libfuse: example/notify_inval_entry.c Source File

libfuse

notify_inval_entry.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
79#define FUSE_USE_VERSION 34
80
81#include <fuse_lowlevel.h>
82#include <stdio.h>
83#include <stdlib.h>
84#include <string.h>
85#include <errno.h>
86#include <fcntl.h>
87#include <assert.h>
88#include <signal.h>
89#include <stddef.h>
90#include <sys/stat.h>
91#include <unistd.h>
92#include <pthread.h>
93
94#define MAX_STR_LEN 128
95static char file_name[MAX_STR_LEN];
96static fuse_ino_t file_ino = 2;
97static int lookup_cnt = 0;
98static pthread_t main_thread;
99
100/* Command line parsing */
101struct options {
102 int no_notify;
103 float timeout;
104 int update_interval;
105 int only_expire;
106};
107static struct options options = {
108 .timeout = 5,
109 .no_notify = 0,
110 .update_interval = 1,
111 .only_expire = 0,
112};
113
114#define OPTION(t, p) \
115 { t, offsetof(struct options, p), 1 }
116static const struct fuse_opt option_spec[] = {
117 OPTION("--no-notify", no_notify),
118 OPTION("--update-interval=%d", update_interval),
119 OPTION("--timeout=%f", timeout),
120 OPTION("--only-expire", only_expire),
121 FUSE_OPT_END
122};
123
124static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
125 stbuf->st_ino = ino;
126 if (ino == FUSE_ROOT_ID) {
127 stbuf->st_mode = S_IFDIR | 0755;
128 stbuf->st_nlink = 1;
129 }
130
131 else if (ino == file_ino) {
132 stbuf->st_mode = S_IFREG | 0000;
133 stbuf->st_nlink = 1;
134 stbuf->st_size = 0;
135 }
136
137 else
138 return -1;
139
140 return 0;
141}
142
143static void tfs_lookup(fuse_req_t req, fuse_ino_t parent,
144 const char *name) {
145 struct fuse_entry_param e;
146 memset(&e, 0, sizeof(e));
147
148 if (parent != FUSE_ROOT_ID)
149 goto err_out;
150 else if (strcmp(name, file_name) == 0) {
151 e.ino = file_ino;
152 lookup_cnt++;
153 } else
154 goto err_out;
155
156 e.attr_timeout = options.timeout;
157 e.entry_timeout = options.timeout;
158 if (tfs_stat(e.ino, &e.attr) != 0)
159 goto err_out;
160 fuse_reply_entry(req, &e);
161 return;
162
163err_out:
164 fuse_reply_err(req, ENOENT);
165}
166
167static void tfs_forget (fuse_req_t req, fuse_ino_t ino,
168 uint64_t nlookup) {
169 (void) req;
170 if(ino == file_ino)
171 lookup_cnt -= nlookup;
172 else
173 assert(ino == FUSE_ROOT_ID);
174 fuse_reply_none(req);
175}
176
177static void tfs_getattr(fuse_req_t req, fuse_ino_t ino,
178 struct fuse_file_info *fi) {
179 struct stat stbuf;
180
181 (void) fi;
182
183 memset(&stbuf, 0, sizeof(stbuf));
184 if (tfs_stat(ino, &stbuf) != 0)
185 fuse_reply_err(req, ENOENT);
186 else
187 fuse_reply_attr(req, &stbuf, options.timeout);
188}
189
190struct dirbuf {
191 char *p;
192 size_t size;
193};
194
195static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
196 fuse_ino_t ino) {
197 struct stat stbuf;
198 size_t oldsize = b->size;
199 b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
200 b->p = (char *) realloc(b->p, b->size);
201 memset(&stbuf, 0, sizeof(stbuf));
202 stbuf.st_ino = ino;
203 fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
204 b->size);
205}
206
207#define min(x, y) ((x) < (y) ? (x) : (y))
208
209static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
210 off_t off, size_t maxsize) {
211 if (off < bufsize)
212 return fuse_reply_buf(req, buf + off,
213 min(bufsize - off, maxsize));
214 else
215 return fuse_reply_buf(req, NULL, 0);
216}
217
218static void tfs_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
219 off_t off, struct fuse_file_info *fi) {
220 (void) fi;
221
222 if (ino != FUSE_ROOT_ID)
223 fuse_reply_err(req, ENOTDIR);
224 else {
225 struct dirbuf b;
226
227 memset(&b, 0, sizeof(b));
228 dirbuf_add(req, &b, file_name, file_ino);
