x86, mm: Add alloc_low_pages(num)

32bit kmap mapping needs pages to be used for low to high.
At this point those pages are still from pgt_buf_* from BRK, so it is
ok now.
But we want to move early_ioremap_page_table_range_init() out of
init_memory_mapping() and only call it one time later, that will
make page_table_range_init/page_table_kmap_check/alloc_low_page to
use memblock to get page.

memblock allocation for pages are from high to low.
So will get panic from page_table_kmap_check() that has BUG_ON to do
ordering checking.

This patch add alloc_low_pages to make it possible to allocate serveral
pages at first, and hand out pages one by one from low to high.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-28-git-send-email-yinghai@kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/mm/mm_internal.h b/arch/x86/mm/mm_internal.h
index b3f993a2555e..7e3b88ee078a 100644
--- a/arch/x86/mm/mm_internal.h
+++ b/arch/x86/mm/mm_internal.h
@@ -1,6 +1,10 @@
 #ifndef __X86_MM_INTERNAL_H
 #define __X86_MM_INTERNAL_H
 
-void *alloc_low_page(void);
+void *alloc_low_pages(unsigned int num);
+static inline void *alloc_low_page(void)
+{
+	return alloc_low_pages(1);
+}
 
 #endif	/* __X86_MM_INTERNAL_H */