a4f4bcba77323f84990d91d6df8df328750f65d3
[lttng-tools.git] / src / common / fd-tracker / fd-tracker.c
1 /*
2 * Copyright (C) 2018 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License, version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
11 * more details.
12 *
13 * You should have received a copy of the GNU General Public License along with
14 * this program; if not, write to the Free Software Foundation, Inc., 51
15 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
16 */
17
18 #include <urcu.h>
19 #include <urcu/list.h>
20 #include <urcu/rculfhash.h>
21
22 #include <sys/stat.h>
23 #include <sys/types.h>
24 #include <fcntl.h>
25 #include <stdbool.h>
26 #include <pthread.h>
27 #include <inttypes.h>
28
29 #include "common/macros.h"
30 #include "common/error.h"
31 #include "common/defaults.h"
32 #include "common/hashtable/utils.h"
33 #include "common/hashtable/hashtable.h"
34
35 #include "fd-tracker.h"
36
37 /* Tracker lock must be taken by the user. */
38 #define TRACKED_COUNT(tracker) \
39 (tracker->count.suspendable.active + \
40 tracker->count.suspendable.suspended + \
41 tracker->count.unsuspendable)
42
43 /* Tracker lock must be taken by the user. */
44 #define ACTIVE_COUNT(tracker) \
45 (tracker->count.suspendable.active + \
46 tracker->count.unsuspendable)
47
48 /* Tracker lock must be taken by the user. */
49 #define SUSPENDED_COUNT(tracker) \
50 (tracker->count.suspendable.suspended)
51
52 /* Tracker lock must be taken by the user. */
53 #define SUSPENDABLE_COUNT(tracker) \
54 (tracker->count.suspendable.active + \
55 tracker->count.suspendable.suspended)
56
57 /* Tracker lock must be taken by the user. */
58 #define UNSUSPENDABLE_COUNT(tracker) \
59 (tracker->count.unsuspendable)
60
61 struct fd_tracker {
62 pthread_mutex_t lock;
63 struct {
64 struct {
65 unsigned int active;
66 unsigned int suspended;
67 } suspendable;
68 unsigned int unsuspendable;
69 } count;
70 unsigned int capacity;
71 struct {
72 uint64_t uses;
73 uint64_t misses;
74 /* Failures to suspend or restore fs handles. */
75 uint64_t errors;
76 } stats;
77 /*
78 * The head of the active_handles list is always the least recently
79 * used active handle. When an handle is used, it is removed from the
80 * list and added to the end. When a file has to be suspended, the
81 * first element in the list is "popped", suspended, and added to the
82 * list of suspended handles.
83 */
84 struct cds_list_head active_handles;
85 struct cds_list_head suspended_handles;
86 struct cds_lfht *unsuspendable_fds;
87 };
88
89 struct open_properties {
90 char *path;
91 int flags;
92 struct {
93 bool is_set;
94 mode_t value;
95 } mode;
96 };
97
98 /*
99 * A fs_handle is not ref-counted. Therefore, it is assumed that a
100 * handle is never in-use while it is being reclaimed. It can be
101 * shared by multiple threads, but external synchronization is required
102 * to ensure it is not still being used when it is reclaimed (close method).
103 * In this respect, it is not different from a regular file descriptor.
104 *
105 * The fs_handle lock always nests _within_ the tracker's lock.
106 */
107 struct fs_handle {
108 pthread_mutex_t lock;
109 /*
110 * Weak reference to the tracker. All fs_handles are assumed to have
111 * been closed at the moment of the destruction of the fd_tracker.
112 */
113 struct fd_tracker *tracker;
114 struct open_properties properties;
115 int fd;
116 /* inode number of the file at the time of the handle's creation. */
117 uint64_t ino;
118 bool in_use;
119 /* Offset to which the file should be restored. */
120 off_t offset;
121 struct cds_list_head handles_list_node;
122 };
123
124 struct unsuspendable_fd {
125 /*
126 * Accesses are only performed through the tracker, which is protected
127 * by its own lock.
