linux-kernel - Re: [PATCH] docs: filesystems: f2fs: fix description about compress ioctl

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Message-ID: <0e451780-31c8-b1e9-0205-b9e68a57e958@kernel.org>
Date:   Fri, 10 Jun 2022 21:05:57 +0800
From:   Chao Yu <chao@...nel.org>
To:     Chao Liu <chaoliu719@...il.com>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-f2fs-devel@...ts.sourceforge.net, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yue Hu <huyue2@...lpad.com>,
        Wayne Zhang <zhangwen@...lpad.com>,
        Chao Liu <liuchao@...lpad.com>
Subject: Re: [PATCH] docs: filesystems: f2fs: fix description about compress
 ioctl

On 2022/6/2 15:25, Chao Liu wrote:
> From: Chao Liu <liuchao@...lpad.com>
> 
> Since commit c61404153eb6 ("f2fs: introduce FI_COMPRESS_RELEASED
> instead of using IMMUTABLE bit"), we no longer use the IMMUTABLE
> bit to prevent writing data for compression. Let's correct the
> corresponding documentation.
> 
> BTW, this patch fixes some alignment issues in the compress
> metadata layout.
> 
> Signed-off-by: Chao Liu <liuchao@...lpad.com>
> ---
>   Documentation/filesystems/f2fs.rst | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> index ad8dc8c040a2..98dc24f5c6f0 100644
> --- a/Documentation/filesystems/f2fs.rst
> +++ b/Documentation/filesystems/f2fs.rst
> @@ -818,10 +818,11 @@ Compression implementation
>     Instead, the main goal is to reduce data writes to flash disk as much as
>     possible, resulting in extending disk life time as well as relaxing IO
>     congestion. Alternatively, we've added ioctl(F2FS_IOC_RELEASE_COMPRESS_BLOCKS)
> -  interface to reclaim compressed space and show it to user after putting the
> -  immutable bit. Immutable bit, after release, it doesn't allow writing/mmaping
> -  on the file, until reserving compressed space via
> -  ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) or truncating filesize to zero.
> +  interface to reclaim compressed space and show it to user after setting a
> +  special flag to the inode. Once the compressed space is released, the flag
> +  will block writing data to the file until either the compressed space is
> +  reserved via ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) or the file size is

s/file size/filesize/

Reviewed-by: Chao Yu <chao@...nel.org>

Thanks,

> +  truncated to zero.
>   
>   Compress metadata layout::
>   
> @@ -830,12 +831,12 @@ Compress metadata layout::
>   		| cluster 1 | cluster 2 | ......... | cluster N |
>   		+-----------------------------------------------+
>   		.           .                       .           .
> -	.                       .                .                      .
> +	  .                      .                .                      .
>       .         Compressed Cluster       .        .        Normal Cluster            .
>       +----------+---------+---------+---------+  +---------+---------+---------+---------+
>       |compr flag| block 1 | block 2 | block 3 |  | block 1 | block 2 | block 3 | block 4 |
>       +----------+---------+---------+---------+  +---------+---------+---------+---------+
> -	    .                             .
> +	       .                             .
>   	    .                                           .
>   	.                                                           .
>   	+-------------+-------------+----------+----------------------------+