[RFC 3/5] io_uring: add infra and support for IORING_OP_URING_CMD

[Kanchan Joshi <joshi.k@samsung.com>]

From: Jens Axboe <axboe@kernel.dk>

This is a file private kind of request. io_uring doesn't know what's
in this command type, it's for the file_operations->async_cmd()
handler to deal with.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 fs/io_uring.c                 | 79 +++++++++++++++++++++++++++++++----
 include/linux/io_uring.h      | 29 +++++++++++++
 include/uapi/linux/io_uring.h |  8 +++-
 3 files changed, 108 insertions(+), 8 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 241ba1cd6dcf..bd0e6b102a7b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -200,13 +200,6 @@ struct io_rings {
 	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
 };
 
-enum io_uring_cmd_flags {
-	IO_URING_F_COMPLETE_DEFER	= 1,
-	IO_URING_F_UNLOCKED		= 2,
-	/* int's last bit, sign checks are usually faster than a bit test */
-	IO_URING_F_NONBLOCK		= INT_MIN,
-};
-
 struct io_mapped_ubuf {
 	u64		ubuf;
 	u64		ubuf_end;
@@ -860,6 +853,7 @@ struct io_kiocb {
 		struct io_mkdir		mkdir;
 		struct io_symlink	symlink;
 		struct io_hardlink	hardlink;
+		struct io_uring_cmd	uring_cmd;
 	};
 
 	u8				opcode;
@@ -1110,6 +1104,9 @@ static const struct io_op_def io_op_defs[] = {
 	[IORING_OP_MKDIRAT] = {},
 	[IORING_OP_SYMLINKAT] = {},
 	[IORING_OP_LINKAT] = {},
+	[IORING_OP_URING_CMD] = {
+		.needs_file		= 1,
+	},
 };
 
 /* requests with any of those set should undergo io_disarm_next() */
@@ -2464,6 +2461,22 @@ static void io_req_task_submit(struct io_kiocb *req, bool *locked)
 		io_req_complete_failed(req, -EFAULT);
 }
 
+static void io_uring_cmd_work(struct io_kiocb *req, bool *locked)
+{
+	req->uring_cmd.driver_cb(&req->uring_cmd);
+}
+
+void io_uring_cmd_complete_in_task(struct io_uring_cmd *ioucmd,
+			void (*driver_cb)(struct io_uring_cmd *))
+{
+	struct io_kiocb *req = container_of(ioucmd, struct io_kiocb, uring_cmd);
+
+	req->uring_cmd.driver_cb = driver_cb;
+	req->io_task_work.func = io_uring_cmd_work;
+	io_req_task_work_add(req, !!(req->ctx->flags & IORING_SETUP_SQPOLL));
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_complete_in_task);
+
 static void io_req_task_queue_fail(struct io_kiocb *req, int ret)
 {
 	req->result = ret;
@@ -4109,6 +4122,51 @@ static int io_linkat(struct io_kiocb *req, unsigned int issue_flags)
 	return 0;
 }
 
+/*
+ * Called by consumers of io_uring_cmd, if they originally returned
+ * -EIOCBQUEUED upon receiving the command.
+ */
+void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret)
+{
+	struct io_kiocb *req = container_of(ioucmd, struct io_kiocb, uring_cmd);
+
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_complete(req, ret);
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_done);
+
+static int io_uring_cmd_prep(struct io_kiocb *req,
+			     const struct io_uring_sqe *sqe)
+{
+	struct io_uring_cmd *ioucmd = &req->uring_cmd;
+
+	if (!req->file->f_op->async_cmd)
+		return -EOPNOTSUPP;
+	if (req->ctx->flags & IORING_SETUP_IOPOLL)
+		return -EOPNOTSUPP;
+	ioucmd->cmd = (void *) &sqe->cmd;
+	ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
+	ioucmd->cmd_len = READ_ONCE(sqe->cmd_len);
+	ioucmd->flags = 0;
+	return 0;
+}
+
+static int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct file *file = req->file;
+	int ret;
+	struct io_uring_cmd *ioucmd = &req->uring_cmd;
+
+	ioucmd->flags |= issue_flags;
+	ret = file->f_op->async_cmd(ioucmd);
+	/* queued async, consumer will call io_uring_cmd_done() when complete */
+	if (ret == -EIOCBQUEUED)
+		return 0;
+	io_uring_cmd_done(ioucmd, ret);
+	return 0;
+}
+
 static int io_shutdown_prep(struct io_kiocb *req,
 			    const struct io_uring_sqe *sqe)
 {
@@ -6588,6 +6646,8 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return io_symlinkat_prep(req, sqe);
 	case IORING_OP_LINKAT:
 		return io_linkat_prep(req, sqe);
+	case IORING_OP_URING_CMD:
+		return io_uring_cmd_prep(req, sqe);
 	}
 
