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Subject: Re: [PATCH v2 2/2] erofs: support reading chunk-based uncompressed
 files
To:     Gao Xiang <hsiangkao@linux.alibaba.com>,
        linux-erofs@lists.ozlabs.org, Chao Yu <chao@kernel.org>,
        Liu Bo <bo.liu@linux.alibaba.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Peng Tao <tao.peng@linux.alibaba.com>,
        Eryu Guan <eguan@linux.alibaba.com>,
        Liu Jiang <gerry@linux.alibaba.com>,
        Tao Ma <boyu.mt@taobao.com>
References: <20210818070713.4437-1-hsiangkao@linux.alibaba.com>
 <20210819063310.177035-1-hsiangkao@linux.alibaba.com>
 <20210819063310.177035-2-hsiangkao@linux.alibaba.com>
From:   Joseph Qi <joseph.qi@linux.alibaba.com>
Message-ID: <e5daab20-ed0a-70de-1f37-0613454a52c3@linux.alibaba.com>
Date:   Thu, 19 Aug 2021 14:37:50 +0800
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On 8/19/21 2:33 PM, Gao Xiang wrote:
> Add runtime support for chunk-based uncompressed files
> described in the previous patch.
> 
> Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> ---
> changes since v1:
>  - use le16_to_cpu instead of __le16_to_cpu pointed out by Chao.
> 
>  fs/erofs/data.c     | 90 ++++++++++++++++++++++++++++++++++++++++-----
>  fs/erofs/inode.c    | 18 ++++++++-
>  fs/erofs/internal.h |  5 +++
>  3 files changed, 102 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 09c46fbdb9b2..ee9a33485313 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -2,6 +2,7 @@
>  /*
>   * Copyright (C) 2017-2018 HUAWEI, Inc.
>   *             https://www.huawei.com/
> + * Copyright (C) 2021, Alibaba Cloud
>   */
>  #include "internal.h"
>  #include <linux/prefetch.h>
> @@ -36,13 +37,6 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
>  	nblocks = DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
>  	lastblk = nblocks - tailendpacking;
>  
> -	if (offset >= inode->i_size) {
> -		/* leave out-of-bound access unmapped */
> -		map->m_flags = 0;
> -		map->m_plen = 0;
> -		goto out;
> -	}
> -
>  	/* there is no hole in flatmode */
>  	map->m_flags = EROFS_MAP_MAPPED;
>  
> @@ -77,14 +71,90 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
>  		goto err_out;
>  	}
>  
> -out:
>  	map->m_llen = map->m_plen;
> -
>  err_out:
>  	trace_erofs_map_blocks_flatmode_exit(inode, map, flags, 0);
>  	return err;
>  }
>  
> +static int erofs_map_blocks(struct inode *inode,
> +			    struct erofs_map_blocks *map, int flags)
> +{
> +	struct super_block *sb = inode->i_sb;
> +	struct erofs_inode *vi = EROFS_I(inode);
> +	struct erofs_inode_chunk_index *idx;
> +	struct page *page;
> +	u64 chunknr;
> +	unsigned int unit;
> +	erofs_off_t pos;
> +	int err = 0;
> +
> +	if (map->m_la >= inode->i_size) {
> +		/* leave out-of-bound access unmapped */
> +		map->m_flags = 0;
> +		map->m_plen = 0;
> +		goto out;
> +	}
> +
> +	if (vi->datalayout != EROFS_INODE_CHUNK_BASED)
> +		return erofs_map_blocks_flatmode(inode, map, flags);
> +
> +	if (vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)
> +		unit = sizeof(*idx);	/* chunk index */
> +	else
> +		unit = 4;		/* block map */
> +
> +	chunknr = map->m_la >> vi->chunkbits;
> +	pos = ALIGN(iloc(EROFS_SB(sb), vi->nid) + vi->inode_isize +
> +		    vi->xattr_isize, unit) + unit * chunknr;
> +
> +	page = erofs_get_meta_page(inode->i_sb, erofs_blknr(pos));
> +	if (IS_ERR(page))
> +		return PTR_ERR(page);
> +
> +	map->m_la = chunknr << vi->chunkbits;
> +	map->m_plen = min_t(erofs_off_t, 1UL << vi->chunkbits,
> +			    roundup(inode->i_size - map->m_la, EROFS_BLKSIZ));
> +
> +	/* handle block map */
> +	if (!(vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)) {
> +		__le32 *blkaddr = page_address(page) + erofs_blkoff(pos);
> +
> +		if (le32_to_cpu(*blkaddr) == EROFS_NULL_ADDR) {
> +			map->m_flags = 0;
> +		} else {
> +			map->m_pa = blknr_to_addr(le32_to_cpu(*blkaddr));
> +			map->m_flags = EROFS_MAP_MAPPED;
> +		}
> +		goto out_unlock;
> +	}
> +	/* parse chunk indexes */
> +	idx = page_address(page) + erofs_blkoff(pos);
> +	switch (le32_to_cpu(idx->blkaddr)) {
> +	case EROFS_NULL_ADDR:
> +		map->m_flags = 0;
> +		break;
> +	default:
> +		/* only one device is supported for now */
> +		if (idx->device_id) {
> +			erofs_err(sb, "invalid device id %u @ %llu for nid %llu",
> +				  le32_to_cpu(idx->device_id),
> +				  chunknr, vi->nid);
> +			err = -EFSCORRUPTED;
> +			goto out_unlock;
> +		}
> +		map->m_pa = blknr_to_addr(le32_to_cpu(idx->blkaddr));
> +		map->m_flags = EROFS_MAP_MAPPED;
> +		break;
> +	}
> +out_unlock:
> +	unlock_page(page);
> +	put_page(page);
> +out:
> +	map->m_llen = map->m_plen;
> +	return err;
> +}
> +
>  static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
>  		unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
>  {
> @@ -94,7 +164,7 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
>  	map.m_la = offset;
>  	map.m_llen = length;
>  
> -	ret = erofs_map_blocks_flatmode(inode, &map, EROFS_GET_BLOCKS_RAW);
> +	ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
>  	if (ret < 0)
>  		return ret;
>  
> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
> index d13e0709599c..4408929bd6f5 100644
> --- a/fs/erofs/inode.c
> +++ b/fs/erofs/inode.c
> @@ -2,6 +2,7 @@
>  /*
>   * Copyright (C) 2017-2018 HUAWEI, Inc.
>   *             https://www.huawei.com/
> + * Copyright (C) 2021, Alibaba Cloud
>   */
>  #include "xattr.h"
>  
> @@ -122,7 +123,9 @@ static struct page *erofs_read_inode(struct inode *inode,
>  		/* total blocks for compressed files */
>  		if (erofs_inode_is_data_compressed(vi->datalayout))
>  			nblks = le32_to_cpu(die->i_u.compressed_blocks);
> -
> +		else if (vi->datalayout == EROFS_INODE_CHUNK_BASED)
> +			/* fill chunked inode summary info */
> +			vi->chunkformat = le16_to_cpu(die->i_u.c.format);

