Merge tag 'fuse-update-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse updates from Miklos Szeredi:
"Add support for io-uring communication between kernel and userspace
using IORING_OP_URING_CMD (Bernd Schubert). Following features enable
gains in performance compared to the regular interface:

- Allow processing multiple requests with less syscall overhead

- Combine commit of old and fetch of new fuse request

- CPU/NUMA affinity of queues

Patches were reviewed by several people, including Pavel Begunkov,
io-uring co-maintainer"

* tag 'fuse-update-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: prevent disabling io-uring on active connections
fuse: enable fuse-over-io-uring
fuse: block request allocation until io-uring init is complete
fuse: {io-uring} Prevent mount point hang on fuse-server termination
fuse: Allow to queue bg requests through io-uring
fuse: Allow to queue fg requests through io-uring
fuse: {io-uring} Make fuse_dev_queue_{interrupt,forget} non-static
fuse: {io-uring} Handle teardown of ring entries
fuse: Add io-uring sqe commit and fetch support
fuse: {io-uring} Make hash-list req unique finding functions non-static
fuse: Add fuse-io-uring handling into fuse_copy
fuse: Make fuse_copy non static
fuse: {io-uring} Handle SQEs - register commands
fuse: make args->in_args[0] to be always the header
fuse: Add fuse-io-uring design documentation
fuse: Move request bits
fuse: Move fuse_get_dev to header file
fuse: rename to fuse_dev_end_requests and make non-static

Documentation/filesystems/fuse-io-uring.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================================
+FUSE-over-io-uring design documentation
+=======================================
+
+This documentation covers basic details how the fuse
+kernel/userspace communication through io-uring is configured
+and works. For generic details about FUSE see fuse.rst.
+
+This document also covers the current interface, which is
+still in development and might change.
+
+Limitations
+===========
+As of now not all requests types are supported through io-uring, userspace
+is required to also handle requests through /dev/fuse after io-uring setup
+is complete. Specifically notifications (initiated from the daemon side)
+and interrupts.
+
+Fuse io-uring configuration
+===========================
+
+Fuse kernel requests are queued through the classical /dev/fuse
+read/write interface - until io-uring setup is complete.
+
+In order to set up fuse-over-io-uring fuse-server (user-space)
+needs to submit SQEs (opcode = IORING_OP_URING_CMD) to the /dev/fuse
+connection file descriptor. Initial submit is with the sub command
+FUSE_URING_REQ_REGISTER, which will just register entries to be
+available in the kernel.
+
+Once at least one entry per queue is submitted, kernel starts
+to enqueue to ring queues.
+Note, every CPU core has its own fuse-io-uring queue.
+Userspace handles the CQE/fuse-request and submits the result as
+subcommand FUSE_URING_REQ_COMMIT_AND_FETCH - kernel completes
+the requests and also marks the entry available again. If there are
+pending requests waiting the request will be immediately submitted
+to the daemon again.
+
+Initial SQE
+-----------::
+
+ |                                    |  FUSE filesystem daemon
+ |                                    |
+ |                                    |  >io_uring_submit()
+ |                                    |   IORING_OP_URING_CMD /
+ |                                    |   FUSE_URING_CMD_REGISTER
+ |                                    |  [wait cqe]
+ |                                    |   >io_uring_wait_cqe() or
+ |                                    |   >io_uring_submit_and_wait()
+ |                                    |
+ |  >fuse_uring_cmd()                 |
+ |   >fuse_uring_register()           |
+
+
+Sending requests with CQEs
+--------------------------::
+
+ |                                           |  FUSE filesystem daemon
+ |                                           |  [waiting for CQEs]
+ |  "rm /mnt/fuse/file"                      |
+ |                                           |
+ |  >sys_unlink()                            |
+ |    >fuse_unlink()                         |
+ |      [allocate request]                   |
+ |      >fuse_send_one()                     |
+ |        ...                                |
+ |       >fuse_uring_queue_fuse_req          |
+ |        [queue request on fg queue]        |
+ |         >fuse_uring_add_req_to_ring_ent() |
+ |         ...                               |
+ |          >fuse_uring_copy_to_ring()       |
+ |          >io_uring_cmd_done()             |
+ |       >request_wait_answer()              |
+ |         [sleep on req->waitq]             |
+ |                                           |  [receives and handles CQE]
+ |                                           |  [submit result and fetch next]
+ |                                           |  >io_uring_submit()
+ |                                           |   IORING_OP_URING_CMD/
+ |                                           |   FUSE_URING_CMD_COMMIT_AND_FETCH
+ |  >fuse_uring_cmd()                        |
+ |   >fuse_uring_commit_fetch()              |
+ |    >fuse_uring_commit()                   |
+ |     >fuse_uring_copy_from_ring()          |
+ |      [ copy the result to the fuse req]   |
+ |     >fuse_uring_req_end()                 |
+ |      >fuse_request_end()                  |
+ |       [wake up req->waitq]                |
+ |    >fuse_uring_next_fuse_req              |
+ |       [wait or handle next req]           |
+ |                                           |
+ |       [req->waitq woken up]               |
+ |    <fuse_unlink()                         |
+ |  <sys_unlink()                            |
+
+
+

Documentation/filesystems/index.rst

···
    hpfs
    fuse
    fuse-io
+   fuse-io-uring
    inotify
    isofs
    nilfs2

fs/fuse/Kconfig

···
 	  to be performed directly on a backing file.
 
 	  If you want to allow passthrough operations, answer Y.
+
+config FUSE_IO_URING
+	bool "FUSE communication over io-uring"
+	default y
+	depends on FUSE_FS
+	depends on IO_URING
+	help
+	  This allows sending FUSE requests over the io-uring interface and
+          also adds request core affinity.
+
+	  If you want to allow fuse server/client communication through io-uring,
+	  answer Y

fs/fuse/Makefile

···
 fuse-$(CONFIG_FUSE_DAX) += dax.o
 fuse-$(CONFIG_FUSE_PASSTHROUGH) += passthrough.o
 fuse-$(CONFIG_SYSCTL) += sysctl.o
+fuse-$(CONFIG_FUSE_IO_URING) += dev_uring.o
 
 virtiofs-y := virtio_fs.o

fs/fuse/dax.c

···
 
 	args.opcode = FUSE_REMOVEMAPPING;
 	args.nodeid = fi->nodeid;
-	args.in_numargs = 2;
-	args.in_args[0].size = sizeof(*inargp);
-	args.in_args[0].value = inargp;
-	args.in_args[1].size = inargp->count * sizeof(*remove_one);
-	args.in_args[1].value = remove_one;
+	args.in_numargs = 3;
+	fuse_set_zero_arg0(&args);
+	args.in_args[1].size = sizeof(*inargp);
+	args.in_args[1].value = inargp;
+	args.in_args[2].size = inargp->count * sizeof(*remove_one);
+	args.in_args[2].value = remove_one;
 	return fuse_simple_request(fm, &args);
 }
 

fs/fuse/dev.c

···
   See the file COPYING.
 */
 
+#include "dev_uring_i.h"
 #include "fuse_i.h"
+#include "fuse_dev_i.h"
 
 #include <linux/init.h>
 #include <linux/module.h>
···
 MODULE_ALIAS_MISCDEV(FUSE_MINOR);
 MODULE_ALIAS("devname:fuse");
 
-/* Ordinary requests have even IDs, while interrupts IDs are odd */
-#define FUSE_INT_REQ_BIT (1ULL << 0)
-#define FUSE_REQ_ID_STEP (1ULL << 1)
-
 static struct kmem_cache *fuse_req_cachep;
-
-static void end_requests(struct list_head *head);
-
-static struct fuse_dev *fuse_get_dev(struct file *file)
-{
-	/*
-	 * Lockless access is OK, because file->private data is set
-	 * once during mount and is valid until the file is released.
-	 */
-	return READ_ONCE(file->private_data);
-}
 
 static void fuse_request_init(struct fuse_mount *fm, struct fuse_req *req)
 {
···
 
 static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
 {
-	return !fc->initialized || (for_background && fc->blocked);
+	return !fc->initialized || (for_background && fc->blocked) ||
+	       (fc->io_uring && !fuse_uring_ready(fc));
 }
 
 static void fuse_drop_waiting(struct fuse_conn *fc)
···
 }
 EXPORT_SYMBOL_GPL(fuse_get_unique);
 
-static unsigned int fuse_req_hash(u64 unique)
+unsigned int fuse_req_hash(u64 unique)
 {
 	return hash_long(unique & ~FUSE_INT_REQ_BIT, FUSE_PQ_HASH_BITS);
 }
···
 	spin_unlock(&fiq->lock);
 }
 
-static void fuse_dev_queue_forget(struct fuse_iqueue *fiq, struct fuse_forget_link *forget)
+void fuse_dev_queue_forget(struct fuse_iqueue *fiq,
+			   struct fuse_forget_link *forget)
 {
 	spin_lock(&fiq->lock);
 	if (fiq->connected) {
···
 	}
 }
 
-static void fuse_dev_queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
+void fuse_dev_queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
 {
 	spin_lock(&fiq->lock);
 	if (list_empty(&req->intr_entry)) {
···
 	return ret;
 }
 
