linux-kernel - Re: [PATCH 3/3] erofs: refine on-disk definition comments

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Message-ID: <20220507134247.00007786.zbestahu@gmail.com>
Date:   Sat, 7 May 2022 13:42:47 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     linux-erofs@...ts.ozlabs.org, Chao Yu <chao@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, huyue2@...lpad.com,
        zhangwen@...lpad.com
Subject: Re: [PATCH 3/3] erofs: refine on-disk definition comments

On Sat,  7 May 2022 03:46:12 +0800
Gao Xiang <hsiangkao@...ux.alibaba.com> wrote:

> Fix some outdated comments and typos, hopefully helpful.
> 
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
> ---
>  fs/erofs/erofs_fs.h | 37 +++++++++++++++++++------------------
>  1 file changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 1238ca104f09..000fa2738974 100644
> --- a/fs/erofs/erofs_fs.h
> +++ b/fs/erofs/erofs_fs.h
> @@ -79,15 +79,15 @@ struct erofs_super_block {
>  
>  /*
>   * erofs inode datalayout (i_format in on-disk inode):
> - * 0 - inode plain without inline data A:
> + * 0 - uncompressed flat inode without tail-packing inline data:
>   * inode, [xattrs], ... | ... | no-holed data
> - * 1 - inode VLE compression B (legacy):
> - * inode, [xattrs], extents ... | ...
> - * 2 - inode plain with inline data C:
> - * inode, [xattrs], last_inline_data, ... | ... | no-holed data
> - * 3 - inode compression D:
> + * 1 - compressed inode with non-compact indexes:
> + * inode, [xattrs], [map_header], extents ... | ...
> + * 2 - uncompressed flat inode with tail-packing inline data:
> + * inode, [xattrs], tailpacking data, ... | ... | no-holed data
> + * 3 - compressed inode with compact indexes:
>   * inode, [xattrs], map_header, extents ... | ...
> - * 4 - inode chunk-based E:
> + * 4 - chunk-based inode with (optional) multi-device support:
>   * inode, [xattrs], chunk indexes ... | ...
>   * 5~7 - reserved
>   */
> @@ -106,7 +106,7 @@ static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
>  		datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
>  }
>  
> -/* bit definitions of inode i_advise */
> +/* bit definitions of inode i_format */
>  #define EROFS_I_VERSION_BITS            1
>  #define EROFS_I_DATALAYOUT_BITS         3
>  
> @@ -140,8 +140,9 @@ struct erofs_inode_compact {
>  	__le32 i_size;
>  	__le32 i_reserved;
>  	union {
> -		/* file total compressed blocks for data mapping 1 */
> +		/* total compressed blocks for compressed inodes */
>  		__le32 compressed_blocks;
> +		/* block address for uncompressed flat inodes */
>  		__le32 raw_blkaddr;
>  
>  		/* for device files, used to indicate old/new device # */
> @@ -156,9 +157,9 @@ struct erofs_inode_compact {
>  	__le32 i_reserved2;
>  };
>  
> -/* 32 bytes on-disk inode */
> +/* 32-byte on-disk inode */
>  #define EROFS_INODE_LAYOUT_COMPACT	0
> -/* 64 bytes on-disk inode */
> +/* 64-byte on-disk inode */
>  #define EROFS_INODE_LAYOUT_EXTENDED	1
>  
>  /* 64-byte complete form of an ondisk inode */
> @@ -171,8 +172,9 @@ struct erofs_inode_extended {
>  	__le16 i_reserved;
>  	__le64 i_size;
>  	union {
> -		/* file total compressed blocks for data mapping 1 */
> +		/* total compressed blocks for compressed inodes */
>  		__le32 compressed_blocks;
> +		/* block address for uncompressed flat inodes */
>  		__le32 raw_blkaddr;
>  
>  		/* for device files, used to indicate old/new device # */
> @@ -365,17 +367,16 @@ enum {
>  
>  struct z_erofs_vle_decompressed_index {
>  	__le16 di_advise;
> -	/* where to decompress in the head cluster */
> +	/* where to decompress in the head lcluster */
>  	__le16 di_clusterofs;
>  
>  	union {
> -		/* for the head cluster */
> +		/* for the HEAD lclusters */
>  		__le32 blkaddr;
>  		/*
> -		 * for the rest clusters
> -		 * eg. for 4k page-sized cluster, maximum 4K*64k = 256M)
> -		 * [0] - pointing to the head cluster
> -		 * [1] - pointing to the tail cluster
> +		 * for the NONHEAD lclusters
> +		 * [0] - distance to its HEAD lcluster
> +		 * [1] - distance to the next HEAD lcluster
>  		 */
>  		__le16 delta[2];
>  	} di_u;

Reviewed-by: Yue Hu <huyue2@...lpad.com>