[sheepdog] [PATCH] cache: correct block size calculation for inode object

[MORITA Kazutaka]

At Wed,  7 Aug 2013 16:10:01 +0800,
Liu Yuan wrote:
> 
> inode and data object have different sizes and thus cache block size is
> different. Current code fail to get the right size for inode object when
> its last bit of bmap is set with the fixed block size.
> 
> This patch tries to get the dynamic block size based on the oid.
> 
> Signed-off-by: Liu Yuan <namei.unix at gmail.com>
> ---
>  sheep/object_cache.c |   36 ++++++++++++++++--------------------
>  1 file changed, 16 insertions(+), 20 deletions(-)
> 
> diff --git a/sheep/object_cache.c b/sheep/object_cache.c
> index dcf6972..957b052 100644
> --- a/sheep/object_cache.c
> +++ b/sheep/object_cache.c
> @@ -28,8 +28,6 @@
>  
>  #define CACHE_INDEX_MASK      (CACHE_CREATE_BIT)
>  
> -#define CACHE_BLOCK_SIZE      ((UINT64_C(1) << 10) * 64) /* 64 KB */
> -
>  #define CACHE_OBJECT_SIZE (SD_DATA_OBJ_SIZE / 1024 / 1024) /* M */
>  
>  /* Kick background pusher if dirty_count greater than it */
> @@ -116,13 +114,19 @@ static inline bool idx_has_vdi_bit(uint32_t idx)
>  	return !!(idx & CACHE_VDI_BIT);
>  }
>  
> -static uint64_t calc_object_bmap(size_t len, off_t offset)
> +static inline int get_cache_block_size(uint64_t oid)
> +{
> +	return DIV_ROUND_UP(get_objsize(oid), sizeof(uint64_t) * BITS_PER_BYTE);
> +}

The size of cache block must be sector-aligned for O_DIRECT.  I'd
suggest rounding up to 4 KB boundary (the size of blocks for most
filesystems) like as follows.

  static inline int get_cache_block_size(uint64_t oid)
  {
      int bsize = DIV_ROUND_UP(get_objsize(oid), sizeof(uint64_t) * BITS_PER_BYTE);

      return round_up(bsize, BLOCK_SIZE);
  }

Thanks,

Kazutaka