linux-kernel - Re: [PATCH] erofs: avoid the potentially wrong m

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Message-ID: <YvYFLF2DHDuRoTpT@B-P7TQMD6M-0146.local>
Date:   Fri, 12 Aug 2022 15:45:48 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Yue Hu <zbestahu@...il.com>
Cc:     xiang@...nel.org, chao@...nel.org, linux-erofs@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, huyue2@...lpad.com,
        zhangwen@...lpad.com
Subject: Re: [PATCH] erofs: avoid the potentially wrong m_plen for big
 pcluster

Hi Yue,

On Fri, Aug 12, 2022 at 02:01:50PM +0800, Yue Hu wrote:
> Actually, 'compressedlcs' stores compressed block count rather than
> lcluster count. Therefore, the number of bits for shifting the count
> should be 'LOG_BLOCK_SIZE' rather than 'lclusterbits' although current
> lcluster size is 4K. The value of 'm_plen' will be wrong once we enable
> the non 4K-sized lcluster.

I'd like to make the last sentence into a separate paragraph.
I could update it when applying.

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

Otherwise it looks good to me,
Reviewed-by: Gao Xiang <hsiangkao@...ux.alibaba.com>

Thanks,
Gao Xiang

> ---
>  fs/erofs/zmap.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> index 572f0b8151ba..d58549ca1df9 100644
> --- a/fs/erofs/zmap.c
> +++ b/fs/erofs/zmap.c
> @@ -141,7 +141,7 @@ struct z_erofs_maprecorder {
>  	u8  type, headtype;
>  	u16 clusterofs;
>  	u16 delta[2];
> -	erofs_blk_t pblk, compressedlcs;
> +	erofs_blk_t pblk, compressedblks;
>  	erofs_off_t nextpackoff;
>  };
>  
> @@ -192,7 +192,7 @@ static int legacy_load_cluster_from_disk(struct z_erofs_maprecorder *m,
>  				DBG_BUGON(1);
>  				return -EFSCORRUPTED;
>  			}
> -			m->compressedlcs = m->delta[0] &
> +			m->compressedblks = m->delta[0] &
>  				~Z_EROFS_VLE_DI_D0_CBLKCNT;
>  			m->delta[0] = 1;
>  		}
> @@ -293,7 +293,7 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,
>  				DBG_BUGON(1);
>  				return -EFSCORRUPTED;
>  			}
> -			m->compressedlcs = lo & ~Z_EROFS_VLE_DI_D0_CBLKCNT;
> +			m->compressedblks = lo & ~Z_EROFS_VLE_DI_D0_CBLKCNT;
>  			m->delta[0] = 1;
>  			return 0;
>  		} else if (i + 1 != (int)vcnt) {
> @@ -497,7 +497,7 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
>  		return 0;
>  	}
>  	lcn = m->lcn + 1;
> -	if (m->compressedlcs)
> +	if (m->compressedblks)
>  		goto out;
>  
>  	err = z_erofs_load_cluster_from_disk(m, lcn, false);
> @@ -506,7 +506,7 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
>  
>  	/*
>  	 * If the 1st NONHEAD lcluster has already been handled initially w/o
> -	 * valid compressedlcs, which means at least it mustn't be CBLKCNT, or
> +	 * valid compressedblks, which means at least it mustn't be CBLKCNT, or
>  	 * an internal implemenatation error is detected.
>  	 *
>  	 * The following code can also handle it properly anyway, but let's
> @@ -523,12 +523,12 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
>  		 * if the 1st NONHEAD lcluster is actually PLAIN or HEAD type
>  		 * rather than CBLKCNT, it's a 1 lcluster-sized pcluster.
>  		 */
> -		m->compressedlcs = 1;
> +		m->compressedblks = 1 << (lclusterbits - LOG_BLOCK_SIZE);
>  		break;
>  	case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
>  		if (m->delta[0] != 1)
>  			goto err_bonus_cblkcnt;
> -		if (m->compressedlcs)
> +		if (m->compressedblks)
>  			break;
>  		fallthrough;
>  	default:
> @@ -539,7 +539,7 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
>  		return -EFSCORRUPTED;
>  	}
>  out:
> -	map->m_plen = (u64)m->compressedlcs << lclusterbits;
> +	map->m_plen = (u64)m->compressedblks << LOG_BLOCK_SIZE;
>  	return 0;
>  err_bonus_cblkcnt:
>  	erofs_err(m->inode->i_sb,
> -- 
> 2.17.1