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

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Message-ID: <qjwm7z3zr4njddcbnt4dqbl3zof4nck5ovfysdopeogcmizsn7@7fei7dldwe6x>
Date: Wed, 23 Apr 2025 15:23:07 -0500
From: John Groves <John@...ves.net>
To: Joanne Koong <joannelkoong@...il.com>
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 25/04/22 06:36PM, Joanne Koong wrote:
> 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?

Another good catch, thanks Joanne! Adding that in -next

John