Re: [PATCH 01/11] btrfs: add macros for compression type and level

Omar Sandoval
2019-01-29T22:30:58Z

On Mon, Jan 28, 2019 at 04:24:27PM -0500, Dennis Zhou wrote:
> It is very easy to miss places that rely on a certain bitshifting for
> decyphering the type_level overloading. Make macros handle this instead.
>
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> ---
> fs/btrfs/compression.c | 2 +-
> fs/btrfs/compression.h | 3 +++
> fs/btrfs/zlib.c | 2 +-
> 3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 548057630b69..586f95ac0aea 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -1036,9 +1036,9 @@ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
> unsigned long *total_in,
> unsigned long *total_out)
> {
> + int type = BTRFS_COMPRESS_TYPE(type_level);
> struct list_head *workspace;
> int ret;
> - int type = type_level & 0xF;
>
> workspace = find_workspace(type);
>
> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
> index ddda9b80bf20..69a9197dadc3 100644
> --- a/fs/btrfs/compression.h
> +++ b/fs/btrfs/compression.h
> @@ -25,6 +25,9 @@
>
> #define BTRFS_ZLIB_DEFAULT_LEVEL 3
>
> +#define BTRFS_COMPRESS_TYPE(type_level) (type_level & 0xF)
> +#define BTRFS_COMPRESS_LEVEL(type_level) ((type_level & 0xF0) >> 4)

Nit: these can be inline functions rather than macros.

> struct compressed_bio {
> /* number of bios pending for this compressed extent */
> refcount_t pending_bios;
> diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
> index 970ff3e35bb3..1480b3eee306 100644
> --- a/fs/btrfs/zlib.c
> +++ b/fs/btrfs/zlib.c
> @@ -393,7 +393,7 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
> static void zlib_set_level(struct list_head *ws, unsigned int type)
> {
> struct workspace *workspace = list_entry(ws, struct workspace, list);
> - unsigned level = (type & 0xF0) >> 4;
> + unsigned int level = BTRFS_COMPRESS_LEVEL(type);
>
> if (level > 9)
> level = 9;
> --
> 2.17.1
>