root / linux-aio.c @ efe72c8d
History | View | Annotate | Download (6.6 kB)
1 |
/*
|
---|---|
2 |
* Linux native AIO support.
|
3 |
*
|
4 |
* Copyright (C) 2009 IBM, Corp.
|
5 |
* Copyright (C) 2009 Red Hat, Inc.
|
6 |
*
|
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_int.h" |
13 |
#include "block/raw-posix-aio.h" |
14 |
|
15 |
#include <sys/eventfd.h> |
16 |
#include <libaio.h> |
17 |
|
18 |
/*
|
19 |
* Queue size (per-device).
|
20 |
*
|
21 |
* XXX: eventually we need to communicate this to the guest and/or make it
|
22 |
* tunable by the guest. If we get more outstanding requests at a time
|
23 |
* than this we will get EAGAIN from io_submit which is communicated to
|
24 |
* the guest as an I/O error.
|
25 |
*/
|
26 |
#define MAX_EVENTS 128 |
27 |
|
28 |
struct qemu_laiocb {
|
29 |
BlockDriverAIOCB common; |
30 |
struct qemu_laio_state *ctx;
|
31 |
struct iocb iocb;
|
32 |
ssize_t ret; |
33 |
size_t nbytes; |
34 |
int async_context_id;
|
35 |
QLIST_ENTRY(qemu_laiocb) node; |
36 |
}; |
37 |
|
38 |
struct qemu_laio_state {
|
39 |
io_context_t ctx; |
40 |
int efd;
|
41 |
int count;
|
42 |
QLIST_HEAD(, qemu_laiocb) completed_reqs; |
43 |
}; |
44 |
|
45 |
static inline ssize_t io_event_ret(struct io_event *ev) |
46 |
{ |
47 |
return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res); |
48 |
} |
49 |
|
50 |
/*
|
51 |
* Completes an AIO request (calls the callback and frees the ACB).
|
52 |
* Be sure to be in the right AsyncContext before calling this function.
|
53 |
*/
|
54 |
static void qemu_laio_process_completion(struct qemu_laio_state *s, |
55 |
struct qemu_laiocb *laiocb)
|
56 |
{ |
57 |
int ret;
|
58 |
|
59 |
s->count--; |
60 |
|
61 |
ret = laiocb->ret; |
62 |
if (ret != -ECANCELED) {
|
63 |
if (ret == laiocb->nbytes)
|
64 |
ret = 0;
|
65 |
else if (ret >= 0) |
66 |
ret = -EINVAL; |
67 |
|
68 |
laiocb->common.cb(laiocb->common.opaque, ret); |
69 |
} |
70 |
|
71 |
qemu_aio_release(laiocb); |
72 |
} |
73 |
|
74 |
/*
|
75 |
* Processes all queued AIO requests, i.e. requests that have return from OS
|
76 |
* but their callback was not called yet. Requests that cannot have their
|
77 |
* callback called in the current AsyncContext, remain in the queue.
|
78 |
*
|
79 |
* Returns 1 if at least one request could be completed, 0 otherwise.
|
80 |
*/
|
81 |
static int qemu_laio_process_requests(void *opaque) |
82 |
{ |
83 |
struct qemu_laio_state *s = opaque;
|
84 |
struct qemu_laiocb *laiocb, *next;
|
85 |
int res = 0; |
86 |
|
87 |
QLIST_FOREACH_SAFE (laiocb, &s->completed_reqs, node, next) { |
88 |
if (laiocb->async_context_id == get_async_context_id()) {
|
89 |
qemu_laio_process_completion(s, laiocb); |
90 |
QLIST_REMOVE(laiocb, node); |
91 |
res = 1;
|
92 |
} |
93 |
} |
94 |
|
95 |
return res;
|
96 |
} |
97 |
|
98 |
/*
|
99 |
* Puts a request in the completion queue so that its callback is called the
|
100 |
* next time when it's possible. If we already are in the right AsyncContext,
|
101 |
* the request is completed immediately instead.
