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

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Date:   Tue, 29 Jan 2019 14:30:53 -0800
From:   Omar Sandoval <osandov@...ndov.com>
To:     Dennis Zhou <dennis@...nel.org>
Cc:     David Sterba <dsterba@...e.com>,
        Josef Bacik <josef@...icpanda.com>, Chris Mason <clm@...com>,
        Nick Terrell <terrelln@...com>, kernel-team@...com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] btrfs: add macros for compression type and level

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@...nel.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
>