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Date:   Mon, 24 Oct 2022 20:56:31 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Steve French <smfrench@gmail.com>
Cc:     CIFS <linux-cifs@vger.kernel.org>
Subject: Re: new statx extensions
Message-ID: <Y1deb+K15rKghuP9@sol.localdomain>
References: <CAH2r5muLCRn1O31yCJ=pemuYBY5JpW3NhOBeRpDDE5=-jcLLpQ@mail.gmail.com>
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Hi Steve,

On Thu, Oct 20, 2022 at 10:24:22PM -0500, Steve French wrote:
> I saw this patch series relating to exposing DIO alignment information
> mentioned in lwn today
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=825cf206ed51
> 
> Do you have any ideas of whether any network filesystem could support
> this?  There are lots of features about the server filesystem and
> preferred i/o sizes etc. that can be sent over the protocol (for
> SMB3.1.1).
> 
> Looking at 6.1-rc1 - it looks like this was mainly for xfs and ext4
> but is there any reason that it would be beneficial for cifs.ko - and
> if so is there more clarification on what information would be needed
> from the server to set this value?
> 

STATX_DIOALIGN can, and should, be supported by any filesystem that supports
O_DIRECT.

Its scope is specifically direct I/O alignment restrictions.  It doesn't include
anything about the preferred I/O size.  Note that the existing field
"stx_blksize" is already documented to be the preferred I/O size.

If you have any more questions or thoughts about this, please bring them up on
linux-fsdevel@vger.kernel.org.  That's where all the STATX_DIOALIGN stuff has
been discussed.

- Eric