-static bool fuse_request_queue_background(struct fuse_req *req)
+#ifdef CONFIG_FUSE_IO_URING
+static bool fuse_request_queue_background_uring(struct fuse_conn *fc,
+					       struct fuse_req *req)
+{
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	req->in.h.unique = fuse_get_unique(fiq);
+	req->in.h.len = sizeof(struct fuse_in_header) +
+		fuse_len_args(req->args->in_numargs,
+			      (struct fuse_arg *) req->args->in_args);
+
+	return fuse_uring_queue_bq_req(req);
+}
+#endif
+
+/*
+ * @return true if queued
+ */
+static int fuse_request_queue_background(struct fuse_req *req)
 {
 	struct fuse_mount *fm = req->fm;
 	struct fuse_conn *fc = fm->fc;
···
 		atomic_inc(&fc->num_waiting);
 	}
 	__set_bit(FR_ISREPLY, &req->flags);
+
+#ifdef CONFIG_FUSE_IO_URING
+	if (fuse_uring_ready(fc))
+		return fuse_request_queue_background_uring(fc, req);
+#endif
+
 	spin_lock(&fc->bg_lock);
 	if (likely(fc->connected)) {
 		fc->num_background++;
···
 	return err;
 }
 
-struct fuse_copy_state {
-	int write;
-	struct fuse_req *req;
-	struct iov_iter *iter;
-	struct pipe_buffer *pipebufs;
-	struct pipe_buffer *currbuf;
-	struct pipe_inode_info *pipe;
-	unsigned long nr_segs;
-	struct page *pg;
-	unsigned len;
-	unsigned offset;
-	unsigned move_pages:1;
-};
-
-static void fuse_copy_init(struct fuse_copy_state *cs, int write,
-			   struct iov_iter *iter)
+void fuse_copy_init(struct fuse_copy_state *cs, int write,
+		    struct iov_iter *iter)
 {
 	memset(cs, 0, sizeof(*cs));
 	cs->write = write;
···
 	*size -= ncpy;
 	cs->len -= ncpy;
 	cs->offset += ncpy;
+	if (cs->is_uring)
+		cs->ring.copied_sz += ncpy;
+
 	return ncpy;
 }
 
···
 }
 
 /* Copy request arguments to/from userspace buffer */
-static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
-			  unsigned argpages, struct fuse_arg *args,
-			  int zeroing)
+int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
+		   unsigned argpages, struct fuse_arg *args,
+		   int zeroing)
 {
 	int err = 0;
 	unsigned i;
···
 	args = &ap->args;
 	args->nodeid = outarg->nodeid;
 	args->opcode = FUSE_NOTIFY_REPLY;
-	args->in_numargs = 2;
+	args->in_numargs = 3;
 	args->in_pages = true;
 	args->end = fuse_retrieve_end;
 
···
 	}
 	ra->inarg.offset = outarg->offset;
 	ra->inarg.size = total_len;
-	args->in_args[0].size = sizeof(ra->inarg);
-	args->in_args[0].value = &ra->inarg;
-	args->in_args[1].size = total_len;
+	fuse_set_zero_arg0(args);
+	args->in_args[1].size = sizeof(ra->inarg);
+	args->in_args[1].value = &ra->inarg;
+	args->in_args[2].size = total_len;
 
 	err = fuse_simple_notify_reply(fm, args, outarg->notify_unique);
 	if (err)
···
 		spin_unlock(&fiq->lock);
 		list_for_each_entry(req, &to_queue, list)
 			clear_bit(FR_PENDING, &req->flags);
-		end_requests(&to_queue);
+		fuse_dev_end_requests(&to_queue);
 		return;
 	}
 	/* iq and pq requests are both oldest to newest */
···
 }
 
 /* Look up request on processing list by unique ID */
-static struct fuse_req *request_find(struct fuse_pqueue *fpq, u64 unique)
+struct fuse_req *fuse_request_find(struct fuse_pqueue *fpq, u64 unique)
 {
 	unsigned int hash = fuse_req_hash(unique);
 	struct fuse_req *req;
···
 	return NULL;
 }
 
-static int copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
-			 unsigned nbytes)
+int fuse_copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
+		       unsigned nbytes)
 {
-	unsigned reqsize = sizeof(struct fuse_out_header);
+
+	unsigned int reqsize = 0;
+
+	/*
+	 * Uring has all headers separated from args - args is payload only
+	 */
+	if (!cs->is_uring)
+		reqsize = sizeof(struct fuse_out_header);
 
 	reqsize += fuse_len_args(args->out_numargs, args->out_args);
 
···
 	spin_lock(&fpq->lock);
 	req = NULL;
 	if (fpq->connected)
-		req = request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
+		req = fuse_request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
 
 	err = -ENOENT;
 	if (!req) {
···
 	if (oh.error)
 		err = nbytes != sizeof(oh) ? -EINVAL : 0;
 	else
-		err = copy_out_args(cs, req->args, nbytes);
+		err = fuse_copy_out_args(cs, req->args, nbytes);
 	fuse_copy_finish(cs);
 
 	spin_lock(&fpq->lock);
···
 }
 
 /* Abort all requests on the given list (pending or processing) */
-static void end_requests(struct list_head *head)
+void fuse_dev_end_requests(struct list_head *head)
 {
 	while (!list_empty(head)) {
 		struct fuse_req *req;
···
 		wake_up_all(&fc->blocked_waitq);
 		spin_unlock(&fc->lock);
 
-		end_requests(&to_end);
+		fuse_dev_end_requests(&to_end);
+
+		/*
+		 * fc->lock must not be taken to avoid conflicts with io-uring
+		 * locks
+		 */
+		fuse_uring_abort(fc);
 	} else {
 		spin_unlock(&fc->lock);
 	}
···
 	/* matches implicit memory barrier in fuse_drop_waiting() */
 	smp_mb();
 	wait_event(fc->blocked_waitq, atomic_read(&fc->num_waiting) == 0);
+
+	fuse_uring_wait_stopped_queues(fc);
 }
 
 int fuse_dev_release(struct inode *inode, struct file *file)
···
 			list_splice_init(&fpq->processing[i], &to_end);
 		spin_unlock(&fpq->lock);
 
-		end_requests(&to_end);
+		fuse_dev_end_requests(&to_end);
 
 		/* Are we the last open device? */
 		if (atomic_dec_and_test(&fc->dev_count)) {
···
 	.fasync		= fuse_dev_fasync,
 	.unlocked_ioctl = fuse_dev_ioctl,
 	.compat_ioctl   = compat_ptr_ioctl,
+#ifdef CONFIG_FUSE_IO_URING
+	.uring_cmd	= fuse_uring_cmd,
+#endif
 };
 EXPORT_SYMBOL_GPL(fuse_dev_operations);
 