229 reply_buf_limited(req, b.p, b.size, off, size);
230 free(b.p);
231 }
232}
233
234static const struct fuse_lowlevel_ops tfs_oper = {
235 .lookup = tfs_lookup,
236 .getattr = tfs_getattr,
237 .readdir = tfs_readdir,
238 .forget = tfs_forget,
239};
240
241static void update_fs(void) {
242 time_t t;
243 struct tm *now;
244 ssize_t ret;
245
246 t = time(NULL);
247 now = localtime(&t);
248 assert(now != NULL);
249
250 ret = strftime(file_name, MAX_STR_LEN,
251 "Time_is_%Hh_%Mm_%Ss", now);
252 assert(ret != 0);
253}
254
255static void* update_fs_loop(void *data) {
256 struct fuse_session *se = (struct fuse_session*) data;
257 char *old_name;
258
259
260 while(!fuse_session_exited(se)) {
261 old_name = strdup(file_name);
262 update_fs();
263
264 if (!options.no_notify && lookup_cnt) {
265 if(options.only_expire) { // expire entry
266 int ret = fuse_lowlevel_notify_expire_entry
267 (se, FUSE_ROOT_ID, old_name, strlen(old_name));
268
269 // no kernel support
270 if (ret == -ENOSYS) {
271 printf("fuse_lowlevel_notify_expire_entry not supported by kernel\n");
272 printf("Exiting...\n");
273
274 fuse_session_exit(se);
275 // Make sure to exit now, rather than on next request from userspace
276 pthread_kill(main_thread, SIGPIPE);
277
278 break;
279 }
280 // 1) ret == 0: successful expire of an existing entry
281 // 2) ret == -ENOENT: kernel has already expired the entry /
282 // entry does not exist anymore in the kernel
283 assert(ret == 0 || ret == -ENOENT);
284 } else { // invalidate entry
285 assert(fuse_lowlevel_notify_inval_entry
286 (se, FUSE_ROOT_ID, old_name, strlen(old_name)) == 0);
287 }
288 }
289 free(old_name);
290 sleep(options.update_interval);
291 }
292 return NULL;
293}
294
295static void show_help(const char *progname)
296{
297 printf("usage: %s [options] <mountpoint>\n\n", progname);
298 printf("File-system specific options:\n"
299 " --timeout=<secs> Timeout for kernel caches\n"
300 " --update-interval=<secs> Update-rate of file system contents\n"
301 " --no-notify Disable kernel notifications\n"
302 " --only-expire Expire entries instead of invalidating them\n"
303 "\n");
304}
305
306int main(int argc, char *argv[]) {
307 struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
308 struct fuse_session *se;
309 struct fuse_cmdline_opts opts;
310 struct fuse_loop_config config;
311 pthread_t updater;
312 int ret = -1;
313
314 if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
315 return 1;
316
317 if (fuse_parse_cmdline(&args, &opts) != 0)
318 return 1;
319 if (opts.show_help) {
320 show_help(argv[0]);
321 fuse_cmdline_help();
322 fuse_lowlevel_help();
323 ret = 0;
324 goto err_out1;
325 } else if (opts.show_version) {
326 printf("FUSE library version %s\n", fuse_pkgversion());
327 fuse_lowlevel_version();
328 ret = 0;
329 goto err_out1;
330 }
331
332 /* Initial contents */
333 update_fs();
334
335 se = fuse_session_new(&args, &tfs_oper,
336 sizeof(tfs_oper), &se);
337 if (se == NULL)
338 goto err_out1;
339
340 if (fuse_set_signal_handlers(se) != 0)
341 goto err_out2;
342
343 if (fuse_session_mount(se, opts.mountpoint) != 0)
344 goto err_out3;
345
346 fuse_daemonize(opts.foreground);
347
348 // Needed to ensure that the main thread continues/restarts processing as soon
349 // as the fuse session ends (immediately after calling fuse_session_exit() )
350 // and not only on the next request from userspace
351 main_thread = pthread_self();
352
353 /* Start thread to update file contents */
354 ret = pthread_create(&updater, NULL, update_fs_loop, (void *)se);
355 if (ret != 0) {
356 fprintf(stderr, "pthread_create failed with %s\n",
357 strerror(ret));
358 goto err_out3;
359 }
360
361 /* Block until ctrl+c or fusermount -u */
362 if (opts.singlethread) {
