345 lines
8.4 KiB
C
345 lines
8.4 KiB
C
/*
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* Linux native AIO support.
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*
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* Copyright (C) 2009 IBM, Corp.
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* Copyright (C) 2009 Red Hat, Inc.
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu-common.h"
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#include "block/aio.h"
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#include "qemu/queue.h"
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#include "block/raw-aio.h"
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#include "qemu/event_notifier.h"
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#include <libaio.h>
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/*
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* Queue size (per-device).
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*
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* XXX: eventually we need to communicate this to the guest and/or make it
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* tunable by the guest. If we get more outstanding requests at a time
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* than this we will get EAGAIN from io_submit which is communicated to
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* the guest as an I/O error.
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*/
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#define MAX_EVENTS 128
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#define MAX_QUEUED_IO 128
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struct qemu_laiocb {
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BlockDriverAIOCB common;
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struct qemu_laio_state *ctx;
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struct iocb iocb;
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ssize_t ret;
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size_t nbytes;
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QEMUIOVector *qiov;
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bool is_read;
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QLIST_ENTRY(qemu_laiocb) node;
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};
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typedef struct {
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struct iocb *iocbs[MAX_QUEUED_IO];
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int plugged;
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unsigned int size;
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unsigned int idx;
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} LaioQueue;
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struct qemu_laio_state {
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io_context_t ctx;
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EventNotifier e;
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/* io queue for submit at batch */
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LaioQueue io_q;
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/* I/O completion processing */
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QEMUBH *completion_bh;
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struct io_event events[MAX_EVENTS];
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int event_idx;
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int event_max;
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};
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static inline ssize_t io_event_ret(struct io_event *ev)
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{
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return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
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}
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/*
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* Completes an AIO request (calls the callback and frees the ACB).
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*/
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static void qemu_laio_process_completion(struct qemu_laio_state *s,
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struct qemu_laiocb *laiocb)
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{
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int ret;
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ret = laiocb->ret;
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if (ret != -ECANCELED) {
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if (ret == laiocb->nbytes) {
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ret = 0;
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} else if (ret >= 0) {
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/* Short reads mean EOF, pad with zeros. */
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if (laiocb->is_read) {
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qemu_iovec_memset(laiocb->qiov, ret, 0,
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laiocb->qiov->size - ret);
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} else {
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ret = -EINVAL;
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}
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}
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}
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laiocb->common.cb(laiocb->common.opaque, ret);
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qemu_aio_unref(laiocb);
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}
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/* The completion BH fetches completed I/O requests and invokes their
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* callbacks.
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*
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* The function is somewhat tricky because it supports nested event loops, for
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* example when a request callback invokes aio_poll(). In order to do this,
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* the completion events array and index are kept in qemu_laio_state. The BH
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* reschedules itself as long as there are completions pending so it will
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* either be called again in a nested event loop or will be called after all
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* events have been completed. When there are no events left to complete, the
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* BH returns without rescheduling.
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*/
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static void qemu_laio_completion_bh(void *opaque)
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{
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struct qemu_laio_state *s = opaque;
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/* Fetch more completion events when empty */
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if (s->event_idx == s->event_max) {
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do {
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struct timespec ts = { 0 };
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s->event_max = io_getevents(s->ctx, MAX_EVENTS, MAX_EVENTS,
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s->events, &ts);
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} while (s->event_max == -EINTR);
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s->event_idx = 0;
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if (s->event_max <= 0) {
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s->event_max = 0;
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return; /* no more events */
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}
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}
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/* Reschedule so nested event loops see currently pending completions */
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qemu_bh_schedule(s->completion_bh);
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/* Process completion events */
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while (s->event_idx < s->event_max) {
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struct iocb *iocb = s->events[s->event_idx].obj;
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struct qemu_laiocb *laiocb =
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container_of(iocb, struct qemu_laiocb, iocb);
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laiocb->ret = io_event_ret(&s->events[s->event_idx]);
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s->event_idx++;
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qemu_laio_process_completion(s, laiocb);
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}
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}
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static void qemu_laio_completion_cb(EventNotifier *e)
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{
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struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e);
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if (event_notifier_test_and_clear(&s->e)) {
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qemu_bh_schedule(s->completion_bh);
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}
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}
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static void laio_cancel(BlockDriverAIOCB *blockacb)
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{
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struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb;
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struct io_event event;
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int ret;
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if (laiocb->ret != -EINPROGRESS) {
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return;
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}
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ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
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laiocb->ret = -ECANCELED;
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if (ret != 0) {
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/* iocb is not cancelled, cb will be called by the event loop later */
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return;
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}
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laiocb->common.cb(laiocb->common.opaque, laiocb->ret);
