libfuse

notify_store_retrieve.c
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1 /*
2 FUSE: Filesystem in Userspace
3 Copyright (C) 2016 Nikolaus Rath <Nikolaus@rath.org>
4
5 This program can be distributed under the terms of the GNU GPLv2.
6 See the file COPYING.
7 */
8
61 #define FUSE_USE_VERSION 34
62
63 #include <fuse_lowlevel.h>
64 #include <stdio.h>
65 #include <stdlib.h>
66 #include <string.h>
67 #include <errno.h>
68 #include <fcntl.h>
69 #include <assert.h>
70 #include <stddef.h>
71 #include <unistd.h>
72 #include <pthread.h>
73
74 /* We can't actually tell the kernel that there is no
75 timeout, so we just send a big value */
76 #define NO_TIMEOUT 500000
77
78 #define MAX_STR_LEN 128
79 #define FILE_INO 2
80 #define FILE_NAME "current_time"
81 static char file_contents[MAX_STR_LEN];
82 static int lookup_cnt = 0;
83 static size_t file_size;
84
85 /* Keep track if we ever stored data (==1), and
86 received it back correctly (==2) */
87 static int retrieve_status = 0;
88
89 /* Command line parsing */
90 struct options {
91 int no_notify;
92 int update_interval;
93 };
94 static struct options options = {
95 .no_notify = 0,
96 .update_interval = 1,
97 };
98
99 #define OPTION(t, p) \
100 { t, offsetof(struct options, p), 1 }
101 static const struct fuse_opt option_spec[] = {
102 OPTION("--no-notify", no_notify),
103 OPTION("--update-interval=%d", update_interval),
104 FUSE_OPT_END
105 };
106
107 static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
108 stbuf->st_ino = ino;
109 if (ino == FUSE_ROOT_ID) {
110 stbuf->st_mode = S_IFDIR | 0755;
111 stbuf->st_nlink = 1;
112 }
113
114 else if (ino == FILE_INO) {
115 stbuf->st_mode = S_IFREG | 0444;
116 stbuf->st_nlink = 1;
117 stbuf->st_size = file_size;
118 }
119
120 else
121 return -1;
122
123 return 0;
124 }
125
126 static void tfs_lookup(fuse_req_t req, fuse_ino_t parent,
127 const char *name) {
128 struct fuse_entry_param e;
129 memset(&e, 0, sizeof(e));
130
131 if (parent != FUSE_ROOT_ID)
132 goto err_out;
133 else if (strcmp(name, FILE_NAME) == 0) {
134 e.ino = FILE_INO;
135 lookup_cnt++;
136 } else
137 goto err_out;
138
139 e.attr_timeout = NO_TIMEOUT;
140 e.entry_timeout = NO_TIMEOUT;
141 if (tfs_stat(e.ino, &e.attr) != 0)
142 goto err_out;
143 fuse_reply_entry(req, &e);
144 return;
145
146 err_out:
147 fuse_reply_err(req, ENOENT);
148 }
149
150 static void tfs_forget (fuse_req_t req, fuse_ino_t ino,
151 uint64_t nlookup) {
152 (void) req;
153 if(ino == FILE_INO)
154 lookup_cnt -= nlookup;
155 else
156 assert(ino == FUSE_ROOT_ID);
157 fuse_reply_none(req);
158 }
159
160 static void tfs_getattr(fuse_req_t req, fuse_ino_t ino,
161 struct fuse_file_info *fi) {
162 struct stat stbuf;
163
164 (void) fi;
165
166 memset(&stbuf, 0, sizeof(stbuf));
167 if (tfs_stat(ino, &stbuf) != 0)
168 fuse_reply_err(req, ENOENT);
169 else
170 fuse_reply_attr(req, &stbuf, NO_TIMEOUT);
171 }
172
173 struct dirbuf {
174 char *p;
175 size_t size;
176 };
177
178 static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
179 fuse_ino_t ino) {
180 struct stat stbuf;
181 size_t oldsize = b->size;
182 b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
183 b->p = (char *) realloc(b->p, b->size);
184 memset(&stbuf, 0, sizeof(stbuf));
185 stbuf.st_ino = ino;
186 fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
187 b->size);
188 }
189
190 #define min(x, y) ((x) < (y) ? (x) : (y))
191
192 static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
193 off_t off, size_t maxsize) {
194 if (off < bufsize)
