libfuse

notify_inval_inode.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 GPL.
6 See the file COPYING.
7 */
8
62 #define FUSE_USE_VERSION 31
63
64 #include <fuse_lowlevel.h>
65 #include <stdio.h>
66 #include <stdlib.h>
67 #include <string.h>
68 #include <errno.h>
69 #include <fcntl.h>
70 #include <assert.h>
71 #include <stddef.h>
72 #include <unistd.h>
73 #include <pthread.h>
74
75 /* We can't actually tell the kernel that there is no
76 timeout, so we just send a big value */
77 #define NO_TIMEOUT 500000
78
79 /* We cannot check directly if e.g. O_RDONLY is set, since this is not
80 * an individual bit (cf. open(2)) */
81 #define ACCESS_MASK (O_RDONLY | O_WRONLY | O_RDWR)
82
83 #define MAX_STR_LEN 128
84 #define FILE_INO 2
85 #define FILE_NAME "current_time"
86 static char file_contents[MAX_STR_LEN];
87 static int lookup_cnt = 0;
88 static size_t file_size;
89
90 /* Command line parsing */
91 struct options {
92 int no_notify;
93 int update_interval;
94 };
95 static struct options options = {
96 .no_notify = 0,
97 .update_interval = 1,
98 };
99
100 #define OPTION(t, p) \
101 { t, offsetof(struct options, p), 1 }
102 static const struct fuse_opt option_spec[] = {
103 OPTION("--no-notify", no_notify),
104 OPTION("--update-interval=%d", update_interval),
105 FUSE_OPT_END
106 };
107
108 static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
109 stbuf->st_ino = ino;
110 if (ino == FUSE_ROOT_ID) {
111 stbuf->st_mode = S_IFDIR | 0755;
112 stbuf->st_nlink = 1;
113 }
114
115 else if (ino == FILE_INO) {
116 stbuf->st_mode = S_IFREG | 0444;
117 stbuf->st_nlink = 1;
118 stbuf->st_size = file_size;
119 }
120
121 else
122 return -1;
123
124 return 0;
125 }
126
127 static void tfs_lookup(fuse_req_t req, fuse_ino_t parent,
128 const char *name) {
129 struct fuse_entry_param e;
130 memset(&e, 0, sizeof(e));
131
132 if (parent != FUSE_ROOT_ID)
133 goto err_out;
134 else if (strcmp(name, FILE_NAME) == 0) {
135 e.ino = FILE_INO;
136 lookup_cnt++;
137 } else
138 goto err_out;
139
140 e.attr_timeout = NO_TIMEOUT;
141 e.entry_timeout = NO_TIMEOUT;
142 if (tfs_stat(e.ino, &e.attr) != 0)
143 goto err_out;
144 fuse_reply_entry(req, &e);
145 return;
146
147 err_out:
148 fuse_reply_err(req, ENOENT);
149 }
150
151 static void tfs_forget (fuse_req_t req, fuse_ino_t ino,
152 uint64_t nlookup) {
153 (void) req;
154 if(ino == FILE_INO)
155 lookup_cnt -= nlookup;
156 else
157 assert(ino == FUSE_ROOT_ID);
158 fuse_reply_none(req);
159 }
160
161 static void tfs_getattr(fuse_req_t req, fuse_ino_t ino,
162 struct fuse_file_info *fi) {
163 struct stat stbuf;
164
165 (void) fi;
166
167 memset(&stbuf, 0, sizeof(stbuf));
168 if (tfs_stat(ino, &stbuf) != 0)
169 fuse_reply_err(req, ENOENT);
170 else
171 fuse_reply_attr(req, &stbuf, NO_TIMEOUT);
172 }
173
174 struct dirbuf {
175 char *p;
176 size_t size;
177 };
178
179 static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
180 fuse_ino_t ino) {
181 struct stat stbuf;
182 size_t oldsize = b->size;
183 b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
184 b->p = (char *) realloc(b->p, b->size);
185 memset(&stbuf, 0, sizeof(stbuf));
186 stbuf.st_ino = ino;
187 fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
188 b->size);
189 }
190
191 #define min(x, y) ((x) < (y) ? (x) : (y))
192
193 static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
194 off_t off, size_t maxsize) {
195 if (off < bufsize)
196 return fuse_reply_buf(req, buf + off,
197 min(bufsize - off, maxsize));
198 else
199 return fuse_reply_buf(req, NULL, 0);
