Re: [PATCH v2] staging: erofs: keep corrupted fs from crashing kernel in erofs_namei()

[Gao Xiang <gaoxiang25@huawei.com>]

Hi Dan,

On 2019/2/15 17:35, Dan Carpenter wrote:
> On Fri, Feb 15, 2019 at 05:32:33PM +0800, Chao Yu wrote:
>> On 2019/2/15 15:57, Dan Carpenter wrote:
>>> On Fri, Feb 15, 2019 at 03:02:25PM +0800, Chao Yu wrote:
>>>> On 2019/2/1 20:16, Gao Xiang wrote:
>>>>> +	/*
>>>>> +	 * on-disk error, let's only BUG_ON in the debugging mode.
>>>>> +	 * otherwise, it will return 1 to just skip the invalid name
>>>>> +	 * and go on (in consideration of the lookup performance).
>>>>> +	 */
>>>>> +	DBG_BUGON(qd->name > qd->end);
>>>>
>>>> qd->name == qd->end is not allowed as well?
>>>>
>>>> So will it be better to return directly here?
>>>>
>>>> 	if (unlikely(qd->name >= qd->end)) {
>>>> 		DBG_BUGON(1);
>>>> 		return 1;
>>>> 	}
>>>
>>> Please don't add likely/unlikely() annotations unless you have
>>> benchmarked it and it makes a difference.
>>
>> Well, it only occur for corrupted image, since the image is readonly, so it
>> is really rare.
> 
> The likely/unlikely() annotations make the code harder to read.  It's
> only worth it if it's is a speedup on a fast path.

Yes, I think abuse of using likely/unlikely() should be avoided (I agree that
some odd likely/unlikely() exists in the current code, that should be cleaned up).

However, likely/unlikely()s are also clearly highlight critical/corner paths).
I personally think it should be used in case-by-case basis rather than a unified
conclusion ("that makes the code harder to read").

Thanks,
Gao Xiang

> 
> regards,
> dan carpenter
> 
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