Re: [PATCH RFC v7 06/16] fuse: {uring} Handle SQEs - register commands

[Joanne Koong <joannelkoong@gmail.com>]

On Wed, Nov 27, 2024 at 5:41 AM Bernd Schubert <bschubert@ddn.com> wrote:
>
> This adds basic support for ring SQEs (with opcode=IORING_OP_URING_CMD).
> For now only FUSE_URING_REQ_FETCH is handled to register queue entries.
>
> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
> ---
>  fs/fuse/Kconfig           |  12 ++
>  fs/fuse/Makefile          |   1 +
>  fs/fuse/dev.c             |   4 +
>  fs/fuse/dev_uring.c       | 318 ++++++++++++++++++++++++++++++++++++++++++++++
>  fs/fuse/dev_uring_i.h     | 115 +++++++++++++++++
>  fs/fuse/fuse_i.h          |   5 +
>  fs/fuse/inode.c           |  10 ++
>  include/uapi/linux/fuse.h |  67 ++++++++++
>  8 files changed, 532 insertions(+)
>
> diff --git a/fs/fuse/Kconfig b/fs/fuse/Kconfig
> index 8674dbfbe59dbf79c304c587b08ebba3cfe405be..11f37cefc94b2af5a675c238801560c822b95f1a 100644
> --- a/fs/fuse/Kconfig
> +++ b/fs/fuse/Kconfig
> @@ -63,3 +63,15 @@ config FUSE_PASSTHROUGH
>           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
> diff --git a/fs/fuse/Makefile b/fs/fuse/Makefile
> index ce0ff7a9007b94b4ab246b5271f227d126c768e8..fcf16b1c391a9bf11ca9f3a25b137acdb203ac47 100644
> --- a/fs/fuse/Makefile
> +++ b/fs/fuse/Makefile
> @@ -14,5 +14,6 @@ fuse-y := dev.o dir.o file.o inode.o control.o xattr.o acl.o readdir.o ioctl.o
>  fuse-y += iomode.o
>  fuse-$(CONFIG_FUSE_DAX) += dax.o
>  fuse-$(CONFIG_FUSE_PASSTHROUGH) += passthrough.o
> +fuse-$(CONFIG_FUSE_IO_URING) += dev_uring.o
>
>  virtiofs-y := virtio_fs.o
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 63c3865aebb7811fdf4a5729b2181ee8321421dc..0770373492ae9ee83c4154fede9dcfd7be9fb33d 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -6,6 +6,7 @@
>    See the file COPYING.
>  */
>
> +#include "dev_uring_i.h"
>  #include "fuse_i.h"
>  #include "fuse_dev_i.h"
>
> @@ -2452,6 +2453,9 @@ const struct file_operations fuse_dev_operations = {
>         .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);
>
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..af9c5f116ba1dcf6c01d0359d1a06491c92c32f9
> --- /dev/null
> +++ b/fs/fuse/dev_uring.c
> @@ -0,0 +1,318 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * FUSE: Filesystem in Userspace
> + * Copyright (c) 2023-2024 DataDirect Networks.
> + */
> +
> +#include <linux/fs.h>

nit: for consistency, should this line be placed directly above the
other "#include <linux..." line?

> +
> +#include "fuse_i.h"
> +#include "dev_uring_i.h"
> +#include "fuse_dev_i.h"
> +
> +#include <linux/io_uring/cmd.h>
> +
> +#ifdef CONFIG_FUSE_IO_URING
> +static bool __read_mostly enable_uring;
> +module_param(enable_uring, bool, 0644);
> +MODULE_PARM_DESC(enable_uring,
> +                "Enable uring userspace communication through uring.");

nit: The double uring seems a bit repetitive to me. Maybe just "enable
uring userspace communication" or "enable userspace communication
through uring"? Also, super nit but I noticed the other
MODULE_PARM_DESCs don't have trailing periods.