fs/fuse/dev_uring.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * FUSE: Filesystem in Userspace
+ * Copyright (c) 2023-2024 DataDirect Networks.
+ */
+
+#include "fuse_i.h"
+#include "dev_uring_i.h"
+#include "fuse_dev_i.h"
+
+#include <linux/fs.h>
+#include <linux/io_uring/cmd.h>
+
+static bool __read_mostly enable_uring;
+module_param(enable_uring, bool, 0644);
+MODULE_PARM_DESC(enable_uring,
+		 "Enable userspace communication through io-uring");
+
+#define FUSE_URING_IOV_SEGS 2 /* header and payload */
+
+
+bool fuse_uring_enabled(void)
+{
+	return enable_uring;
+}
+
+struct fuse_uring_pdu {
+	struct fuse_ring_ent *ent;
+};
+
+static const struct fuse_iqueue_ops fuse_io_uring_ops;
+
+static void uring_cmd_set_ring_ent(struct io_uring_cmd *cmd,
+				   struct fuse_ring_ent *ring_ent)
+{
+	struct fuse_uring_pdu *pdu =
+		io_uring_cmd_to_pdu(cmd, struct fuse_uring_pdu);
+
+	pdu->ent = ring_ent;
+}
+
+static struct fuse_ring_ent *uring_cmd_to_ring_ent(struct io_uring_cmd *cmd)
+{
+	struct fuse_uring_pdu *pdu =
+		io_uring_cmd_to_pdu(cmd, struct fuse_uring_pdu);
+
+	return pdu->ent;
+}
+
+static void fuse_uring_flush_bg(struct fuse_ring_queue *queue)
+{
+	struct fuse_ring *ring = queue->ring;
+	struct fuse_conn *fc = ring->fc;
+
+	lockdep_assert_held(&queue->lock);
+	lockdep_assert_held(&fc->bg_lock);
+
+	/*
+	 * Allow one bg request per queue, ignoring global fc limits.
+	 * This prevents a single queue from consuming all resources and
+	 * eliminates the need for remote queue wake-ups when global
+	 * limits are met but this queue has no more waiting requests.
+	 */
+	while ((fc->active_background < fc->max_background ||
+		!queue->active_background) &&
+	       (!list_empty(&queue->fuse_req_bg_queue))) {
+		struct fuse_req *req;
+
+		req = list_first_entry(&queue->fuse_req_bg_queue,
+				       struct fuse_req, list);
+		fc->active_background++;
+		queue->active_background++;
+
+		list_move_tail(&req->list, &queue->fuse_req_queue);
+	}
+}
+
+static void fuse_uring_req_end(struct fuse_ring_ent *ent, struct fuse_req *req,
+			       int error)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+	struct fuse_ring *ring = queue->ring;
+	struct fuse_conn *fc = ring->fc;
+
+	lockdep_assert_not_held(&queue->lock);
+	spin_lock(&queue->lock);
+	ent->fuse_req = NULL;
+	if (test_bit(FR_BACKGROUND, &req->flags)) {
+		queue->active_background--;
+		spin_lock(&fc->bg_lock);
+		fuse_uring_flush_bg(queue);
+		spin_unlock(&fc->bg_lock);
+	}
+
+	spin_unlock(&queue->lock);
+
+	if (error)
+		req->out.h.error = error;
+
+	clear_bit(FR_SENT, &req->flags);
+	fuse_request_end(req);
+}
+
+/* Abort all list queued request on the given ring queue */
+static void fuse_uring_abort_end_queue_requests(struct fuse_ring_queue *queue)
+{
+	struct fuse_req *req;
+	LIST_HEAD(req_list);
+
+	spin_lock(&queue->lock);
+	list_for_each_entry(req, &queue->fuse_req_queue, list)
+		clear_bit(FR_PENDING, &req->flags);
+	list_splice_init(&queue->fuse_req_queue, &req_list);
+	spin_unlock(&queue->lock);
+
+	/* must not hold queue lock to avoid order issues with fi->lock */
+	fuse_dev_end_requests(&req_list);
+}
+
+void fuse_uring_abort_end_requests(struct fuse_ring *ring)
+{
+	int qid;
+	struct fuse_ring_queue *queue;
+	struct fuse_conn *fc = ring->fc;
+
+	for (qid = 0; qid < ring->nr_queues; qid++) {
+		queue = READ_ONCE(ring->queues[qid]);
+		if (!queue)
+			continue;
+
+		queue->stopped = true;
+
+		WARN_ON_ONCE(ring->fc->max_background != UINT_MAX);
+		spin_lock(&queue->lock);
+		spin_lock(&fc->bg_lock);
+		fuse_uring_flush_bg(queue);
+		spin_unlock(&fc->bg_lock);
+		spin_unlock(&queue->lock);
+		fuse_uring_abort_end_queue_requests(queue);
+	}
+}
+
+void fuse_uring_destruct(struct fuse_conn *fc)
+{
+	struct fuse_ring *ring = fc->ring;
+	int qid;
+
+	if (!ring)
+		return;
+
+	for (qid = 0; qid < ring->nr_queues; qid++) {
+		struct fuse_ring_queue *queue = ring->queues[qid];
+		struct fuse_ring_ent *ent, *next;
+
+		if (!queue)
+			continue;
+
+		WARN_ON(!list_empty(&queue->ent_avail_queue));
+		WARN_ON(!list_empty(&queue->ent_w_req_queue));
+		WARN_ON(!list_empty(&queue->ent_commit_queue));
+		WARN_ON(!list_empty(&queue->ent_in_userspace));
+
+		list_for_each_entry_safe(ent, next, &queue->ent_released,
+					 list) {
+			list_del_init(&ent->list);
+			kfree(ent);
+		}
+
+		kfree(queue->fpq.processing);
+		kfree(queue);
+		ring->queues[qid] = NULL;
+	}
+
+	kfree(ring->queues);
+	kfree(ring);
+	fc->ring = NULL;
+}
+
+/*
+ * Basic ring setup for this connection based on the provided configuration
+ */
+static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc)
+{
+	struct fuse_ring *ring;
+	size_t nr_queues = num_possible_cpus();
+	struct fuse_ring *res = NULL;
+	size_t max_payload_size;
+
+	ring = kzalloc(sizeof(*fc->ring), GFP_KERNEL_ACCOUNT);
+	if (!ring)
+		return NULL;
+
+	ring->queues = kcalloc(nr_queues, sizeof(struct fuse_ring_queue *),
+			       GFP_KERNEL_ACCOUNT);
+	if (!ring->queues)
+		goto out_err;
+
+	max_payload_size = max(FUSE_MIN_READ_BUFFER, fc->max_write);
+	max_payload_size = max(max_payload_size, fc->max_pages * PAGE_SIZE);
+
+	spin_lock(&fc->lock);
+	if (fc->ring) {
+		/* race, another thread created the ring in the meantime */
+		spin_unlock(&fc->lock);
+		res = fc->ring;
+		goto out_err;
+	}
+
+	init_waitqueue_head(&ring->stop_waitq);
+
+	fc->ring = ring;
+	ring->nr_queues = nr_queues;
+	ring->fc = fc;
+	ring->max_payload_sz = max_payload_size;
+	atomic_set(&ring->queue_refs, 0);
+
+	spin_unlock(&fc->lock);
+	return ring;
+
+out_err:
+	kfree(ring->queues);
+	kfree(ring);
+	return res;
+}
+
+static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring,
+						       int qid)
+{
+	struct fuse_conn *fc = ring->fc;
+	struct fuse_ring_queue *queue;
+	struct list_head *pq;
+
+	queue = kzalloc(sizeof(*queue), GFP_KERNEL_ACCOUNT);
+	if (!queue)
+		return NULL;
+	pq = kcalloc(FUSE_PQ_HASH_SIZE, sizeof(struct list_head), GFP_KERNEL);
+	if (!pq) {
+		kfree(queue);
+		return NULL;
+	}
+
+	queue->qid = qid;
+	queue->ring = ring;
+	spin_lock_init(&queue->lock);
+
+	INIT_LIST_HEAD(&queue->ent_avail_queue);
+	INIT_LIST_HEAD(&queue->ent_commit_queue);
+	INIT_LIST_HEAD(&queue->ent_w_req_queue);
+	INIT_LIST_HEAD(&queue->ent_in_userspace);
+	INIT_LIST_HEAD(&queue->fuse_req_queue);
+	INIT_LIST_HEAD(&queue->fuse_req_bg_queue);
+	INIT_LIST_HEAD(&queue->ent_released);
+
+	queue->fpq.processing = pq;
+	fuse_pqueue_init(&queue->fpq);
+
+	spin_lock(&fc->lock);
+	if (ring->queues[qid]) {
+		spin_unlock(&fc->lock);
+		kfree(queue->fpq.processing);
+		kfree(queue);
+		return ring->queues[qid];
+	}
+
+	/*
+	 * write_once and lock as the caller mostly doesn't take the lock at all
+	 */
+	WRITE_ONCE(ring->queues[qid], queue);
+	spin_unlock(&fc->lock);
+
+	return queue;
+}
+
+static void fuse_uring_stop_fuse_req_end(struct fuse_req *req)
+{
+	clear_bit(FR_SENT, &req->flags);
+	req->out.h.error = -ECONNABORTED;
+	fuse_request_end(req);
+}
+
+/*
+ * Release a request/entry on connection tear down
+ */
+static void fuse_uring_entry_teardown(struct fuse_ring_ent *ent)
+{
+	struct fuse_req *req;
+	struct io_uring_cmd *cmd;
+
+	struct fuse_ring_queue *queue = ent->queue;
+
+	spin_lock(&queue->lock);
+	cmd = ent->cmd;
+	ent->cmd = NULL;
+	req = ent->fuse_req;
+	ent->fuse_req = NULL;
+	if (req) {
+		/* remove entry from queue->fpq->processing */
+		list_del_init(&req->list);
+	}
+
+	/*
+	 * The entry must not be freed immediately, due to access of direct
+	 * pointer access of entries through IO_URING_F_CANCEL - there is a risk
+	 * of race between daemon termination (which triggers IO_URING_F_CANCEL
+	 * and accesses entries without checking the list state first
+	 */
+	list_move(&ent->list, &queue->ent_released);
+	ent->state = FRRS_RELEASED;
+	spin_unlock(&queue->lock);
+
+	if (cmd)
+		io_uring_cmd_done(cmd, -ENOTCONN, 0, IO_URING_F_UNLOCKED);
+
+	if (req)
+		fuse_uring_stop_fuse_req_end(req);
+}
+
+static void fuse_uring_stop_list_entries(struct list_head *head,
+					 struct fuse_ring_queue *queue,
+					 enum fuse_ring_req_state exp_state)
+{
+	struct fuse_ring *ring = queue->ring;
+	struct fuse_ring_ent *ent, *next;
+	ssize_t queue_refs = SSIZE_MAX;
+	LIST_HEAD(to_teardown);
+
+	spin_lock(&queue->lock);
+	list_for_each_entry_safe(ent, next, head, list) {
+		if (ent->state != exp_state) {
+			pr_warn("entry teardown qid=%d state=%d expected=%d",
