[PATCH v10 10/17] fuse: Add io-uring sqe commit and fetch support

Bernd Schubert
2025-01-20T01:29:21Z

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>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> # io_uring
---
fs/fuse/dev_uring.c | 448 ++++++++++++++++++++++++++++++++++++++++++++++++++
fs/fuse/dev_uring_i.h | 12 ++
fs/fuse/fuse_i.h | 4 +
3 files changed, 464 insertions(+)

diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index 60e38ff1ecef3b007bae7ceedd7dd997439e463a..74aa5ccaff30998cf58e805f7c1b7ebf70d5cd6d 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -24,6 +24,18 @@ bool fuse_uring_enabled(void)
return enable_uring;
}

+static void fuse_uring_req_end(struct fuse_ring_ent *ent, int error)
+{
+ struct fuse_req *req = ent->fuse_req;
+
+ if (error)
+ req->out.h.error = error;
+
+ clear_bit(FR_SENT, &req->flags);
+ fuse_request_end(ent->fuse_req);
+ ent->fuse_req = NULL;
+}
+
void fuse_uring_destruct(struct fuse_conn *fc)
{
struct fuse_ring *ring = fc->ring;
@@ -39,8 +51,11 @@ 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;
}
@@ -99,20 +114,34 @@ 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];
}
@@ -126,6 +155,213 @@ 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 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 = ent->fuse_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, 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,
+ unsigned int issue_flags)
+{
+ struct fuse_ring_queue *queue = ent->queue;
+ int err;
+ struct io_uring_cmd *cmd;
+
+ err = fuse_uring_prepare_send(ent);
+ 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
*/
@@ -137,6 +373,210 @@ static void fuse_uring_ent_avail(struct fuse_ring_ent *ent,
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);
+}
+
+/*
+ * 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 *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 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 *ent,
+ unsigned int issue_flags)
+{
+ struct fuse_ring *ring = ent->queue->ring;
+ struct fuse_conn *fc = ring->fc;
+ struct fuse_req *req = ent->fuse_req;
+ 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 = 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, ent);
+out:
+ fuse_uring_req_end(ent, 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;
+ bool has_next;
+
+retry:
+ spin_lock(&queue->lock);
+ fuse_uring_ent_avail(ent, queue);
+ has_next = fuse_uring_ent_assign_req(ent);
+ spin_unlock(&queue->lock);
+
+ if (has_next) {
+ err = fuse_uring_send_next_to_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 *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);
+ 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_commit(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(ent, queue, issue_flags);
+ return 0;
+}
+
/*
* fuse_uring_req_fetch command handling
*/
@@ -318,6 +758,14 @@ 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 ae1536355b368583132d2ab6878b5490510b28e8..44bf237f0d5abcadbb768ba3940c3fec813b079d 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,
};
@@ -67,7 +70,16 @@ 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