quorum: Avoid bdrv_aio_writev() for rewrites
[qemu.git] / io / channel-command.c
1 /*
2 * QEMU I/O channels external command driver
3 *
4 * Copyright (c) 2015 Red Hat, Inc.
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 *
19 */
20
21 #include "qemu/osdep.h"
22 #include "io/channel-command.h"
23 #include "io/channel-watch.h"
24 #include "qapi/error.h"
25 #include "qemu/sockets.h"
26 #include "trace.h"
27
28
29 QIOChannelCommand *
30 qio_channel_command_new_pid(int writefd,
31 int readfd,
32 pid_t pid)
33 {
34 QIOChannelCommand *ioc;
35
36 ioc = QIO_CHANNEL_COMMAND(object_new(TYPE_QIO_CHANNEL_COMMAND));
37
38 ioc->readfd = readfd;
39 ioc->writefd = writefd;
40 ioc->pid = pid;
41
42 trace_qio_channel_command_new_pid(ioc, writefd, readfd, pid);
43 return ioc;
44 }
45
46
47 #ifndef WIN32
48 QIOChannelCommand *
49 qio_channel_command_new_spawn(const char *const argv[],
50 int flags,
51 Error **errp)
52 {
53 pid_t pid = -1;
54 int stdinfd[2] = { -1, -1 };
55 int stdoutfd[2] = { -1, -1 };
56 int devnull = -1;
57 bool stdinnull = false, stdoutnull = false;
58 QIOChannelCommand *ioc;
59
60 flags = flags & O_ACCMODE;
61
62 if (flags == O_RDONLY) {
63 stdinnull = true;
64 }
65 if (flags == O_WRONLY) {
66 stdoutnull = true;
67 }
68
69 if (stdinnull || stdoutnull) {
70 devnull = open("/dev/null", O_RDWR);
71 if (devnull < 0) {
72 error_setg_errno(errp, errno,
73 "Unable to open /dev/null");
74 goto error;
75 }
76 }
77
78 if ((!stdinnull && pipe(stdinfd) < 0) ||
79 (!stdoutnull && pipe(stdoutfd) < 0)) {
80 error_setg_errno(errp, errno,
81 "Unable to open pipe");
82 goto error;
83 }
84
85 pid = qemu_fork(errp);
86 if (pid < 0) {
87 goto error;
88 }
89
90 if (pid == 0) { /* child */
91 dup2(stdinnull ? devnull : stdinfd[0], STDIN_FILENO);
92 dup2(stdoutnull ? devnull : stdoutfd[1], STDOUT_FILENO);
93 /* Leave stderr connected to qemu's stderr */
94
95 if (!stdinnull) {
96 close(stdinfd[0]);
97 close(stdinfd[1]);
98 }
99 if (!stdoutnull) {
100 close(stdoutfd[0]);
101 close(stdoutfd[1]);
102 }
103 if (devnull != -1) {
104 close(devnull);
105 }
106
107 execv(argv[0], (char * const *)argv);
108 _exit(1);
109 }
110
111 if (!stdinnull) {
112 close(stdinfd[0]);
113 }
114 if (!stdoutnull) {
115 close(stdoutfd[1]);
116 }
117
118 ioc = qio_channel_command_new_pid(stdinnull ? devnull : stdinfd[1],
119 stdoutnull ? devnull : stdoutfd[0],
120 pid);
121 trace_qio_channel_command_new_spawn(ioc, argv[0], flags);
122 return ioc;
123
124 error:
125 if (devnull != -1) {
126 close(devnull);
127 }
128 if (stdinfd[0] != -1) {
129 close(stdinfd[0]);
130 }
131 if (stdinfd[1] != -1) {
132 close(stdinfd[1]);
133 }
134 if (stdoutfd[0] != -1) {
135 close(stdoutfd[0]);
136 }
137 if (stdoutfd[1] != -1) {
138 close(stdoutfd[1]);
139 }
140 return NULL;
141 }
142
143 #else /* WIN32 */
144 QIOChannelCommand *
145 qio_channel_command_new_spawn(const char *const argv[],
146 int flags,
147 Error **errp)
148 {
149 error_setg_errno(errp, ENOSYS,
150 "Command spawn not supported on this platform");
151 return NULL;
152 }
153 #endif /* WIN32 */
154
155 #ifndef WIN32
156 static int qio_channel_command_abort(QIOChannelCommand *ioc,
157 Error **errp)
158 {
159 pid_t ret;
160 int status;
161 int step = 0;
162
163 /* See if intermediate process has exited; if not, try a nice
164 * SIGTERM followed by a more severe SIGKILL.