+				queue->qid, ent->state, exp_state);
+			continue;
+		}
+
+		ent->state = FRRS_TEARDOWN;
+		list_move(&ent->list, &to_teardown);
+	}
+	spin_unlock(&queue->lock);
+
+	/* no queue lock to avoid lock order issues */
+	list_for_each_entry_safe(ent, next, &to_teardown, list) {
+		fuse_uring_entry_teardown(ent);
+		queue_refs = atomic_dec_return(&ring->queue_refs);
+		WARN_ON_ONCE(queue_refs < 0);
+	}
+}
+
+static void fuse_uring_teardown_entries(struct fuse_ring_queue *queue)
+{
+	fuse_uring_stop_list_entries(&queue->ent_in_userspace, queue,
+				     FRRS_USERSPACE);
+	fuse_uring_stop_list_entries(&queue->ent_avail_queue, queue,
+				     FRRS_AVAILABLE);
+}
+
+/*
+ * Log state debug info
+ */
+static void fuse_uring_log_ent_state(struct fuse_ring *ring)
+{
+	int qid;
+	struct fuse_ring_ent *ent;
+
+	for (qid = 0; qid < ring->nr_queues; qid++) {
+		struct fuse_ring_queue *queue = ring->queues[qid];
+
+		if (!queue)
+			continue;
+
+		spin_lock(&queue->lock);
+		/*
+		 * Log entries from the intermediate queue, the other queues
+		 * should be empty
+		 */
+		list_for_each_entry(ent, &queue->ent_w_req_queue, list) {
+			pr_info(" ent-req-queue ring=%p qid=%d ent=%p state=%d\n",
+				ring, qid, ent, ent->state);
+		}
+		list_for_each_entry(ent, &queue->ent_commit_queue, list) {
+			pr_info(" ent-commit-queue ring=%p qid=%d ent=%p state=%d\n",
+				ring, qid, ent, ent->state);
+		}
+		spin_unlock(&queue->lock);
+	}
+	ring->stop_debug_log = 1;
+}
+
+static void fuse_uring_async_stop_queues(struct work_struct *work)
+{
+	int qid;
+	struct fuse_ring *ring =
+		container_of(work, struct fuse_ring, async_teardown_work.work);
+
+	/* XXX code dup */
+	for (qid = 0; qid < ring->nr_queues; qid++) {
+		struct fuse_ring_queue *queue = READ_ONCE(ring->queues[qid]);
+
+		if (!queue)
+			continue;
+
+		fuse_uring_teardown_entries(queue);
+	}
+
+	/*
+	 * Some ring entries might be in the middle of IO operations,
+	 * i.e. in process to get handled by file_operations::uring_cmd
+	 * or on the way to userspace - we could handle that with conditions in
+	 * run time code, but easier/cleaner to have an async tear down handler
+	 * If there are still queue references left
+	 */
+	if (atomic_read(&ring->queue_refs) > 0) {
+		if (time_after(jiffies,
+			       ring->teardown_time + FUSE_URING_TEARDOWN_TIMEOUT))
+			fuse_uring_log_ent_state(ring);
+
+		schedule_delayed_work(&ring->async_teardown_work,
+				      FUSE_URING_TEARDOWN_INTERVAL);
+	} else {
+		wake_up_all(&ring->stop_waitq);
+	}
+}
+
+/*
+ * Stop the ring queues
+ */
+void fuse_uring_stop_queues(struct fuse_ring *ring)
+{
+	int qid;
+
+	for (qid = 0; qid < ring->nr_queues; qid++) {
+		struct fuse_ring_queue *queue = READ_ONCE(ring->queues[qid]);
+
+		if (!queue)
+			continue;
+
+		fuse_uring_teardown_entries(queue);
+	}
+
+	if (atomic_read(&ring->queue_refs) > 0) {
+		ring->teardown_time = jiffies;
+		INIT_DELAYED_WORK(&ring->async_teardown_work,
+				  fuse_uring_async_stop_queues);
+		schedule_delayed_work(&ring->async_teardown_work,
+				      FUSE_URING_TEARDOWN_INTERVAL);
+	} else {
+		wake_up_all(&ring->stop_waitq);
+	}
+}
+
+/*
+ * Handle IO_URING_F_CANCEL, typically should come on daemon termination.
+ *
+ * Releasing the last entry should trigger fuse_dev_release() if
+ * the daemon was terminated
+ */
+static void fuse_uring_cancel(struct io_uring_cmd *cmd,
+			      unsigned int issue_flags)
+{
+	struct fuse_ring_ent *ent = uring_cmd_to_ring_ent(cmd);
+	struct fuse_ring_queue *queue;
+	bool need_cmd_done = false;
+
+	/*
+	 * direct access on ent - it must not be destructed as long as
+	 * IO_URING_F_CANCEL might come up
+	 */
+	queue = ent->queue;
+	spin_lock(&queue->lock);
+	if (ent->state == FRRS_AVAILABLE) {
+		ent->state = FRRS_USERSPACE;
+		list_move(&ent->list, &queue->ent_in_userspace);
+		need_cmd_done = true;
+		ent->cmd = NULL;
+	}
+	spin_unlock(&queue->lock);
+
+	if (need_cmd_done) {
+		/* no queue lock to avoid lock order issues */
+		io_uring_cmd_done(cmd, -ENOTCONN, 0, issue_flags);
+	}
+}
+
+static void fuse_uring_prepare_cancel(struct io_uring_cmd *cmd, int issue_flags,
+				      struct fuse_ring_ent *ring_ent)
+{
+	uring_cmd_set_ring_ent(cmd, ring_ent);
+	io_uring_cmd_mark_cancelable(cmd, issue_flags);
+}
+
+/*
+ * Checks for errors and stores it into the request
+ */
+static int fuse_uring_out_header_has_err(struct fuse_out_header *oh,
+					 struct fuse_req *req,
+					 struct fuse_conn *fc)
+{
+	int err;
+
+	err = -EINVAL;
+	if (oh->unique == 0) {
+		/* Not supported through io-uring yet */
+		pr_warn_once("notify through fuse-io-uring not supported\n");
+		goto err;
+	}
+
+	if (oh->error <= -ERESTARTSYS || oh->error > 0)
+		goto err;
+
+	if (oh->error) {
+		err = oh->error;
+		goto err;
+	}
+
+	err = -ENOENT;
+	if ((oh->unique & ~FUSE_INT_REQ_BIT) != req->in.h.unique) {
+		pr_warn_ratelimited("unique mismatch, expected: %llu got %llu\n",
+				    req->in.h.unique,
+				    oh->unique & ~FUSE_INT_REQ_BIT);
+		goto err;
+	}
+
+	/*
+	 * Is it an interrupt reply ID?
+	 * XXX: Not supported through fuse-io-uring yet, it should not even
+	 *      find the request - should not happen.
+	 */
+	WARN_ON_ONCE(oh->unique & FUSE_INT_REQ_BIT);
+
+	err = 0;
+err:
+	return err;
+}
+
+static int fuse_uring_copy_from_ring(struct fuse_ring *ring,
+				     struct fuse_req *req,
+				     struct fuse_ring_ent *ent)
+{
+	struct fuse_copy_state cs;
+	struct fuse_args *args = req->args;
+	struct iov_iter iter;
+	int err;
+	struct fuse_uring_ent_in_out ring_in_out;
+
+	err = copy_from_user(&ring_in_out, &ent->headers->ring_ent_in_out,
+			     sizeof(ring_in_out));
+	if (err)
+		return -EFAULT;
+
+	err = import_ubuf(ITER_SOURCE, ent->payload, ring->max_payload_sz,
+			  &iter);
+	if (err)
+		return err;
+
+	fuse_copy_init(&cs, 0, &iter);
+	cs.is_uring = 1;
+	cs.req = req;
+
+	return fuse_copy_out_args(&cs, args, ring_in_out.payload_sz);
+}
+
+ /*
+  * Copy data from the req to the ring buffer
+  */
+static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
+				   struct fuse_ring_ent *ent)
+{
+	struct fuse_copy_state cs;
+	struct fuse_args *args = req->args;
+	struct fuse_in_arg *in_args = args->in_args;
+	int num_args = args->in_numargs;
+	int err;
+	struct iov_iter iter;
+	struct fuse_uring_ent_in_out ent_in_out = {
+		.flags = 0,
+		.commit_id = req->in.h.unique,
+	};
+
+	err = import_ubuf(ITER_DEST, ent->payload, ring->max_payload_sz, &iter);
+	if (err) {
+		pr_info_ratelimited("fuse: Import of user buffer failed\n");
+		return err;
+	}
+
+	fuse_copy_init(&cs, 1, &iter);
+	cs.is_uring = 1;
+	cs.req = req;
+
+	if (num_args > 0) {
+		/*
+		 * Expectation is that the first argument is the per op header.
+		 * Some op code have that as zero size.
+		 */
+		if (args->in_args[0].size > 0) {
+			err = copy_to_user(&ent->headers->op_in, in_args->value,
+					   in_args->size);
+			if (err) {
+				pr_info_ratelimited(
+					"Copying the header failed.\n");
+				return -EFAULT;
+			}
+		}
+		in_args++;
+		num_args--;
+	}
+
+	/* copy the payload */
+	err = fuse_copy_args(&cs, num_args, args->in_pages,
+			     (struct fuse_arg *)in_args, 0);
+	if (err) {
+		pr_info_ratelimited("%s fuse_copy_args failed\n", __func__);
+		return err;
+	}
+
+	ent_in_out.payload_sz = cs.ring.copied_sz;
+	err = copy_to_user(&ent->headers->ring_ent_in_out, &ent_in_out,
+			   sizeof(ent_in_out));
+	return err ? -EFAULT : 0;
+}
+
+static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
+				   struct fuse_req *req)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+	struct fuse_ring *ring = queue->ring;
+	int err;
+
+	err = -EIO;
+	if (WARN_ON(ent->state != FRRS_FUSE_REQ)) {
+		pr_err("qid=%d ring-req=%p invalid state %d on send\n",
+		       queue->qid, ent, ent->state);
+		return err;
+	}
+
+	err = -EINVAL;
+	if (WARN_ON(req->in.h.unique == 0))
+		return err;
+
+	/* copy the request */
+	err = fuse_uring_args_to_ring(ring, req, ent);
+	if (unlikely(err)) {
+		pr_info_ratelimited("Copy to ring failed: %d\n", err);
+		return err;
+	}
+
+	/* copy fuse_in_header */
+	err = copy_to_user(&ent->headers->in_out, &req->in.h,
+			   sizeof(req->in.h));
+	if (err) {
+		err = -EFAULT;
+		return err;
+	}
+
+	return 0;
+}
+
+static int fuse_uring_prepare_send(struct fuse_ring_ent *ent,
+				   struct fuse_req *req)
+{
+	int err;
+
