157 строки
3.5 KiB
C
157 строки
3.5 KiB
C
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/mman.h>
|
|
#include <unistd.h>
|
|
#include <errno.h>
|
|
#include <string.h>
|
|
|
|
#include "liburing.h"
|
|
#include "barrier.h"
|
|
|
|
static int __io_uring_get_cqe(struct io_uring *ring,
|
|
struct io_uring_cqe **cqe_ptr, int wait)
|
|
{
|
|
struct io_uring_cq *cq = &ring->cq;
|
|
const unsigned mask = *cq->kring_mask;
|
|
unsigned head;
|
|
int ret;
|
|
|
|
*cqe_ptr = NULL;
|
|
head = *cq->khead;
|
|
do {
|
|
/*
|
|
* It's necessary to use a read_barrier() before reading
|
|
* the CQ tail, since the kernel updates it locklessly. The
|
|
* kernel has the matching store barrier for the update. The
|
|
* kernel also ensures that previous stores to CQEs are ordered
|
|
* with the tail update.
|
|
*/
|
|
read_barrier();
|
|
if (head != *cq->ktail) {
|
|
*cqe_ptr = &cq->cqes[head & mask];
|
|
break;
|
|
}
|
|
if (!wait)
|
|
break;
|
|
ret = io_uring_enter(ring->ring_fd, 0, 1,
|
|
IORING_ENTER_GETEVENTS, NULL);
|
|
if (ret < 0)
|
|
return -errno;
|
|
} while (1);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Return an IO completion, if one is readily available. Returns 0 with
|
|
* cqe_ptr filled in on success, -errno on failure.
|
|
*/
|
|
int io_uring_peek_cqe(struct io_uring *ring, struct io_uring_cqe **cqe_ptr)
|
|
{
|
|
return __io_uring_get_cqe(ring, cqe_ptr, 0);
|
|
}
|
|
|
|
/*
|
|
* Return an IO completion, waiting for it if necessary. Returns 0 with
|
|
* cqe_ptr filled in on success, -errno on failure.
|
|
*/
|
|
int io_uring_wait_cqe(struct io_uring *ring, struct io_uring_cqe **cqe_ptr)
|
|
{
|
|
return __io_uring_get_cqe(ring, cqe_ptr, 1);
|
|
}
|
|
|
|
/*
|
|
* Submit sqes acquired from io_uring_get_sqe() to the kernel.
|
|
*
|
|
* Returns number of sqes submitted
|
|
*/
|
|
int io_uring_submit(struct io_uring *ring)
|
|
{
|
|
struct io_uring_sq *sq = &ring->sq;
|
|
const unsigned mask = *sq->kring_mask;
|
|
unsigned ktail, ktail_next, submitted, to_submit;
|
|
int ret;
|
|
|
|
/*
|
|
* If we have pending IO in the kring, submit it first. We need a
|
|
* read barrier here to match the kernels store barrier when updating
|
|
* the SQ head.
|
|
*/
|
|
read_barrier();
|
|
if (*sq->khead != *sq->ktail) {
|
|
submitted = *sq->kring_entries;
|
|
goto submit;
|
|
}
|
|
|
|
if (sq->sqe_head == sq->sqe_tail)
|
|
return 0;
|
|
|
|
/*
|
|
* Fill in sqes that we have queued up, adding them to the kernel ring
|
|
*/
|
|
submitted = 0;
|
|
ktail = ktail_next = *sq->ktail;
|
|
to_submit = sq->sqe_tail - sq->sqe_head;
|
|
while (to_submit--) {
|
|
ktail_next++;
|
|
read_barrier();
|
|
|
|
sq->array[ktail & mask] = sq->sqe_head & mask;
|
|
ktail = ktail_next;
|
|
|
|
sq->sqe_head++;
|
|
submitted++;
|
|
}
|
|
|
|
if (!submitted)
|
|
return 0;
|
|
|
|
if (*sq->ktail != ktail) {
|
|
/*
|
|
* First write barrier ensures that the SQE stores are updated
|
|
* with the tail update. This is needed so that the kernel
|
|
* will never see a tail update without the preceeding sQE
|
|
* stores being done.
|
|
*/
|
|
write_barrier();
|
|
*sq->ktail = ktail;
|
|
/*
|
|
* The kernel has the matching read barrier for reading the
|
|
* SQ tail.
|
|
*/
|
|
write_barrier();
|
|
}
|
|
|
|
submit:
|
|
ret = io_uring_enter(ring->ring_fd, submitted, 0,
|
|
IORING_ENTER_GETEVENTS, NULL);
|
|
if (ret < 0)
|
|
return -errno;
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Return an sqe 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 sqe, or NULL if we're full.
|
|
*/
|
|
struct io_uring_sqe *io_uring_get_sqe(struct io_uring *ring)
|
|
{
|
|
struct io_uring_sq *sq = &ring->sq;
|
|
unsigned next = sq->sqe_tail + 1;
|
|
struct io_uring_sqe *sqe;
|
|
|
|
/*
|
|
* All sqes are used
|
|
*/
|
|
if (next - sq->sqe_head > *sq->kring_entries)
|
|
return NULL;
|
|
|
|
sqe = &sq->sqes[sq->sqe_tail & *sq->kring_mask];
|
|
sq->sqe_tail = next;
|
|
return sqe;
|
|
}
|