diff --git a/fs/bcachefs/thread_with_file.c b/fs/bcachefs/thread_with_file.c
new file mode 100644
index 000000000000..b24baeabf998
--- /dev/null
+++ b/fs/bcachefs/thread_with_file.c
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bcachefs.h"
+#include "printbuf.h"
+#include "thread_with_file.h"
+
+#include <linux/anon_inodes.h>
+#include <linux/file.h>
+#include <linux/kthread.h>
+#include <linux/pagemap.h>
+#include <linux/poll.h>
+
+void bch2_thread_with_file_exit(struct thread_with_file *thr)
+{
+	if (thr->task) {
+		kthread_stop(thr->task);
+		put_task_struct(thr->task);
+	}
+}
+
+int bch2_run_thread_with_file(struct thread_with_file *thr,
+			      const struct file_operations *fops,
+			      int (*fn)(void *))
+{
+	struct file *file = NULL;
+	int ret, fd = -1;
+	unsigned fd_flags = O_CLOEXEC;
+
+	if (fops->read && fops->write)
+		fd_flags |= O_RDWR;
+	else if (fops->read)
+		fd_flags |= O_RDONLY;
+	else if (fops->write)
+		fd_flags |= O_WRONLY;
+
+	char name[TASK_COMM_LEN];
+	get_task_comm(name, current);
+
+	thr->ret = 0;
+	thr->task = kthread_create(fn, thr, "%s", name);
+	ret = PTR_ERR_OR_ZERO(thr->task);
+	if (ret)
+		return ret;
+
+	ret = get_unused_fd_flags(fd_flags);
+	if (ret < 0)
+		goto err;
+	fd = ret;
+
+	file = anon_inode_getfile(name, fops, thr, fd_flags);
+	ret = PTR_ERR_OR_ZERO(file);
+	if (ret)
+		goto err;
+
+	fd_install(fd, file);
+	get_task_struct(thr->task);
+	wake_up_process(thr->task);
+	return fd;
+err:
+	if (fd >= 0)
+		put_unused_fd(fd);
+	if (thr->task)
+		kthread_stop(thr->task);
+	return ret;
+}
+
+static inline bool thread_with_stdio_has_output(struct thread_with_stdio *thr)
+{
+	return thr->stdio.output_buf.pos ||
+		thr->output2.nr ||
+		thr->thr.done;
+}
+
+static ssize_t thread_with_stdio_read(struct file *file, char __user *buf,
+				      size_t len, loff_t *ppos)
+{
+	struct thread_with_stdio *thr =
+		container_of(file->private_data, struct thread_with_stdio, thr);
+	size_t copied = 0, b;
+	int ret = 0;
+
+	if ((file->f_flags & O_NONBLOCK) &&
+	    !thread_with_stdio_has_output(thr))
+		return -EAGAIN;
+
+	ret = wait_event_interruptible(thr->stdio.output_wait,
+		thread_with_stdio_has_output(thr));
+	if (ret)
+		return ret;
+
+	if (thr->thr.done)
+		return 0;
+
+	while (len) {
+		ret = darray_make_room(&thr->output2, thr->stdio.output_buf.pos);
+		if (ret)
+			break;
+
+		spin_lock_irq(&thr->stdio.output_lock);
+		b = min_t(size_t, darray_room(thr->output2), thr->stdio.output_buf.pos);
+
+		memcpy(&darray_top(thr->output2), thr->stdio.output_buf.buf, b);
+		memmove(thr->stdio.output_buf.buf,
+			thr->stdio.output_buf.buf + b,
+			thr->stdio.output_buf.pos - b);
+
+		thr->output2.nr += b;
+		thr->stdio.output_buf.pos -= b;
+		spin_unlock_irq(&thr->stdio.output_lock);
+
+		b = min(len, thr->output2.nr);
+		if (!b)
+			break;
+
+		b -= copy_to_user(buf, thr->output2.data, b);
+		if (!b) {
+			ret = -EFAULT;
+			break;
+		}
+
+		copied	+= b;
+		buf	+= b;
+		len	-= b;
+
+		memmove(thr->output2.data,
+			thr->output2.data + b,
+			thr->output2.nr - b);
+		thr->output2.nr -= b;
+	}
+
+	return copied ?: ret;