+	err = fuse_uring_copy_to_ring(ent, req);
+	if (!err)
+		set_bit(FR_SENT, &req->flags);
+	else
+		fuse_uring_req_end(ent, req, err);
+
+	return err;
+}
+
+/*
+ * Write data to the ring buffer and send the request to userspace,
+ * userspace will read it
+ * This is comparable with classical read(/dev/fuse)
+ */
+static int fuse_uring_send_next_to_ring(struct fuse_ring_ent *ent,
+					struct fuse_req *req,
+					unsigned int issue_flags)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+	int err;
+	struct io_uring_cmd *cmd;
+
+	err = fuse_uring_prepare_send(ent, req);
+	if (err)
+		return err;
+
+	spin_lock(&queue->lock);
+	cmd = ent->cmd;
+	ent->cmd = NULL;
+	ent->state = FRRS_USERSPACE;
+	list_move(&ent->list, &queue->ent_in_userspace);
+	spin_unlock(&queue->lock);
+
+	io_uring_cmd_done(cmd, 0, 0, issue_flags);
+	return 0;
+}
+
+/*
+ * Make a ring entry available for fuse_req assignment
+ */
+static void fuse_uring_ent_avail(struct fuse_ring_ent *ent,
+				 struct fuse_ring_queue *queue)
+{
+	WARN_ON_ONCE(!ent->cmd);
+	list_move(&ent->list, &queue->ent_avail_queue);
+	ent->state = FRRS_AVAILABLE;
+}
+
+/* Used to find the request on SQE commit */
+static void fuse_uring_add_to_pq(struct fuse_ring_ent *ent,
+				 struct fuse_req *req)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+	struct fuse_pqueue *fpq = &queue->fpq;
+	unsigned int hash;
+
+	req->ring_entry = ent;
+	hash = fuse_req_hash(req->in.h.unique);
+	list_move_tail(&req->list, &fpq->processing[hash]);
+}
+
+/*
+ * Assign a fuse queue entry to the given entry
+ */
+static void fuse_uring_add_req_to_ring_ent(struct fuse_ring_ent *ent,
+					   struct fuse_req *req)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+	struct fuse_conn *fc = req->fm->fc;
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	lockdep_assert_held(&queue->lock);
+
+	if (WARN_ON_ONCE(ent->state != FRRS_AVAILABLE &&
+			 ent->state != FRRS_COMMIT)) {
+		pr_warn("%s qid=%d state=%d\n", __func__, ent->queue->qid,
+			ent->state);
+	}
+
+	spin_lock(&fiq->lock);
+	clear_bit(FR_PENDING, &req->flags);
+	spin_unlock(&fiq->lock);
+	ent->fuse_req = req;
+	ent->state = FRRS_FUSE_REQ;
+	list_move(&ent->list, &queue->ent_w_req_queue);
+	fuse_uring_add_to_pq(ent, req);
+}
+
+/* Fetch the next fuse request if available */
+static struct fuse_req *fuse_uring_ent_assign_req(struct fuse_ring_ent *ent)
+	__must_hold(&queue->lock)
+{
+	struct fuse_req *req;
+	struct fuse_ring_queue *queue = ent->queue;
+	struct list_head *req_queue = &queue->fuse_req_queue;
+
+	lockdep_assert_held(&queue->lock);
+
+	/* get and assign the next entry while it is still holding the lock */
+	req = list_first_entry_or_null(req_queue, struct fuse_req, list);
+	if (req)
+		fuse_uring_add_req_to_ring_ent(ent, req);
+
+	return req;
+}
+
+/*
+ * Read data from the ring buffer, which user space has written to
+ * This is comparible with handling of classical write(/dev/fuse).
+ * Also make the ring request available again for new fuse requests.
+ */
+static void fuse_uring_commit(struct fuse_ring_ent *ent, struct fuse_req *req,
+			      unsigned int issue_flags)
+{
+	struct fuse_ring *ring = ent->queue->ring;
+	struct fuse_conn *fc = ring->fc;
+	ssize_t err = 0;
+
+	err = copy_from_user(&req->out.h, &ent->headers->in_out,
+			     sizeof(req->out.h));
+	if (err) {
+		req->out.h.error = -EFAULT;
+		goto out;
+	}
+
+	err = fuse_uring_out_header_has_err(&req->out.h, req, fc);
+	if (err) {
+		/* req->out.h.error already set */
+		goto out;
+	}
+
+	err = fuse_uring_copy_from_ring(ring, req, ent);
+out:
+	fuse_uring_req_end(ent, req, err);
+}
+
+/*
+ * Get the next fuse req and send it
+ */
+static void fuse_uring_next_fuse_req(struct fuse_ring_ent *ent,
+				     struct fuse_ring_queue *queue,
+				     unsigned int issue_flags)
+{
+	int err;
+	struct fuse_req *req;
+
+retry:
+	spin_lock(&queue->lock);
+	fuse_uring_ent_avail(ent, queue);
+	req = fuse_uring_ent_assign_req(ent);
+	spin_unlock(&queue->lock);
+
+	if (req) {
+		err = fuse_uring_send_next_to_ring(ent, req, issue_flags);
+		if (err)
+			goto retry;
+	}
+}
+
+static int fuse_ring_ent_set_commit(struct fuse_ring_ent *ent)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+
+	lockdep_assert_held(&queue->lock);
+
+	if (WARN_ON_ONCE(ent->state != FRRS_USERSPACE))
+		return -EIO;
+
+	ent->state = FRRS_COMMIT;
+	list_move(&ent->list, &queue->ent_commit_queue);
+
+	return 0;
+}
+
+/* FUSE_URING_CMD_COMMIT_AND_FETCH handler */
+static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_flags,
+				   struct fuse_conn *fc)
+{
+	const struct fuse_uring_cmd_req *cmd_req = io_uring_sqe_cmd(cmd->sqe);
+	struct fuse_ring_ent *ent;
+	int err;
+	struct fuse_ring *ring = fc->ring;
+	struct fuse_ring_queue *queue;
+	uint64_t commit_id = READ_ONCE(cmd_req->commit_id);
+	unsigned int qid = READ_ONCE(cmd_req->qid);
+	struct fuse_pqueue *fpq;
+	struct fuse_req *req;
+
+	err = -ENOTCONN;
+	if (!ring)
+		return err;
+
+	if (qid >= ring->nr_queues)
+		return -EINVAL;
+
+	queue = ring->queues[qid];
+	if (!queue)
+		return err;
+	fpq = &queue->fpq;
+
+	if (!READ_ONCE(fc->connected) || READ_ONCE(queue->stopped))
+		return err;
+
+	spin_lock(&queue->lock);
+	/* Find a request based on the unique ID of the fuse request
+	 * This should get revised, as it needs a hash calculation and list
+	 * search. And full struct fuse_pqueue is needed (memory overhead).
+	 * As well as the link from req to ring_ent.
+	 */
+	req = fuse_request_find(fpq, commit_id);
+	err = -ENOENT;
+	if (!req) {
+		pr_info("qid=%d commit_id %llu not found\n", queue->qid,
+			commit_id);
+		spin_unlock(&queue->lock);
+		return err;
+	}
+	list_del_init(&req->list);
+	ent = req->ring_entry;
+	req->ring_entry = NULL;
+
+	err = fuse_ring_ent_set_commit(ent);
+	if (err != 0) {
+		pr_info_ratelimited("qid=%d commit_id %llu state %d",
+				    queue->qid, commit_id, ent->state);
+		spin_unlock(&queue->lock);
+		req->out.h.error = err;
+		clear_bit(FR_SENT, &req->flags);
+		fuse_request_end(req);
+		return err;
+	}
+
+	ent->cmd = cmd;
+	spin_unlock(&queue->lock);
+
+	/* without the queue lock, as other locks are taken */
+	fuse_uring_prepare_cancel(cmd, issue_flags, ent);
+	fuse_uring_commit(ent, req, issue_flags);
+
+	/*
+	 * Fetching the next request is absolutely required as queued
+	 * fuse requests would otherwise not get processed - committing
+	 * and fetching is done in one step vs legacy fuse, which has separated
+	 * read (fetch request) and write (commit result).
+	 */
+	fuse_uring_next_fuse_req(ent, queue, issue_flags);
+	return 0;
+}
+
+static bool is_ring_ready(struct fuse_ring *ring, int current_qid)
+{
+	int qid;
+	struct fuse_ring_queue *queue;
+	bool ready = true;
+
+	for (qid = 0; qid < ring->nr_queues && ready; qid++) {
+		if (current_qid == qid)
+			continue;
+
+		queue = ring->queues[qid];
+		if (!queue) {
+			ready = false;
+			break;
+		}
+
+		spin_lock(&queue->lock);
+		if (list_empty(&queue->ent_avail_queue))
+			ready = false;
+		spin_unlock(&queue->lock);
+	}
+
+	return ready;
+}
+
+/*
+ * fuse_uring_req_fetch command handling
+ */
+static void fuse_uring_do_register(struct fuse_ring_ent *ent,
+				   struct io_uring_cmd *cmd,
+				   unsigned int issue_flags)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+	struct fuse_ring *ring = queue->ring;
+	struct fuse_conn *fc = ring->fc;
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	fuse_uring_prepare_cancel(cmd, issue_flags, ent);
+
+	spin_lock(&queue->lock);
+	ent->cmd = cmd;
+	fuse_uring_ent_avail(ent, queue);
+	spin_unlock(&queue->lock);
+
+	if (!ring->ready) {
+		bool ready = is_ring_ready(ring, queue->qid);
+
+		if (ready) {
+			WRITE_ONCE(fiq->ops, &fuse_io_uring_ops);
+			WRITE_ONCE(ring->ready, true);
+			wake_up_all(&fc->blocked_waitq);
+		}
+	}
+}
+
+/*
+ * sqe->addr is a ptr to an iovec array, iov[0] has the headers, iov[1]
+ * the payload
+ */
+static int fuse_uring_get_iovec_from_sqe(const struct io_uring_sqe *sqe,
+					 struct iovec iov[FUSE_URING_IOV_SEGS])
+{
+	struct iovec __user *uiov = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	struct iov_iter iter;
+	ssize_t ret;
+
+	if (sqe->len != FUSE_URING_IOV_SEGS)
+		return -EINVAL;
+
+	/*
+	 * Direction for buffer access will actually be READ and WRITE,
+	 * using write for the import should include READ access as well.
+	 */
+	ret = import_iovec(WRITE, uiov, FUSE_URING_IOV_SEGS,
