bcachefs: thread_with_file

Abstract out a new helper from the data job code, for connecting a
kthread to a file descriptor.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/chardev.c

@@ -29,6 +29,62 @@ static int copy_to_user_errcode(void __user *to, const void *from, unsigned long
 	return copy_to_user(to, from, n) ? -EFAULT : 0;
 }
 
+struct thread_with_file {
+	struct task_struct	*task;
+	int			ret;
+};
+
+static void thread_with_file_exit(struct thread_with_file *thr)
+{
+	kthread_stop(thr->task);
+	put_task_struct(thr->task);
+}
+
+__printf(4, 0)
+static int run_thread_with_file(struct thread_with_file *thr,
+				const struct file_operations *fops,
+				int (*fn)(void *), const char *fmt, ...)
+{
+	va_list args;
+	struct file *file = NULL;
+	int ret, fd = -1;
+	struct printbuf name = PRINTBUF;
+	unsigned fd_flags = O_RDONLY|O_CLOEXEC|O_NONBLOCK;
+
+	va_start(args, fmt);
+	prt_vprintf(&name, fmt, args);
+	va_end(args);
+
+	thr->ret = 0;
+	thr->task = kthread_create(fn, thr, name.buf);
+	ret = PTR_ERR_OR_ZERO(thr->task);
+	if (ret)
+		goto err;
+
+	ret = get_unused_fd_flags(fd_flags);
+	if (ret < 0)
+		goto err_stop_task;
+	fd = ret;
+
+	file = anon_inode_getfile(name.buf, fops, thr, fd_flags);
+	ret = PTR_ERR_OR_ZERO(file);
+	if (ret)
+		goto err_put_fd;
+
+	fd_install(fd, file);
+	get_task_struct(thr->task);
+	wake_up_process(thr->task);
+	printbuf_exit(&name);
+	return fd;
+err_put_fd:
+	put_unused_fd(fd);
+err_stop_task:
+	kthread_stop(thr->task);
+err:
+	printbuf_exit(&name);
+	return ret;
+}
+
 /* returns with ref on ca->ref */
 static struct bch_dev *bch2_device_lookup(struct bch_fs *c, u64 dev,
 					  unsigned flags)
@@ -299,31 +355,27 @@ static long bch2_ioctl_disk_set_state(struct bch_fs *c,
 }
 
 struct bch_data_ctx {
+	struct thread_with_file		thr;
+
 	struct bch_fs			*c;
 	struct bch_ioctl_data		arg;
 	struct bch_move_stats		stats;
-
-	int				ret;
-
-	struct task_struct		*thread;
 };
 
 static int bch2_data_thread(void *arg)
 {
-	struct bch_data_ctx *ctx = arg;
-
-	ctx->ret = bch2_data_job(ctx->c, &ctx->stats, ctx->arg);
+	struct bch_data_ctx *ctx = container_of(arg, struct bch_data_ctx, thr);
 
+	ctx->thr.ret = bch2_data_job(ctx->c, &ctx->stats, ctx->arg);
 	ctx->stats.data_type = U8_MAX;
 	return 0;
 }
 
 static int bch2_data_job_release(struct inode *inode, struct file *file)
 {
-	struct bch_data_ctx *ctx = file->private_data;
+	struct bch_data_ctx *ctx = container_of(file->private_data, struct bch_data_ctx, thr);
 
-	kthread_stop(ctx->thread);
-	put_task_struct(ctx->thread);
+	thread_with_file_exit(&ctx->thr);
 	kfree(ctx);
 	return 0;
 }
@@ -331,7 +383,7 @@ static int bch2_data_job_release(struct inode *inode, struct file *file)
 static ssize_t bch2_data_job_read(struct file *file, char __user *buf,
 				  size_t len, loff_t *ppos)
 {
-	struct bch_data_ctx *ctx = file->private_data;
+	struct bch_data_ctx *ctx = container_of(file->private_data, struct bch_data_ctx, thr);
 	struct bch_fs *c = ctx->c;
 	struct bch_ioctl_data_event e = {
 		.type			= BCH_DATA_EVENT_PROGRESS,
@@ -357,10 +409,8 @@ static const struct file_operations bcachefs_data_ops = {
 static long bch2_ioctl_data(struct bch_fs *c,
 			    struct bch_ioctl_data arg)
 {
-	struct bch_data_ctx *ctx = NULL;
-	struct file *file = NULL;
-	unsigned flags = O_RDONLY|O_CLOEXEC|O_NONBLOCK;
-	int ret, fd = -1;
+	struct bch_data_ctx *ctx;
+	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -375,35 +425,11 @@ static long bch2_ioctl_data(struct bch_fs *c,
 	ctx->c = c;
 	ctx->arg = arg;
 
-	ctx->thread = kthread_create(bch2_data_thread, ctx,
+	ret = run_thread_with_file(&ctx->thr,
+				   &bcachefs_data_ops,
+				   bch2_data_thread,
 				   "bch-data/%s", c->name);
-	if (IS_ERR(ctx->thread)) {
-		ret = PTR_ERR(ctx->thread);
-		goto err;
-	}
-
-	ret = get_unused_fd_flags(flags);
 	if (ret < 0)
-		goto err;
-	fd = ret;
-
-	file = anon_inode_getfile("[bcachefs]", &bcachefs_data_ops, ctx, flags);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto err;
-	}
-
-	fd_install(fd, file);
-
-	get_task_struct(ctx->thread);
-	wake_up_process(ctx->thread);
-
-	return fd;
-err:
-	if (fd >= 0)
-		put_unused_fd(fd);
-	if (!IS_ERR_OR_NULL(ctx->thread))
-		kthread_stop(ctx->thread);
 		kfree(ctx);
 	return ret;
 }