195 return fuse_reply_buf(req, buf + off,
196 min(bufsize - off, maxsize));
197 else
198 return fuse_reply_buf(req, NULL, 0);
199 }
200
201 static void tfs_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
202 off_t off, struct fuse_file_info *fi) {
203 (void) fi;
204
205 if (ino != FUSE_ROOT_ID)
206 fuse_reply_err(req, ENOTDIR);
207 else {
208 struct dirbuf b;
209
210 memset(&b, 0, sizeof(b));
211 dirbuf_add(req, &b, FILE_NAME, FILE_INO);
212 reply_buf_limited(req, b.p, b.size, off, size);
213 free(b.p);
214 }
215 }
216
217 static void tfs_open(fuse_req_t req, fuse_ino_t ino,
218 struct fuse_file_info *fi) {
219
220 /* Make cache persistent even if file is closed,
221 this makes it easier to see the effects */
222 fi->keep_cache = 1;
223
224 if (ino == FUSE_ROOT_ID)
225 fuse_reply_err(req, EISDIR);
226 else if ((fi->flags & O_ACCMODE) != O_RDONLY)
227 fuse_reply_err(req, EACCES);
228 else if (ino == FILE_INO)
229 fuse_reply_open(req, fi);
230 else {
231 // This should not happen
232 fprintf(stderr, "Got open for non-existing inode!\n");
233 fuse_reply_err(req, ENOENT);
234 }
235 }
236
237 static void tfs_read(fuse_req_t req, fuse_ino_t ino, size_t size,
238 off_t off, struct fuse_file_info *fi) {
239 (void) fi;
240
241 assert(ino == FILE_INO);
242 reply_buf_limited(req, file_contents, file_size, off, size);
243 }
244
245 static void tfs_retrieve_reply(fuse_req_t req, void *cookie, fuse_ino_t ino,
246 off_t offset, struct fuse_bufvec *data) {
247 struct fuse_bufvec bufv;
248 char buf[MAX_STR_LEN];
249 char *expected;
250 ssize_t ret;
251
252 assert(ino == FILE_INO);
253 assert(offset == 0);
254 expected = (char*) cookie;
255
256 bufv.count = 1;
257 bufv.idx = 0;
258 bufv.off = 0;
259 bufv.buf[0].size = MAX_STR_LEN;
260 bufv.buf[0].mem = buf;
261 bufv.buf[0].flags = 0;
262
263 ret = fuse_buf_copy(&bufv, data, 0);
264 assert(ret > 0);
265 assert(strncmp(buf, expected, ret) == 0);
266 free(expected);
267 retrieve_status = 2;
268 fuse_reply_none(req);
269 }
270
271
272 static const struct fuse_lowlevel_ops tfs_oper = {
273 .lookup = tfs_lookup,
274 .getattr = tfs_getattr,
275 .readdir = tfs_readdir,
276 .open = tfs_open,
277 .read = tfs_read,
278 .forget = tfs_forget,
279 .retrieve_reply = tfs_retrieve_reply,
280 };
281
282 static void update_fs(void) {
283 struct tm *now;
284 time_t t;
285 t = time(NULL);
286 now = localtime(&t);
287 assert(now != NULL);
288
289 file_size = strftime(file_contents, MAX_STR_LEN,
290 "The current time is %H:%M:%S\n", now);
291 assert(file_size != 0);
292 }
293
294 static void* update_fs_loop(void *data) {
295 struct fuse_session *se = (struct fuse_session*) data;
296 struct fuse_bufvec bufv;
297 int ret;
298
299 while(1) {
300 update_fs();
301 if (!options.no_notify && lookup_cnt) {
302 /* Only send notification if the kernel
303 is aware of the inode */
304 bufv.count = 1;
305 bufv.idx = 0;
306 bufv.off = 0;
307 bufv.buf[0].size = file_size;
308 bufv.buf[0].mem = file_contents;
309 bufv.buf[0].flags = 0;
310
311 /* This shouldn't fail, but apparently it sometimes
312 does - see https://github.com/libfuse/libfuse/issues/105 */
313 ret = fuse_lowlevel_notify_store(se, FILE_INO, 0, &bufv, 0);
314 if (-ret == ENODEV) {
315 // File system was unmounted
316 break;
317 }
318 else if (ret != 0) {
319 fprintf(stderr, "ERROR: fuse_lowlevel_notify_store() failed with %s (%d)\n",
320 strerror(-ret), -ret);
321 abort();
322 }
323
324 /* To make sure that everything worked correctly, ask the
325 kernel to send us back the stored data */
