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
19 typedef struct AioHandler AioHandler;
20
21 /* The list of registered AIO handlers */
22 static QLIST_HEAD(, AioHandler) aio_handlers;
23
24 /* This is a simple lock used to protect the aio_handlers list. Specifically,
25 * it's used to ensure that no callbacks are removed while we're walking and
26 * dispatching callbacks.
27 */
28 static int walking_handlers;
29
30 struct AioHandler
31 {
32 int fd;
33 IOHandler *io_read;
34 IOHandler *io_write;
35 AioFlushHandler *io_flush;
36 AioProcessQueue *io_process_queue;
37 int deleted;
38 void *opaque;
39 QLIST_ENTRY(AioHandler) node;
40 };
41
find_aio_handler(int fd)42 static AioHandler *find_aio_handler(int fd)
43 {
44 AioHandler *node;
45
46 QLIST_FOREACH(node, &aio_handlers, node) {
47 if (node->fd == fd)
48 if (!node->deleted)
49 return node;
50 }
51
52 return NULL;
53 }
54
qemu_aio_set_fd_handler(int fd,IOHandler * io_read,IOHandler * io_write,AioFlushHandler * io_flush,AioProcessQueue * io_process_queue,void * opaque)55 int qemu_aio_set_fd_handler(int fd,
56 IOHandler *io_read,
57 IOHandler *io_write,
58 AioFlushHandler *io_flush,
59 AioProcessQueue *io_process_queue,
60 void *opaque)
61 {
62 AioHandler *node;
63
64 node = find_aio_handler(fd);
65
66 /* Are we deleting the fd handler? */
67 if (!io_read && !io_write) {
68 if (node) {
69 /* If the lock is held, just mark the node as deleted */
70 if (walking_handlers)
71 node->deleted = 1;
72 else {
73 /* Otherwise, delete it for real. We can't just mark it as
74 * deleted because deleted nodes are only cleaned up after
75 * releasing the walking_handlers lock.
76 */
77 QLIST_REMOVE(node, node);
78 qemu_free(node);
79 }
80 }
81 } else {
82 if (node == NULL) {
83 /* Alloc and insert if it's not already there */
84 node = qemu_mallocz(sizeof(AioHandler));
85 node->fd = fd;
86 QLIST_INSERT_HEAD(&aio_handlers, node, node);
87 }
88 /* Update handler with latest information */
89 node->io_read = io_read;
90 node->io_write = io_write;
91 node->io_flush = io_flush;
92 node->io_process_queue = io_process_queue;
93 node->opaque = opaque;
94 }
95
96 qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
97
98 return 0;
99 }
100
qemu_aio_flush(void)101 void qemu_aio_flush(void)
102 {
103 AioHandler *node;
104 int ret;
105
106 do {
107 ret = 0;
108
109 /*
110 * If there are pending emulated aio start them now so flush
111 * will be able to return 1.
112 */
113 qemu_aio_wait();
114
115 QLIST_FOREACH(node, &aio_handlers, node) {
116 if (node->io_flush) {
117 ret |= node->io_flush(node->opaque);
118 }
119 }
120 } while (qemu_bh_poll() || ret > 0);
121 }
122
qemu_aio_process_queue(void)123 int qemu_aio_process_queue(void)
124 {
125 AioHandler *node;
126 int ret = 0;
127
128 walking_handlers = 1;
129
130 QLIST_FOREACH(node, &aio_handlers, node) {
131 if (node->io_process_queue) {
132 if (node->io_process_queue(node->opaque)) {
133 ret = 1;
134 }
135 }
136 }
137
138 walking_handlers = 0;
139
140 return ret;
141 }
142
qemu_aio_wait(void)143 void qemu_aio_wait(void)
144 {
145 int ret;
146
147 if (qemu_bh_poll())
148 return;
149
150 /*
151 * If there are callbacks left that have been queued, we need to call then.
152 * Return afterwards to avoid waiting needlessly in select().
153 */
154 if (qemu_aio_process_queue())
155 return;
156
157 do {
158 AioHandler *node;
159 fd_set rdfds, wrfds;
160 int max_fd = -1;
161
162 walking_handlers = 1;
163
164 FD_ZERO(&rdfds);
165 FD_ZERO(&wrfds);
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 FD_SET(node->fd, &rdfds);
178 max_fd = MAX(max_fd, node->fd + 1);
179 }
180 if (!node->deleted && node->io_write) {
181 FD_SET(node->fd, &wrfds);
182 max_fd = MAX(max_fd, node->fd + 1);
183 }
184 }
185
186 walking_handlers = 0;
187
188 /* No AIO operations? Get us out of here */
189 if (max_fd == -1)
190 break;
191
192 /* wait until next event */
193 ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);
194 if (ret == -1 && errno == EINTR)
195 continue;
196
197 /* if we have any readable fds, dispatch event */
198 if (ret > 0) {
199 walking_handlers = 1;
200
201 /* we have to walk very carefully in case
202 * qemu_aio_set_fd_handler is called while we're walking */
203 node = QLIST_FIRST(&aio_handlers);
204 while (node) {
205 AioHandler *tmp;
206
207 if (!node->deleted &&
208 FD_ISSET(node->fd, &rdfds) &&
209 node->io_read) {
210 node->io_read(node->opaque);
211 }
212 if (!node->deleted &&
213 FD_ISSET(node->fd, &wrfds) &&
214 node->io_write) {
215 node->io_write(node->opaque);
216 }
217
218 tmp = node;
219 node = QLIST_NEXT(node, node);
220
221 if (tmp->deleted) {
222 QLIST_REMOVE(tmp, node);
223 qemu_free(tmp);
224 }
225 }
226
227 walking_handlers = 0;
228 }
229 } while (ret == 0);
230 }
231