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

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Date:   Wed, 27 May 2020 22:25:43 +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
> 

Thank you
This is the POSIX mkdir():
https://pubs.opengroup.org/onlinepubs/009695399/functions/mkdir.html

How about adding an improved mkdir to POSIX and the Linux kernel? Let's call it mkdir2()

It has one more error, for EISDIR

[EEXIST]
The named file exists.

[EISDIR]
Directory with that name exists.

I'm tempted to suggest this new function mkdir2() returns 0 on success, or an error number directly number. That would 
do away with 'errno' for this as well.

Regards, Jonny