linux-kernel - Re: [PATCH] Fix logically dead code

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Message-ID: <c973f853-87b6-4dba-955f-1eccecd60f8c@wanadoo.fr>
Date: Fri, 4 Oct 2024 20:12:30 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Shuah Khan <skhan@...uxfoundation.org>,
 Advait Dhamorikar <advaitdhamorikar@...il.com>,
 Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.com>,
 Ronnie Sahlberg <ronniesahlberg@...il.com>,
 Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
 Bharath SM <bharathsm@...rosoft.com>, David Howells <dhowells@...hat.com>,
 Enzo Matsumiya <ematsumiya@...e.de>
Cc: linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
 linux-kernel@...r.kernel.org, anupnewsmail@...il.com
Subject: Re: [PATCH] Fix logically dead code

Le 04/10/2024 à 20:00, Shuah Khan a écrit :
> On 10/4/24 04:30, Advait Dhamorikar wrote:
>> The if condition in collect_sample: can never be satisfied
>> because of a logical contradiction.
> 
> Add a better change log explaining how you found the problem.
> 
> Also your short log is missing subsystem information.
> Check submitting patches document for details on how
> to write shot logs and change logs.
> 
>>
>> Fixes: 94ae8c3fee94 ("smb: client: compress: LZ77 code improvements 
>> cleanup")
>> Signed-off-by: Advait Dhamorikar <advaitdhamorikar@...il.com>
>> ---
>>   fs/smb/client/compress.c | 4 ----
>>   1 file changed, 4 deletions(-)
>>
>> diff --git a/fs/smb/client/compress.c b/fs/smb/client/compress.c
>> index 63b5a55b7a57..766b4de13da7 100644
>> --- a/fs/smb/client/compress.c
>> +++ b/fs/smb/client/compress.c
>> @@ -166,7 +166,6 @@ static int collect_sample(const struct iov_iter 
>> *iter, ssize_t max, u8 *sample)
>>       loff_t start = iter->xarray_start + iter->iov_offset;
>>       pgoff_t last, index = start / PAGE_SIZE;
>>       size_t len, off, foff;
>> -    ssize_t ret = 0;
>>       void *p;
>>       int s = 0;
>> @@ -193,9 +192,6 @@ static int collect_sample(const struct iov_iter 
>> *iter, ssize_t max, u8 *sample)
>>                   memcpy(&sample[s], p, len2);
>>                   kunmap_local(p);
>> -                if (ret < 0)
>> -                    return ret;
>> -
> 
> The change itself looks good to me - unless the intent is to
> check the return from kunmap_local() and take action based on
> it instead of removing the conditional that checks the ret value.

IIUC, kunmap_local() does not return anything.

CJ

> 
>>                   s += len2;
>>                   if (len2 < SZ_2K || s >= max - SZ_2K)
> 
> thanks,
> -- Shuah
> 
>