linux-kernel - Re: [PATCH v3 2/2] exfat: keep trailing dots in paths if keep_last

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Date:   Wed, 16 Mar 2022 19:06:15 +0100
From:   David Disseldorp <ddiss@...e.de>
To:     Vasant Karasulli <vkarasulli@...e.de>
Cc:     Namjae Jeon <linkinjeon@...nel.org>,
        Sungjong Seo <sj1557.seo@...sung.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH v3 2/2] exfat: keep trailing dots in paths if
 keep_last_dots is

Hi Vasant,

A couple of things I missed in the previous round...

On Fri, 11 Mar 2022 12:47:46 +0100, Vasant Karasulli wrote:

> exfat currently unconditionally strips trailing
> periods '.' when performing path lookup, but allows them in the filenames
> during file creation.

Trailing periods *are* currently stripped during creation, so that
statement should be removed, e.g.

  The Linux kernel exfat driver currently unconditionally strips
  trailing periods '.' from path components.

> This is done intentionally, loosely following Windows
> behaviour and specifications which state:
> 
>   #exFAT
>   The concatenated file name has the same set of illegal characters as
>   other FAT-based file systems (see Table 31).
> 
>   #FAT
>   ...
>   Leading and trailing spaces in a long name are ignored.
>   Leading and embedded periods are allowed in a name and are stored in
>   the long name. Trailing periods are ignored.
> 
> Note: Leading and trailing space ' ' characters are currently retained
> by Linux kernel exfat, in conflict with the above specification.
> On Windows 10, File Explore application retains leading and trailing
> space characters. But on the commandline behavior was exactly the opposite.

As mentioned earlier, my observations from Windows10 CopyFile() win32
API calls were that trailing spaces and periods are stripped. AFAICT
that's also the case for Windows Explorer and cmd.exe paths.

Cheers, David