On Thu, Jul 03, 2025 at 01:50:25PM -0500, John Groves wrote:
> * -o shadow=<shadowpath>
What is a shadow?
> * -o daxdev=<daxdev>
And, uh, if there's a FUSE_GET_DAXDEV command, then what does this mount
option do? Pre-populate the first element of that set?
--D
> Signed-off-by: John Groves <john@xxxxxxxxxx>
> ---
> fs/fuse/fuse_i.h | 8 +++++++-
> fs/fuse/inode.c | 28 +++++++++++++++++++++++++++-
> 2 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index a592c1002861..f4ee61046578 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -583,9 +583,11 @@ 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;
> };
> @@ -941,6 +943,10 @@ 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 e48e11c3f9f3..a7e1cf8257b0 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;
> }
>
> @@ -1017,6 +1036,9 @@ void fuse_conn_put(struct fuse_conn *fc)
> }
> if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
> fuse_backing_files_free(fc);
> +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)
> + kfree(fc->shadow);
> +#endif
> call_rcu(&fc->rcu, delayed_release);
> }
> }
> @@ -1834,6 +1856,10 @@ 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
> mutex_unlock(&fuse_mutex);
> return 0;
>
> --
> 2.49.0
>
>
