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/*
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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 "qemu-aio.h" |
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#include "block_int.h" |
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#include "block/raw-posix-aio.h" |
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#include <sys/eventfd.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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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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struct qemu_laio_state {
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io_context_t ctx; |
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int efd;
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int count;
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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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s->count--; |
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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_skip(laiocb->qiov, 0,
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laiocb->qiov->size - ret, ret); |
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} else {
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ret = -EINVAL; |
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} |
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} |
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laiocb->common.cb(laiocb->common.opaque, ret); |
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} |
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qemu_aio_release(laiocb); |
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} |
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static void qemu_laio_completion_cb(void *opaque) |
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{ |
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struct qemu_laio_state *s = opaque;
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while (1) { |
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struct io_event events[MAX_EVENTS];
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uint64_t val; |
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ssize_t ret; |
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struct timespec ts = { 0 }; |
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int nevents, i;
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do {
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ret = read(s->efd, &val, sizeof(val));
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} while (ret == -1 && errno == EINTR); |
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if (ret == -1 && errno == EAGAIN) |
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break;
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if (ret != 8) |
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break;
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do {
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nevents = io_getevents(s->ctx, val, MAX_EVENTS, events, &ts); |
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} while (nevents == -EINTR);
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for (i = 0; i < nevents; i++) { |
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struct iocb *iocb = events[i].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(&events[i]); |
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qemu_laio_process_completion(s, laiocb); |
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} |
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} |
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} |
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static int qemu_laio_flush_cb(void *opaque) |
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{ |
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struct qemu_laio_state *s = opaque;
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return (s->count > 0) ? 1 : 0; |
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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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* Note that as of Linux 2.6.31 neither the block device code nor any
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* filesystem implements cancellation of AIO request.
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* Thus the polling loop below is the normal code path.
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*/
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ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event); |
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if (ret == 0) { |
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laiocb->ret = -ECANCELED; |
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return;
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} |
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/*
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* We have to wait for the iocb to finish.
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*
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* The only way to get the iocb status update is by polling the io context.
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* We might be able to do this slightly more optimal by removing the
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* O_NONBLOCK flag.
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*/
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while (laiocb->ret == -EINPROGRESS)
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qemu_laio_completion_cb(laiocb->ctx); |
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} |
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static AIOPool laio_pool = {
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.aiocb_size = sizeof(struct qemu_laiocb), |
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.cancel = laio_cancel, |
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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_pool, 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, s->efd); |
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s->count++; |
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if (io_submit(s->ctx, 1, &iocbs) < 0) |
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goto out_dec_count;
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return &laiocb->common;
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out_dec_count:
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s->count--; |
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out_free_aiocb:
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qemu_aio_release(laiocb); |
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return NULL; |
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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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s->efd = eventfd(0, 0); |
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if (s->efd == -1) |
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goto out_free_state;
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fcntl(s->efd, F_SETFL, O_NONBLOCK); |
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if (io_setup(MAX_EVENTS, &s->ctx) != 0) |
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goto out_close_efd;
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qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
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qemu_laio_flush_cb, NULL, s);
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return s;
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out_close_efd:
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close(s->efd); |
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out_free_state:
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g_free(s); |
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return NULL; |
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} |