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 GPLv2.
6 See the file COPYING.
7 */
8
62 #define FUSE_USE_VERSION 34
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 #define MAX_STR_LEN 128
80 #define FILE_INO 2
81 #define FILE_NAME "current_time"
82 static char file_contents[MAX_STR_LEN];
83 static int lookup_cnt = 0;
84 static size_t file_size;
85
86 /* Command line parsing */
87 struct options {
88 int no_notify;
89 int update_interval;
90 };
91 static struct options options = {
92 .no_notify = 0,
93 .update_interval = 1,
94 };
95
96 #define OPTION(t, p) \
97 { t, offsetof(struct options, p), 1 }
98 static const struct fuse_opt option_spec[] = {
99 OPTION("--no-notify", no_notify),
100 OPTION("--update-interval=%d", update_interval),
101 FUSE_OPT_END
102 };
103
104 static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
105 stbuf->st_ino = ino;
106 if (ino == FUSE_ROOT_ID) {
107 stbuf->st_mode = S_IFDIR | 0755;
108 stbuf->st_nlink = 1;
109 }
110
111 else if (ino == FILE_INO) {
112 stbuf->st_mode = S_IFREG | 0444;
113 stbuf->st_nlink = 1;
114 stbuf->st_size = file_size;
115 }
116
117 else
118 return -1;
119
120 return 0;
121 }
122
123 static void tfs_lookup(fuse_req_t req, fuse_ino_t parent,
124 const char *name) {
125 struct fuse_entry_param e;
126 memset(&e, 0, sizeof(e));
127
128 if (parent != FUSE_ROOT_ID)
129 goto err_out;
130 else if (strcmp(name, FILE_NAME) == 0) {
131 e.ino = FILE_INO;
132 lookup_cnt++;
133 } else
134 goto err_out;
135
136 e.attr_timeout = NO_TIMEOUT;
137 e.entry_timeout = NO_TIMEOUT;
138 if (tfs_stat(e.ino, &e.attr) != 0)
139 goto err_out;
140 fuse_reply_entry(req, &e);
141 return;
142
143 err_out:
144 fuse_reply_err(req, ENOENT);
145 }
146
147 static void tfs_forget (fuse_req_t req, fuse_ino_t ino,
148 uint64_t nlookup) {
149 (void) req;
150 if(ino == FILE_INO)
151 lookup_cnt -= nlookup;
152 else
153 assert(ino == FUSE_ROOT_ID);
154 fuse_reply_none(req);
155 }
156
157 static void tfs_getattr(fuse_req_t req, fuse_ino_t ino,
158 struct fuse_file_info *fi) {
159 struct stat stbuf;
160
161 (void) fi;
162
163 memset(&stbuf, 0, sizeof(stbuf));
164 if (tfs_stat(ino, &stbuf) != 0)
165 fuse_reply_err(req, ENOENT);
166 else
167 fuse_reply_attr(req, &stbuf, NO_TIMEOUT);
168 }
169
170 struct dirbuf {
171 char *p;
172 size_t size;
173 };
174
175 static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
176 fuse_ino_t ino) {
177 struct stat stbuf;
178 size_t oldsize = b->size;
179 b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
180 b->p = (char *) realloc(b->p, b->size);
181 memset(&stbuf, 0, sizeof(stbuf));
182 stbuf.st_ino = ino;
183 fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
184 b->size);
185 }
186
187 #define min(x, y) ((x) < (y) ? (x) : (y))
188
189 static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
190 off_t off, size_t maxsize) {
191 if (off < bufsize)
192 return fuse_reply_buf(req, buf + off,
193 min(bufsize - off, maxsize));
194 else
195 return fuse_reply_buf(req, NULL, 0);
196 }
197
198 static void tfs_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
199 off_t off, struct fuse_file_info *fi) {
200 (void) fi;
201
202 if (ino != FUSE_ROOT_ID)
203 fuse_reply_err(req, ENOTDIR);
204 else {
205 struct dirbuf b;
206
207 memset(&b, 0, sizeof(b));
208 dirbuf_add(req, &b, FILE_NAME, FILE_INO);
209 reply_buf_limited(req, b.p, b.size, off, size);
210 free(b.p);
211 }
212 }
213
214 static void tfs_open(fuse_req_t req, fuse_ino_t ino,
215 struct fuse_file_info *fi) {
216
217 /* Make cache persistent even if file is closed,
218 this makes it easier to see the effects */
219 fi->keep_cache = 1;
220
221 if (ino == FUSE_ROOT_ID)
222 fuse_reply_err(req, EISDIR);
223 else if ((fi->flags & O_ACCMODE) != O_RDONLY)
224 fuse_reply_err(req, EACCES);
225 else if (ino == FILE_INO)
226 fuse_reply_open(req, fi);
227 else {
228 // This should not happen
229 fprintf(stderr, "Got open for non-existing inode!\n");
230 fuse_reply_err(req, ENOENT);
231 }
232 }
233
234 static void tfs_read(fuse_req_t req, fuse_ino_t ino, size_t size,
235 off_t off, struct fuse_file_info *fi) {
236 (void) fi;
237
238 assert(ino == FILE_INO);
239 reply_buf_limited(req, file_contents, file_size, off, size);
240 }
241
242 static const struct fuse_lowlevel_ops tfs_oper = {
243 .lookup = tfs_lookup,
244 .getattr = tfs_getattr,
245 .readdir = tfs_readdir,
246 .open = tfs_open,
247 .read = tfs_read,
248 .forget = tfs_forget,
249 };
250
251 static void update_fs(void) {
252 struct tm *now;
253 time_t t;
254 t = time(NULL);
255 now = localtime(&t);
256 assert(now != NULL);
257
258 file_size = strftime(file_contents, MAX_STR_LEN,
