Re: [PATCH] f2fs: compress: support zstd compress algorithm

[Eric Biggers]

On Fri, Feb 28, 2020 at 07:14:56PM +0800, Chao Yu wrote:
> Add zstd compress algorithm support, use "compress_algorithm=zstd"
> mountoption to enable it.
> 
> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> ---
>  Documentation/filesystems/f2fs.txt |   4 +-
>  fs/f2fs/Kconfig                    |   9 ++
>  fs/f2fs/compress.c                 | 151 +++++++++++++++++++++++++++++
>  fs/f2fs/f2fs.h                     |   2 +
>  fs/f2fs/super.c                    |   7 ++
>  include/trace/events/f2fs.h        |   3 +-
>  6 files changed, 173 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
> index 4eb3e2ddd00e..b1a66cf0e967 100644
> --- a/Documentation/filesystems/f2fs.txt
> +++ b/Documentation/filesystems/f2fs.txt
> @@ -235,8 +235,8 @@ checkpoint=%s[:%u[%]]     Set to "disable" to turn off checkpointing. Set to "en
>                         hide up to all remaining free space. The actual space that
>                         would be unusable can be viewed at /sys/fs/f2fs/<disk>/unusable
>                         This space is reclaimed once checkpoint=enable.
> -compress_algorithm=%s  Control compress algorithm, currently f2fs supports "lzo"
> -                       and "lz4" algorithm.
> +compress_algorithm=%s  Control compress algorithm, currently f2fs supports "lzo",
> +                       "lz4" and "zstd" algorithm.
>  compress_log_size=%u   Support configuring compress cluster size, the size will
>                         be 4KB * (1 << %u), 16KB is minimum size, also it's
>                         default size.
> diff --git a/fs/f2fs/Kconfig b/fs/f2fs/Kconfig
> index f0faada30f30..bb68d21e1f8c 100644
> --- a/fs/f2fs/Kconfig
> +++ b/fs/f2fs/Kconfig
> @@ -118,3 +118,12 @@ config F2FS_FS_LZ4
>  	default y
>  	help
>  	  Support LZ4 compress algorithm, if unsure, say Y.
> +
> +config F2FS_FS_ZSTD
> +	bool "ZSTD compression support"
> +	depends on F2FS_FS_COMPRESSION
> +	select ZSTD_COMPRESS
> +	select ZSTD_DECOMPRESS
> +	default y
> +	help
> +	  Support ZSTD compress algorithm, if unsure, say Y.
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index bd3ea01db448..c8e1175eaf4e 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -11,6 +11,7 @@
>  #include <linux/backing-dev.h>
>  #include <linux/lzo.h>
>  #include <linux/lz4.h>
> +#include <linux/zstd.h>
>  
>  #include "f2fs.h"
>  #include "node.h"
> @@ -291,6 +292,151 @@ static const struct f2fs_compress_ops f2fs_lz4_ops = {
>  };
>  #endif
>  
> +#ifdef CONFIG_F2FS_FS_ZSTD
> +#define F2FS_ZSTD_DEFAULT_CLEVEL	1
> +
> +static int zstd_init_compress_ctx(struct compress_ctx *cc)
> +{
> +	return 0;
> +}
> +
> +static void zstd_destroy_compress_ctx(struct compress_ctx *cc)
> +{
> +}
> +
> +static int zstd_compress_pages(struct compress_ctx *cc)
> +{
> +	ZSTD_parameters params;
> +	ZSTD_CStream *stream;
> +	ZSTD_inBuffer inbuf;
> +	ZSTD_outBuffer outbuf;
> +	void *workspace;
> +	unsigned int workspace_size;
> +	int src_size = cc->rlen;
> +	int dst_size = src_size - PAGE_SIZE - COMPRESS_HEADER_SIZE;
> +	int ret;
> +
> +	params = ZSTD_getParams(F2FS_ZSTD_DEFAULT_CLEVEL, src_size, 0);
> +	workspace_size = ZSTD_CStreamWorkspaceBound(params.cParams);
> +
> +	workspace = f2fs_kvmalloc(F2FS_I_SB(cc->inode),
> +					workspace_size, GFP_NOFS);
> +	if (!workspace)
> +		return -ENOMEM;
> +
> +	stream = ZSTD_initCStream(params, 0,
> +					workspace, workspace_size);

Why is this allocating the memory for every compression operation, instead of
ahead of time in ->init_compress_ctx()?

- Eric