+}
+
+static int thread_with_stdio_release(struct inode *inode, struct file *file)
+{
+	struct thread_with_stdio *thr =
+		container_of(file->private_data, struct thread_with_stdio, thr);
+
+	bch2_thread_with_file_exit(&thr->thr);
+	printbuf_exit(&thr->stdio.input_buf);
+	printbuf_exit(&thr->stdio.output_buf);
+	darray_exit(&thr->output2);
+	thr->exit(thr);
+	return 0;
+}
+
+#define WRITE_BUFFER		4096
+
+static inline bool thread_with_stdio_has_input_space(struct thread_with_stdio *thr)
+{
+	return thr->stdio.input_buf.pos < WRITE_BUFFER || thr->thr.done;
+}
+
+static ssize_t thread_with_stdio_write(struct file *file, const char __user *ubuf,
+				       size_t len, loff_t *ppos)
+{
+	struct thread_with_stdio *thr =
+		container_of(file->private_data, struct thread_with_stdio, thr);
+	struct printbuf *buf = &thr->stdio.input_buf;
+	size_t copied = 0;
+	ssize_t ret = 0;
+
+	while (len) {
+		if (thr->thr.done) {
+			ret = -EPIPE;
+			break;
+		}
+
+		size_t b = len - fault_in_readable(ubuf, len);
+		if (!b) {
+			ret = -EFAULT;
+			break;
+		}
+
+		spin_lock(&thr->stdio.input_lock);
+		if (buf->pos < WRITE_BUFFER)
+			bch2_printbuf_make_room(buf, min(b, WRITE_BUFFER - buf->pos));
+		b = min(len, printbuf_remaining_size(buf));
+
+		if (b && !copy_from_user_nofault(&buf->buf[buf->pos], ubuf, b)) {
+			ubuf += b;
+			len -= b;
+			copied += b;
+			buf->pos += b;
+		}
+		spin_unlock(&thr->stdio.input_lock);
+
+		if (b) {
+			wake_up(&thr->stdio.input_wait);
+		} else {
+			if ((file->f_flags & O_NONBLOCK)) {
+				ret = -EAGAIN;
+				break;
+			}
+
+			ret = wait_event_interruptible(thr->stdio.input_wait,
+					thread_with_stdio_has_input_space(thr));
+			if (ret)
+				break;
+		}
+	}
+
+	return copied ?: ret;
+}
+
+static __poll_t thread_with_stdio_poll(struct file *file, struct poll_table_struct *wait)
+{
+	struct thread_with_stdio *thr =
+		container_of(file->private_data, struct thread_with_stdio, thr);
+
+	poll_wait(file, &thr->stdio.output_wait, wait);
+	poll_wait(file, &thr->stdio.input_wait, wait);
+
+	__poll_t mask = 0;
+
+	if (thread_with_stdio_has_output(thr))
+		mask |= EPOLLIN;
+	if (thread_with_stdio_has_input_space(thr))
+		mask |= EPOLLOUT;
+	if (thr->thr.done)
+		mask |= EPOLLHUP|EPOLLERR;
+	return mask;
+}
+
+static const struct file_operations thread_with_stdio_fops = {
+	.release	= thread_with_stdio_release,
+	.read		= thread_with_stdio_read,
+	.write		= thread_with_stdio_write,
+	.poll		= thread_with_stdio_poll,
+	.llseek		= no_llseek,
+};
+
+int bch2_run_thread_with_stdio(struct thread_with_stdio *thr,
+			       void (*exit)(struct thread_with_stdio *),
+			       int (*fn)(void *))
+{
+	thr->stdio.input_buf = PRINTBUF;
+	thr->stdio.input_buf.atomic++;
+	spin_lock_init(&thr->stdio.input_lock);
+	init_waitqueue_head(&thr->stdio.input_wait);
+
+	thr->stdio.output_buf = PRINTBUF;
+	thr->stdio.output_buf.atomic++;
+	spin_lock_init(&thr->stdio.output_lock);
+	init_waitqueue_head(&thr->stdio.output_wait);
+
+	darray_init(&thr->output2);
+	thr->exit = exit;
+
+	return bch2_run_thread_with_file(&thr->thr, &thread_with_stdio_fops, fn);
+}
+
