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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 | * Contributions after 2012-01-13 are licensed under the terms of the | |
13 | * GNU GPL, version 2 or (at your option) any later version. | |
14 | */ | |
15 | ||
16 | #include "qemu-common.h" | |
17 | #include "block.h" | |
18 | #include "qemu-queue.h" | |
19 | #include "qemu_socket.h" | |
20 | ||
21 | typedef struct AioHandler AioHandler; | |
22 | ||
23 | /* The list of registered AIO handlers */ | |
24 | static QLIST_HEAD(, AioHandler) aio_handlers; | |
25 | ||
26 | /* This is a simple lock used to protect the aio_handlers list. Specifically, | |
27 | * it's used to ensure that no callbacks are removed while we're walking and | |
28 | * dispatching callbacks. | |
29 | */ | |
30 | static int walking_handlers; | |
31 | ||
32 | struct AioHandler | |
33 | { | |
34 | int fd; | |
35 | IOHandler *io_read; | |
36 | IOHandler *io_write; | |
37 | AioFlushHandler *io_flush; | |
38 | int deleted; | |
39 | void *opaque; | |
40 | QLIST_ENTRY(AioHandler) node; | |
41 | }; | |
42 | ||
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 | ||
56 | int qemu_aio_set_fd_handler(int fd, | |
57 | IOHandler *io_read, | |
58 | IOHandler *io_write, | |
59 | AioFlushHandler *io_flush, | |
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 | g_free(node); | |
79 | } | |
80 | } | |
81 | } else { | |
82 | if (node == NULL) { | |
83 | /* Alloc and insert if it's not already there */ | |
84 | node = g_malloc0(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->opaque = opaque; | |
93 | } | |
94 | ||
95 | qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque); | |
96 | ||
97 | return 0; | |
98 | } | |
99 | ||
100 | void qemu_aio_flush(void) | |
101 | { | |
102 | while (qemu_aio_wait()); | |
103 | } | |
104 | ||
105 | bool qemu_aio_wait(void) | |
106 | { | |
107 | AioHandler *node; | |
108 | fd_set rdfds, wrfds; | |
109 | int max_fd = -1; | |
110 | int ret; | |
111 | bool busy; | |
112 | ||
113 | /* | |
114 | * If there are callbacks left that have been queued, we need to call then. | |
115 | * Do not call select in this case, because it is possible that the caller | |
116 | * does not need a complete flush (as is the case for qemu_aio_wait loops). | |
117 | */ | |
118 | if (qemu_bh_poll()) { | |
119 | return true; | |
120 | } | |
121 | ||
122 | walking_handlers++; | |
123 | ||
124 | FD_ZERO(&rdfds); | |
125 | FD_ZERO(&wrfds); | |
126 | ||
127 | /* fill fd sets */ | |
128 | busy = false; | |
129 | QLIST_FOREACH(node, &aio_handlers, node) { | |
130 | /* If there aren't pending AIO operations, don't invoke callbacks. | |
131 | * Otherwise, if there are no AIO requests, qemu_aio_wait() would | |
132 | * wait indefinitely. | |
133 | */ | |
134 | if (node->io_flush) { | |
135 | if (node->io_flush(node->opaque) == 0) { | |
136 | continue; | |
137 | } | |
138 | busy = true; | |
139 | } | |
140 | if (!node->deleted && node->io_read) { | |
141 | FD_SET(node->fd, &rdfds); | |
142 | max_fd = MAX(max_fd, node->fd + 1); | |
143 | } | |
144 | if (!node->deleted && node->io_write) { | |
145 | FD_SET(node->fd, &wrfds); | |
146 | max_fd = MAX(max_fd, node->fd + 1); | |
147 | } | |
148 | } | |
149 | ||
150 | walking_handlers--; | |
151 | ||
152 | /* No AIO operations? Get us out of here */ | |
153 | if (!busy) { | |
154 | return false; | |
155 | } | |
156 | ||
157 | /* wait until next event */ | |
158 | ret = select(max_fd, &rdfds, &wrfds, NULL, NULL); | |
159 | ||
160 | /* if we have any readable fds, dispatch event */ | |
161 | if (ret > 0) { | |
162 | /* we have to walk very carefully in case | |
163 | * qemu_aio_set_fd_handler is called while we're walking */ | |
164 | node = QLIST_FIRST(&aio_handlers); | |
165 | while (node) { | |
166 | AioHandler *tmp; | |
167 | ||
168 | walking_handlers++; | |
169 | ||
170 | if (!node->deleted && | |
171 | FD_ISSET(node->fd, &rdfds) && | |
172 | node->io_read) { | |
173 | node->io_read(node->opaque); | |
174 | } | |
175 | if (!node->deleted && | |
176 | FD_ISSET(node->fd, &wrfds) && | |
177 | node->io_write) { | |
178 | node->io_write(node->opaque); | |
179 | } | |
180 | ||
181 | tmp = node; | |
182 | node = QLIST_NEXT(node, node); | |
183 | ||
184 | walking_handlers--; | |
185 | ||
186 | if (!walking_handlers && tmp->deleted) { | |
187 | QLIST_REMOVE(tmp, node); | |
188 | g_free(tmp); | |
189 | } | |
190 | } | |
191 | } | |
192 | ||
193 | return true; | |
194 | } |