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