200 }
201
202 static void tfs_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
203 off_t off, struct fuse_file_info *fi) {
204 (void) fi;
205
206 if (ino != FUSE_ROOT_ID)
207 fuse_reply_err(req, ENOTDIR);
208 else {
209 struct dirbuf b;
210
211 memset(&b, 0, sizeof(b));
212 dirbuf_add(req, &b, FILE_NAME, FILE_INO);
213 reply_buf_limited(req, b.p, b.size, off, size);
214 free(b.p);
215 }
216 }
217
218 static void tfs_open(fuse_req_t req, fuse_ino_t ino,
219 struct fuse_file_info *fi) {
220
221 /* Make cache persistent even if file is closed,
222 this makes it easier to see the effects */
223 fi->keep_cache = 1;
224
225 if (ino == FUSE_ROOT_ID)
226 fuse_reply_err(req, EISDIR);
227 else if ((fi->flags & ACCESS_MASK) != O_RDONLY)
228 fuse_reply_err(req, EACCES);
229 else if (ino == FILE_INO)
230 fuse_reply_open(req, fi);
231 else {
232 // This should not happen
233 fprintf(stderr, "Got open for non-existing inode!\n");
234 fuse_reply_err(req, ENOENT);
235 }
236 }
237
238 static void tfs_read(fuse_req_t req, fuse_ino_t ino, size_t size,
239 off_t off, struct fuse_file_info *fi) {
240 (void) fi;
241
242 assert(ino == FILE_INO);
243 reply_buf_limited(req, file_contents, file_size, off, size);
244 }
245
246 static struct fuse_lowlevel_ops tfs_oper = {
247 .lookup = tfs_lookup,
248 .getattr = tfs_getattr,
249 .readdir = tfs_readdir,
250 .open = tfs_open,
251 .read = tfs_read,
252 .forget = tfs_forget,
253 };
254
255 static void update_fs(void) {
256 struct tm *now;
257 time_t t;
258 t = time(NULL);
259 now = localtime(&t);
260 assert(now != NULL);
261
262 file_size = strftime(file_contents, MAX_STR_LEN,
263 "The current time is %H:%M:%S\n", now);
264 assert(file_size != 0);
265 }
266
267 static void* update_fs_loop(void *data) {
268 struct fuse_session *se = (struct fuse_session*) data;
269
270 while(1) {
271 update_fs();
272 if (!options.no_notify && lookup_cnt) {
273 /* Only send notification if the kernel
274 is aware of the inode */
275 assert(fuse_lowlevel_notify_inval_inode
276 (se, FILE_INO, 0, 0) == 0);
277 }
278 sleep(options.update_interval);
279 }
280 return NULL;
281 }
282
283 static void show_help(const char *progname)
284 {
285 printf("usage: %s [options] <mountpoint>\n\n", progname);
286 printf("File-system specific options:\n"
287 " --update-interval=<secs> Update-rate of file system contents\n"
288 " --no-notify Disable kernel notifications\n"
289 "\n");
290 }
291
292 int main(int argc, char *argv[]) {
293 struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
294 struct fuse_session *se;
295 struct fuse_cmdline_opts opts;
296 pthread_t updater;
297 int ret = -1;
298
299 if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
300 return 1;
301
302 if (fuse_parse_cmdline(&args, &opts) != 0) {
303 ret = 1;
304 goto err_out1;
305 }
306
307 if (opts.show_help) {
308 show_help(argv[0]);
309 fuse_cmdline_help();
310 fuse_lowlevel_help();
311 ret = 0;
312 goto err_out1;
313 } else if (opts.show_version) {
314 printf("FUSE library version %s\n", fuse_pkgversion());
315 fuse_lowlevel_version();
316 ret = 0;
317 goto err_out1;
318 }
319
320 /* Initial contents */
321 update_fs();
322
323 se = fuse_session_new(&args, &tfs_oper,
324 sizeof(tfs_oper), NULL);
325 if (se == NULL)
326 goto err_out1;
327
328 if (fuse_set_signal_handlers(se) != 0)
329 goto err_out2;
330
331 if (fuse_session_mount(se, opts.mountpoint) != 0)
332 goto err_out3;
333
334 fuse_daemonize(opts.foreground);
335
336 /* Start thread to update file contents */
