Re: [PATCH 11/11] btrfs: use the flags of an extent map to identify the compression type

[David Sterba <dsterba@suse.cz>]

On Mon, Dec 04, 2023 at 04:20:33PM +0000, fdmanana@kernel.org wrote:
> +	else if (type == BTRFS_COMPRESS_LZO)
> +		em->flags |= EXTENT_FLAG_COMPRESS_LZO;
> +	else if (type == BTRFS_COMPRESS_ZSTD)
> +		em->flags |= EXTENT_FLAG_COMPRESS_ZSTD;
> +}
> +
> +static inline enum btrfs_compression_type extent_map_compression(const struct extent_map *em)
> +{
> +	if (em->flags & EXTENT_FLAG_COMPRESS_ZLIB)
> +		return BTRFS_COMPRESS_ZLIB;
> +
> +	if (em->flags & EXTENT_FLAG_COMPRESS_LZO)
> +		return BTRFS_COMPRESS_LZO;
> +
> +	if (em->flags & EXTENT_FLAG_COMPRESS_ZSTD)
> +		return BTRFS_COMPRESS_ZSTD;
> +
> +	return BTRFS_COMPRESS_NONE;
> +}
> +
> +/*
> + * More efficient way to determine if extent is compressed, instead of using
> + * 'extent_map_compression() != BTRFS_COMPRESS_NONE'.
> + */
> +static inline bool extent_map_is_compressed(const struct extent_map *em)
> +{
> +	return (em->flags & (EXTENT_FLAG_COMPRESS_ZLIB |
> +			     EXTENT_FLAG_COMPRESS_LZO |
> +			     EXTENT_FLAG_COMPRESS_ZSTD)) != 0;

As a minor optimizations, you could add another bit flag when any of the
zlib/lzo/std is set and test just that.

Otherwise, I like the changes and space savings.