+			   FUSE_URING_IOV_SEGS, &iov, &iter);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static struct fuse_ring_ent *
+fuse_uring_create_ring_ent(struct io_uring_cmd *cmd,
+			   struct fuse_ring_queue *queue)
+{
+	struct fuse_ring *ring = queue->ring;
+	struct fuse_ring_ent *ent;
+	size_t payload_size;
+	struct iovec iov[FUSE_URING_IOV_SEGS];
+	int err;
+
+	err = fuse_uring_get_iovec_from_sqe(cmd->sqe, iov);
+	if (err) {
+		pr_info_ratelimited("Failed to get iovec from sqe, err=%d\n",
+				    err);
+		return ERR_PTR(err);
+	}
+
+	err = -EINVAL;
+	if (iov[0].iov_len < sizeof(struct fuse_uring_req_header)) {
+		pr_info_ratelimited("Invalid header len %zu\n", iov[0].iov_len);
+		return ERR_PTR(err);
+	}
+
+	payload_size = iov[1].iov_len;
+	if (payload_size < ring->max_payload_sz) {
+		pr_info_ratelimited("Invalid req payload len %zu\n",
+				    payload_size);
+		return ERR_PTR(err);
+	}
+
+	err = -ENOMEM;
+	ent = kzalloc(sizeof(*ent), GFP_KERNEL_ACCOUNT);
+	if (!ent)
+		return ERR_PTR(err);
+
+	INIT_LIST_HEAD(&ent->list);
+
+	ent->queue = queue;
+	ent->headers = iov[0].iov_base;
+	ent->payload = iov[1].iov_base;
+
+	atomic_inc(&ring->queue_refs);
+	return ent;
+}
+
+/*
+ * Register header and payload buffer with the kernel and puts the
+ * entry as "ready to get fuse requests" on the queue
+ */
+static int fuse_uring_register(struct io_uring_cmd *cmd,
+			       unsigned int issue_flags, struct fuse_conn *fc)
+{
+	const struct fuse_uring_cmd_req *cmd_req = io_uring_sqe_cmd(cmd->sqe);
+	struct fuse_ring *ring = fc->ring;
+	struct fuse_ring_queue *queue;
+	struct fuse_ring_ent *ent;
+	int err;
+	unsigned int qid = READ_ONCE(cmd_req->qid);
+
+	err = -ENOMEM;
+	if (!ring) {
+		ring = fuse_uring_create(fc);
+		if (!ring)
+			return err;
+	}
+
+	if (qid >= ring->nr_queues) {
+		pr_info_ratelimited("fuse: Invalid ring qid %u\n", qid);
+		return -EINVAL;
+	}
+
+	queue = ring->queues[qid];
+	if (!queue) {
+		queue = fuse_uring_create_queue(ring, qid);
+		if (!queue)
+			return err;
+	}
+
+	/*
+	 * The created queue above does not need to be destructed in
+	 * case of entry errors below, will be done at ring destruction time.
+	 */
+
+	ent = fuse_uring_create_ring_ent(cmd, queue);
+	if (IS_ERR(ent))
+		return PTR_ERR(ent);
+
+	fuse_uring_do_register(ent, cmd, issue_flags);
+
+	return 0;
+}
+
+/*
+ * Entry function from io_uring to handle the given passthrough command
+ * (op code IORING_OP_URING_CMD)
+ */
+int fuse_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+	struct fuse_dev *fud;
+	struct fuse_conn *fc;
+	u32 cmd_op = cmd->cmd_op;
+	int err;
+
+	if ((unlikely(issue_flags & IO_URING_F_CANCEL))) {
+		fuse_uring_cancel(cmd, issue_flags);
+		return 0;
+	}
+
+	/* This extra SQE size holds struct fuse_uring_cmd_req */
+	if (!(issue_flags & IO_URING_F_SQE128))
+		return -EINVAL;
+
+	fud = fuse_get_dev(cmd->file);
+	if (!fud) {
+		pr_info_ratelimited("No fuse device found\n");
+		return -ENOTCONN;
+	}
+	fc = fud->fc;
+
+	/* Once a connection has io-uring enabled on it, it can't be disabled */
+	if (!enable_uring && !fc->io_uring) {
+		pr_info_ratelimited("fuse-io-uring is disabled\n");
+		return -EOPNOTSUPP;
+	}
+
+	if (fc->aborted)
+		return -ECONNABORTED;
+	if (!fc->connected)
+		return -ENOTCONN;
+
+	/*
+	 * fuse_uring_register() needs the ring to be initialized,
+	 * we need to know the max payload size
+	 */
+	if (!fc->initialized)
+		return -EAGAIN;
+
+	switch (cmd_op) {
+	case FUSE_IO_URING_CMD_REGISTER:
+		err = fuse_uring_register(cmd, issue_flags, fc);
+		if (err) {
+			pr_info_once("FUSE_IO_URING_CMD_REGISTER failed err=%d\n",
+				     err);
+			fc->io_uring = 0;
+			wake_up_all(&fc->blocked_waitq);
+			return err;
+		}
+		break;
+	case FUSE_IO_URING_CMD_COMMIT_AND_FETCH:
+		err = fuse_uring_commit_fetch(cmd, issue_flags, fc);
+		if (err) {
+			pr_info_once("FUSE_IO_URING_COMMIT_AND_FETCH failed err=%d\n",
+				     err);
+			return err;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return -EIOCBQUEUED;
+}
+
+static void fuse_uring_send(struct fuse_ring_ent *ent, struct io_uring_cmd *cmd,
+			    ssize_t ret, unsigned int issue_flags)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+
+	spin_lock(&queue->lock);
+	ent->state = FRRS_USERSPACE;
+	list_move(&ent->list, &queue->ent_in_userspace);
+	ent->cmd = NULL;
+	spin_unlock(&queue->lock);
+
+	io_uring_cmd_done(cmd, ret, 0, issue_flags);
+}
+
+/*
+ * This prepares and sends the ring request in fuse-uring task context.
+ * User buffers are not mapped yet - the application does not have permission
+ * to write to it - this has to be executed in ring task context.
+ */
+static void fuse_uring_send_in_task(struct io_uring_cmd *cmd,
+				    unsigned int issue_flags)
+{
+	struct fuse_ring_ent *ent = uring_cmd_to_ring_ent(cmd);
+	struct fuse_ring_queue *queue = ent->queue;
+	int err;
+
+	if (!(issue_flags & IO_URING_F_TASK_DEAD)) {
+		err = fuse_uring_prepare_send(ent, ent->fuse_req);
+		if (err) {
+			fuse_uring_next_fuse_req(ent, queue, issue_flags);
+			return;
+		}
+	} else {
+		err = -ECANCELED;
+	}
+
+	fuse_uring_send(ent, cmd, err, issue_flags);
+}
+
+static struct fuse_ring_queue *fuse_uring_task_to_queue(struct fuse_ring *ring)
+{
+	unsigned int qid;
+	struct fuse_ring_queue *queue;
+
+	qid = task_cpu(current);
+
+	if (WARN_ONCE(qid >= ring->nr_queues,
+		      "Core number (%u) exceeds nr queues (%zu)\n", qid,
+		      ring->nr_queues))
+		qid = 0;
+
+	queue = ring->queues[qid];
+	WARN_ONCE(!queue, "Missing queue for qid %d\n", qid);
+
+	return queue;
+}
+
+static void fuse_uring_dispatch_ent(struct fuse_ring_ent *ent)
+{
+	struct io_uring_cmd *cmd = ent->cmd;
+
+	uring_cmd_set_ring_ent(cmd, ent);
+	io_uring_cmd_complete_in_task(cmd, fuse_uring_send_in_task);
+}
+
+/* queue a fuse request and send it if a ring entry is available */
+void fuse_uring_queue_fuse_req(struct fuse_iqueue *fiq, struct fuse_req *req)
+{
+	struct fuse_conn *fc = req->fm->fc;
+	struct fuse_ring *ring = fc->ring;
+	struct fuse_ring_queue *queue;
+	struct fuse_ring_ent *ent = NULL;
+	int err;
+
+	err = -EINVAL;
+	queue = fuse_uring_task_to_queue(ring);
+	if (!queue)
+		goto err;
+
+	if (req->in.h.opcode != FUSE_NOTIFY_REPLY)
+		req->in.h.unique = fuse_get_unique(fiq);
+
+	spin_lock(&queue->lock);
+	err = -ENOTCONN;
+	if (unlikely(queue->stopped))
+		goto err_unlock;
+
+	ent = list_first_entry_or_null(&queue->ent_avail_queue,
+				       struct fuse_ring_ent, list);
+	if (ent)
+		fuse_uring_add_req_to_ring_ent(ent, req);
+	else
+		list_add_tail(&req->list, &queue->fuse_req_queue);
+	spin_unlock(&queue->lock);
+
+	if (ent)
+		fuse_uring_dispatch_ent(ent);
+
+	return;
+
+err_unlock:
+	spin_unlock(&queue->lock);
+err:
+	req->out.h.error = err;
+	clear_bit(FR_PENDING, &req->flags);
+	fuse_request_end(req);
+}
+
+bool fuse_uring_queue_bq_req(struct fuse_req *req)
+{
+	struct fuse_conn *fc = req->fm->fc;
+	struct fuse_ring *ring = fc->ring;
+	struct fuse_ring_queue *queue;
+	struct fuse_ring_ent *ent = NULL;
+
+	queue = fuse_uring_task_to_queue(ring);
+	if (!queue)
+		return false;
+
+	spin_lock(&queue->lock);
+	if (unlikely(queue->stopped)) {
+		spin_unlock(&queue->lock);
+		return false;
+	}
+
+	list_add_tail(&req->list, &queue->fuse_req_bg_queue);
+
+	ent = list_first_entry_or_null(&queue->ent_avail_queue,
+				       struct fuse_ring_ent, list);
+	spin_lock(&fc->bg_lock);
+	fc->num_background++;
+	if (fc->num_background == fc->max_background)
+		fc->blocked = 1;
+	fuse_uring_flush_bg(queue);
+	spin_unlock(&fc->bg_lock);
+
+	/*
+	 * Due to bg_queue flush limits there might be other bg requests
+	 * in the queue that need to be handled first. Or no further req
+	 * might be available.
+	 */
+	req = list_first_entry_or_null(&queue->fuse_req_queue, struct fuse_req,
+				       list);
+	if (ent && req) {
+		fuse_uring_add_req_to_ring_ent(ent, req);
+		spin_unlock(&queue->lock);
+
+		fuse_uring_dispatch_ent(ent);
+	} else {
+		spin_unlock(&queue->lock);
+	}
+
+	return true;
+}
+
+static const struct fuse_iqueue_ops fuse_io_uring_ops = {
+	/* should be send over io-uring as enhancement */
+	.send_forget = fuse_dev_queue_forget,
+
+	/*
+	 * could be send over io-uring, but interrupts should be rare,
+	 * no need to make the code complex
+	 */
+	.send_interrupt = fuse_dev_queue_interrupt,
+	.send_req = fuse_uring_queue_fuse_req,
+};

