summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat (limited to 'linux-aio.c')
-rw-r--r--linux-aio.c204
1 files changed, 204 insertions, 0 deletions
diff --git a/linux-aio.c b/linux-aio.c
new file mode 100644
index 000000000..f53a08cb0
--- /dev/null
+++ b/linux-aio.c
@@ -0,0 +1,204 @@
+/*
+ * 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 "block_int.h"
+#include "block/raw-posix-aio.h"
+
+#include <sys/eventfd.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;
+};
+
+struct qemu_laio_state {
+ io_context_t ctx;
+ int efd;
+ int count;
+};
+
+static inline ssize_t io_event_ret(struct io_event *ev)
+{
+ return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
+}
+
+static void qemu_laio_completion_cb(void *opaque)
+{
+ struct qemu_laio_state *s = opaque;
+
+ while (1) {
+ struct io_event events[MAX_EVENTS];
+ uint64_t val;
+ ssize_t ret;
+ struct timespec ts = { 0 };
+ int nevents, i;
+
+ do {
+ ret = read(s->efd, &val, sizeof(val));
+ } while (ret == 1 && errno == EINTR);
+
+ if (ret == -1 && errno == EAGAIN)
+ break;
+
+ if (ret != 8)
+ break;
+
+ do {
+ nevents = io_getevents(s->ctx, val, 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);
+
+ s->count--;
+
+ ret = laiocb->ret = io_event_ret(&events[i]);
+ if (ret != -ECANCELED) {
+ if (ret == laiocb->nbytes)
+ ret = 0;
+ else if (ret >= 0)
+ ret = -EINVAL;
+
+ laiocb->common.cb(laiocb->common.opaque, ret);
+ }
+
+ qemu_aio_release(laiocb);
+ }
+ }
+}
+
+static int qemu_laio_flush_cb(void *opaque)
+{
+ struct qemu_laio_state *s = opaque;
+
+ 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);
+}
+
+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);
+ if (!laiocb)
+ return NULL;
+ laiocb->nbytes = nb_sectors * 512;
+ laiocb->ctx = s;
+ laiocb->ret = -EINPROGRESS;
+
+ 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;
+ default:
+ fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
+ __func__, type);
+ goto out_free_aiocb;
+ }
+ io_set_eventfd(&laiocb->iocb, s->efd);
+ s->count++;
+
+ if (io_submit(s->ctx, 1, &iocbs) < 0)
+ goto out_dec_count;
+ return &laiocb->common;
+
+out_free_aiocb:
+ qemu_aio_release(laiocb);
+out_dec_count:
+ s->count--;
+ return NULL;
+}
+
+void *laio_init(void)
+{
+ struct qemu_laio_state *s;
+
+ s = qemu_mallocz(sizeof(*s));
+ s->efd = eventfd(0, 0);
+ if (s->efd == -1)
+ goto out_free_state;
+ fcntl(s->efd, F_SETFL, O_NONBLOCK);
+
+ if (io_setup(MAX_EVENTS, &s->ctx) != 0)
+ goto out_close_efd;
+
+ qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb,
+ NULL, qemu_laio_flush_cb, s);
+
+ return s;
+
+out_close_efd:
+ close(s->efd);
+out_free_state:
+ qemu_free(s);
+ return NULL;
+}