fuse: allow setting of root nodeid Provide a new mount option so that fuse servers can actually set the root nodeid. Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 27c35a1..6b8228d 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h

@@ -636,6 +636,7 @@ struct fuse_fs_context {
 	int fd;
 	struct file *file;
 	unsigned int rootmode;
+	u64 root_nodeid;
 	kuid_t user_id;
 	kgid_t group_id;
 	bool is_bdev:1;
@@ -649,6 +650,7 @@ struct fuse_fs_context {
 	bool no_control:1;
 	bool no_force_umount:1;
 	bool legacy_opts_show:1;
+	bool root_nodeid_present:1;
 	enum fuse_dax_mode dax_mode;
 	unsigned int max_read;
 	unsigned int blksize;

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 04ee77e..00ec50d5 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c

@@ -813,6 +813,7 @@ enum {
 	OPT_ALLOW_OTHER,
 	OPT_MAX_READ,
 	OPT_BLKSIZE,
+	OPT_ROOT_NODEID,
 	OPT_ERR
 };
 
@@ -827,6 +828,7 @@ 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),
+	fsparam_u64	("root_nodeid",		OPT_ROOT_NODEID),
 	{}
 };
 
@@ -922,6 +924,11 @@ static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param)
 		ctx->blksize = result.uint_32;
 		break;
 
+	case OPT_ROOT_NODEID:
+		ctx->root_nodeid = result.uint_64;
+		ctx->root_nodeid_present = true;
+		break;
+
 	default:
 		return -EINVAL;
 	}
@@ -957,6 +964,8 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
 			seq_printf(m, ",max_read=%u", fc->max_read);
 		if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
 			seq_printf(m, ",blksize=%lu", sb->s_blocksize);
+		if (fc->root_nodeid && fc->root_nodeid != FUSE_ROOT_ID)
+			seq_printf(m, ",root_nodeid=%llu", fc->root_nodeid);
 	}
 #ifdef CONFIG_FUSE_DAX
 	if (fc->dax_mode == FUSE_DAX_ALWAYS)
@@ -2006,6 +2015,8 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 	sb->s_flags |= SB_POSIXACL;
 
 	fc->default_permissions = ctx->default_permissions;
+	if (ctx->root_nodeid_present)
+		fc->root_nodeid = ctx->root_nodeid;
 	fc->allow_other = ctx->allow_other;
 	fc->user_id = ctx->user_id;
 	fc->group_id = ctx->group_id;