Merge branch 'upstream-merge'
[qemu-kvm.git] / linux-aio.c
blobce9b5d4be807378f16845f1e9aa339bc66cd3214
1 /*
2 * Linux native AIO support.
4 * Copyright (C) 2009 IBM, Corp.
5 * Copyright (C) 2009 Red Hat, Inc.
7 * This work is licensed under the terms of the GNU GPL, version 2 or later.
8 * See the COPYING file in the top-level directory.
9 */
10 #include "qemu-common.h"
11 #include "qemu-aio.h"
12 #include "block/raw-posix-aio.h"
14 #include <sys/eventfd.h>
15 #include <libaio.h>
18 * Queue size (per-device).
20 * XXX: eventually we need to communicate this to the guest and/or make it
21 * tunable by the guest. If we get more outstanding requests at a time
22 * than this we will get EAGAIN from io_submit which is communicated to
23 * the guest as an I/O error.
25 #define MAX_EVENTS 128
27 struct qemu_laiocb {
28 BlockDriverAIOCB common;
29 struct qemu_laio_state *ctx;
30 struct iocb iocb;
31 ssize_t ret;
32 size_t nbytes;
33 QEMUIOVector *qiov;
34 bool is_read;
35 QLIST_ENTRY(qemu_laiocb) node;
38 struct qemu_laio_state {
39 io_context_t ctx;
40 int efd;
41 int count;
44 static inline ssize_t io_event_ret(struct io_event *ev)
46 return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
50 * Completes an AIO request (calls the callback and frees the ACB).
52 static void qemu_laio_process_completion(struct qemu_laio_state *s,
53 struct qemu_laiocb *laiocb)
55 int ret;
57 s->count--;
59 ret = laiocb->ret;
60 if (ret != -ECANCELED) {
61 if (ret == laiocb->nbytes) {
62 ret = 0;
63 } else if (ret >= 0) {
64 /* Short reads mean EOF, pad with zeros. */
65 if (laiocb->is_read) {
66 qemu_iovec_memset(laiocb->qiov, ret, 0,
67 laiocb->qiov->size - ret);
68 } else {
69 ret = -EINVAL;
73 laiocb->common.cb(laiocb->common.opaque, ret);
76 qemu_aio_release(laiocb);
79 static void qemu_laio_completion_cb(void *opaque)
81 struct qemu_laio_state *s = opaque;
83 while (1) {
84 struct io_event events[MAX_EVENTS];
85 uint64_t val;
86 ssize_t ret;
87 struct timespec ts = { 0 };
88 int nevents, i;
90 do {
91 ret = read(s->efd, &val, sizeof(val));
92 } while (ret == -1 && errno == EINTR);
94 if (ret == -1 && errno == EAGAIN)
95 break;
97 if (ret != 8)
98 break;
100 do {
101 nevents = io_getevents(s->ctx, val, MAX_EVENTS, events, &ts);
102 } while (nevents == -EINTR);
104 for (i = 0; i < nevents; i++) {
105 struct iocb *iocb = events[i].obj;
106 struct qemu_laiocb *laiocb =
107 container_of(iocb, struct qemu_laiocb, iocb);
109 laiocb->ret = io_event_ret(&events[i]);
110 qemu_laio_process_completion(s, laiocb);
115 static int qemu_laio_flush_cb(void *opaque)
117 struct qemu_laio_state *s = opaque;
119 return (s->count > 0) ? 1 : 0;
122 static void laio_cancel(BlockDriverAIOCB *blockacb)
124 struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb;
125 struct io_event event;
126 int ret;
128 if (laiocb->ret != -EINPROGRESS)
129 return;
132 * Note that as of Linux 2.6.31 neither the block device code nor any
133 * filesystem implements cancellation of AIO request.
134 * Thus the polling loop below is the normal code path.
136 ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
137 if (ret == 0) {
138 laiocb->ret = -ECANCELED;
139 return;
143 * We have to wait for the iocb to finish.
145 * The only way to get the iocb status update is by polling the io context.
146 * We might be able to do this slightly more optimal by removing the
147 * O_NONBLOCK flag.
149 while (laiocb->ret == -EINPROGRESS)
150 qemu_laio_completion_cb(laiocb->ctx);
153 static AIOPool laio_pool = {
154 .aiocb_size = sizeof(struct qemu_laiocb),
155 .cancel = laio_cancel,
158 BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
159 int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
160 BlockDriverCompletionFunc *cb, void *opaque, int type)
162 struct qemu_laio_state *s = aio_ctx;
163 struct qemu_laiocb *laiocb;
164 struct iocb *iocbs;
165 off_t offset = sector_num * 512;
167 laiocb = qemu_aio_get(&laio_pool, bs, cb, opaque);
168 laiocb->nbytes = nb_sectors * 512;
169 laiocb->ctx = s;
170 laiocb->ret = -EINPROGRESS;
171 laiocb->is_read = (type == QEMU_AIO_READ);
172 laiocb->qiov = qiov;
174 iocbs = &laiocb->iocb;
176 switch (type) {
177 case QEMU_AIO_WRITE:
178 io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset);
179 break;
180 case QEMU_AIO_READ:
181 io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset);
182 break;
183 /* Currently Linux kernel does not support other operations */
184 default:
185 fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
186 __func__, type);
187 goto out_free_aiocb;
189 io_set_eventfd(&laiocb->iocb, s->efd);
190 s->count++;
192 if (io_submit(s->ctx, 1, &iocbs) < 0)
193 goto out_dec_count;
194 return &laiocb->common;
196 out_dec_count:
197 s->count--;
198 out_free_aiocb:
199 qemu_aio_release(laiocb);
200 return NULL;
203 void *laio_init(void)
205 struct qemu_laio_state *s;
207 s = g_malloc0(sizeof(*s));
208 s->efd = eventfd(0, 0);
209 if (s->efd == -1)
210 goto out_free_state;
211 fcntl(s->efd, F_SETFL, O_NONBLOCK);
213 if (io_setup(MAX_EVENTS, &s->ctx) != 0)
214 goto out_close_efd;
216 qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
217 qemu_laio_flush_cb, s);
219 return s;
221 out_close_efd:
222 close(s->efd);
223 out_free_state:
224 g_free(s);
225 return NULL;