linux-kernel - Re: [f2fs-dev] [PATCH 1/2] f2fs: add disable_auto

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Message-ID: <X7NOPrbIMtHFvVwp@sol.localdomain>
Date:   Mon, 16 Nov 2020 20:14:54 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daeho Jeong <daeho43@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: add disable_auto_compr mount option

This patchset doesn't have a cover letter, and it doesn't apply to f2fs/dev, so
I'm not sure what its purpose is.

On Tue, Nov 17, 2020 at 01:02:22PM +0900, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@...gle.com>
> 
> We will add a new disable_auto_compr mount option to turn off the
> automaic compression on the compression enabled file, in order to
> give discretion of choosing the target file and the timing of
> compression to the user.
> 
> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> ---
>  Documentation/filesystems/f2fs.rst |  4 ++++
>  fs/f2fs/data.c                     | 10 +++++-----
>  fs/f2fs/f2fs.h                     |  8 ++++++++
>  fs/f2fs/segment.c                  |  2 +-
>  fs/f2fs/super.c                    |  9 +++++++++
>  5 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> index b8ee761c9922..c36ca1e0f7ab 100644
> --- a/Documentation/filesystems/f2fs.rst
> +++ b/Documentation/filesystems/f2fs.rst
> @@ -260,6 +260,10 @@ compress_extension=%s	 Support adding specified extension, so that f2fs can enab
>  			 For other files, we can still enable compression via ioctl.
>  			 Note that, there is one reserved special extension '*', it
>  			 can be set to enable compression for all files.
> +disable_auto_compr       Even if compression feature is enabled, this option can
> +                         disable automaic compression on the compression enabled
> +                         file to give discretion of choosing the target file and
> +                         the timing of compression to the user.

I don't understand.  How is this different from just not specifying the
compress_extension mount option?  And how can a file have compression both
enabled and disabled at the same time?

- Eric