linux-kernel - Re: [PATCH v2] docs: filesystems: f2fs: fix description about compress ioctl

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Date:   Mon, 13 Jun 2022 16:02:00 +0800
From:   Chao Liu <chaoliu719@...il.com>
To:     Matthew Wilcox <willy@...radead.org>, Chao Yu <chao@...nel.org>
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>, Jonathan Corbet <corbet@....net>,
        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 v2] docs: filesystems: f2fs: fix description about
 compress ioctl

On Mon, Jun 13, 2022 at 04:37:01AM +0100, Matthew Wilcox wrote:
> On Mon, Jun 13, 2022 at 10:08:00AM +0800, Chao Liu wrote:
> > v2:
> > - s/file size/filesize/
>
> Why would you change it to be wrong?
>

This is a suggestion from Chao Yu. Maybe he has some other considerations.

Hi Chao,

Can you help with this question?

Thanks.

> >  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..531b0f8a3946 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 filesize is
> > +  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 |
> >      +----------+---------+---------+---------+  +---------+---------+---------+---------+
> > -	    .                             .
> > +	       .                             .
> >  	    .                                           .
> >  	.                                                           .
> >  	+-------------+-------------+----------+----------------------------+
> > --
> > 2.36.1
> >