fs/fuse/dev_uring_i.h

···
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * FUSE: Filesystem in Userspace
+ * Copyright (c) 2023-2024 DataDirect Networks.
+ */
+
+#ifndef _FS_FUSE_DEV_URING_I_H
+#define _FS_FUSE_DEV_URING_I_H
+
+#include "fuse_i.h"
+
+#ifdef CONFIG_FUSE_IO_URING
+
+#define FUSE_URING_TEARDOWN_TIMEOUT (5 * HZ)
+#define FUSE_URING_TEARDOWN_INTERVAL (HZ/20)
+
+enum fuse_ring_req_state {
+	FRRS_INVALID = 0,
+
+	/* The ring entry received from userspace and it is being processed */
+	FRRS_COMMIT,
+
+	/* The ring entry is waiting for new fuse requests */
+	FRRS_AVAILABLE,
+
+	/* The ring entry got assigned a fuse req */
+	FRRS_FUSE_REQ,
+
+	/* The ring entry is in or on the way to user space */
+	FRRS_USERSPACE,
+
+	/* The ring entry is in teardown */
+	FRRS_TEARDOWN,
+
+	/* The ring entry is released, but not freed yet */
+	FRRS_RELEASED,
+};
+
+/** A fuse ring entry, part of the ring queue */
+struct fuse_ring_ent {
+	/* userspace buffer */
+	struct fuse_uring_req_header __user *headers;
+	void __user *payload;
+
+	/* the ring queue that owns the request */
+	struct fuse_ring_queue *queue;
+
+	/* fields below are protected by queue->lock */
+
+	struct io_uring_cmd *cmd;
+
+	struct list_head list;
+
+	enum fuse_ring_req_state state;
+
+	struct fuse_req *fuse_req;
+};
+
+struct fuse_ring_queue {
+	/*
+	 * back pointer to the main fuse uring structure that holds this
+	 * queue
+	 */
+	struct fuse_ring *ring;
+
+	/* queue id, corresponds to the cpu core */
+	unsigned int qid;
+
+	/*
+	 * queue lock, taken when any value in the queue changes _and_ also
+	 * a ring entry state changes.
+	 */
+	spinlock_t lock;
+
+	/* available ring entries (struct fuse_ring_ent) */
+	struct list_head ent_avail_queue;
+
+	/*
+	 * entries in the process of being committed or in the process
+	 * to be sent to userspace
+	 */
+	struct list_head ent_w_req_queue;
+	struct list_head ent_commit_queue;
+
+	/* entries in userspace */
+	struct list_head ent_in_userspace;
+
+	/* entries that are released */
+	struct list_head ent_released;
+
+	/* fuse requests waiting for an entry slot */
+	struct list_head fuse_req_queue;
+
+	/* background fuse requests */
+	struct list_head fuse_req_bg_queue;
+
+	struct fuse_pqueue fpq;
+
+	unsigned int active_background;
+
+	bool stopped;
+};
+
+/**
+ * Describes if uring is for communication and holds alls the data needed
+ * for uring communication
+ */
+struct fuse_ring {
+	/* back pointer */
+	struct fuse_conn *fc;
+
+	/* number of ring queues */
+	size_t nr_queues;
+
+	/* maximum payload/arg size */
+	size_t max_payload_sz;
+
+	struct fuse_ring_queue **queues;
+
+	/*
+	 * Log ring entry states on stop when entries cannot be released
+	 */
+	unsigned int stop_debug_log : 1;
+
+	wait_queue_head_t stop_waitq;
+
+	/* async tear down */
+	struct delayed_work async_teardown_work;
+
+	/* log */
+	unsigned long teardown_time;
+
+	atomic_t queue_refs;
+
+	bool ready;
+};
+
+bool fuse_uring_enabled(void);
+void fuse_uring_destruct(struct fuse_conn *fc);
+void fuse_uring_stop_queues(struct fuse_ring *ring);
+void fuse_uring_abort_end_requests(struct fuse_ring *ring);
+int fuse_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags);
+void fuse_uring_queue_fuse_req(struct fuse_iqueue *fiq, struct fuse_req *req);
+bool fuse_uring_queue_bq_req(struct fuse_req *req);
+
+static inline void fuse_uring_abort(struct fuse_conn *fc)
+{
+	struct fuse_ring *ring = fc->ring;
+
+	if (ring == NULL)
+		return;
+
+	if (atomic_read(&ring->queue_refs) > 0) {
+		fuse_uring_abort_end_requests(ring);
+		fuse_uring_stop_queues(ring);
+	}
+}
+
+static inline void fuse_uring_wait_stopped_queues(struct fuse_conn *fc)
+{
+	struct fuse_ring *ring = fc->ring;
+
+	if (ring)
+		wait_event(ring->stop_waitq,
+			   atomic_read(&ring->queue_refs) == 0);
+}
+
+static inline bool fuse_uring_ready(struct fuse_conn *fc)
+{
+	return fc->ring && fc->ring->ready;
+}
+
+#else /* CONFIG_FUSE_IO_URING */
+
+struct fuse_ring;
+
+static inline void fuse_uring_create(struct fuse_conn *fc)
+{
+}
+
+static inline void fuse_uring_destruct(struct fuse_conn *fc)
+{
+}
+
+static inline bool fuse_uring_enabled(void)
+{
+	return false;
+}
+
+static inline void fuse_uring_abort(struct fuse_conn *fc)
+{
+}
+
+static inline void fuse_uring_wait_stopped_queues(struct fuse_conn *fc)
+{
+}
+
+static inline bool fuse_uring_ready(struct fuse_conn *fc)
+{
+	return false;
+}
+
+#endif /* CONFIG_FUSE_IO_URING */
+
+#endif /* _FS_FUSE_DEV_URING_I_H */

fs/fuse/dir.c

···
 	memset(outarg, 0, sizeof(struct fuse_entry_out));
 	args->opcode = FUSE_LOOKUP;
 	args->nodeid = nodeid;
-	args->in_numargs = 1;
-	args->in_args[0].size = name->len + 1;
-	args->in_args[0].value = name->name;
+	args->in_numargs = 2;
+	fuse_set_zero_arg0(args);
+	args->in_args[1].size = name->len + 1;
+	args->in_args[1].value = name->name;
 	args->out_numargs = 1;
 	args->out_args[0].size = sizeof(struct fuse_entry_out);
 	args->out_args[0].value = outarg;
···
 	FUSE_ARGS(args);
 
 	args.opcode = FUSE_SYMLINK;
-	args.in_numargs = 2;
-	args.in_args[0].size = entry->d_name.len + 1;
-	args.in_args[0].value = entry->d_name.name;
-	args.in_args[1].size = len;
-	args.in_args[1].value = link;
+	args.in_numargs = 3;
+	fuse_set_zero_arg0(&args);
+	args.in_args[1].size = entry->d_name.len + 1;
+	args.in_args[1].value = entry->d_name.name;
+	args.in_args[2].size = len;
+	args.in_args[2].value = link;
 	return create_new_entry(idmap, fm, &args, dir, entry, S_IFLNK);
 }
 