> +#endif
> +
> +bool fuse_uring_enabled(void)
> +{
> +       return enable_uring;
> +}
> +
> +static int fuse_ring_ent_unset_userspace(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;
> +}
> +
> +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];
> +
> +               if (!queue)
> +                       continue;
> +
> +               WARN_ON(!list_empty(&queue->ent_avail_queue));
> +               WARN_ON(!list_empty(&queue->ent_commit_queue));
> +
> +               kfree(queue);
> +               ring->queues[qid] = NULL;
> +       }
> +
> +       kfree(ring->queues);
> +       kfree(ring);
> +       fc->ring = NULL;
> +}
> +
> +#define FUSE_URING_IOV_SEGS 2 /* header and payload */

nit: to make the code flow easier, might be better to move #defines to
the top of the file after the includes.

> +
> +/*
> + * 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 = NULL;
> +       size_t nr_queues = num_possible_cpus();
> +       struct fuse_ring *res = NULL;
> +
> +       ring = kzalloc(sizeof(*fc->ring) +
> +                              nr_queues * sizeof(struct fuse_ring_queue),

I think you just need kzalloc(sizeof(*fc->ring)); here since you're
allocating ring->queues later below

> +                      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;
> +
> +       spin_lock(&fc->lock);
> +       if (fc->ring) {
> +               /* race, another thread created the ring in the mean time */

nit: s/mean time/meantime

> +               spin_unlock(&fc->lock);
> +               res = fc->ring;
> +               goto out_err;
> +       }
> +
> +       fc->ring = ring;
> +       ring->nr_queues = nr_queues;
> +       ring->fc = fc;
> +
> +       spin_unlock(&fc->lock);
> +       return ring;
> +
> +out_err:
> +       if (ring)

I think you meant if (ring->queues)

> +               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;
> +
> +       queue = kzalloc(sizeof(*queue), GFP_KERNEL_ACCOUNT);
> +       if (!queue)
> +               return ERR_PTR(-ENOMEM);
> +       spin_lock(&fc->lock);

This probably doesn't make much of a difference but might be better to
minimize logic inside the lock, eg do the queue initialization stuff
outside the lock

> +       if (ring->queues[qid]) {
> +               spin_unlock(&fc->lock);
> +               kfree(queue);
> +               return ring->queues[qid];
> +       }
> +
> +       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);
> +
> +       WRITE_ONCE(ring->queues[qid], queue);

Just curious, why do we need WRITE_ONCE here if it's already protected
by the fc->lock?

> +       spin_unlock(&fc->lock);
> +
> +       return queue;
> +}
> +
> +/*
> + * Make a ring entry available for fuse_req assignment
> + */
> +static void fuse_uring_ent_avail(struct fuse_ring_ent *ring_ent,
> +                                struct fuse_ring_queue *queue)
> +{
> +       list_move(&ring_ent->list, &queue->ent_avail_queue);
> +       ring_ent->state = FRRS_WAIT;
> +}
> +
> +/*
> + * fuse_uring_req_fetch command handling
> + */
> +static void _fuse_uring_fetch(struct fuse_ring_ent *ring_ent,
> +                             struct io_uring_cmd *cmd,
> +                             unsigned int issue_flags)
> +{
> +       struct fuse_ring_queue *queue = ring_ent->queue;
> +
> +       spin_lock(&queue->lock);
> +       fuse_uring_ent_avail(ring_ent, queue);
> +       ring_ent->cmd = cmd;
> +       spin_unlock(&queue->lock);
> +}
> +
> +/*
> + * 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 int fuse_uring_fetch(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 *ring_ent;
> +       int err;
> +       struct iovec iov[FUSE_URING_IOV_SEGS];
> +
> +       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;
> +       }
> +
> +       err = -ENOMEM;
> +       if (!ring) {
> +               ring = fuse_uring_create(fc);
> +               if (!ring)
> +                       return err;
> +       }
> +
> +       queue = ring->queues[cmd_req->qid];
> +       if (!queue) {
> +               queue = fuse_uring_create_queue(ring, cmd_req->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.
> +        */
> +
> +       ring_ent = kzalloc(sizeof(*ring_ent), GFP_KERNEL_ACCOUNT);
> +       if (ring_ent == NULL)

nit: !ring_ent

> +               return err;
> +
> +       INIT_LIST_HEAD(&ring_ent->list);
> +
> +       ring_ent->queue = queue;
> +       ring_ent->cmd = cmd;
> +
> +       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);
> +               goto err;
> +       }
> +
> +       ring_ent->headers = iov[0].iov_base;
> +       ring_ent->payload = iov[1].iov_base;
> +       ring_ent->max_arg_len = iov[1].iov_len;
> +
> +       if (ring_ent->max_arg_len <
> +           max_t(size_t, FUSE_MIN_READ_BUFFER, fc->max_write)) {

If I'm understanding this correctly, iov[0] is the header and iov[1]
is the payload. Is this right that the payload len must always be
equal to fc->max_write?

