linux-kernel - Re: [RFC PATCH 11/19] famfs_fuse: Basic famfs mount opts

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Message-ID: <4lknmgdq4d6xlmejrddwumpxuwog3l5iwtmoaet7w6swbtc37i@33xmye5u3g5a>
Date: Wed, 23 Apr 2025 15:19:02 -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 11/19] famfs_fuse: Basic famfs mount opts

On 25/04/22 06:51PM, Joanne Koong wrote:
> On Sun, Apr 20, 2025 at 6:34 PM John Groves <John@...ves.net> wrote:
> >
> > * -o shadow=<shadowpath>
> > * -o daxdev=<daxdev>
> >
> > Signed-off-by: John Groves <john@...ves.net>
> > ---
> >  fs/fuse/fuse_i.h |  8 +++++++-
> >  fs/fuse/inode.c  | 25 ++++++++++++++++++++++++-
> >  2 files changed, 31 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> > index b2c563b1a1c8..931613102d32 100644
> > --- a/fs/fuse/fuse_i.h
> > +++ b/fs/fuse/fuse_i.h
> > @@ -580,9 +580,11 @@ struct fuse_fs_context {
> >         unsigned int blksize;
> >         const char *subtype;
> >
> > -       /* DAX device, may be NULL */
> > +       /* DAX device for virtiofs, may be NULL */
> >         struct dax_device *dax_dev;
> >
> > +       const char *shadow; /* famfs - null if not famfs */
> > +
> >         /* fuse_dev pointer to fill in, should contain NULL on entry */
> >         void **fudptr;
> >  };
> > @@ -938,6 +940,10 @@ struct fuse_conn {
> >         /**  uring connection information*/
> >         struct fuse_ring *ring;
> >  #endif
> > +
> > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> > +       char *shadow;
> > +#endif
> >  };
> >
> >  /*
> > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> > index 5c6947b12503..7f4b73e739cb 100644
> > --- a/fs/fuse/inode.c
> > +++ b/fs/fuse/inode.c
> > @@ -766,6 +766,9 @@ enum {
> >         OPT_ALLOW_OTHER,
> >         OPT_MAX_READ,
> >         OPT_BLKSIZE,
> > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> > +       OPT_SHADOW,
> > +#endif
> >         OPT_ERR
> >  };
> >
> > @@ -780,6 +783,9 @@ static const struct fs_parameter_spec fuse_fs_parameters[] = {
> >         fsparam_u32     ("max_read",            OPT_MAX_READ),
> >         fsparam_u32     ("blksize",             OPT_BLKSIZE),
> >         fsparam_string  ("subtype",             OPT_SUBTYPE),
> > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> > +       fsparam_string("shadow",                OPT_SHADOW),
> > +#endif
> >         {}
> >  };
> >
> > @@ -875,6 +881,15 @@ static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param)
> >                 ctx->blksize = result.uint_32;
> >                 break;
> >
> > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> > +       case OPT_SHADOW:
> > +               if (ctx->shadow)
> > +                       return invalfc(fsc, "Multiple shadows specified");
> > +               ctx->shadow = param->string;
> > +               param->string = NULL;
> > +               break;
> > +#endif
> > +
> >         default:
> >                 return -EINVAL;
> >         }
> > @@ -888,6 +903,7 @@ static void fuse_free_fsc(struct fs_context *fsc)
> >
> >         if (ctx) {
> >                 kfree(ctx->subtype);
> > +               kfree(ctx->shadow);
> >                 kfree(ctx);
> >         }
> >  }
> > @@ -919,7 +935,10 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
> >         else if (fc->dax_mode == FUSE_DAX_INODE_USER)
> >                 seq_puts(m, ",dax=inode");
> >  #endif
> > -
> > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> > +       if (fc->shadow)
> > +               seq_printf(m, ",shadow=%s", fc->shadow);
> > +#endif
> >         return 0;
> >  }
> >
> > @@ -1825,6 +1844,10 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
> >         sb->s_root = root_dentry;
> >         if (ctx->fudptr)
> >                 *ctx->fudptr = fud;
> > +
> > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> > +       fc->shadow = kstrdup(ctx->shadow, GFP_KERNEL);
> > +#endif
> 
> Since this is kstrdup-ed, I think you meant to also kfree this in
> fuse_conn_put() when the last refcount on fc gets dropped?

Good catch Joanne! That's queued in my "-next" branch.

Thanks,
John