1 /*
2 * QEMU aio implementation
3 *
4 * Copyright IBM, Corp. 2008
5 *
6 * Authors:
7 * Anthony Liguori <aliguori@us.ibm.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2. See
10 * the COPYING file in the top-level directory.
11 *
12 */
13
14 #include "qemu-common.h"
15 #include "block.h"
16 #include "qemu-queue.h"
17 #include "qemu_socket.h"
18 #include "iolooper.h"
19
20 typedef struct AioHandler AioHandler;
21
22 /* The list of registered AIO handlers */
23 static QLIST_HEAD(, AioHandler) aio_handlers;
24
25 /* This is a simple lock used to protect the aio_handlers list. Specifically,
26 * it's used to ensure that no callbacks are removed while we're walking and
27 * dispatching callbacks.
28 */
29 static int walking_handlers;
30
31 struct AioHandler
32 {
33 int fd;
34 IOHandler *io_read;
35 IOHandler *io_write;
36 AioFlushHandler *io_flush;
37 AioProcessQueue *io_process_queue;
38 int deleted;
39 void *opaque;
40 QLIST_ENTRY(AioHandler) node;
41 };
42
find_aio_handler(int fd)43 static AioHandler *find_aio_handler(int fd)
44 {
45 AioHandler *node;
46
47 QLIST_FOREACH(node, &aio_handlers, node) {
48 if (node->fd == fd)
49 if (!node->deleted)
50 return node;
51 }
52
53 return NULL;
54 }
55
qemu_aio_set_fd_handler(int fd,IOHandler * io_read,IOHandler * io_write,AioFlushHandler * io_flush,AioProcessQueue * io_process_queue,void * opaque)56 int qemu_aio_set_fd_handler(int fd,
57 IOHandler *io_read,
58 IOHandler *io_write,
59 AioFlushHandler *io_flush,
60 AioProcessQueue *io_process_queue,
61 void *opaque)
62 {
63 AioHandler *node;
64
65 node = find_aio_handler(fd);
66
67 /* Are we deleting the fd handler? */
68 if (!io_read && !io_write) {
69 if (node) {
70 /* If the lock is held, just mark the node as deleted */
71 if (walking_handlers)
72 node->deleted = 1;
73 else {
74 /* Otherwise, delete it for real. We can't just mark it as
75 * deleted because deleted nodes are only cleaned up after
76 * releasing the walking_handlers lock.
77 */
78 QLIST_REMOVE(node, node);
79 qemu_free(node);
80 }
81 }
82 } else {
83 if (node == NULL) {
84 /* Alloc and insert if it's not already there */
85 node = qemu_mallocz(sizeof(AioHandler));
86 node->fd = fd;
87 QLIST_INSERT_HEAD(&aio_handlers, node, node);
88 }
89 /* Update handler with latest information */
90 node->io_read = io_read;
91 node->io_write = io_write;
92 node->io_flush = io_flush;
93 node->io_process_queue = io_process_queue;
94 node->opaque = opaque;
95 }
96
97 qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
98
99 return 0;
100 }
101
qemu_aio_flush(void)102 void qemu_aio_flush(void)
103 {
104 AioHandler *node;
105 int ret;
106
107 do {
108 ret = 0;
109
110 /*
111 * If there are pending emulated aio start them now so flush
112 * will be able to return 1.
113 */
114 qemu_aio_wait();
115
116 QLIST_FOREACH(node, &aio_handlers, node) {
117 if (node->io_flush) {
118 ret |= node->io_flush(node->opaque);
119 }
120 }
121 } while (qemu_bh_poll() || ret > 0);
122 }
123
qemu_aio_process_queue(void)124 int qemu_aio_process_queue(void)
125 {
126 AioHandler *node;
127 int ret = 0;
128
129 walking_handlers = 1;
130
131 QLIST_FOREACH(node, &aio_handlers, node) {
132 if (node->io_process_queue) {
133 if (node->io_process_queue(node->opaque)) {
134 ret = 1;
135 }
136 }
137 }
138
139 walking_handlers = 0;
140
141 return ret;
142 }
143
qemu_aio_wait(void)144 void qemu_aio_wait(void)
145 {
146 int ret;
147 IoLooper* looper;
148
149 if (qemu_bh_poll())
150 return;
151
152 /*
153 * If there are callbacks left that have been queued, we need to call then.
154 * Return afterwards to avoid waiting needlessly in select().
155 */
156 if (qemu_aio_process_queue())
157 return;
158
159 looper = iolooper_new();
160
161 do {
162 AioHandler *node;
163
164 iolooper_reset(looper);
165 walking_handlers = 1;
166
167 /* fill fd sets */
168 QLIST_FOREACH(node, &aio_handlers, node) {
169 /* If there aren't pending AIO operations, don't invoke callbacks.
170 * Otherwise, if there are no AIO requests, qemu_aio_wait() would
171 * wait indefinitely.
172 */
173 if (node->io_flush && node->io_flush(node->opaque) == 0)
174 continue;
175
176 if (!node->deleted && node->io_read) {
177 iolooper_add_read(looper, node->fd);
178 }
179 if (!node->deleted && node->io_write) {
180 iolooper_add_write(looper, node->fd);
181 }
182 }
183
184 walking_handlers = 0;
185
186 /* No AIO operations? Get us out of here */
187 if (!iolooper_has_operations(looper)) {
188 break;
189 }
190
191 /* wait until next event */
192 ret = iolooper_wait(looper, -1);
193
194 /* if we have any readable fds, dispatch event */
195 if (ret > 0) {
196 walking_handlers = 1;
197
198 /* we have to walk very carefully in case
199 * qemu_aio_set_fd_handler is called while we're walking */
200 node = QLIST_FIRST(&aio_handlers);
201 while (node) {
202 AioHandler *tmp;
203
204 if (!node->deleted &&
205 iolooper_is_read(looper, node->fd) &&
206 node->io_read) {
207 node->io_read(node->opaque);
208 }
209 if (!node->deleted &&
210 iolooper_is_write(looper, node->fd) &&
211 node->io_write) {
212 node->io_write(node->opaque);
213 }
214
215 tmp = node;
216 node = QLIST_NEXT(node, node);
217
218 if (tmp->deleted) {
219 QLIST_REMOVE(tmp, node);
220 qemu_free(tmp);
221 }
222 }
223
224 walking_handlers = 0;
225 }
226 } while (ret == 0);
227
228 iolooper_free(looper);
229 }
230