Re: [PATCH v4] erofs: avoid using generic_block_bmap

[Chao Yu <yuchao0@huawei.com>]

On 2020/12/9 10:39, Huang Jianan wrote:
> iblock indicates the number of i_blkbits-sized blocks rather than
> sectors.
> 
> In addition, considering buffer_head limits mapped size to 32-bits,
> should avoid using generic_block_bmap.
> 
> Fixes: 9da681e017a3 ("staging: erofs: support bmap")
> Signed-off-by: Huang Jianan <huangjianan@oppo.com>
> Signed-off-by: Guo Weichao <guoweichao@oppo.com>
> ---
>   fs/erofs/data.c | 30 ++++++++++--------------------
>   1 file changed, 10 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 347be146884c..d6ea0a216b57 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -312,36 +312,26 @@ static void erofs_raw_access_readahead(struct readahead_control *rac)
>   		submit_bio(bio);
>   }
>   
> -static int erofs_get_block(struct inode *inode, sector_t iblock,
> -			   struct buffer_head *bh, int create)
> -{
> -	struct erofs_map_blocks map = {
> -		.m_la = iblock << 9,
> -	};
> -	int err;
> -
> -	err = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
> -	if (err)
> -		return err;
> -
> -	if (map.m_flags & EROFS_MAP_MAPPED)
> -		bh->b_blocknr = erofs_blknr(map.m_pa);
> -
> -	return err;
> -}
> -
>   static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
>   {
>   	struct inode *inode = mapping->host;
> +	struct erofs_map_blocks map = {
> +		.m_la = blknr_to_addr(block),
> +	};
> +	sector_t blknr = 0;

It could be removed?

>   
>   	if (EROFS_I(inode)->datalayout == EROFS_INODE_FLAT_INLINE) {
>   		erofs_blk_t blks = i_size_read(inode) >> LOG_BLOCK_SIZE;
>   
>   		if (block >> LOG_SECTORS_PER_BLOCK >= blks)
> -			return 0;

return 0;

> +			goto out;
>   	}
>   
> -	return generic_block_bmap(mapping, block, erofs_get_block);
> +	if (!erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW))
> +		blknr = erofs_blknr(map.m_pa);

return erofs_blknr(map.m_pa);

> +
> +out:
> +	return blknr;

return 0;

Anyway, LGTM.

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

>   }
>   
>   /* for uncompressed (aligned) files and raw access for other files */
>