fuse: convert destroy to simple api

We can use the "force" flag to make sure the DESTROY request is always sent
to userspace.  So no need to keep it allocated during the lifetime of the
filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/file.c

@@ -279,7 +279,7 @@ void fuse_release_common(struct file *file, bool isdir)
 	 * synchronous RELEASE is allowed (and desirable) in this case
 	 * because the server can be trusted not to screw up.
 	 */
-	fuse_file_put(ff, ff->fc->destroy_req != NULL, isdir);
+	fuse_file_put(ff, ff->fc->destroy, isdir);
 }
 
 static int fuse_open(struct inode *inode, struct file *file)

fs/fuse/fuse_i.h

@@ -715,6 +715,9 @@ struct fuse_conn {
 	/** Does the filesystem support copy_file_range? */
 	unsigned no_copy_file_range:1;
 
+	/* Send DESTROY request */
+	unsigned int destroy:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 
@@ -736,9 +739,6 @@ struct fuse_conn {
 	/** Key for lock owner ID scrambling */
 	u32 scramble_key[4];
 
-	/** Reserved request for the DESTROY message */
-	struct fuse_req *destroy_req;
-
 	/** Version counter for attribute changes */
 	atomic64_t attr_version;
 

fs/fuse/inode.c

@@ -386,14 +386,13 @@ static void fuse_umount_begin(struct super_block *sb)
 
 static void fuse_send_destroy(struct fuse_conn *fc)
 {
-	struct fuse_req *req = fc->destroy_req;
-	if (req && fc->conn_init) {
-		fc->destroy_req = NULL;
-		req->in.h.opcode = FUSE_DESTROY;
-		__set_bit(FR_FORCE, &req->flags);
-		__clear_bit(FR_BACKGROUND, &req->flags);
-		fuse_request_send(fc, req);
-		fuse_put_request(fc, req);
+	if (fc->conn_init) {
+		FUSE_ARGS(args);
+
+		args.opcode = FUSE_DESTROY;
+		args.force = true;
+		args.nocreds = true;
+		fuse_simple_request(fc, &args);
 	}
 }
 
@@ -640,8 +639,6 @@ EXPORT_SYMBOL_GPL(fuse_conn_init);
 void fuse_conn_put(struct fuse_conn *fc)
 {
 	if (refcount_dec_and_test(&fc->count)) {
-		if (fc->destroy_req)
-			fuse_request_free(fc->destroy_req);
 		put_pid_ns(fc->pid_ns);
 		put_user_ns(fc->user_ns);
 		fc->release(fc);
@@ -1171,6 +1168,7 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
 	fc->user_id = ctx->user_id;
 	fc->group_id = ctx->group_id;
 	fc->max_read = max_t(unsigned, 4096, ctx->max_read);
+	fc->destroy = is_bdev;
 
 	/* Used by get_root_inode() */
 	sb->s_fs_info = fc;
@@ -1189,12 +1187,6 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
 		goto err_put_root;
 	__set_bit(FR_BACKGROUND, &init_req->flags);
 
-	if (is_bdev) {
-		fc->destroy_req = fuse_request_alloc(0);
-		if (!fc->destroy_req)
-			goto err_free_init_req;
-	}
-
 	mutex_lock(&fuse_mutex);
 	err = -EINVAL;
 	if (file->private_data)
@@ -1221,7 +1213,6 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
 
  err_unlock:
 	mutex_unlock(&fuse_mutex);
- err_free_init_req:
 	fuse_request_free(init_req);
  err_put_root:
 	dput(root_dentry);
@@ -1287,7 +1278,8 @@ static void fuse_sb_destroy(struct super_block *sb)
 	struct fuse_conn *fc = get_fuse_conn_super(sb);
 
 	if (fc) {
-		fuse_send_destroy(fc);
+		if (fc->destroy)
+			fuse_send_destroy(fc);
 
 		fuse_abort_conn(fc);
 		fuse_wait_aborted(fc);