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

include/uapi/linux/fuse.h

@@ -220,6 +220,15 @@
  *
  *  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
@@ -255,7 +264,7 @@
 #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
@@ -425,6 +434,7 @@ 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 +481,7 @@ 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 +1217,67 @@ 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
+
+/* 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 */