Also, do we need to take into account fc->max_pages too?

> +               pr_info_ratelimited("Invalid req payload len %zu\n",
> +                                   ring_ent->max_arg_len);
> +               goto err;
> +       }
> +
> +       spin_lock(&queue->lock);
> +
> +       /*
> +        * FUSE_URING_REQ_FETCH is an initialization exception, needs
> +        * state override
> +        */
> +       ring_ent->state = FRRS_USERSPACE;
> +       err = fuse_ring_ent_unset_userspace(ring_ent);
> +       spin_unlock(&queue->lock);
> +       if (WARN_ON_ONCE(err != 0))

nit: WARN_ON_ONCE(err)

> +               goto err;
> +
> +       _fuse_uring_fetch(ring_ent, cmd, issue_flags);
> +
> +       return 0;
> +err:
> +       list_del_init(&ring_ent->list);
> +       kfree(ring_ent);
> +       return err;
> +}
> +
> +/*
> + * Entry function from io_uring to handle the given passthrough command
> + * (op cocde 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;
> +
> +       /* Disabled for now, especially as teardown is not implemented yet */
> +       pr_info_ratelimited("fuse-io-uring is not enabled yet\n");
> +       return -EOPNOTSUPP;
> +
> +       if (!enable_uring) {
> +               pr_info_ratelimited("fuse-io-uring is disabled\n");
> +               return -EOPNOTSUPP;
> +       }
> +
> +       fud = fuse_get_dev(cmd->file);
> +       if (!fud) {
> +               pr_info_ratelimited("No fuse device found\n");
> +               return -ENOTCONN;
> +       }
> +       fc = fud->fc;
> +
> +       if (!fc->connected || fc->aborted)
> +               return fc->aborted ? -ECONNABORTED : -ENOTCONN;

I find
if (fc->aborted)
  return -ECONNABORTED;
if (!fc->connected)
   return -ENOTCONN;

easier to read
> +
> +       switch (cmd_op) {
> +       case FUSE_URING_REQ_FETCH:

FUSE_URING_REQ_FETCH is only used for initialization, would it be
clearer if this was named FUSE_URING_INIT or something like that?

> +               err = fuse_uring_fetch(cmd, issue_flags, fc);
> +               if (err) {
> +                       pr_info_once("fuse_uring_fetch failed err=%d\n", err);
> +                       return err;
> +               }
> +               break;
> +       default:
> +               return -EINVAL;
> +       }
> +
> +       return -EIOCBQUEUED;
> +}
> diff --git a/fs/fuse/dev_uring_i.h b/fs/fuse/dev_uring_i.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..75c644cc0b2bb3721b08f8695964815d53f46e92
> --- /dev/null
> +++ b/fs/fuse/dev_uring_i.h
> @@ -0,0 +1,115 @@
> +/* 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
> +
> +enum fuse_ring_req_state {
> +       FRRS_INVALID = 0,
> +
> +       /* The ring entry received from userspace and it being processed */

nit: "it is being processed"

