[PATCH v9 10/17] fuse: Add io-uring sqe commit and fetch support

[Bernd Schubert <bschubert@ddn.com>]

This adds support for fuse request completion through ring SQEs
(FUSE_URING_CMD_COMMIT_AND_FETCH handling). After committing
the ring entry it becomes available for new fuse requests.
Handling of requests through the ring (SQE/CQE handling)
is complete now.

Fuse request data are copied through the mmaped ring buffer,
there is no support for any zero copy yet.

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
---
 fs/fuse/dev_uring.c   | 450 ++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/fuse/dev_uring_i.h |  12 ++
 fs/fuse/fuse_i.h      |   4 +
 3 files changed, 466 insertions(+)

diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index b44ba4033615e01041313c040035b6da6af0ee17..f44e66a7ea577390da87e9ac7d118a9416898c28 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -26,6 +26,19 @@ bool fuse_uring_enabled(void)
 	return enable_uring;
 }
 
+static void fuse_uring_req_end(struct fuse_ring_ent *ring_ent, bool set_err,
+			       int error)
+{
+	struct fuse_req *req = ring_ent->fuse_req;
+
+	if (set_err)
+		req->out.h.error = error;
+
+	clear_bit(FR_SENT, &req->flags);
+	fuse_request_end(ring_ent->fuse_req);
+	ring_ent->fuse_req = NULL;
+}
+
 void fuse_uring_destruct(struct fuse_conn *fc)
 {
 	struct fuse_ring *ring = fc->ring;
@@ -41,8 +54,11 @@ void fuse_uring_destruct(struct fuse_conn *fc)
 			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));
 
+		kfree(queue->fpq.processing);
 		kfree(queue);
 		ring->queues[qid] = NULL;
 	}
@@ -101,20 +117,34 @@ static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring,
 {
 	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);
+
+	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];
 	}
@@ -128,6 +158,214 @@ static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring,
 	return queue;
 }
 
+/*
+ * 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 supportd through io-uring yet */
+		pr_warn_once("notify through fuse-io-uring not supported\n");
+		goto seterr;
+	}
+
+	err = -EINVAL;
+	if (oh->error <= -ERESTARTSYS || oh->error > 0)
+		goto seterr;
+
+	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 seterr;
+	}
+
+	/*
+	 * 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);
+
+	return 0;
+
+seterr:
+	oh->error = err;
+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, res;
+	struct fuse_uring_ent_in_out ring_in_out;
+
+	res = copy_from_user(&ring_in_out, &ent->headers->ring_ent_in_out,
+			     sizeof(ring_in_out));
+	if (res)
+		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_copy_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, res;
+	struct iov_iter iter;
+	struct fuse_uring_ent_in_out ent_in_out = {
+		.flags = 0,
+		.commit_id = ent->commit_id,
+	};
+
+	if (WARN_ON(ent_in_out.commit_id == 0))
+		return -EINVAL;
+
+	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.
+		 */
+		if (args->in_args[0].size > 0) {
+			res = copy_to_user(&ent->headers->op_in, in_args->value,
+					   in_args->size);
+			err = res > 0 ? -EFAULT : res;
+			if (err) {
+				pr_info_ratelimited(
+					"Copying the header failed.\n");
+				return err;
+			}
+		}
+		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;
+	res = copy_to_user(&ent->headers->ring_ent_in_out, &ent_in_out,
+			   sizeof(ent_in_out));
+	err = res > 0 ? -EFAULT : res;
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int
+fuse_uring_prepare_send(struct fuse_ring_ent *ring_ent)
+{
+	struct fuse_ring_queue *queue = ring_ent->queue;
+	struct fuse_ring *ring = queue->ring;
+	struct fuse_req *req = ring_ent->fuse_req;
+	int err, res;
+
+	err = -EIO;
+	if (WARN_ON(ring_ent->state != FRRS_FUSE_REQ)) {
+		pr_err("qid=%d ring-req=%p invalid state %d on send\n",
+		       queue->qid, ring_ent, ring_ent->state);
+		err = -EIO;
+		goto err;
+	}
+
+	/* copy the request */
+	err = fuse_uring_copy_to_ring(ring, req, ring_ent);
+	if (unlikely(err)) {
+		pr_info_ratelimited("Copy to ring failed: %d\n", err);
+		goto err;
+	}
+
+	/* copy fuse_in_header */
+	res = copy_to_user(&ring_ent->headers->in_out, &req->in.h,
+			   sizeof(req->in.h));
+	err = res > 0 ? -EFAULT : res;
+	if (err)
+		goto err;
+
+	set_bit(FR_SENT, &req->flags);
+	return 0;
+
+err:
+	fuse_uring_req_end(ring_ent, true, 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 *ring_ent,
+					unsigned int issue_flags)
+{
+	int err = 0;
+	struct fuse_ring_queue *queue = ring_ent->queue;
+
+	err = fuse_uring_prepare_send(ring_ent);
+	if (err)
+		goto err;
+
+	spin_lock(&queue->lock);
+	ring_ent->state = FRRS_USERSPACE;
+	list_move(&ring_ent->list, &queue->ent_in_userspace);
+	spin_unlock(&queue->lock);
+
+	io_uring_cmd_done(ring_ent->cmd, 0, 0, issue_flags);
+	ring_ent->cmd = NULL;
+	return 0;
+
+err:
+	return err;
+}
+
 /*
  * Make a ring entry available for fuse_req assignment
  */
@@ -138,6 +376,210 @@ static void fuse_uring_ent_avail(struct fuse_ring_ent *ring_ent,
 	ring_ent->state = FRRS_AVAILABLE;
 }
 