 	printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
@@ -6871,6 +6931,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 	case IORING_OP_LINKAT:
 		ret = io_linkat(req, issue_flags);
 		break;
+	case IORING_OP_URING_CMD:
+		ret = io_uring_cmd(req, issue_flags);
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -11215,6 +11278,8 @@ static int __init io_uring_init(void)
 	BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST);
 	BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof(int));
 
+	BUILD_BUG_ON(sizeof(struct io_uring_cmd) > 64);
+
 	req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
 				SLAB_ACCOUNT);
 	return 0;
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 649a4d7c241b..cedc68201469 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -5,7 +5,29 @@
 #include <linux/sched.h>
 #include <linux/xarray.h>
 
+enum io_uring_cmd_flags {
+	IO_URING_F_COMPLETE_DEFER	= 1,
+	IO_URING_F_UNLOCKED		= 2,
+	/* int's last bit, sign checks are usually faster than a bit test */
+	IO_URING_F_NONBLOCK		= INT_MIN,
+};
+
+struct io_uring_cmd {
+	struct file     *file;
+	void            *cmd;
+	/* for irq-completion - if driver requires doing stuff in task-context*/
+	void (*driver_cb)(struct io_uring_cmd *cmd);
+	u32             flags;
+	u32             cmd_op;
+	u16		cmd_len;
+	u16		unused;
+	u8		pdu[28]; /* available inline for free use */
+};
+
 #if defined(CONFIG_IO_URING)
+void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret);
+void io_uring_cmd_complete_in_task(struct io_uring_cmd *ioucmd,
+			void (*driver_cb)(struct io_uring_cmd *));
 struct sock *io_uring_get_socket(struct file *file);
 void __io_uring_cancel(bool cancel_all);
 void __io_uring_free(struct task_struct *tsk);
@@ -26,6 +48,13 @@ static inline void io_uring_free(struct task_struct *tsk)
 		__io_uring_free(tsk);
 }
 #else
+static inline void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret)
+{
+}
+static inline void io_uring_cmd_complete_in_task(struct io_uring_cmd *ioucmd,
+			void (*driver_cb)(struct io_uring_cmd *))
+{
+}
 static inline struct sock *io_uring_get_socket(struct file *file)
 {
 	return NULL;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index c5db68433ca5..d7a4bdb9bf3b 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -22,10 +22,12 @@ struct io_uring_sqe {
 	union {
 		__u64	off;	/* offset into file */
 		__u64	addr2;
+		__u32	cmd_op;
 	};
 	union {
 		__u64	addr;	/* pointer to buffer or iovecs */
 		__u64	splice_off_in;
+		__u16	cmd_len;
 	};
 	__u32	len;		/* buffer size or number of iovecs */
 	union {
@@ -60,7 +62,10 @@ struct io_uring_sqe {
 		__s32	splice_fd_in;
 		__u32	file_index;
 	};
-	__u64	__pad2[2];
+	union {
+		__u64	__pad2[2];
+		__u64	cmd;
+	};
 
 	/*
 	 * If the ring is initializefd with IORING_SETUP_SQE128, then this field
@@ -150,6 +155,7 @@ enum {
 	IORING_OP_MKDIRAT,
 	IORING_OP_SYMLINKAT,
 	IORING_OP_LINKAT,
+	IORING_OP_URING_CMD,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
-- 
2.25.1