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
20typedef struct AioHandler AioHandler;
21
22/* The list of registered AIO handlers */
23static 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 */
29static int walking_handlers;
30
31struct 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
43static 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
56int 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
102void 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
124int 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
144void 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