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

From: Theodore Ts'o
Date: Fri Nov 25 2016 - 00:27:06 EST

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@xxxxxxxxx>

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


- Ted