165 */
166 rewait:
167 trace_qio_channel_command_abort(ioc, ioc->pid);
168 ret = waitpid(ioc->pid, &status, WNOHANG);
169 trace_qio_channel_command_wait(ioc, ioc->pid, ret, status);
170 if (ret == (pid_t)-1) {
171 if (errno == EINTR) {
172 goto rewait;
173 } else {
174 error_setg_errno(errp, errno,
175 "Cannot wait on pid %llu",
176 (unsigned long long)ioc->pid);
177 return -1;
178 }
179 } else if (ret == 0) {
180 if (step == 0) {
181 kill(ioc->pid, SIGTERM);
182 } else if (step == 1) {
183 kill(ioc->pid, SIGKILL);
184 } else {
185 error_setg(errp,
186 "Process %llu refused to die",
187 (unsigned long long)ioc->pid);
188 return -1;
189 }
190 step++;
191 usleep(10 * 1000);
192 goto rewait;
193 }
194
195 return 0;
196 }
197 #endif /* ! WIN32 */
198
199
200 static void qio_channel_command_init(Object *obj)
201 {
202 QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
203 ioc->readfd = -1;
204 ioc->writefd = -1;
205 ioc->pid = -1;
206 }
207
208 static void qio_channel_command_finalize(Object *obj)
209 {
210 QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
211 if (ioc->readfd != -1) {
212 close(ioc->readfd);
213 }
214 if (ioc->writefd != -1 &&
215 ioc->writefd != ioc->readfd) {
216 close(ioc->writefd);
217 }
218 ioc->writefd = ioc->readfd = -1;
219 if (ioc->pid > 0) {
220 #ifndef WIN32
221 qio_channel_command_abort(ioc, NULL);
222 #endif
223 }
224 }
225
226
227 static ssize_t qio_channel_command_readv(QIOChannel *ioc,
228 const struct iovec *iov,
229 size_t niov,
230 int **fds,
231 size_t *nfds,
232 Error **errp)
233 {
234 QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
235 ssize_t ret;
236
237 retry:
238 ret = readv(cioc->readfd, iov, niov);
239 if (ret < 0) {
240 if (errno == EAGAIN) {
241 return QIO_CHANNEL_ERR_BLOCK;
242 }
243 if (errno == EINTR) {
244 goto retry;
245 }
246
247 error_setg_errno(errp, errno,
248 "Unable to read from command");
249 return -1;
250 }
251
252 return ret;
253 }
254
255 static ssize_t qio_channel_command_writev(QIOChannel *ioc,
256 const struct iovec *iov,
257 size_t niov,
258 int *fds,
259 size_t nfds,
260 Error **errp)
261 {
262 QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
263 ssize_t ret;
264
265 retry:
266 ret = writev(cioc->writefd, iov, niov);
267 if (ret <= 0) {
268 if (errno == EAGAIN) {
269 return QIO_CHANNEL_ERR_BLOCK;
270 }
271 if (errno == EINTR) {
272 goto retry;
273 }
274 error_setg_errno(errp, errno, "%s",
275 "Unable to write to command");
276 return -1;
277 }
278 return ret;
279 }
280
281 static int qio_channel_command_set_blocking(QIOChannel *ioc,
282 bool enabled,
283 Error **errp)
284 {
285 QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
286
287 if (enabled) {
288 qemu_set_block(cioc->writefd);
289 qemu_set_block(cioc->readfd);
290 } else {
291 qemu_set_nonblock(cioc->writefd);
292 qemu_set_nonblock(cioc->readfd);
293 }
294
295 return 0;
296 }
297
298
299 static int qio_channel_command_close(QIOChannel *ioc,
300 Error **errp)
301 {
302 QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
303 int rv = 0;
304
305 /* We close FDs before killing, because that
306 * gives a better chance of clean shutdown
307 */
308 if (cioc->readfd != -1 &&
309 close(cioc->readfd) < 0) {
310 rv = -1;
311 }
312 if (cioc->writefd != -1 &&
313 cioc->writefd != cioc->readfd &&
314 close(cioc->writefd) < 0) {
315 rv = -1;
316 }
317 cioc->writefd = cioc->readfd = -1;
318 #ifndef WIN32
319 if (qio_channel_command_abort(cioc, errp) < 0) {
320 return -1;
321 }
322 #endif
323 if (rv < 0) {
324 error_setg_errno(errp, errno, "%s",
325 "Unable to close command");
326 }
327 return rv;
328 }
329
330
331 static GSource *qio_channel_command_create_watch(QIOChannel *ioc,
332 GIOCondition condition)
333 {
334 QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
335 return qio_channel_create_fd_pair_watch(ioc,
336 cioc->readfd,
337 cioc->writefd,
338 condition);
339 }
340
341
342 static void qio_channel_command_class_init(ObjectClass *klass,
343 void *class_data G_GNUC_UNUSED)
344 {
345 QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
346
347 ioc_klass->io_writev = qio_channel_command_writev;
348 ioc_klass->io_readv = qio_channel_command_readv;
349 ioc_klass->io_set_blocking = qio_channel_command_set_blocking;
350 ioc_klass->io_close = qio_channel_command_close;
351 ioc_klass->io_create_watch = qio_channel_command_create_watch;
352 }
353
354 static const TypeInfo qio_channel_command_info = {
355 .parent = TYPE_QIO_CHANNEL,
356 .name = TYPE_QIO_CHANNEL_COMMAND,
357 .instance_size = sizeof(QIOChannelCommand),
358 .instance_init = qio_channel_command_init,
359 .instance_finalize = qio_channel_command_finalize,
360 .class_init = qio_channel_command_class_init,
361 };
362
363 static void qio_channel_command_register_types(void)
364 {
365 type_register_static(&qio_channel_command_info);
366 }
367
368 type_init(qio_channel_command_register_types);