326 ret = fuse_lowlevel_notify_retrieve(se, FILE_INO, MAX_STR_LEN,
327 0, (void*) strdup(file_contents));
328 if (-ret == ENODEV) { // File system was unmounted
329 break;
330 }
331 assert(ret == 0);
332 if(retrieve_status == 0)
333 retrieve_status = 1;
334 }
335 sleep(options.update_interval);
336 }
337 return NULL;
338 }
339
340 static void show_help(const char *progname)
341 {
342 printf("usage: %s [options] <mountpoint>\n\n", progname);
343 printf("File-system specific options:\n"
344 " --update-interval=<secs> Update-rate of file system contents\n"
345 " --no-notify Disable kernel notifications\n"
346 "\n");
347 }
348
349 int main(int argc, char *argv[]) {
350 struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
351 struct fuse_session *se;
352 struct fuse_cmdline_opts opts;
353 struct fuse_loop_config config;
354 pthread_t updater;
355 int ret = -1;
356
357 if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
358 return 1;
359
360 if (fuse_parse_cmdline(&args, &opts) != 0)
361 return 1;
362 if (opts.show_help) {
363 show_help(argv[0]);
364 fuse_cmdline_help();
365 fuse_lowlevel_help();
366 ret = 0;
367 goto err_out1;
368 } else if (opts.show_version) {
369 printf("FUSE library version %s\n", fuse_pkgversion());
370 fuse_lowlevel_version();
371 ret = 0;
372 goto err_out1;
373 }
374
375 /* Initial contents */
376 update_fs();
377
378 se = fuse_session_new(&args, &tfs_oper,
379 sizeof(tfs_oper), NULL);
380 if (se == NULL)
381 goto err_out1;
382
383 if (fuse_set_signal_handlers(se) != 0)
384 goto err_out2;
385
386 if (fuse_session_mount(se, opts.mountpoint) != 0)
387 goto err_out3;
388
389 fuse_daemonize(opts.foreground);
390
391 /* Start thread to update file contents */
392 ret = pthread_create(&updater, NULL, update_fs_loop, (void *)se);
393 if (ret != 0) {
394 fprintf(stderr, "pthread_create failed with %s\n",
395 strerror(ret));
396 goto err_out3;
397 }
398
399 /* Block until ctrl+c or fusermount -u */
400 if (opts.singlethread)
401 ret = fuse_session_loop(se);
402 else {
403 config.clone_fd = opts.clone_fd;
404 config.max_idle_threads = opts.max_idle_threads;
405 ret = fuse_session_loop_mt(se, &config);
406 }
407
408 assert(retrieve_status != 1);
409 fuse_session_unmount(se);
410 err_out3:
411 fuse_remove_signal_handlers(se);
412 err_out2:
413 fuse_session_destroy(se);
414 err_out1:
415 free(opts.mountpoint);
416 fuse_opt_free_args(&args);
417
418 return ret ? 1 : 0;
419 }
420
421
fuse_session_destroy
void fuse_session_destroy(struct fuse_session *se)
Definition: fuse_lowlevel.c:2708
fuse_reply_err
int fuse_reply_err(fuse_req_t req, int err)
Definition: fuse_lowlevel.c:311
fuse_session_new
struct fuse_session * fuse_session_new(struct fuse_args *args, const struct fuse_lowlevel_ops *op, size_t op_size, void *userdata)
Definition: fuse_lowlevel.c:2894
fuse_session_loop
int fuse_session_loop(struct fuse_session *se)
Definition: fuse_loop.c:19
fuse_lowlevel_notify_retrieve
int fuse_lowlevel_notify_retrieve(struct fuse_session *se, fuse_ino_t ino, size_t size, off_t offset, void *cookie)
Definition: fuse_lowlevel.c:2379
fuse_lowlevel_help
void fuse_lowlevel_help(void)
Definition: fuse_lowlevel.c:2698
fuse_daemonize
int fuse_daemonize(int foreground)
Definition: helper.c:225
fuse_session_mount
int fuse_session_mount(struct fuse_session *se, const char *mountpoint)
Definition: fuse_lowlevel.c:2990
fuse_opt_parse
int fuse_opt_parse(struct fuse_args *args, void *data, const struct fuse_opt opts[], fuse_opt_proc_t proc)
