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Date:   Mon, 7 Dec 2020 10:13:06 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     jaegeuk@kernel.org, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v5 RESEND] f2fs: compress: add compress_inode
 to cache compressed blocks
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References: <20201207095220.73093-1-yuchao0@huawei.com>
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On Mon, Dec 07, 2020 at 05:52:20PM +0800, Chao Yu wrote:
> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> index dae15c96e659..fd413d319e93 100644
> --- a/Documentation/filesystems/f2fs.rst
> +++ b/Documentation/filesystems/f2fs.rst
> @@ -268,6 +268,9 @@ compress_mode=%s	 Control file compression mode. This supports "fs" and "user"
>  			 choosing the target file and the timing. The user can do manual
>  			 compression/decompression on the compression enabled files using
>  			 ioctls.
> +compress_cache		 Support to use address space of inner inode to cache
> +			 compressed block, in order to improve cache hit ratio of
> +			 random read.

What is an "inner inode"?  Mount options should be understandable without
understanding filesystem implementation details.

> +const struct address_space_operations f2fs_compress_aops = {
> +	.releasepage = f2fs_release_page,
> +	.invalidatepage = f2fs_invalidate_page,
> +};
> +
> +struct address_space *COMPRESS_MAPPING(struct f2fs_sb_info *sbi)
> +{
> +	return sbi->compress_inode->i_mapping;
> +}
> +
> +void invalidate_compress_page(struct f2fs_sb_info *sbi, block_t blkaddr)
> +{
> +	if (!sbi->compress_inode)
> +		return;
> +	invalidate_mapping_pages(COMPRESS_MAPPING(sbi), blkaddr, blkaddr);
> +}

Global functions should have the "f2fs_" prefix.

- Eric