259 "The current time is %H:%M:%S\n", now);
260 assert(file_size != 0);
261 }
262
263 static void* update_fs_loop(void *data) {
264 struct fuse_session *se = (struct fuse_session*) data;
265
266 while(1) {
267 update_fs();
268 if (!options.no_notify && lookup_cnt) {
269 /* Only send notification if the kernel
270 is aware of the inode */
271 assert(fuse_lowlevel_notify_inval_inode
272 (se, FILE_INO, 0, 0) == 0);
273 }
274 sleep(options.update_interval);
275 }
276 return NULL;
277 }
278
279 static void show_help(const char *progname)
280 {
281 printf("usage: %s [options] <mountpoint>\n\n", progname);
282 printf("File-system specific options:\n"
283 " --update-interval=<secs> Update-rate of file system contents\n"
284 " --no-notify Disable kernel notifications\n"
285 "\n");
286 }
287
288 int main(int argc, char *argv[]) {
289 struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
290 struct fuse_session *se;
291 struct fuse_cmdline_opts opts;
292 struct fuse_loop_config config;
293 pthread_t updater;
294 int ret = -1;
295
296 if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
297 return 1;
298
299 if (fuse_parse_cmdline(&args, &opts) != 0) {
300 ret = 1;
301 goto err_out1;
302 }
303
304 if (opts.show_help) {
305 show_help(argv[0]);
306 fuse_cmdline_help();
307 fuse_lowlevel_help();
308 ret = 0;
309 goto err_out1;
310 } else if (opts.show_version) {
311 printf("FUSE library version %s\n", fuse_pkgversion());
312 fuse_lowlevel_version();
313 ret = 0;
314 goto err_out1;
315 }
316
317 /* Initial contents */
318 update_fs();
319
320 se = fuse_session_new(&args, &tfs_oper,
321 sizeof(tfs_oper), NULL);
322 if (se == NULL)
323 goto err_out1;
324
325 if (fuse_set_signal_handlers(se) != 0)
326 goto err_out2;
327
328 if (fuse_session_mount(se, opts.mountpoint) != 0)
329 goto err_out3;
330
331 fuse_daemonize(opts.foreground);
332
333 /* Start thread to update file contents */
334 ret = pthread_create(&updater, NULL, update_fs_loop, (void *)se);
335 if (ret != 0) {
336 fprintf(stderr, "pthread_create failed with %s\n",
337 strerror(ret));
338 goto err_out3;
339 }
340
341 /* Block until ctrl+c or fusermount -u */
342 if (opts.singlethread)
343 ret = fuse_session_loop(se);
344 else {
345 config.clone_fd = opts.clone_fd;
346 config.max_idle_threads = opts.max_idle_threads;
347 ret = fuse_session_loop_mt(se, &config);
348 }
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_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:5122
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:225
fuse_session_destroy
void fuse_session_destroy(struct fuse_session *se)
Definition: fuse_lowlevel.c:2708
FUSE_ROOT_ID
#define FUSE_ROOT_ID
Definition: fuse_lowlevel.h:43
fuse_reply_open
int fuse_reply_open(fuse_req_t req, const struct fuse_file_info *fi)
Definition: fuse_lowlevel.c:452
fuse_reply_err
int fuse_reply_err(fuse_req_t req, int err)
Definition: fuse_lowlevel.c:311
fuse_reply_buf
int fuse_reply_buf(fuse_req_t req, const char *buf, size_t size)
Definition: fuse_lowlevel.c:471
fuse_req_t
struct fuse_req * fuse_req_t
Definition: fuse_lowlevel.h:49
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:400
fuse_session_unmount
void fuse_session_unmount(struct fuse_session *se)
Definition: fuse_lowlevel.c:3045
fuse_cmdline_help
void fuse_cmdline_help(void)
Definition: helper.c:129
fuse_parse_cmdline
int fuse_parse_cmdline(struct fuse_args *args, struct fuse_cmdline_opts *opts)
Definition: helper.c:202
fuse_reply_none
void fuse_reply_none(fuse_req_t req)
Definition: fuse_lowlevel.c:316
fuse_lowlevel_help
void fuse_lowlevel_help(void)
Definition: fuse_lowlevel.c:2698
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:2227
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_mount
int fuse_session_mount(struct fuse_session *se, const char *mountpoint)
Definition: fuse_lowlevel.c:2990
fuse_lowlevel_version
void fuse_lowlevel_version(void)
Definition: fuse_lowlevel.c:2691
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:266
fuse_reply_attr
int fuse_reply_attr(fuse_req_t req, const struct stat *attr, double attr_timeout)
Definition: fuse_lowlevel.c:432
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:1871
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:44
fuse_file_info::keep_cache
unsigned int keep_cache
Definition: fuse_common.h:64
fuse_file_info::flags
int flags
Definition: fuse_common.h:46
fuse_loop_config
Definition: fuse_common.h:107
fuse_lowlevel_ops
Definition: fuse_lowlevel.h:172
fuse_lowlevel_ops::lookup
void(* lookup)(fuse_req_t req, fuse_ino_t parent, const char *name)
Definition: fuse_lowlevel.h:215
fuse_opt
Definition: fuse_opt.h:77