[PATCH] i386 bootmem restrictions

(Comment changes only)

The bootmem allocator is initialised before the kernel virtual address
space has been fully established.  As a result, any allocations which are
made before paging_init() has completed may point to invalid kernel
addresses.  This patch notes this limitation and indicates where the
allocator is fully available.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/setup.c

@@ -1355,7 +1355,12 @@ void __init setup_arch(char **cmdline_p)
 
 	/*
 	 * NOTE: before this point _nobody_ is allowed to allocate
-	 * any memory using the bootmem allocator.
+	 * any memory using the bootmem allocator.  Although the
+	 * alloctor is now initialised only the first 8Mb of the kernel
+	 * virtual address space has been mapped.  All allocations before
+	 * paging_init() has completed must use the alloc_bootmem_low_pages()
+	 * variant (which allocates DMA'able memory) and care must be taken
+	 * not to exceed the 8Mb limit.
 	 */
 
 #ifdef CONFIG_SMP
@@ -1363,6 +1368,10 @@ void __init setup_arch(char **cmdline_p)
 #endif
 	paging_init();
 
+	/*
+	 * NOTE: at this point the bootmem allocator is fully available.
+	 */
+
 #ifdef CONFIG_EARLY_PRINTK
 	{
 		char *s = strstr(*cmdline_p, "earlyprintk=");