[Virtio-fs] [PATCH v6 4/7] fuse: negotiate per-file DAX in FUSE_INIT

[Vivek Goyal]

On Mon, Oct 11, 2021 at 11:00:49AM +0800, Jeffle Xu wrote:
> Among the FUSE_INIT phase, client shall advertise per-file DAX if it's
> mounted with "-o dax=inode". Then server is aware that client is in
> per-file DAX mode, and will construct per-inode DAX attribute
> accordingly.
> 
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
>  fs/fuse/inode.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index b4b41683e97e..f4ad99e2415b 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1203,6 +1203,8 @@ void fuse_send_init(struct fuse_mount *fm)
>  #ifdef CONFIG_FUSE_DAX
>  	if (fm->fc->dax)
>  		ia->in.flags |= FUSE_MAP_ALIGNMENT;
> +	if (fm->fc->dax_mode == FUSE_DAX_INODE)
> +		ia->in.flags |= FUSE_PERFILE_DAX;

Are you not keeping track of server's response whether server supports
per inode dax or not. Client might be new and server might be old and
server might not support per inode dax. In that case, we probably 
should error out if user mounted with "-o dax=inode".

Vivek

>  #endif
>  	if (fm->fc->auto_submounts)
>  		ia->in.flags |= FUSE_SUBMOUNTS;
> -- 
> 2.27.0
>