+/* Used to find the request on SQE commit */
+static void fuse_uring_add_to_pq(struct fuse_ring_ent *ring_ent,
+				 struct fuse_req *req)
+{
+	struct fuse_ring_queue *queue = ring_ent->queue;
+	struct fuse_pqueue *fpq = &queue->fpq;
+	unsigned int hash;
+
+	/* commit_id is the unique id of the request */
+	ring_ent->commit_id = req->in.h.unique;
+
+	req->ring_entry = ring_ent;
+	hash = fuse_req_hash(ring_ent->commit_id);
+	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 *ring_ent,
+					   struct fuse_req *req)
+{
+	struct fuse_ring_queue *queue = ring_ent->queue;
+
+	lockdep_assert_held(&queue->lock);
+
+	if (WARN_ON_ONCE(ring_ent->state != FRRS_AVAILABLE &&
+			 ring_ent->state != FRRS_COMMIT)) {
+		pr_warn("%s qid=%d state=%d\n", __func__, ring_ent->queue->qid,
+			ring_ent->state);
+	}
+	list_del_init(&req->list);
+	clear_bit(FR_PENDING, &req->flags);
+	ring_ent->fuse_req = req;
+	ring_ent->state = FRRS_FUSE_REQ;
+	list_move(&ring_ent->list, &queue->ent_w_req_queue);
+	fuse_uring_add_to_pq(ring_ent, req);
+}
+
+/*
+ * Release the ring entry and fetch the next fuse request if available
+ *
+ * @return true if a new request has been fetched
+ */
+static bool fuse_uring_ent_assign_req(struct fuse_ring_ent *ring_ent)
+	__must_hold(&queue->lock)
+{
+	struct fuse_req *req;
+	struct fuse_ring_queue *queue = ring_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(ring_ent, req);
+		return true;
+	}
+
+	return false;
+}
+
+/*
+ * 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 *ring_ent,
+			      unsigned int issue_flags)
+{
+	struct fuse_ring *ring = ring_ent->queue->ring;
+	struct fuse_conn *fc = ring->fc;
+	struct fuse_req *req = ring_ent->fuse_req;
+	ssize_t err = 0;
+	bool set_err = false;
+
+	err = copy_from_user(&req->out.h, &ring_ent->headers->in_out,
+			     sizeof(req->out.h));
+	if (err) {
+		req->out.h.error = err;
+		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, ring_ent);
+	if (err)
+		set_err = true;
+
+out:
+	fuse_uring_req_end(ring_ent, set_err, err);
+}
+
+/*
+ * Get the next fuse req and send it
+ */
+static void fuse_uring_next_fuse_req(struct fuse_ring_ent *ring_ent,
+				     struct fuse_ring_queue *queue,
+				     unsigned int issue_flags)
+{
+	int err;
+	bool has_next;
+
+retry:
+	spin_lock(&queue->lock);
+	fuse_uring_ent_avail(ring_ent, queue);
+	has_next = fuse_uring_ent_assign_req(ring_ent);
+	spin_unlock(&queue->lock);
+
+	if (has_next) {
+		err = fuse_uring_send_next_to_ring(ring_ent, 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 *ring_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;
+
+	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);
+	ring_ent = req->ring_entry;
+	req->ring_entry = NULL;
+
+	err = fuse_ring_ent_set_commit(ring_ent);
+	if (err != 0) {
+		pr_info_ratelimited("qid=%d commit_id %llu state %d",
+				    queue->qid, commit_id, ring_ent->state);
+		spin_unlock(&queue->lock);
+		return err;
+	}
+
+	ring_ent->cmd = cmd;
+	spin_unlock(&queue->lock);
+
+	/* without the queue lock, as other locks are taken */
+	fuse_uring_commit(ring_ent, 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(ring_ent, queue, issue_flags);
+	return 0;
+}
+
 /*
  * fuse_uring_req_fetch command handling
  */
@@ -325,6 +767,14 @@ int __maybe_unused fuse_uring_cmd(struct io_uring_cmd *cmd,
 			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;
 	}
diff --git a/fs/fuse/dev_uring_i.h b/fs/fuse/dev_uring_i.h
index 4e46dd65196d26dabc62dada33b17de9aa511c08..80f1c62d4df7f0ca77c4d5179068df6ffdbf7d85 100644
--- a/fs/fuse/dev_uring_i.h
+++ b/fs/fuse/dev_uring_i.h
@@ -20,6 +20,9 @@ enum fuse_ring_req_state {
 	/* 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,
 };
@@ -70,7 +73,16 @@ struct fuse_ring_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;
+
+	/* fuse requests waiting for an entry slot */
+	struct list_head fuse_req_queue;
+
+	struct fuse_pqueue fpq;
 };
 
 /**
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e545b0864dd51e82df61cc39bdf65d3d36a418dc..e71556894bc25808581424ec7bdd4afeebc81f15 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -438,6 +438,10 @@ struct fuse_req {
 
 	/** fuse_mount this request belongs to */
 	struct fuse_mount *fm;
+
+#ifdef CONFIG_FUSE_IO_URING
+	void *ring_entry;
+#endif
 };
 
 struct fuse_iqueue;

-- 
2.43.0