Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <9f2948cb-a4b0-bced-1d11-cf9fc712ba9b@kernel.org>
Date:   Wed, 31 May 2023 09:11:54 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.0
Subject: Re: [PATCH v2 1/1] f2fs: fix args passed to trace_f2fs_lookup_end
Content-Language: en-US
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Wu Bo <bo.wu@vivo.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, wubo.oduw@gmail.com
References: <20230530012118.74228-1-bo.wu@vivo.com>
 <ZHaHknKmSQIdQzBC@google.com>
From:   Chao Yu <chao@kernel.org>
In-Reply-To: <ZHaHknKmSQIdQzBC@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2023/5/31 7:32, Jaegeuk Kim wrote:
> On 05/30, Wu Bo wrote:
>> The NULL return of 'd_splice_alias' dosen't mean error. Thus the
>> successful case will also return NULL, which makes the tracepoint always
>> print 'err=-ENOENT'.
>>
>> Signed-off-by: Wu Bo <bo.wu@vivo.com>
>> ---
>>   fs/f2fs/namei.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
>> index 77a71276ecb1..0c5e4c424eab 100644
>> --- a/fs/f2fs/namei.c
>> +++ b/fs/f2fs/namei.c
>> @@ -576,8 +576,9 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
>>   	}
>>   #endif
>>   	new = d_splice_alias(inode, dentry);
>> -	err = PTR_ERR_OR_ZERO(new);
>> -	trace_f2fs_lookup_end(dir, dentry, ino, !new ? -ENOENT : err);
>> +	if (IS_ERR(new))
>> +		err = PTR_ERR(new);
>> +	trace_f2fs_lookup_end(dir, new ? new : dentry, ino, err);
> 
> Again, new can be an error pointer, and the previous err was supposed to be
> zero or -ENOENT.
> 
> case 1) dentry exists: err (0) with new (NULL) --> dentry, err=0
> case 2) dentry exists: err (0) with new (VALID) --> new, err=0
> case 3) dentry exists: err (0) with new (ERR) --> dentry, err=ERR
> case 4) no dentry exists: err (-ENOENT) with new (NULL) --> dentry, err=-ENOENT
> case 4) no dentry exists: err (-ENOENT) with new (VALID) --> new, err=-ENOENT
> case 5) no dentry exists: err (-ENOENT) with new (ERR) --> dentry, err=ERR
> 
> 	trace_f2fs_lookup_end(dir, !IS_ERR_OR_NULL(new) ? new : dentry,
> 				ino, IS_ERR(new) ? PTR_ERR(new) : err);

Agreed, could you please add above description in commit message?

Thanks,

> 
> 
>>   	return new;
>>   out_iput:
>>   	iput(inode);
>> -- 
>> 2.35.3