337 ret = pthread_create(&updater, NULL, update_fs_loop, (void *)se);
338 if (ret != 0) {
339 fprintf(stderr, "pthread_create failed with %s\n",
340 strerror(ret));
341 goto err_out3;
342 }
343
344 /* Block until ctrl+c or fusermount -u */
345 if (opts.singlethread)
346 ret = fuse_session_loop(se);
347 else
348 ret = fuse_session_loop_mt(se, opts.clone_fd);
349
350 fuse_session_unmount(se);
351 err_out3:
352 fuse_remove_signal_handlers(se);
353 err_out2:
354 fuse_session_destroy(se);
355 err_out1:
356 fuse_opt_free_args(&args);
357 free(opts.mountpoint);
358
359 return ret ? 1 : 0;
360 }
361
362
fuse_parse_cmdline
int fuse_parse_cmdline(struct fuse_args *args, struct fuse_cmdline_opts *opts)
Definition: helper.c:197
fuse_lowlevel_ops::lookup
void(* lookup)(fuse_req_t req, fuse_ino_t parent, const char *name)
Definition: fuse_lowlevel.h:218
fuse_req_t
struct fuse_req * fuse_req_t
Definition: fuse_lowlevel.h:49
fuse_ino_t
uint64_t fuse_ino_t
Definition: fuse_lowlevel.h:46
fuse_pkgversion
const char * fuse_pkgversion(void)
Definition: fuse.c:4926
fuse_session_unmount
void fuse_session_unmount(struct fuse_session *se)
Definition: fuse_lowlevel.c:2916
fuse_file_info::keep_cache
unsigned int keep_cache
Definition: fuse_common.h:51
fuse_entry_param
Definition: fuse_lowlevel.h:59
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:398
fuse_session_mount
int fuse_session_mount(struct fuse_session *se, const char *mountpoint)
Definition: fuse_lowlevel.c:2879
fuse_daemonize
int fuse_daemonize(int foreground)
Definition: helper.c:220
fuse_file_info
Definition: fuse_common.h:37
fuse_lowlevel_help
void fuse_lowlevel_help(void)
Definition: fuse_lowlevel.c:2587
fuse_file_info::flags
int flags
Definition: fuse_common.h:39
FUSE_ARGS_INIT
#define FUSE_ARGS_INIT(argc, argv)
Definition: fuse_opt.h:123
fuse_reply_err
int fuse_reply_err(fuse_req_t req, int err)
Definition: fuse_lowlevel.c:311
fuse_cmdline_help
void fuse_cmdline_help(void)
Definition: helper.c:128
fuse_reply_none
void fuse_reply_none(fuse_req_t req)
Definition: fuse_lowlevel.c:316
fuse_set_signal_handlers
int fuse_set_signal_handlers(struct fuse_session *se)
Definition: fuse_signals.c:62
fuse_session_destroy
void fuse_session_destroy(struct fuse_session *se)
Definition: fuse_lowlevel.c:2597
fuse_reply_open
int fuse_reply_open(fuse_req_t req, const struct fuse_file_info *fi)
Definition: fuse_lowlevel.c:450
fuse_reply_attr
int fuse_reply_attr(fuse_req_t req, const struct stat *attr, double attr_timeout)
Definition: fuse_lowlevel.c:430
fuse_opt_free_args
void fuse_opt_free_args(struct fuse_args *args)
Definition: fuse_opt.c:33
fuse_lowlevel_ops
Definition: fuse_lowlevel.h:175
fuse_opt
Definition: fuse_opt.h:77
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:2785
fuse_args
Definition: fuse_opt.h:109
fuse_lowlevel_notify_inval_inode
int fuse_lowlevel_notify_inval_inode(struct fuse_session *se, fuse_ino_t ino, off_t off, off_t len)
Definition: fuse_lowlevel.c:2118
fuse_lowlevel_version
void fuse_lowlevel_version(void)
Definition: fuse_lowlevel.c:2580
FUSE_OPT_END
#define FUSE_OPT_END
Definition: fuse_opt.h:104
fuse_remove_signal_handlers
void fuse_remove_signal_handlers(struct fuse_session *se)
Definition: fuse_signals.c:79
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:397
fuse_reply_buf
int fuse_reply_buf(fuse_req_t req, const char *buf, size_t size)
Definition: fuse_lowlevel.c:469
FUSE_ROOT_ID
#define FUSE_ROOT_ID
Definition: fuse_lowlevel.h:43
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