linux-ext4 - Re: [PATCH v2] ext4: fix bug for rename with RENAME

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Date:   Tue, 5 Jan 2021 13:58:00 +0800
From:   yangerkun <yangerkun@...wei.com>
To:     Jan Kara <jack@...e.cz>
CC:     <linux-ext4@...r.kernel.org>, <tytso@....edu>,
        <adilger.kernel@...ger.ca>, <yi.zhang@...wei.com>,
        <lihaotian9@...wei.com>, <lutianxiong@...wei.com>,
        <linfeilong@...wei.com>
Subject: Re: [PATCH v2] ext4: fix bug for rename with RENAME_WHITEOUT



在 2021/1/4 22:19, Jan Kara 写道:
> 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@...wei.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
>>