diff options
Diffstat (limited to 'block/linux-aio.c')
| -rw-r--r-- | block/linux-aio.c | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/block/linux-aio.c b/block/linux-aio.c new file mode 100644 index 0000000000..6ca984dbe8 --- /dev/null +++ b/block/linux-aio.c @@ -0,0 +1,216 @@ +/* + * 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 "qemu-aio.h" +#include "qemu-queue.h" +#include "block/raw-aio.h" +#include "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 + +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; +}; + +struct qemu_laio_state { + io_context_t ctx; + EventNotifier e; + int count; +}; + +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; + + s->count--; + + 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 int qemu_laio_flush_cb(EventNotifier *e) +{ + struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e); + + return (s->count > 0) ? 1 : 0; +} + +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 AIOPool laio_pool = { + .aiocb_size = sizeof(struct qemu_laiocb), + .cancel = laio_cancel, +}; + +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_pool, 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)); + s->count++; + + if (io_submit(s->ctx, 1, &iocbs) < 0) + goto out_dec_count; + return &laiocb->common; + +out_dec_count: + s->count--; +out_free_aiocb: + qemu_aio_release(laiocb); + return NULL; +} + +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; + } + + qemu_aio_set_event_notifier(&s->e, qemu_laio_completion_cb, + qemu_laio_flush_cb); + + return s; + +out_close_efd: + event_notifier_cleanup(&s->e); +out_free_state: + g_free(s); + return NULL; +} |