linux-kernel - Re: [PATCH 1/1 linux-next] ext4: add compatibility flag check

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Date:   Fri, 25 Nov 2016 07:14:33 +0100 (CET)
From:   Fabian Frederick <fabf@...net.be>
To:     Theodore Ts'o <tytso@....edu>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jan Kara <jack@...e.com>, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/1 linux-next] ext4: add compatibility flag check



> On 25 November 2016 at 06:26 Theodore Ts'o <tytso@....edu> wrote:
>
>
> On Thu, Nov 24, 2016 at 08:47:41PM +0100, Fabian Frederick wrote:
> > data=journal mount option should disable O_DIRECT access
> > (See Documentation/filesystems/ext4.txt) but open operations
> > using O_CREAT|O_RDWR|O_DIRECT|O_SYNC have no warning in return and file is
> > being
> > created. This patch adds vfs super_operations compatibility flag function
> > returning -EPERM in such a case.
> >
> > Signed-off-by: Fabian Frederick <fabf@...net.be>
>
> The general practice by most file systems in Linux (for better or for
> worse) is to silently fall back to buffered I/O instead of failing the
> O_DIRECT open.  Feel free to try to convince linux-fsdevel otherwise,
> but that is the general and historical consensus of Linux file system
> developers.
>
> Cheers,

Thanks a lot Ted, I'll have a closer look at vfs/ext4 documentation and add some
details if required.

Regards,
Fabian

>
>                                       - Ted