2022-06-02 08:56:57

by Chao Liu

Subject: [PATCH] docs: filesystems: f2fs: fix description about compress ioctl

From: Chao Liu <[email protected]>

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 <[email protected]>
---
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
+ 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

2022-06-10 13:35:13

by Chao Yu

Subject: Re: [PATCH] docs: filesystems: f2fs: fix description about compress ioctl

On 2022/6/2 15:25, Chao Liu wrote:
> From: Chao Liu <[email protected]>
>
> 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 <[email protected]>
> ---
> 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 <[email protected]>

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 |
> +----------+---------+---------+---------+ +---------+---------+---------+---------+
> - . .
> + . .
> . .
> . .
> +-------------+-------------+----------+----------------------------+