linux-ext4 - Re: /fs/ext4/namei.c ext4_find_dest

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Date:   Mon, 4 May 2020 08:38:33 +0100
From:   Jonny Grant <jg@...k.org>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: /fs/ext4/namei.c ext4_find_dest_de()

On 04/05/2020 02:51, Theodore Y. Ts'o wrote:
> On Sun, May 03, 2020 at 02:00:25PM +0100, Jonny Grant wrote:
>> Hi
>>
>> I noticed that mkdir() returns EEXIST if a directory already exists.
>> strerror(EEXIST) text is "File exists"
>>
>> Can ext4_find_dest_de() be amended to return EISDIR if a directory already
>> exists? This will make the error message clearer.
> 
> No; this will confuse potentially a large number of existing programs.
> Also, the current behavior is required by POSIx and the Single Unix
> Specification standards.
> 
> 	https://pubs.opengroup.org/onlinepubs/009695399/
> 
> Regards,
> 
> 						- Ted

Hi,

Is it likely POSIX would introduce this change? It's a shame we're still 
constrained by old standards (SVr4, BSD), but it's fine if they can be 
updated.

As  developer, I can see it feels more confusing for users as it is. 
This issue shows up in various programs.

$ mkdir test
$ mkdir test
mkdir: cannot create directory ‘test’: File exists

I would expect it to be clear for users:

$ mkdir test
$ mkdir test
mkdir: cannot create directory ‘test’: Is a directory

The 'mkdir' team don't want to add a call to stat() to give a more 
appropriate error message.

Cheers, Jonny