Re: [RFC PATCH 3/3] fuse: add per-file DAX flag

On 7/16/21 9:32 AM, Vivek Goyal wrote:

On Fri, Jul 16, 2021 at 09:18:34AM +0800, JeffleXu wrote:

quoted

On 7/16/21 8:51 AM, Vivek Goyal wrote:

quoted

On Fri, Jul 16, 2021 at 08:40:29AM +0800, Liu Bo wrote:

quoted

On Thu, Jul 15, 2021 at 05:30:31PM +0800, Jeffle Xu wrote:

quoted

Add one flag for fuse_attr.flags indicating if DAX shall be enabled for
this file.

When the per-file DAX flag changes for an *opened* file, the state of
the file won't be updated until this file is closed and reopened later.

Currently it is not implemented yet to change per-file DAX flag inside
guest kernel, e.g., by chattr(1).

Thanks for the patch, it looks good to me.

I think it's a good starting point, what I'd like to discuss here is
whether we're going to let chattr to toggle the dax flag.

I have the same question. Why not take chattr approach as taken
by ext4/xfs as well.

Vivek

Thanks.

We can implement the chattr approach as ext4/xfs do, if we have this use
scenario. It's an RFC patch, and I want to collect more feedback as soon
as possible.

I guess chattr approach will allow client (as well as server) to control
which files should be DAX. While this approach allows only server to
specify which files should use DAX. Given currently we let client
control whether to use dax or not (-o dax), it probably will make
sense to use chattr based approach?

Yes, changing the per-file DAX flag from guest side, such as by chattr,
may be needed for completeness. I will include this in the next version.

I will look at the patches. Do you have a corresponding user space
implementation somewhere so that I can test it?

Thanks. I have sent the corresponding patch in-reply-to your mail.

-- 
Thanks,
Jeffle
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization