linux-kernel - Re: [RFC PATCH 10/19] famfs_fuse: Basic fuse kernel ABI enablement for famfs

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Message-ID: <CAJnrk1aROUeJY2g8vHtTgVc=mb+1+7jhJE=B3R0qV_=o6jjNTA@mail.gmail.com>
Date: Tue, 22 Apr 2025 18:36:08 -0700
From: Joanne Koong <joannelkoong@...il.com>
To: John Groves <John@...ves.net>
Cc: Dan Williams <dan.j.williams@...el.com>, Miklos Szeredi <miklos@...redb.hu>, 
	Bernd Schubert <bschubert@....com>, John Groves <jgroves@...ron.com>, Jonathan Corbet <corbet@....net>, 
	Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, 
	Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, 
	"Darrick J . Wong" <djwong@...nel.org>, Luis Henriques <luis@...lia.com>, 
	Randy Dunlap <rdunlap@...radead.org>, Jeff Layton <jlayton@...nel.org>, 
	Kent Overstreet <kent.overstreet@...ux.dev>, Petr Vorel <pvorel@...e.cz>, 
	Brian Foster <bfoster@...hat.com>, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev, 
	linux-cxl@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	Amir Goldstein <amir73il@...il.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
	Stefan Hajnoczi <shajnocz@...hat.com>, Josef Bacik <josef@...icpanda.com>, 
	Aravind Ramesh <arramesh@...ron.com>, Ajay Joshi <ajayjoshi@...ron.com>
Subject: Re: [RFC PATCH 10/19] famfs_fuse: Basic fuse kernel ABI enablement
 for famfs

On Sun, Apr 20, 2025 at 6:34 PM John Groves <John@...ves.net> wrote:
>
> * FUSE_DAX_FMAP flag in INIT request/reply
>
> * fuse_conn->famfs_iomap (enable famfs-mapped files) to denote a
>   famfs-enabled connection
>
> Signed-off-by: John Groves <john@...ves.net>
> ---
>  fs/fuse/fuse_i.h          | 3 +++
>  fs/fuse/inode.c           | 5 +++++
>  include/uapi/linux/fuse.h | 2 ++
>  3 files changed, 10 insertions(+)
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index e04d160fa995..b2c563b1a1c8 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -870,6 +870,9 @@ struct fuse_conn {
>         /* Use io_uring for communication */
>         unsigned int io_uring;
>
> +       /* dev_dax_iomap support for famfs */
> +       unsigned int famfs_iomap:1;
> +
>         /** Maximum stack depth for passthrough backing files */
>         int max_stack_depth;
>
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 29147657a99f..5c6947b12503 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1392,6 +1392,9 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
>                         }
>                         if (flags & FUSE_OVER_IO_URING && fuse_uring_enabled())
>                                 fc->io_uring = 1;
> +                       if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX) &&
> +                                      flags & FUSE_DAX_FMAP)
> +                               fc->famfs_iomap = 1;
>                 } else {
>                         ra_pages = fc->max_read / PAGE_SIZE;
>                         fc->no_lock = 1;
> @@ -1450,6 +1453,8 @@ void fuse_send_init(struct fuse_mount *fm)
>                 flags |= FUSE_SUBMOUNTS;
>         if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
>                 flags |= FUSE_PASSTHROUGH;
> +       if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX))
> +               flags |= FUSE_DAX_FMAP;
>
>         /*
>          * This is just an information flag for fuse server. No need to check
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index 5e0eb41d967e..f9e14180367a 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -435,6 +435,7 @@ struct fuse_file_lock {
>   *                 of the request ID indicates resend requests
>   * FUSE_ALLOW_IDMAP: allow creation of idmapped mounts
>   * FUSE_OVER_IO_URING: Indicate that client supports io-uring
> + * FUSE_DAX_FMAP: kernel supports dev_dax_iomap (aka famfs) fmaps
>   */
>  #define FUSE_ASYNC_READ                (1 << 0)
>  #define FUSE_POSIX_LOCKS       (1 << 1)
> @@ -482,6 +483,7 @@ struct fuse_file_lock {
>  #define FUSE_DIRECT_IO_RELAX   FUSE_DIRECT_IO_ALLOW_MMAP
>  #define FUSE_ALLOW_IDMAP       (1ULL << 40)
>  #define FUSE_OVER_IO_URING     (1ULL << 41)
> +#define FUSE_DAX_FMAP          (1ULL << 42)

There's also a protocol changelog at the top of this file that tracks
any updates made to the uapi. We should probably also update that to
include this?


Thanks,
Joanne
>
>  /**
>   * CUSE INIT request/reply flags
> --
> 2.49.0
>