[PATCH 4/5] block: add example ioctl

[Jens Axboe <axboe@kernel.dk>]

Example code, to issue BLKBSZGET through IORING_OP_URING_CMD:

struct block_uring_cmd {
	__u16 	op;
	__u16	pad;
	union {
		__u32	size;
		__u32	ioctl_cmd;
	};
	__u64	addr;
	__u64	unused[2];
	__u64	reserved;	/* can never be used */
	__u64	unused2;
};

static int get_bs(struct io_uring *ring, const char *dev)
{
	struct io_uring_cqe *cqe;
	struct io_uring_sqe *sqe;
	struct block_uring_cmd *cmd;
	int ret, fd;

	fd = open(dev, O_RDONLY);
	if (fd < 0) {
		perror("open");
		return 1;
	}

	sqe = io_uring_get_sqe(ring);
	if (!sqe) {
		fprintf(stderr, "get sqe failed\n");
		goto err;
	}

	memset(sqe, 0, sizeof(*sqe));
	sqe->opcode = IORING_OP_URING_CMD;
	sqe->fd = fd;
	cmd = (void *) &sqe->off;
	cmd->op = BLOCK_URING_OP_IOCTL;
	cmd->ioctl_cmd = BLKBSZGET;
	sqe->user_data = 0x1234;

	ret = io_uring_submit(ring);
	if (ret <= 0) {
		fprintf(stderr, "sqe submit failed: %d\n", ret);
		goto err;
	}

	ret = io_uring_wait_cqe(ring, &cqe);
	if (ret < 0) {
		fprintf(stderr, "wait completion %d\n", ret);
		goto err;
	}
	printf("bs=%d\n", cqe->res);
	io_uring_cqe_seen(ring, cqe);
	return 0;
err:
	return 1;
}

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/block_dev.c         | 19 +++++++++++++++++++
 include/linux/blkdev.h | 17 +++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index c837912c1d72..7cb1b24ebbb5 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -302,10 +302,29 @@ struct blkdev_dio {
 
 static struct bio_set blkdev_dio_pool;
 
+static int blkdev_uring_ioctl(struct block_device *bdev,
+			      struct block_uring_cmd *bcmd)
+{
+	switch (bcmd->ioctl_cmd) {
+	case BLKBSZGET:
+		return block_size(bdev);
+	default:
+		return -ENOTTY;
+	}
+}
+
 static int blkdev_uring_cmd(struct io_uring_cmd *cmd,
 			    enum io_uring_cmd_flags flags)
 {
 	struct block_device *bdev = I_BDEV(cmd->file->f_mapping->host);
+	struct block_uring_cmd *bcmd = (struct block_uring_cmd *) &cmd->pdu;
+
+	switch (bcmd->op) {
+	case BLOCK_URING_OP_IOCTL:
+		return blkdev_uring_ioctl(bdev, bcmd);
+	default:
+		break;
+	}
 
 	return blk_uring_cmd(bdev, cmd, flags);
 }
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d5af592d73fe..48ac8ccbffe2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -44,6 +44,23 @@ struct blk_queue_stats;
 struct blk_stat_callback;
 struct blk_keyslot_manager;
 
+enum {
+	BLOCK_URING_OP_IOCTL = 1,
+};
+
+struct block_uring_cmd {
+	__u16 	op;
+	__u16	pad;
+	union {
+		__u32	size;
+		__u32	ioctl_cmd;
+	};
+	__u64	addr;
+	__u64	unused[2];
+	__u64	reserved;	/* can never be used */
+	__u64	unused2;
+};
+
 #define BLKDEV_MIN_RQ	4
 #define BLKDEV_MAX_RQ	128	/* Default maximum */
 
-- 
2.30.0