linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: set zstd default compression level to 3

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Date:   Mon, 12 Jun 2023 08:16:17 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: set zstd default compression level to 3

On 06/12, Chao Yu wrote:
> On 2023/6/8 0:29, Jaegeuk Kim wrote:
> > ZSTD does not support compress_level=0.
> 
> IIUC, it looks the range is [0, ZSTD_MAX_CLEVEL], 0 equals to default
> (ZSTD_CLEVEL_DEFAULT).

Ok, that seems a quick workaround of zstd, since it'd be quite hard to know
level=0 will be interpreted to whatever default behind the scenes.

> 
> zstd_compress.c
> 
>     /* row */
>     if (compressionLevel == 0) row = ZSTD_CLEVEL_DEFAULT;   /* 0 == default */
>     else if (compressionLevel < 0) row = 0;   /* entry 0 is baseline for fast mode */
>     else if (compressionLevel > ZSTD_MAX_CLEVEL) row = ZSTD_MAX_CLEVEL;
>     else row = compressionLevel;
> 
> Thanks,
> 
> > 
> > The commit d7ffafc99c42 ("f2fs: add sanity compress level check for compressed file")
> > revealed the issue.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >   fs/f2fs/super.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 8fd23caa1ed9..1fb8d4f27a40 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -627,7 +627,7 @@ static int f2fs_set_zstd_level(struct f2fs_sb_info *sbi, const char *str)
> >   	int len = 4;
> >   	if (strlen(str) == len) {
> > -		F2FS_OPTION(sbi).compress_level = 0;
> > +		F2FS_OPTION(sbi).compress_level = 3;
> >   		return 0;
> >   	}