> +       FRRS_COMMIT,
> +
> +       /* The ring entry is waiting for new fuse requests */
> +       FRRS_WAIT,
> +
> +       /* The ring entry is in or on the way to user space */
> +       FRRS_USERSPACE,
> +};
> +
> +/** 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;
> +
> +       struct io_uring_cmd *cmd;
> +
> +       struct list_head list;
> +
> +       /* size of payload buffer */
> +       size_t max_arg_len;
> +
> +       /*
> +        * state the request is currently in
> +        * (enum fuse_ring_req_state)
> +        */
> +       unsigned int 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, typically also 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 send to userspace
> +        */
> +       struct list_head ent_commit_queue;
> +};
> +
> +/**
> + * 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;
> +
> +       struct fuse_ring_queue **queues;
> +};
> +
> +bool fuse_uring_enabled(void);
> +void fuse_uring_destruct(struct fuse_conn *fc);
> +int fuse_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags);
> +
> +#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;
> +}
> +
> +#endif /* CONFIG_FUSE_IO_URING */
> +
> +#endif /* _FS_FUSE_DEV_URING_I_H */
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index e3748751e231d0991c050b31bdd84db0b8016f9f..a21256ec4c3b4bd7c67eae2d03b68d87dcc8234b 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -914,6 +914,11 @@ struct fuse_conn {
>         /** IDR for backing files ids */
>         struct idr backing_files_map;
>  #endif
> +
> +#ifdef CONFIG_FUSE_IO_URING
> +       /**  uring connection information*/
> +       struct fuse_ring *ring;
> +#endif
>  };
>
>  /*
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index fd3321e29a3e569bf06be22a5383cf34fd42c051..76267c79e920204175e5713853de8214c5555d46 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -7,6 +7,7 @@
>  */
>
>  #include "fuse_i.h"
> +#include "dev_uring_i.h"
>
>  #include <linux/pagemap.h>
>  #include <linux/slab.h>
> @@ -959,6 +960,8 @@ 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);
>  }
> @@ -1413,6 +1416,13 @@ void fuse_send_init(struct fuse_mount *fm)
>         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;
>
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index f1e99458e29e4fdce5273bc3def242342f207ebd..6d39077edf8cde4fa77130efcec16323839a676c 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
> @@ -220,6 +220,14 @@
>   *
>   *  7.41
>   *  - add FUSE_ALLOW_IDMAP
> + *  7.42
> + *  - Add FUSE_OVER_IO_URING and all other io-uring related flags and data
> + *    structures:
> + *    - fuse_uring_ent_in_out
> + *    - fuse_uring_req_header
> + *    - fuse_uring_cmd_req
> + *    - FUSE_URING_IN_OUT_HEADER_SZ
> + *    - FUSE_URING_OP_IN_OUT_SZ
>   */
>
>  #ifndef _LINUX_FUSE_H
> @@ -425,6 +433,7 @@ struct fuse_file_lock {
>   * 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)
> @@ -471,6 +480,7 @@ struct fuse_file_lock {
>  /* 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
> @@ -1206,4 +1216,61 @@ struct fuse_supp_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
> +
> +struct fuse_uring_ent_in_out {
> +       uint64_t flags;
> +
> +       /* size of use payload buffer */
> +       uint32_t payload_sz;
> +       uint32_t padding;
> +
> +       uint8_t reserved[30];

out of curiosity, how was 30 chosen here? I think this makes the
struct 46 bytes?

> +};
> +
> +/**
> + * This structure mapped onto the
> + */
> +struct fuse_uring_req_header {
> +       /* struct fuse_in / struct fuse_out */
> +       char in_out[FUSE_URING_IN_OUT_HEADER_SZ];
> +
> +       /* per op code structs */
> +       char op_in[FUSE_URING_OP_IN_OUT_SZ];
> +
> +       /* struct fuse_ring_in_out */
> +       char ring_ent_in_out[sizeof(struct fuse_uring_ent_in_out)];
> +};
> +
> +/**
> + * sqe commands to the kernel
> + */
> +enum fuse_uring_cmd {
> +       FUSE_URING_REQ_INVALID = 0,
> +
> +       /* submit sqe to kernel to get a request */
> +       FUSE_URING_REQ_FETCH = 1,
> +
> +       /* commit result and fetch next request */
> +       FUSE_URING_REQ_COMMIT_AND_FETCH = 2,
> +};
> +
> +/**
> + * In the 80B command area of the SQE.
> + */
> +struct fuse_uring_cmd_req {
> +       uint64_t flags;
> +
> +       /* entry identifier */
> +       uint64_t commit_id;
> +
> +       /* queue the command is for (queue index) */
> +       uint16_t qid;
> +       uint8_t padding[6];
> +};
> +
>  #endif /* _LINUX_FUSE_H */
>

I'll be out the rest of this week for an American holiday
(Thanksgiving) and next week for a work trip but will review the rest
of this patchset after that when i get back.

Thanks,
Joanne
> --
> 2.43.0
>