On Fri, Mar 29, 2013 at 10:44:43PM +0900, Akinobu Mita wrote:
> 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@xxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: sparclinux@xxxxxxxxxxxxxxx
> ---
>
> This patch is a combination of the patches I sent:
> "sparc: clear bitmap correctly in bit_map_init()" and
> "sparc/srmmu: use BITS_TO_LONGS() to calculate bitmap size", but
> the patch description is rewritten.
>
> arch/sparc/lib/bitext.c | 6 +-----
> arch/sparc/mm/srmmu.c | 4 +++-
> 2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/arch/sparc/lib/bitext.c b/arch/sparc/lib/bitext.c
> index d516fda..04d8bad 100644
> --- a/arch/sparc/lib/bitext.c
> +++ b/arch/sparc/lib/bitext.c
> @@ -111,11 +111,7 @@ void bit_map_clear(struct bit_map *t, int offset, int len)
>
> void bit_map_init(struct bit_map *t, unsigned long *map, int size)
> {
> -
> - if ((size & 07) != 0)
> - BUG();
> - memset(map, 0, size>>3);
> -
> + bitmap_zero(map, size);
> memset(t, 0, sizeof *t);
> spin_lock_init(&t->lock);
> t->map = map;
This mixes sparc internal bit_map functions with lib/bitmap functions.
Please do not do this.
> diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
> index c38bb72..036c279 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);
Anything that touches the sparc32 nocache stuff should improve read-ability
or fix real bugs. This does neither - so I prefer to leave it as is.
Sam
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