(crash_base,
+				 crash_base + crash_size, crash_size, 1<<20);
 		if (start != crash_base) {
 			pr_info("crashkernel reservation failed - memory is in use.\n");
 			return;