Introduce flags for reserve_bootmem()

This patchset adds a flags variable to reserve_bootmem() and uses the
BOOTMEM_EXCLUSIVE flag in crashkernel reservation code to detect collisions
between crashkernel area and already used memory.

This patch:

Change the reserve_bootmem() function to accept a new flag BOOTMEM_EXCLUSIVE.
If that flag is set, the function returns with -EBUSY if the memory already
has been reserved in the past.  This is to avoid conflicts.

Because that code runs before SMP initialisation, there's no race condition
inside reserve_bootmem_core().

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix powerpc build]
Signed-off-by: Bernhard Walle <bwalle@suse.de>
Cc: <linux-arch@vger.kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/kernel/core_irongate.c

@@ -241,7 +241,8 @@ albacore_init_arch(void)
 				       size / 1024);
 		}
 #endif
-		reserve_bootmem_node(NODE_DATA(0), pci_mem, memtop - pci_mem);
+		reserve_bootmem_node(NODE_DATA(0), pci_mem, memtop -
+				pci_mem, BOOTMEM_DEFAULT);
 		printk("irongate_init_arch: temporarily reserving "
 			"region %08lx-%08lx for PCI\n", pci_mem, memtop - 1);
 	}