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Subject: Re: [PATCH v2] ext4: fix bug for rename with RENAME_WHITEOUT
To:     Jan Kara <jack@suse.cz>
CC:     <linux-ext4@vger.kernel.org>, <tytso@mit.edu>,
        <adilger.kernel@dilger.ca>, <yi.zhang@huawei.com>,
        <lihaotian9@huawei.com>, <lutianxiong@huawei.com>,
        <linfeilong@huawei.com>
References: <20201229090208.1113218-1-yangerkun@huawei.com>
 <20210104141953.GF4018@quack2.suse.cz>
From:   yangerkun <yangerkun@huawei.com>
Message-ID: <b2829aa0-7c7e-077f-3b89-7c3b8fe7b3f9@huawei.com>
Date:   Tue, 5 Jan 2021 13:58:00 +0800
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?? 2021/1/4 22:19, Jan Kara д??:
> On Tue 29-12-20 17:02:08, yangerkun wrote:
>> ext4_rename will create a special inode for whiteout and use this 'ino'
>> to replace the source file's dir entry 'ino'. Once error happens
>> latter(small ext4 img, and consume all space, so the rename with dst
>> path not exist will fail due to the ENOSPC return from ext4_add_entry in
>> ext4_rename), the cleanup do drop the nlink for whiteout, but forget to
>> restore 'ino' with source file. This will lead to "deleted inode
>> referenced".
>>
>> Signed-off-by: yangerkun <yangerkun@huawei.com>
> 
> Thanks for the patch! It looks mostly good, just one comment below:
> 
>>   end_rename:
>> -	brelse(old.dir_bh);
>> -	brelse(old.bh);
>> -	brelse(new.bh);
>>   	if (whiteout) {
>> +		ext4_setent(handle, &old,
>> +			    old.inode->i_ino, old_file_type);
> 
> I'm wondering here - how is it correct to reset the 'old' entry whenever
> whiteout != NULL? I'd expect this to be guarded by the if (retval) check...

Thanks a lot! This is actually a bug and sorry for that. We need check
retval to prevent call for ext4_setent for the correct case. I will
resend the patch!

> 
> 									Honza
> 
>>   		if (retval)
>>   			drop_nlink(whiteout);
>>   		unlock_new_inode(whiteout);
>>   		iput(whiteout);
>>   	}
>> +	brelse(old.dir_bh);
>> +	brelse(old.bh);
>> +	brelse(new.bh);
>>   	if (handle)
>>   		ext4_journal_stop(handle);
>>   	return retval;
>> -- 
>> 2.25.4
>>