1 files changed, 193 insertions, 0 deletions
diff --git a/src/io_uring.c b/src/io_uring.c
new file mode 100644
index 0000000..52b3553
--- /dev/null
+++ b/src/io_uring.c
@@ -0,0 +1,193 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+
+#include "io_uring.h"
+#include "liburing.h"
+#include "barrier.h"
+
+/*
+ * Return an IO completion, waiting for it it necessary.
+ */
+int io_uring_get_completion(int fd, struct io_uring_cq *cq,
+			    struct io_uring_event **ev_ptr)
+{
+	const unsigned mask = *cq->kring_mask;
+	struct io_uring_event *ev = NULL;
+	unsigned head;
+	int ret;
+
+	head = *cq->khead;
+	do {
+		read_barrier();
+		if (head != *cq->ktail) {
+			ev = &cq->events[head & mask];
+			break;
+		}
+		ret = io_uring_enter(fd, 0, 1, IORING_ENTER_GETEVENTS);
+		if (ret < 0)
+			return -errno;
+	} while (1);
+
+	if (ev) {
+		*cq->khead = head + 1;
+		write_barrier();
+	}
+
+	*ev_ptr = ev;
+	return 0;
+}
+
+/*
+ * Submit iocbs acquired from io_uring_get_iocb() to the kernel.
+ *
+ * Returns number of iocbs submitted
+ */
+int io_uring_submit(int fd, struct io_uring_sq *sq)
+{
+	const unsigned mask = *sq->kring_mask;
+	unsigned ktail, ktail_next, submitted;
+
+	/*
+	 * If we have pending IO in the kring, submit it first
+	 */
+	read_barrier();
+	if (*sq->khead != *sq->ktail) {
+		submitted = *sq->kring_entries;
+		goto submit;
+	}
+
+	if (sq->iocb_head == sq->iocb_tail)
+		return 0;
+
+	/*
+	 * Fill in iocbs that we have queued up, adding them to the kernel ring
+	 */
+	submitted = 0;
+	ktail = ktail_next = *sq->ktail;
+	while (sq->iocb_head < sq->iocb_tail) {
+		ktail_next++;
+		read_barrier();
+		if (ktail_next == *sq->khead)
+			break;
+
+		sq->array[ktail & mask] = sq->iocb_head & mask;
+		ktail = ktail_next;
+
+		sq->iocb_head++;
+		submitted++;
+	}
+
+	if (!submitted)
+		return 0;
+
+	if (*sq->ktail != ktail) {
+		write_barrier();
+		*sq->ktail = ktail;
+		write_barrier();
+	}
+
+submit:
+	return io_uring_enter(fd, submitted, 0, IORING_ENTER_GETEVENTS);
+}
+
+/*
+ * Return an iocb to fill. Application must later call io_uring_submit()
+ * when it's ready to tell the kernel about it. The caller may call this
+ * function multiple times before calling io_uring_submit().
+ *
+ * Returns a vacant iocb, or NULL if we're full.
+ */
+struct io_uring_iocb *io_uring_get_iocb(struct io_uring_sq *sq)
+{
+	unsigned next = sq->iocb_tail + 1;
+	struct io_uring_iocb *iocb;
+
+	/*
+	 * All iocbs are used
+	 */
+	if (next - sq->iocb_head > *sq->kring_entries)
+		return NULL;
+
+	iocb = &sq->iocbs[sq->iocb_tail & *sq->kring_mask];
+	sq->iocb_tail = next;
+	return iocb;
+}
+
+static int io_uring_mmap(int fd, struct io_uring_params *p,
+			 struct io_uring_sq *sq, struct io_uring_cq *cq)
+{
+	size_t size;
+	void *ptr;
+	int ret;
+
+	sq->ring_sz = p->sq_off.array + p->sq_entries * sizeof(unsigned);
+	ptr = mmap(0, sq->ring_sz, PROT_READ | PROT_WRITE,
+			MAP_SHARED | MAP_POPULATE, fd, IORING_OFF_SQ_RING);
+	if (ptr == MAP_FAILED)
+		return -errno;
+	sq->khead = ptr + p->sq_off.head;
+	sq->ktail = ptr + p->sq_off.tail;
+	sq->kring_mask = ptr + p->sq_off.ring_mask;
+	sq->kring_entries = ptr + p->sq_off.ring_entries;
+	sq->kflags = ptr + p->sq_off.flags;
+	sq->kdropped = ptr + p->sq_off.dropped;
+	sq->array = ptr + p->sq_off.array;
+
+	size = p->sq_entries * sizeof(struct io_uring_iocb);
+	sq->iocbs = mmap(0, size, PROT_READ | PROT_WRITE,
+				MAP_SHARED | MAP_POPULATE, fd,
+				IORING_OFF_IOCB);
+	if (sq->iocbs == MAP_FAILED) {
+		ret = -errno;
+err:
+		munmap(sq->khead, sq->ring_sz);
+		return ret;
+	}
+
+	cq->ring_sz = p->cq_off.events + p->cq_entries * sizeof(struct io_uring_event);
+	ptr = mmap(0, cq->ring_sz, PROT_READ | PROT_WRITE,
+			MAP_SHARED | MAP_POPULATE, fd, IORING_OFF_CQ_RING);
+	if (ptr == MAP_FAILED) {
+		ret = -errno;
+		munmap(sq->iocbs, p->sq_entries * sizeof(struct io_uring_iocb));
+		goto err;
+	}
+	cq->khead = ptr + p->cq_off.head;
+	cq->ktail = ptr + p->cq_off.tail;
+	cq->kring_mask = ptr + p->cq_off.ring_mask;
+	cq->kring_entries = ptr + p->cq_off.ring_entries;
+	cq->koverflow = ptr + p->cq_off.overflow;
+	cq->events = ptr + p->cq_off.events;
+	return fd;
+}
+
+/*
+ * Returns -1 on error, or an 'fd' on success. On success, 'sq' and 'cq'
+ * contain the necessary information to read/write to the rings.
+ */
+int io_uring_queue_init(unsigned entries, struct io_uring_params *p,
+			struct iovec *iovecs, struct io_uring_sq *sq,
+			struct io_uring_cq *cq)
+{
+	int fd;
+
+	fd = io_uring_setup(entries, iovecs, p);
+	if (fd < 0)
+		return fd;
+
+	memset(sq, 0, sizeof(*sq));
+	memset(cq, 0, sizeof(*cq));
+	return io_uring_mmap(fd, p, sq, cq);
+}
+
+void io_uring_queue_exit(int fd, struct io_uring_sq *sq, struct io_uring_cq *cq)
+{
+	munmap(sq->iocbs, *sq->kring_entries * sizeof(struct io_uring_iocb));
+	munmap(sq->khead, sq->ring_sz);
+	munmap(cq->khead, cq->ring_sz);
+	close(fd);
+}