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/block.h"
16#include "qemu/queue.h"
17#include "qemu/sockets.h"
18
19typedef struct AioHandler AioHandler;
20
21/* The list of registered AIO handlers */
22static 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 */
28static int walking_handlers;
29
30struct 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
42static 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
55int 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                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->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
101void 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
123int 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
143void 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                    g_free(tmp);
224                }
225            }
226
227            walking_handlers = 0;
228        }
229    } while (ret == 0);
230}
231