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

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Message-ID: <CAJnrk1a40QE+8q-PTTP6GgpDO9d9i_biuN8zk-KSEEiK7S34kA@mail.gmail.com>
Date: Tue, 22 Apr 2025 18:51:12 -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 11/19] famfs_fuse: Basic famfs mount opts

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?


Thanks,
Joanne

>         mutex_unlock(&fuse_mutex);
>         return 0;
>
> --
> 2.49.0
>