···
 
 	args.opcode = FUSE_UNLINK;
 	args.nodeid = get_node_id(dir);
-	args.in_numargs = 1;
-	args.in_args[0].size = entry->d_name.len + 1;
-	args.in_args[0].value = entry->d_name.name;
+	args.in_numargs = 2;
+	fuse_set_zero_arg0(&args);
+	args.in_args[1].size = entry->d_name.len + 1;
+	args.in_args[1].value = entry->d_name.name;
 	err = fuse_simple_request(fm, &args);
 	if (!err) {
 		fuse_dir_changed(dir);
···
 
 	args.opcode = FUSE_RMDIR;
 	args.nodeid = get_node_id(dir);
-	args.in_numargs = 1;
-	args.in_args[0].size = entry->d_name.len + 1;
-	args.in_args[0].value = entry->d_name.name;
+	args.in_numargs = 2;
+	fuse_set_zero_arg0(&args);
+	args.in_args[1].size = entry->d_name.len + 1;
+	args.in_args[1].value = entry->d_name.name;
 	err = fuse_simple_request(fm, &args);
 	if (!err) {
 		fuse_dir_changed(dir);

fs/fuse/fuse_dev_i.h

···
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * FUSE: Filesystem in Userspace
+ * Copyright (C) 2001-2008  Miklos Szeredi <[e-mail]>
+ */
+#ifndef _FS_FUSE_DEV_I_H
+#define _FS_FUSE_DEV_I_H
+
+#include <linux/types.h>
+
+/* Ordinary requests have even IDs, while interrupts IDs are odd */
+#define FUSE_INT_REQ_BIT (1ULL << 0)
+#define FUSE_REQ_ID_STEP (1ULL << 1)
+
+struct fuse_arg;
+struct fuse_args;
+struct fuse_pqueue;
+struct fuse_req;
+struct fuse_iqueue;
+struct fuse_forget_link;
+
+struct fuse_copy_state {
+	int write;
+	struct fuse_req *req;
+	struct iov_iter *iter;
+	struct pipe_buffer *pipebufs;
+	struct pipe_buffer *currbuf;
+	struct pipe_inode_info *pipe;
+	unsigned long nr_segs;
+	struct page *pg;
+	unsigned int len;
+	unsigned int offset;
+	unsigned int move_pages:1;
+	unsigned int is_uring:1;
+	struct {
+		unsigned int copied_sz; /* copied size into the user buffer */
+	} ring;
+};
+
+static inline struct fuse_dev *fuse_get_dev(struct file *file)
+{
+	/*
+	 * Lockless access is OK, because file->private data is set
+	 * once during mount and is valid until the file is released.
+	 */
+	return READ_ONCE(file->private_data);
+}
+
+unsigned int fuse_req_hash(u64 unique);
+struct fuse_req *fuse_request_find(struct fuse_pqueue *fpq, u64 unique);
+
+void fuse_dev_end_requests(struct list_head *head);
+
+void fuse_copy_init(struct fuse_copy_state *cs, int write,
+			   struct iov_iter *iter);
+int fuse_copy_args(struct fuse_copy_state *cs, unsigned int numargs,
+		   unsigned int argpages, struct fuse_arg *args,
+		   int zeroing);
+int fuse_copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
+		       unsigned int nbytes);
+void fuse_dev_queue_forget(struct fuse_iqueue *fiq,
+			   struct fuse_forget_link *forget);
+void fuse_dev_queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req);
+
+#endif
+

fs/fuse/fuse_i.h

···
 	bool is_ext:1;
 	bool is_pinned:1;
 	bool invalidate_vmap:1;
-	struct fuse_in_arg in_args[3];
+	struct fuse_in_arg in_args[4];
 	struct fuse_arg out_args[2];
 	void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
 	/* Used for kvec iter backed by vmalloc address */
···
 
 	/** fuse_mount this request belongs to */
 	struct fuse_mount *fm;
+
+#ifdef CONFIG_FUSE_IO_URING
+	void *ring_entry;
+#endif
 };
 
 struct fuse_iqueue;
···
 	/* Use pages instead of pointer for kernel I/O */
 	unsigned int use_pages_for_kvec_io:1;
 
+	/* Use io_uring for communication */
+	unsigned int io_uring;
+
 	/** Maximum stack depth for passthrough backing files */
 	int max_stack_depth;
 
···
 	/** IDR for backing files ids */
 	struct idr backing_files_map;
 #endif
+
+#ifdef CONFIG_FUSE_IO_URING
+	/**  uring connection information*/
+	struct fuse_ring *ring;
+#endif
 };
 
 /*
···
 	struct list_head fc_entry;
 	struct rcu_head rcu;
 };
+
+/*
+ * Empty header for FUSE opcodes without specific header needs.
+ * Used as a placeholder in args->in_args[0] for consistency
+ * across all FUSE operations, simplifying request handling.
+ */
+struct fuse_zero_header {};
+
+static inline void fuse_set_zero_arg0(struct fuse_args *args)
+{
+	args->in_args[0].size = sizeof(struct fuse_zero_header);
+	args->in_args[0].value = NULL;
+}
 
 static inline struct fuse_mount *get_fuse_mount_super(struct super_block *sb)
 {
···
  * Acquire reference to fuse_conn
  */
 struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
+
+/**
+ * Initialize the fuse processing queue
+ */
+void fuse_pqueue_init(struct fuse_pqueue *fpq);
 
 /**
  * Initialize fuse_conn

fs/fuse/inode.c

···
 */
 
 #include "fuse_i.h"
+#include "dev_uring_i.h"
 
 #include <linux/pagemap.h>
 #include <linux/slab.h>
···
 	fiq->priv = priv;
 }
 
-static void fuse_pqueue_init(struct fuse_pqueue *fpq)
+void fuse_pqueue_init(struct fuse_pqueue *fpq)
 {
 	unsigned int i;
 
···
 static void delayed_release(struct rcu_head *p)
 {
 	struct fuse_conn *fc = container_of(p, struct fuse_conn, rcu);
+
+	fuse_uring_destruct(fc);
 
 	put_user_ns(fc->user_ns);
 	fc->release(fc);
···
 				else
 					ok = false;
 			}
+			if (flags & FUSE_OVER_IO_URING && fuse_uring_enabled())
+				fc->io_uring = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_SIZE;
 			fc->no_lock = 1;
···
 		flags |= FUSE_SUBMOUNTS;
 	if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
 		flags |= FUSE_PASSTHROUGH;
+
+	/*
+	 * This is just an information flag for fuse server. No need to check
+	 * the reply - server is either sending IORING_OP_URING_CMD or not.
+	 */
+	if (fuse_uring_enabled())
+		flags |= FUSE_OVER_IO_URING;
 
 	ia->in.flags = flags;
 	ia->in.flags2 = flags >> 32;

fs/fuse/xattr.c

···
 
 	args.opcode = FUSE_REMOVEXATTR;
 	args.nodeid = get_node_id(inode);
-	args.in_numargs = 1;
-	args.in_args[0].size = strlen(name) + 1;
-	args.in_args[0].value = name;
+	args.in_numargs = 2;
+	fuse_set_zero_arg0(&args);
+	args.in_args[1].size = strlen(name) + 1;
+	args.in_args[1].value = name;
 	err = fuse_simple_request(fm, &args);
 	if (err == -ENOSYS) {
 		fm->fc->no_removexattr = 1;

include/uapi/linux/fuse.h

···
  *
  *  7.41
  *  - add FUSE_ALLOW_IDMAP
+ *  7.42
+ *  - Add FUSE_OVER_IO_URING and all other io-uring related flags and data
+ *    structures:
+ *    - struct fuse_uring_ent_in_out
+ *    - struct fuse_uring_req_header
+ *    - struct fuse_uring_cmd_req
+ *    - FUSE_URING_IN_OUT_HEADER_SZ
+ *    - FUSE_URING_OP_IN_OUT_SZ
+ *    - enum fuse_uring_cmd
  */
 
 #ifndef _LINUX_FUSE_H
···
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 41
+#define FUSE_KERNEL_MINOR_VERSION 42
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
···
  * FUSE_HAS_RESEND: kernel supports resending pending requests, and the high bit
  *		    of the request ID indicates resend requests
  * FUSE_ALLOW_IDMAP: allow creation of idmapped mounts
+ * FUSE_OVER_IO_URING: Indicate that client supports io-uring
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
···
 /* Obsolete alias for FUSE_DIRECT_IO_ALLOW_MMAP */
 #define FUSE_DIRECT_IO_RELAX	FUSE_DIRECT_IO_ALLOW_MMAP
 #define FUSE_ALLOW_IDMAP	(1ULL << 40)
+#define FUSE_OVER_IO_URING	(1ULL << 41)
 
 /**
  * CUSE INIT request/reply flags
···
 struct fuse_supp_groups {
 	uint32_t	nr_groups;
 	uint32_t	groups[];
+};
+
+/**
+ * Size of the ring buffer header
+ */
+#define FUSE_URING_IN_OUT_HEADER_SZ 128
+#define FUSE_URING_OP_IN_OUT_SZ 128
+
+/* Used as part of the fuse_uring_req_header */
+struct fuse_uring_ent_in_out {
+	uint64_t flags;
+
+	/*
+	 * commit ID to be used in a reply to a ring request (see also
+	 * struct fuse_uring_cmd_req)
+	 */
+	uint64_t commit_id;
+
+	/* size of user payload buffer */
+	uint32_t payload_sz;
+	uint32_t padding;
+
+	uint64_t reserved;
+};
+
+/**
+ * Header for all fuse-io-uring requests
+ */
+struct fuse_uring_req_header {
+	/* struct fuse_in_header / struct fuse_out_header */
+	char in_out[FUSE_URING_IN_OUT_HEADER_SZ];
+
+	/* per op code header */
+	char op_in[FUSE_URING_OP_IN_OUT_SZ];
+
+	struct fuse_uring_ent_in_out ring_ent_in_out;
+};
+
+/**
+ * sqe commands to the kernel
+ */
+enum fuse_uring_cmd {
+	FUSE_IO_URING_CMD_INVALID = 0,
+
+	/* register the request buffer and fetch a fuse request */
+	FUSE_IO_URING_CMD_REGISTER = 1,
+
+	/* commit fuse request result and fetch next request */
+	FUSE_IO_URING_CMD_COMMIT_AND_FETCH = 2,
+};
+
+/**
+ * In the 80B command area of the SQE.
+ */
+struct fuse_uring_cmd_req {
+	uint64_t flags;
+
+	/* entry identifier for commits */
+	uint64_t commit_id;
+
+	/* queue the command is for (queue index) */
+	uint16_t qid;
+	uint8_t padding[6];
 };
 
 #endif /* _LINUX_FUSE_H */