linux-kernel - Re: [PATCH v2] erofs: use Z_EROFS_LCLUSTER_TYPE

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Message-ID: <10e648ae-7e0b-4560-a73d-b728efbc9e15@huawei.com>
Date: Fri, 7 Feb 2025 16:57:01 +0800
From: Hongbo Li <lihongbo22@...wei.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>, Hongzhen Luo
	<hongzhen@...ux.alibaba.com>, <linux-erofs@...ts.ozlabs.org>
CC: <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] erofs: use Z_EROFS_LCLUSTER_TYPE_MAX to simplify
 switches



On 2025/2/7 16:29, Gao Xiang wrote:
> 
> 
> On 2025/2/7 16:08, Hongzhen Luo wrote:
>> There's no need to enumerate each type.  No logic changes.
>>
>> Signed-off-by: Hongzhen Luo <hongzhen@...ux.alibaba.com>
>> ---
>> Changes since v1: Put the exception branch at the beginning.
>>
>> v1: 
>> https://lore.kernel.org/all/20250207064135.2249529-1-hongzhen@linux.alibaba.com/
>> ---
>>   fs/erofs/zmap.c | 65 +++++++++++++++++++++----------------------------
>>   1 file changed, 28 insertions(+), 37 deletions(-)
>>
>> diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
>> index 689437e99a5a..f65c76991e02 100644
>> --- a/fs/erofs/zmap.c
>> +++ b/fs/erofs/zmap.c
>> @@ -265,23 +265,22 @@ static int z_erofs_extent_lookback(struct 
>> z_erofs_maprecorder *m,
>>           if (err)
>>               return err;
>> -        switch (m->type) {
>> -        case Z_EROFS_LCLUSTER_TYPE_NONHEAD:
>> +        if (m->type >= Z_EROFS_LCLUSTER_TYPE_MAX) {
>> +            erofs_err(sb, "unknown type %u @ lcn %lu of nid %llu",
>> +                  m->type, lcn, vi->nid);
>> +            DBG_BUGON(1);
>> +            return -EOPNOTSUPP;
>> +        }
>> +
>> +        if (m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
>>               lookback_distance = m->delta[0];
>>               if (!lookback_distance)
>>                   goto err_bogus;
>>               continue;
>> -        case Z_EROFS_LCLUSTER_TYPE_PLAIN:
>> -        case Z_EROFS_LCLUSTER_TYPE_HEAD1:
>> -        case Z_EROFS_LCLUSTER_TYPE_HEAD2:
>> +        } else if (m->type < Z_EROFS_LCLUSTER_TYPE_MAX) {
> 
> 
> Just `} else {` here?
> 
>>               m->headtype = m->type;
>>               m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
>>               return 0;
>> -        default:
>> -            erofs_err(sb, "unknown type %u @ lcn %lu of nid %llu",
>> -                  m->type, lcn, vi->nid);
>> -            DBG_BUGON(1);
>> -            return -EOPNOTSUPP;
>>           }
>>       }
>>   err_bogus:
>> @@ -329,35 +328,31 @@ static int 
>> z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
>>       DBG_BUGON(lcn == initial_lcn &&
>>             m->type == Z_EROFS_LCLUSTER_TYPE_NONHEAD);
>> -    switch (m->type) {
>> -    case Z_EROFS_LCLUSTER_TYPE_PLAIN:
>> -    case Z_EROFS_LCLUSTER_TYPE_HEAD1:
>> -    case Z_EROFS_LCLUSTER_TYPE_HEAD2:
>> +    if (m->type >= Z_EROFS_LCLUSTER_TYPE_MAX) {
>> +        erofs_err(sb, "cannot found CBLKCNT @ lcn %lu of nid %llu", 
>> lcn, vi->nid);
>> +        DBG_BUGON(1);
>> +        return -EFSCORRUPTED;
>> +    }
> 
> No, I don't think it's equivalent, please use
> the previous version for this part instead.

I think this version doesn't consider the fallthrough case. May be just 
use the goto statement can keep equivalent.

Thanks,
Hongbo

> 
> Thanks,
> Gao Xiang