x86/mm: Fix the size calculation of mapping tables

For machines that enable PSE, the first 2/4M memory region still uses
4K pages, so needs more PTEs in this case, but
find_early_table_space() doesn't count this.

This patch fixes it.

The bug was found via code review, no misbehavior of the kernel
was observed.

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: <ianfang.cn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-kq6a00qe33h7c7ais2xsywnh@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 6cabf65..2e92fdc 100644 (file)
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -30,8 +30,14 @@ int direct_gbpages
 #endif
 ;
 
-static void __init find_early_table_space(unsigned long end, int use_pse,
-                                         int use_gbpages)
+struct map_range {
+       unsigned long start;
+       unsigned long end;
+       unsigned page_size_mask;
+};
+
+static void __init find_early_table_space(struct map_range *mr, unsigned long end,
+                                         int use_pse, int use_gbpages)
 {
        unsigned long puds, pmds, ptes, tables, start = 0, good_end = end;
        phys_addr_t base;
@@ -56,6 +62,9 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
 #ifdef CONFIG_X86_32
                extra += PMD_SIZE;
 #endif
+               /* The first 2/4M doesn't use large pages. */
+               extra += mr->end - mr->start;
+
                ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
        } else
                ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
@@ -85,12 +94,6 @@ void __init native_pagetable_reserve(u64 start, u64 end)
        memblock_reserve(start, end - start);
 }
 
-struct map_range {
-       unsigned long start;
-       unsigned long end;
-       unsigned page_size_mask;
-};
-
 #ifdef CONFIG_X86_32
 #define NR_RANGE_MR 3
 #else /* CONFIG_X86_64 */
@@ -262,7 +265,7 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
         * nodes are discovered.
         */
        if (!after_bootmem)
-               find_early_table_space(end, use_pse, use_gbpages);
+               find_early_table_space(&mr[0], end, use_pse, use_gbpages);
 
        for (i = 0; i < nr_range; i++)
                ret = kernel_physical_mapping_init(mr[i].start, mr[i].end,