|
102 |
*/
|
103 |
static void qemu_laio_enqueue_completed(struct qemu_laio_state *s, |
104 |
struct qemu_laiocb* laiocb)
|
105 |
{ |
106 |
if (laiocb->async_context_id == get_async_context_id()) {
|
107 |
qemu_laio_process_completion(s, laiocb); |
108 |
} else {
|
109 |
QLIST_INSERT_HEAD(&s->completed_reqs, laiocb, node); |
110 |
} |
111 |
} |
112 |
|
113 |
static void qemu_laio_completion_cb(void *opaque) |
114 |
{ |
115 |
struct qemu_laio_state *s = opaque;
|
116 |
|
117 |
while (1) { |
118 |
struct io_event events[MAX_EVENTS];
|
119 |
uint64_t val; |
120 |
ssize_t ret; |
121 |
struct timespec ts = { 0 }; |
122 |
int nevents, i;
|
123 |
|
124 |
do {
|
125 |
ret = read(s->efd, &val, sizeof(val));
|
126 |
} while (ret == 1 && errno == EINTR); |
127 |
|
128 |
if (ret == -1 && errno == EAGAIN) |
129 |
break;
|
130 |
|
131 |
if (ret != 8) |
132 |
break;
|
133 |
|
134 |
do {
|
135 |
nevents = io_getevents(s->ctx, val, MAX_EVENTS, events, &ts); |
136 |
} while (nevents == -EINTR);
|
137 |
|
138 |
for (i = 0; i < nevents; i++) { |
139 |
struct iocb *iocb = events[i].obj;
|
140 |
struct qemu_laiocb *laiocb =
|
141 |
container_of(iocb, struct qemu_laiocb, iocb);
|
142 |
|
143 |
laiocb->ret = io_event_ret(&events[i]); |
144 |
qemu_laio_enqueue_completed(s, laiocb); |
145 |
} |
146 |
} |
147 |
} |
148 |
|
149 |
static int qemu_laio_flush_cb(void *opaque) |
150 |
{ |
151 |
struct qemu_laio_state *s = opaque;
|
152 |
|
153 |
return (s->count > 0) ? 1 : 0; |
154 |
} |
155 |
|
156 |
static void laio_cancel(BlockDriverAIOCB *blockacb) |
157 |
{ |
158 |
struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb; |
159 |
struct io_event event;
|
160 |
int ret;
|
161 |
|
162 |
if (laiocb->ret != -EINPROGRESS)
|
163 |
return;
|
164 |
|
165 |
/*
|
166 |
* Note that as of Linux 2.6.31 neither the block device code nor any
|
167 |
* filesystem implements cancellation of AIO request.
|
168 |
* Thus the polling loop below is the normal code path.
|
169 |
*/
|
170 |
ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event); |
171 |
if (ret == 0) { |
172 |
laiocb->ret = -ECANCELED; |
173 |
return;
|
174 |
} |
175 |
|
176 |
/*
|
177 |
* We have to wait for the iocb to finish.
|
178 |
*
|
179 |
* The only way to get the iocb status update is by polling the io context.
|
180 |
* We might be able to do this slightly more optimal by removing the
|
181 |
* O_NONBLOCK flag.
|
182 |
*/
|
183 |
while (laiocb->ret == -EINPROGRESS)
|
184 |
qemu_laio_completion_cb(laiocb->ctx); |
185 |
} |
186 |
|
187 |
static AIOPool laio_pool = {
|
188 |
.aiocb_size = sizeof(struct qemu_laiocb), |
189 |
.cancel = laio_cancel, |
190 |
}; |
191 |
|
192 |
BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd, |
193 |
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
|
194 |
BlockDriverCompletionFunc *cb, void *opaque, int type) |
195 |
{ |
196 |
struct qemu_laio_state *s = aio_ctx;
|
197 |
struct qemu_laiocb *laiocb;
|
198 |
struct iocb *iocbs;
|
199 |
off_t offset = sector_num * 512;
|
200 |
|
201 |
laiocb = qemu_aio_get(&laio_pool, bs, cb, opaque); |
202 |
if (!laiocb)
|
203 |
return NULL; |
204 |
laiocb->nbytes = nb_sectors * 512;
|
205 |
laiocb->ctx = s; |
206 |
laiocb->ret = -EINPROGRESS; |
207 |
laiocb->async_context_id = get_async_context_id(); |
208 |
|
209 |
iocbs = &laiocb->iocb; |
210 |
|
211 |
switch (type) {
|
212 |
case QEMU_AIO_WRITE:
|
213 |
io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset); |
214 |
break;
|
215 |
case QEMU_AIO_READ:
|
216 |
io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset); |
217 |
break;
|
218 |
default:
|
219 |
fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
|
220 |
__func__, type); |
221 |
goto out_free_aiocb;
|
222 |
} |
223 |
io_set_eventfd(&laiocb->iocb, s->efd); |
224 |
s->count++; |
225 |
|
226 |
if (io_submit(s->ctx, 1, &iocbs) < 0) |
227 |
goto out_dec_count;
|
228 |
return &laiocb->common;
|
229 |
|
230 |
out_free_aiocb:
|
231 |
qemu_aio_release(laiocb); |
232 |
out_dec_count:
|
233 |
s->count--; |
234 |
return NULL; |
235 |
} |
236 |
|
237 |
void *laio_init(void) |
238 |
{ |
239 |
struct qemu_laio_state *s;
|
240 |
|
241 |
s = qemu_mallocz(sizeof(*s));
|
242 |
QLIST_INIT(&s->completed_reqs); |
243 |
s->efd = eventfd(0, 0); |
244 |
if (s->efd == -1) |
245 |
goto out_free_state;
|
246 |
fcntl(s->efd, F_SETFL, O_NONBLOCK); |
247 |
|
248 |
if (io_setup(MAX_EVENTS, &s->ctx) != 0) |
249 |
goto out_close_efd;
|
250 |
|
251 |
qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
|
252 |
qemu_laio_flush_cb, qemu_laio_process_requests, s); |
253 |
|
254 |
return s;
|
255 |
|
256 |
out_close_efd:
|
257 |
close(s->efd); |
258 |
out_free_state:
|
259 |
qemu_free(s); |
260 |
return NULL; |
261 |
} |