/* * 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 { BlockDriverAIOCB common; struct qemu_laio_state *ctx; struct iocb iocb; ssize_t ret; size_t nbytes; QEMUIOVector *qiov; bool is_read; QLIST_ENTRY(qemu_laiocb) node; }; typedef struct { struct iocb *iocbs[MAX_QUEUED_IO]; int plugged; unsigned int size; unsigned int idx; } LaioQueue; struct qemu_laio_state { io_context_t ctx; EventNotifier e; /* io queue for submit at batch */ LaioQueue io_q; }; 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_release(laiocb); } static void qemu_laio_completion_cb(EventNotifier *e) { struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e); while (event_notifier_test_and_clear(&s->e)) { struct io_event events[MAX_EVENTS]; struct timespec ts = { 0 }; int nevents, i; do { nevents = io_getevents(s->ctx, MAX_EVENTS, MAX_EVENTS, events, &ts); } while (nevents == -EINTR); for (i = 0; i < nevents; i++) { struct iocb *iocb = events[i].obj; struct qemu_laiocb *laiocb = container_of(iocb, struct qemu_laiocb, iocb); laiocb->ret = io_event_ret(&events[i]); qemu_laio_process_completion(s, laiocb); } } } static void laio_cancel(BlockDriverAIOCB *blockacb) { struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb; struct io_event event; int ret; if (laiocb->ret != -EINPROGRESS) return; /* * Note that as of Linux 2.6.31 neither the block device code nor any * filesystem implements cancellation of AIO request. * Thus the polling loop below is the normal code path. */ ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event); if (ret == 0) { laiocb->ret = -ECANCELED; return; } /* * We have to wait for the iocb to finish. * * The only way to get the iocb status update is by polling the io context. * We might be able to do this slightly more optimal by removing the * O_NONBLOCK flag. */ while (laiocb->ret == -EINPROGRESS) { qemu_laio_completion_cb(&laiocb->ctx->e); } } static const AIOCBInfo laio_aiocb_info = { .aiocb_size = sizeof(struct qemu_laiocb), .cancel = laio_cancel, }; static void ioq_init(LaioQueue *io_q) { io_q->size = MAX_QUEUED_IO; io_q->idx = 0; io_q->plugged = 0; } static int ioq_submit(struct qemu_laio_state *s) { int ret, i = 0; int len = s->io_q.idx; do { ret = io_submit(s->ctx, len, s->io_q.iocbs); } while (i++ < 3 && ret == -EAGAIN); /* empty io queue */ s->io_q.idx = 0; if (ret < 0) { i = 0; } else { i = ret; } for (; i < len; i++) { struct qemu_laiocb *laiocb = container_of(s->io_q.iocbs[i], struct qemu_laiocb, iocb); laiocb->ret = (ret < 0) ? ret : -EIO; qemu_laio_process_completion(s, laiocb); } return ret; } static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb) { unsigned int idx = s->io_q.idx; s->io_q.iocbs[idx++] = iocb; s->io_q.idx = idx; /* submit immediately if queue is full */ if (idx == s->io_q.size) { ioq_submit(s); } } void laio_io_plug(BlockDriverState *bs, void *aio_ctx) { struct qemu_laio_state *s = aio_ctx; s->io_q.plugged++; } int laio_io_unplug(BlockDriverState *bs, void *aio_ctx, bool unplug) { struct qemu_laio_state *s = aio_ctx; int ret = 0; assert(s->io_q.plugged > 0 || !unplug); if (unplug && --s->io_q.plugged > 0) { return 0; } if (s->io_q.idx > 0) { ret = ioq_submit(s); } return ret; } BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd, int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, BlockDriverCompletionFunc *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)); if (!s->io_q.plugged) { if (io_submit(s->ctx, 1, &iocbs) < 0) { goto out_free_aiocb; } } else { ioq_enqueue(s, iocbs); } return &laiocb->common; out_free_aiocb: qemu_aio_release(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); } void laio_attach_aio_context(void *s_, AioContext *new_context) { struct qemu_laio_state *s = 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); }