fuse: allow skipping control interface and forced unmount

virtio-fs does not support aborting requests which are being
processed. That is requests which have been sent to fuse daemon on host.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/fuse_i.h

@@ -468,6 +468,8 @@ struct fuse_fs_context {
 	bool default_permissions:1;
 	bool allow_other:1;
 	bool destroy:1;
+	bool no_control:1;
+	bool no_force_umount:1;
 	unsigned int max_read;
 	unsigned int blksize;
 	const char *subtype;
@@ -696,6 +698,12 @@ struct fuse_conn {
 	/* Delete dentries that have gone stale */
 	unsigned int delete_stale:1;
 
+	/** Do not create entry in fusectl fs */
+	unsigned int no_control:1;
+
+	/** Do not allow MNT_FORCE umount */
+	unsigned int no_force_umount:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 

fs/fuse/inode.c

@@ -364,7 +364,10 @@ void fuse_unlock_inode(struct inode *inode, bool locked)
 
 static void fuse_umount_begin(struct super_block *sb)
 {
-	fuse_abort_conn(get_fuse_conn_super(sb));
+	struct fuse_conn *fc = get_fuse_conn_super(sb);
+
+	if (!fc->no_force_umount)
+		fuse_abort_conn(fc);
 }
 
 static void fuse_send_destroy(struct fuse_conn *fc)
@@ -1171,6 +1174,8 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 	fc->group_id = ctx->group_id;
 	fc->max_read = max_t(unsigned, 4096, ctx->max_read);
 	fc->destroy = ctx->destroy;
+	fc->no_control = ctx->no_control;
+	fc->no_force_umount = ctx->no_force_umount;
 
 	err = -ENOMEM;
 	root = fuse_get_root_inode(sb, ctx->rootmode);