+int bch2_stdio_redirect_read(struct stdio_redirect *stdio, char *buf, size_t len)
+{
+	wait_event(stdio->input_wait,
+		   stdio->input_buf.pos || stdio->done);
+
+	if (stdio->done)
+		return -1;
+
+	spin_lock(&stdio->input_lock);
+	int ret = min(len, stdio->input_buf.pos);
+	stdio->input_buf.pos -= ret;
+	memcpy(buf, stdio->input_buf.buf, ret);
+	memmove(stdio->input_buf.buf,
+		stdio->input_buf.buf + ret,
+		stdio->input_buf.pos);
+	spin_unlock(&stdio->input_lock);
+
+	wake_up(&stdio->input_wait);
+	return ret;
+}
+
+int bch2_stdio_redirect_readline(struct stdio_redirect *stdio, char *buf, size_t len)
+{
+	wait_event(stdio->input_wait,
+		   stdio->input_buf.pos || stdio->done);
+
+	if (stdio->done)
+		return -1;
+
+	spin_lock(&stdio->input_lock);
+	int ret = min(len, stdio->input_buf.pos);
+	char *n = memchr(stdio->input_buf.buf, '\n', ret);
+	if (n)
+		ret = min(ret, n + 1 - stdio->input_buf.buf);
+	stdio->input_buf.pos -= ret;
+	memcpy(buf, stdio->input_buf.buf, ret);
+	memmove(stdio->input_buf.buf,
+		stdio->input_buf.buf + ret,
+		stdio->input_buf.pos);
+	spin_unlock(&stdio->input_lock);
+
+	wake_up(&stdio->input_wait);
+	return ret;
+}
diff --git a/fs/bcachefs/thread_with_file.h b/fs/bcachefs/thread_with_file.h
new file mode 100644
index 000000000000..05879c5048c8
--- /dev/null
+++ b/fs/bcachefs/thread_with_file.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_THREAD_WITH_FILE_H
+#define _BCACHEFS_THREAD_WITH_FILE_H
+
+#include "thread_with_file_types.h"
+
+struct task_struct;
+
+struct thread_with_file {
+	struct task_struct	*task;
+	int			ret;
+	bool			done;
+};
+
+void bch2_thread_with_file_exit(struct thread_with_file *);
+int bch2_run_thread_with_file(struct thread_with_file *,
+			      const struct file_operations *,
+			      int (*fn)(void *));
+
+struct thread_with_stdio {
+	struct thread_with_file	thr;
+	struct stdio_redirect	stdio;
+	DARRAY(char)		output2;
+	void			(*exit)(struct thread_with_stdio *);
+};
+
+static inline void thread_with_stdio_done(struct thread_with_stdio *thr)
+{
+	thr->thr.done = true;
+	thr->stdio.done = true;
+	wake_up(&thr->stdio.input_wait);
+	wake_up(&thr->stdio.output_wait);
+}
+
+int bch2_run_thread_with_stdio(struct thread_with_stdio *,
+			       void (*exit)(struct thread_with_stdio *),
+			       int (*fn)(void *));
+int bch2_stdio_redirect_read(struct stdio_redirect *, char *, size_t);
+int bch2_stdio_redirect_readline(struct stdio_redirect *, char *, size_t);
+
+#endif /* _BCACHEFS_THREAD_WITH_FILE_H */
diff --git a/fs/bcachefs/thread_with_file_types.h b/fs/bcachefs/thread_with_file_types.h
new file mode 100644
index 000000000000..90b5e645e98c
--- /dev/null
+++ b/fs/bcachefs/thread_with_file_types.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_THREAD_WITH_FILE_TYPES_H
+#define _BCACHEFS_THREAD_WITH_FILE_TYPES_H
+
+struct stdio_redirect {
+	spinlock_t		output_lock;
+	wait_queue_head_t	output_wait;
+	struct printbuf		output_buf;
+
+	spinlock_t		input_lock;
+	wait_queue_head_t	input_wait;
+	struct printbuf		input_buf;
+	bool			done;
+};
+
+#endif /* _BCACHEFS_THREAD_WITH_FILE_TYPES_H */
