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

Bernd Schubert
2024-11-27T13:41:00Z

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>
+
+#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.");
+#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 */
+
+/*
+ * 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),
+ 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 */
+ 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)
+ 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);
+ 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);
+ 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)
+ 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)) {
+ 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))
+ 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;
+
+ switch (cmd_op) {
+ case FUSE_URING_REQ_FETCH:
+ 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 */
+ 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];
+};
+
+/**
+ * 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 */

--
2.43.0