linux-ext4 - Re: [PATCH v4 2/5] fs: Check if utf8 encoding is loaded before calling utf8

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Date:   Thu, 25 Mar 2021 15:31:42 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Shreeya Patel <shreeya.patel@...labora.com>, tytso@....edu,
        adilger.kernel@...ger.ca, jaegeuk@...nel.org, chao@...nel.org,
        drosen@...gle.com, yuchao0@...wei.com, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, kernel@...labora.com,
        andre.almeida@...labora.com
Subject: Re: [PATCH v4 2/5] fs: Check if utf8 encoding is loaded before
 calling utf8_unload()

Eric Biggers <ebiggers@...nel.org> writes:

> On Thu, Mar 25, 2021 at 05:38:08AM +0530, Shreeya Patel wrote:
>> utf8_unload is being called if CONFIG_UNICODE is enabled.
>> The ifdef block doesn't check if utf8 encoding has been loaded
>> or not before calling the utf8_unload() function.
>> This is not the expected behavior since it would sometimes lead
>> to unloading utf8 even before loading it.
>> Hence, add a condition which will check if sb->encoding is NOT NULL
>> before calling the utf8_unload().
>> 
>> Reviewed-by: Gabriel Krisman Bertazi <krisman@...labora.com>
>> Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
>> ---
>>  fs/ext4/super.c | 6 ++++--
>>  fs/f2fs/super.c | 9 ++++++---
>>  2 files changed, 10 insertions(+), 5 deletions(-)
>> 
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index ad34a37278cd..e438d14f9a87 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -1259,7 +1259,8 @@ static void ext4_put_super(struct super_block *sb)
>>  	fs_put_dax(sbi->s_daxdev);
>>  	fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy);
>>  #ifdef CONFIG_UNICODE
>> -	utf8_unload(sb->s_encoding);
>> +	if (sb->s_encoding)
>> +		utf8_unload(sb->s_encoding);
>>  #endif
>>  	kfree(sbi);
>>  }
>
>
> What's the benefit of this change?  utf8_unload is a no-op when passed a NULL
> pointer; why not keep it that way?

For the record, it no longer is a no-op after patch 5 of this series.
Honestly, I prefer making it explicitly at the caller that we are not
entering the function, like the patch does, instead of returning from it
immediately.  Makes it more readable, IMO.

-- 
Gabriel Krisman Bertazi