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}
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static const AIOCBInfo laio_aiocb_info = {
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.aiocb_size = sizeof(struct qemu_laiocb),
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.cancel_async = laio_cancel,
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};
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static void ioq_init(LaioQueue *io_q)
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{
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io_q->size = MAX_QUEUED_IO;
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io_q->idx = 0;
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io_q->plugged = 0;
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}
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static int ioq_submit(struct qemu_laio_state *s)
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{
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int ret, i = 0;
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int len = s->io_q.idx;
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do {
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ret = io_submit(s->ctx, len, s->io_q.iocbs);
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} while (i++ < 3 && ret == -EAGAIN);
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/* empty io queue */
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s->io_q.idx = 0;
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if (ret < 0) {
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i = 0;
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} else {
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i = ret;
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}
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for (; i < len; i++) {
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struct qemu_laiocb *laiocb =
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container_of(s->io_q.iocbs[i], struct qemu_laiocb, iocb);
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laiocb->ret = (ret < 0) ? ret : -EIO;
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qemu_laio_process_completion(s, laiocb);
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}
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return ret;
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}
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static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
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{
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unsigned int idx = s->io_q.idx;
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s->io_q.iocbs[idx++] = iocb;
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s->io_q.idx = idx;
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/* submit immediately if queue is full */
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if (idx == s->io_q.size) {
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ioq_submit(s);
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}
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}
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void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
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{
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struct qemu_laio_state *s = aio_ctx;
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s->io_q.plugged++;
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}
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int laio_io_unplug(BlockDriverState *bs, void *aio_ctx, bool unplug)
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{
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struct qemu_laio_state *s = aio_ctx;
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int ret = 0;
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assert(s->io_q.plugged > 0 || !unplug);
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if (unplug && --s->io_q.plugged > 0) {
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return 0;
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}
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if (s->io_q.idx > 0) {
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ret = ioq_submit(s);
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}
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return ret;
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}
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BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
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int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
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BlockDriverCompletionFunc *cb, void *opaque, int type)
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{
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struct qemu_laio_state *s = aio_ctx;
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struct qemu_laiocb *laiocb;
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struct iocb *iocbs;
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off_t offset = sector_num * 512;
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laiocb = qemu_aio_get(&laio_aiocb_info, bs, cb, opaque);
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laiocb->nbytes = nb_sectors * 512;
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laiocb->ctx = s;
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laiocb->ret = -EINPROGRESS;
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laiocb->is_read = (type == QEMU_AIO_READ);
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laiocb->qiov = qiov;
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iocbs = &laiocb->iocb;
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switch (type) {
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case QEMU_AIO_WRITE:
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io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset);
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break;
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case QEMU_AIO_READ:
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io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset);
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break;
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/* Currently Linux kernel does not support other operations */
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default:
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fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
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__func__, type);
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goto out_free_aiocb;
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}
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io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
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if (!s->io_q.plugged) {
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if (io_submit(s->ctx, 1, &iocbs) < 0) {
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goto out_free_aiocb;
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}
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} else {
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ioq_enqueue(s, iocbs);
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}
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return &laiocb->common;
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out_free_aiocb:
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qemu_aio_unref(laiocb);
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return NULL;
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}
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void laio_detach_aio_context(void *s_, AioContext *old_context)
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{
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struct qemu_laio_state *s = s_;
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aio_set_event_notifier(old_context, &s->e, NULL);
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qemu_bh_delete(s->completion_bh);
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}
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void laio_attach_aio_context(void *s_, AioContext *new_context)
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{
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struct qemu_laio_state *s = s_;
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s->completion_bh = aio_bh_new(new_context, qemu_laio_completion_bh, s);
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aio_set_event_notifier(new_context, &s->e, qemu_laio_completion_cb);
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}
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void *laio_init(void)
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{
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struct qemu_laio_state *s;
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s = g_malloc0(sizeof(*s));
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if (event_notifier_init(&s->e, false) < 0) {
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goto out_free_state;
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}
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if (io_setup(MAX_EVENTS, &s->ctx) != 0) {
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goto out_close_efd;
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}
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ioq_init(&s->io_q);
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return s;
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out_close_efd:
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event_notifier_cleanup(&s->e);
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out_free_state:
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g_free(s);
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return NULL;
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}
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void laio_cleanup(void *s_)
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{
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struct qemu_laio_state *s = s_;
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event_notifier_cleanup(&s->e);
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if (io_destroy(s->ctx) != 0) {
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fprintf(stderr, "%s: destroy AIO context %p failed\n",
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__func__, &s->ctx);
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}
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g_free(s);
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}
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