Re: [f2fs-dev] [PATCH v4] f2fs: compress: allow write compress released file after truncate to zero

[Chao Yu <chao@kernel.org>]

On 2021/8/6 17:59, Fengnan Chang wrote:
> For compressed file, after release compress blocks, don't allow write
> direct, but we should allow write direct after truncate to zero.
> 
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
> ---
>   Documentation/filesystems/f2fs.rst | 7 +++++--
>   fs/f2fs/file.c                     | 8 ++++++++
>   2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> index 8f251a662542..d4de7ea4a83d 100644
> --- a/Documentation/filesystems/f2fs.rst
> +++ b/Documentation/filesystems/f2fs.rst
> @@ -865,8 +865,11 @@ Compression implementation
>     directly in order to guarantee potential data updates later to the space.
>     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 interface to reclaim compressed
> -  space and show it to user after putting the immutable bit.
> +  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. After call ioctl release compreesed space, don't allow write

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.

Otherwise, it looks good to me.

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

Thanks,

> +  file directly, unless call ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) to reserve
> +  compreesed space or file truncated be zero.
>   
>   Compress metadata layout::
>   
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 7d8ee60f6c1f..d4fc5e0d2ffe 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -753,6 +753,14 @@ int f2fs_truncate_blocks(struct inode *inode, u64 from, bool lock)
>   		return err;
>   
>   #ifdef CONFIG_F2FS_FS_COMPRESSION
> +	/*
> +	 * For compressed file, after release compress blocks, don't allow write
> +	 * direct, but we should allow write direct after truncate to zero.
> +	 */
> +	if (f2fs_compressed_file(inode) && !free_from
> +			&& is_inode_flag_set(inode, FI_COMPRESS_RELEASED))
> +		clear_inode_flag(inode, FI_COMPRESS_RELEASED);
> +
>   	if (from != free_from) {
>   		err = f2fs_truncate_partial_cluster(inode, from, lock);
>   		if (err)
> 


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