Definition: fuse_opt.c:398
fuse_req_t
struct fuse_req * fuse_req_t
Definition: fuse_lowlevel.h:49
fuse_add_direntry
size_t fuse_add_direntry(fuse_req_t req, char *buf, size_t bufsize, const char *name, const struct stat *stbuf, off_t off)
Definition: fuse_lowlevel.c:266
fuse_file_info::keep_cache
unsigned int keep_cache
Definition: fuse_common.h:64
fuse_entry_param
Definition: fuse_lowlevel.h:59
fuse_parse_cmdline
int fuse_parse_cmdline(struct fuse_args *args, struct fuse_cmdline_opts *opts)
Definition: helper.c:202
fuse_cmdline_help
void fuse_cmdline_help(void)
Definition: helper.c:129
fuse_reply_entry
int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)
Definition: fuse_lowlevel.c:400
fuse_set_signal_handlers
int fuse_set_signal_handlers(struct fuse_session *se)
Definition: fuse_signals.c:62
fuse_remove_signal_handlers
void fuse_remove_signal_handlers(struct fuse_session *se)
Definition: fuse_signals.c:79
fuse_lowlevel_notify_store
int fuse_lowlevel_notify_store(struct fuse_session *se, fuse_ino_t ino, off_t offset, struct fuse_bufvec *bufv, enum fuse_buf_copy_flags flags)
Definition: fuse_lowlevel.c:2299
fuse_file_info
Definition: fuse_common.h:44
fuse_lowlevel_version
void fuse_lowlevel_version(void)
Definition: fuse_lowlevel.c:2691
fuse_reply_none
void fuse_reply_none(fuse_req_t req)
Definition: fuse_lowlevel.c:316
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int flags
Definition: fuse_common.h:46
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Definition: fuse_common.h:743
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Definition: fuse_common.h:107
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void fuse_opt_free_args(struct fuse_args *args)
Definition: fuse_opt.c:34
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int fuse_reply_attr(fuse_req_t req, const struct stat *attr, double attr_timeout)
Definition: fuse_lowlevel.c:432
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void fuse_session_unmount(struct fuse_session *se)
Definition: fuse_lowlevel.c:3045
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#define FUSE_OPT_END
Definition: fuse_opt.h:104
fuse_buf::flags
enum fuse_buf_flags flags
Definition: fuse_common.h:711
fuse_lowlevel_ops::lookup
void(* lookup)(fuse_req_t req, fuse_ino_t parent, const char *name)
Definition: fuse_lowlevel.h:215
FUSE_ROOT_ID
#define FUSE_ROOT_ID
Definition: fuse_lowlevel.h:43
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uint64_t fuse_ino_t
Definition: fuse_lowlevel.h:46
fuse_session_loop_mt
int fuse_session_loop_mt(struct fuse_session *se, struct fuse_loop_config *config)
fuse_reply_open
int fuse_reply_open(fuse_req_t req, const struct fuse_file_info *fi)
Definition: fuse_lowlevel.c:452
fuse_lowlevel.h
fuse_lowlevel_ops
Definition: fuse_lowlevel.h:172
fuse_bufvec::buf
struct fuse_buf buf[1]
Definition: fuse_common.h:762
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Definition: fuse_opt.h:77
fuse_args
Definition: fuse_opt.h:109
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const char * fuse_pkgversion(void)
Definition: fuse.c:5122
FUSE_ARGS_INIT
#define FUSE_ARGS_INIT(argc, argv)
Definition: fuse_opt.h:123
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ssize_t fuse_buf_copy(struct fuse_bufvec *dst, struct fuse_bufvec *src, enum fuse_buf_copy_flags flags)
Definition: buffer.c:284
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int fuse_reply_buf(fuse_req_t req, const char *buf, size_t size)
Definition: fuse_lowlevel.c:471