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SubjectRe: [PATCH] f2fs: compress: support zstd compress algorithm
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On 2020/3/3 1:50, Eric Biggers wrote:
> 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@huawei.com>
>> ---
>> 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()?

Actually, zstd decompression flow needs workspace like its compression flow,
however I realized that we don't have related callback interfaces in decompress
path, so I just add all steps of {,de}compression into .{,de}compress_pages()
functions.

In order to not break callback function fwk of compression, how about adding
{init,destroy}_decompress_ctx() callback interfaces, and relocating
initialization and destroy step into correct callback functions?

Thanks,

>
> - Eric
> .
>

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