363 ret = fuse_session_loop(se);
364 } else {
365 config.clone_fd = opts.clone_fd;
366 config.max_idle_threads = opts.max_idle_threads;
367 ret = fuse_session_loop_mt(se, &config);
368 }
369
370 fuse_session_unmount(se);
371err_out3:
372 fuse_remove_signal_handlers(se);
373err_out2:
374 fuse_session_destroy(se);
375err_out1:
376 free(opts.mountpoint);
377 fuse_opt_free_args(&args);
378
379 return ret ? 1 : 0;
380}
381
382
fuse_set_signal_handlers
int fuse_set_signal_handlers(struct fuse_session *se)
Definition: fuse_signals.c:62
fuse_pkgversion
const char * fuse_pkgversion(void)
Definition: fuse.c:5124
fuse_remove_signal_handlers
void fuse_remove_signal_handlers(struct fuse_session *se)
Definition: fuse_signals.c:79
fuse_daemonize
int fuse_daemonize(int foreground)
Definition: helper.c:253
fuse_lowlevel.h
fuse_session_destroy
void fuse_session_destroy(struct fuse_session *se)
Definition: fuse_lowlevel.c:2813
FUSE_ROOT_ID
#define FUSE_ROOT_ID
Definition: fuse_lowlevel.h:43
fuse_session_exit
void fuse_session_exit(struct fuse_session *se)
fuse_reply_err
int fuse_reply_err(fuse_req_t req, int err)
Definition: fuse_lowlevel.c:324
fuse_reply_buf
int fuse_reply_buf(fuse_req_t req, const char *buf, size_t size)
Definition: fuse_lowlevel.c:488
fuse_req_t
struct fuse_req * fuse_req_t
Definition: fuse_lowlevel.h:49
fuse_session_exited
int fuse_session_exited(struct fuse_session *se)
fuse_session_loop
int fuse_session_loop(struct fuse_session *se)
Definition: fuse_loop.c:19
fuse_reply_entry
int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)
Definition: fuse_lowlevel.c:417
fuse_session_unmount
void fuse_session_unmount(struct fuse_session *se)
Definition: fuse_lowlevel.c:3199
fuse_cmdline_help
void fuse_cmdline_help(void)
Definition: helper.c:130
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:3014
fuse_reply_none
void fuse_reply_none(fuse_req_t req)
Definition: fuse_lowlevel.c:329
fuse_lowlevel_notify_expire_entry
int fuse_lowlevel_notify_expire_entry(struct fuse_session *se, fuse_ino_t parent, const char *name, size_t namelen)
Definition: fuse_lowlevel.c:2365
fuse_lowlevel_help
void fuse_lowlevel_help(void)
Definition: fuse_lowlevel.c:2803
fuse_session_mount
int fuse_session_mount(struct fuse_session *se, const char *mountpoint)
Definition: fuse_lowlevel.c:3144
fuse_lowlevel_notify_inval_entry
int fuse_lowlevel_notify_inval_entry(struct fuse_session *se, fuse_ino_t parent, const char *name, size_t namelen)
Definition: fuse_lowlevel.c:2359
fuse_lowlevel_version
void fuse_lowlevel_version(void)
Definition: fuse_lowlevel.c:2796
fuse_ino_t
uint64_t fuse_ino_t
Definition: fuse_lowlevel.h:46
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:279
fuse_reply_attr
int fuse_reply_attr(fuse_req_t req, const struct stat *attr, double attr_timeout)
Definition: fuse_lowlevel.c:449
fuse_opt_free_args
void fuse_opt_free_args(struct fuse_args *args)
Definition: fuse_opt.c:34
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_ARGS_INIT
#define FUSE_ARGS_INIT(argc, argv)
Definition: fuse_opt.h:123
FUSE_OPT_END
#define FUSE_OPT_END
Definition: fuse_opt.h:104
fuse_args
Definition: fuse_opt.h:109
fuse_args::argc
int argc
Definition: fuse_opt.h:111
fuse_args::argv
char ** argv
Definition: fuse_opt.h:114
fuse_cmdline_opts
Definition: fuse_lowlevel.h:1941
fuse_entry_param
Definition: fuse_lowlevel.h:59
fuse_entry_param::ino
fuse_ino_t ino
Definition: fuse_lowlevel.h:67
fuse_file_info
Definition: fuse_common.h:50
fuse_loop_config
Definition: fuse_common.h:126
fuse_lowlevel_ops
Definition: fuse_lowlevel.h:201
fuse_lowlevel_ops::lookup
void(* lookup)(fuse_req_t req, fuse_ino_t parent, const char *name)
Definition: fuse_lowlevel.h:244
fuse_opt
Definition: fuse_opt.h:77