Better to add braces for if/else.

Thanks,
Joseph

>  		kfree(copied);
>  		break;
>  	case EROFS_INODE_LAYOUT_COMPACT:
> @@ -160,6 +163,8 @@ static struct page *erofs_read_inode(struct inode *inode,
>  		inode->i_size = le32_to_cpu(dic->i_size);
>  		if (erofs_inode_is_data_compressed(vi->datalayout))
>  			nblks = le32_to_cpu(dic->i_u.compressed_blocks);
> +		else if (vi->datalayout == EROFS_INODE_CHUNK_BASED)
> +			vi->chunkformat = le16_to_cpu(dic->i_u.c.format);
>  		break;
>  	default:
>  		erofs_err(inode->i_sb,
> @@ -169,6 +174,17 @@ static struct page *erofs_read_inode(struct inode *inode,
>  		goto err_out;
>  	}
>  
> +	if (vi->datalayout == EROFS_INODE_CHUNK_BASED) {
> +		if (!(vi->chunkformat & EROFS_CHUNK_FORMAT_ALL)) {
> +			erofs_err(inode->i_sb,
> +				  "unsupported chunk format %x of nid %llu",
> +				  vi->chunkformat, vi->nid);
> +			err = -EOPNOTSUPP;
> +			goto err_out;
> +		}
> +		vi->chunkbits = LOG_BLOCK_SIZE +
> +			(vi->chunkformat & EROFS_CHUNK_FORMAT_BLKBITS_MASK);
> +	}
>  	inode->i_mtime.tv_sec = inode->i_ctime.tv_sec;
>  	inode->i_atime.tv_sec = inode->i_ctime.tv_sec;
>  	inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec;
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 91089ab8a816..9524e155b38f 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -2,6 +2,7 @@
>  /*
>   * Copyright (C) 2017-2018 HUAWEI, Inc.
>   *             https://www.huawei.com/
> + * Copyright (C) 2021, Alibaba Cloud
>   */
>  #ifndef __EROFS_INTERNAL_H
>  #define __EROFS_INTERNAL_H
> @@ -261,6 +262,10 @@ struct erofs_inode {
>  
>  	union {
>  		erofs_blk_t raw_blkaddr;
> +		struct {
> +			unsigned short	chunkformat;
> +			unsigned char	chunkbits;
> +		};
>  #ifdef CONFIG_EROFS_FS_ZIP
>  		struct {
>  			unsigned short z_advise;
>