sparc/srmmu: clear trailing edge of bitmap properly

srmmu_nocache_bitmap is cleared by bit_map_init().  But bit_map_init()
attempts to clear by memset(), so it can't clear the trailing edge of
bitmap properly on big-endian architecture if the number of bits is not
a multiple of BITS_PER_LONG.

Actually, the number of bits in srmmu_nocache_bitmap is not always
a multiple of BITS_PER_LONG.  It is calculated as below:

        bitmap_bits = srmmu_nocache_size >> SRMMU_NOCACHE_BITMAP_SHIFT;

srmmu_nocache_size is decided proportionally by the amount of system RAM
and it is rounded to a multiple of PAGE_SIZE.  SRMMU_NOCACHE_BITMAP_SHIFT
is defined as (PAGE_SHIFT - 4).  So it can only be said that bitmap_bits
is a multiple of 16.

This fixes the problem by using bitmap_clear() instead of memset()
in bit_map_init() and this also uses BITS_TO_LONGS() to calculate correct
size at bitmap allocation time.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index c38bb72e3e80..036c2797dece 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -280,7 +280,9 @@ static void __init srmmu_nocache_init(void)
                 SRMMU_NOCACHE_ALIGN_MAX, 0UL);
         memset(srmmu_nocache_pool, 0, srmmu_nocache_size);
 
-        srmmu_nocache_bitmap = __alloc_bootmem(bitmap_bits >> 3, SMP_CACHE_BYTES, 0UL);
+        srmmu_nocache_bitmap =
+                __alloc_bootmem(BITS_TO_LONGS(bitmap_bits) * sizeof(long),
+                                SMP_CACHE_BYTES, 0UL);
         bit_map_init(&srmmu_nocache_map, srmmu_nocache_bitmap, bitmap_bits);
 
         srmmu_swapper_pg_dir = __srmmu_get_nocache(SRMMU_PGD_TABLE_SIZE, SRMMU_PGD_TABLE_SIZE);