128 */
129 int fd;
130 char *name;
131 struct cds_lfht_node tracker_node;
132 struct rcu_head rcu_head;
133 };
134
135 static struct {
136 pthread_mutex_t lock;
137 bool initialized;
138 unsigned long value;
139 } seed = {
140 .lock = PTHREAD_MUTEX_INITIALIZER,
141 };
142
143 static int match_fd(struct cds_lfht_node *node, const void *key);
144 static void unsuspendable_fd_destroy(struct unsuspendable_fd *entry);
145 static struct unsuspendable_fd *unsuspendable_fd_create(const char *name,
146 int fd);
147 static int open_from_properties(struct open_properties *properties);
148
149 static void fs_handle_log(struct fs_handle *handle);
150 static int fs_handle_suspend(struct fs_handle *handle);
151 static int fs_handle_restore(struct fs_handle *handle);
152
153 static void fd_tracker_track(struct fd_tracker *tracker,
154 struct fs_handle *handle);
155 static void fd_tracker_untrack(struct fd_tracker *tracker,
156 struct fs_handle *handle);
157 static int fd_tracker_suspend_handles(struct fd_tracker *tracker,
158 unsigned int count);
159 static int fd_tracker_restore_handle(struct fd_tracker *tracker,
160 struct fs_handle *handle);
161
162 /* Match function of the tracker's unsuspendable_fds hash table. */
163 static
164 int match_fd(struct cds_lfht_node *node, const void *key)
165 {
166 struct unsuspendable_fd *entry =
167 caa_container_of(node, struct unsuspendable_fd, tracker_node);
168
169 return hash_match_key_ulong((void *) (unsigned long) entry->fd,
170 (void *) key);
171 }
172
173 static
174 void delete_unsuspendable_fd(struct rcu_head *head)
175 {
176 struct unsuspendable_fd *fd = caa_container_of(head,
177 struct unsuspendable_fd, rcu_head);
178
179 free(fd->name);
180 free(fd);
181 }
182
183 static
184 void unsuspendable_fd_destroy(struct unsuspendable_fd *entry)
185 {
186 if (!entry) {
187 return;
188 }
189 call_rcu(&entry->rcu_head, delete_unsuspendable_fd);
190 }
191
192 static
193 struct unsuspendable_fd *unsuspendable_fd_create(const char *name, int fd)
194 {
195 struct unsuspendable_fd *entry =
196 zmalloc(sizeof(*entry));
197
198 if (!entry) {
199 goto error;
200 }
201 if (name) {
202 entry->name = strdup(name);
203 if (!entry->name) {
204 goto error;
205 }
206 }
207 cds_lfht_node_init(&entry->tracker_node);
208 entry->fd = fd;
209 return entry;
210 error:
211 unsuspendable_fd_destroy(entry);
212 return NULL;
213 }
214
215 static
216 void fs_handle_log(struct fs_handle *handle)
217 {
218 pthread_mutex_lock(&handle->lock);
219 if (handle->fd >= 0) {
220 DBG_NO_LOC(" %s [active, fd %d%s]",
221 handle->properties.path,
222 handle->fd,
223 handle->in_use ? ", in use" : "");
224 } else {
225 DBG_NO_LOC(" %s [suspended]", handle->properties.path);
226 }
227 pthread_mutex_unlock(&handle->lock);
228 }
229
230 static
231 int fs_handle_suspend(struct fs_handle *handle)
232 {
233 int ret = 0;
234 struct stat fs_stat;
235
236 pthread_mutex_lock(&handle->lock);
237 assert(handle->fd >= 0);
238 if (handle->in_use) {
239 /* This handle can't be suspended as it is currently in use. */
240 ret = -EAGAIN;
241 goto end;
242 }
243
244 ret = stat(handle->properties.path, &fs_stat);
245 if (ret) {
246 PERROR("Filesystem handle to %s cannot be suspended as stat() failed",
247 handle->properties.path);
248 ret = -errno;
249 goto end;
250 }
251
252 if (fs_stat.st_ino != handle->ino) {
253 /* Don't suspend as the handle would not be restorable. */
254 WARN("Filesystem handle to %s cannot be suspended as its inode changed",
255 handle->properties.path);
256 ret = -ENOENT;
257 goto end;
258 }
259
260 handle->offset = lseek(handle->fd, 0, SEEK_CUR);
261 if (handle->offset == -1) {
262 WARN("Filesystem handle to %s cannot be suspended as lseek() failed to sample its current position",
263 handle->properties.path);
264 ret = -errno;
265 goto end;
266 }
267
268 ret = close(handle->fd);
269 if (ret) {
270 PERROR("Filesystem handle to %s cannot be suspended as close() failed",
271 handle->properties.path);
272 ret = -errno;
273 goto end;
274 }
275 DBG("Suspended filesystem handle to %s (fd %i) at position %" PRId64,
276 handle->properties.path, handle->fd, handle->offset);
277 handle->fd = -1;
278 end:
279 if (ret) {
280 handle->tracker->stats.errors++;
281 }
282 pthread_mutex_unlock(&handle->lock);
283 return ret;
284 }
285
286 /* Caller must hold the tracker and handle's locks. */
287 static
288 int fs_handle_restore(struct fs_handle *handle)
289 {
290 int ret, fd = -1;
291
292 assert(handle->fd == -1);
293 ret = open_from_properties(&handle->properties);
294 if (ret < 0) {
295 PERROR("Failed to restore filesystem handle to %s, open() failed",
296 handle->properties.path);
297 ret = -errno;
298 goto end;
299 }
300 fd = ret;
301
302 ret = lseek(fd, handle->offset, SEEK_SET);
303 if (ret < 0) {
304 PERROR("Failed to restore filesystem handle to %s, lseek() failed",
305 handle->properties.path);
306 ret = -errno;
307 goto end;
308 }
309 DBG("Restored filesystem handle to %s (fd %i) at position %" PRId64,
310 handle->properties.path, fd, handle->offset);
311 ret = 0;
312 handle->fd = fd;
313 fd = -1;
314 end:
315 if (fd >= 0) {
316 (void) close(fd);
317 }
318 return ret;
319 }
320
321 static
322 int open_from_properties(struct open_properties *properties)
323 {
324 int ret;
325
326 /*
327 * open() ignores the 'flags' parameter unless the O_CREAT or O_TMPFILE
328 * flags are set. O_TMPFILE would not make sense in the context of a
329 * suspendable fs_handle as it would not be restorable (see OPEN(2)),
330 * thus it is ignored here.
331 */
332 if ((properties->flags & O_CREAT) && properties->mode.is_set) {
333 ret = open(properties->path, properties->flags,
334 properties->mode.value);
335 } else {
336 ret = open(properties->path, properties->flags);
337 }
338 /*
339 * Some flags should not be used beyond the initial open() of a
340 * restorable file system handle. O_CREAT and O_TRUNC must
341 * be cleared since it would be unexpected to re-use them
342 * when the handle is retored:
343 * - O_CREAT should not be needed as the file has been created
344 * on the initial call to open(),
345 * - O_TRUNC would destroy the file's contents by truncating it
346 * to length 0.
347 */
348 properties->flags &= ~(O_CREAT | O_TRUNC);
349 if (ret < 0) {
350 ret = -errno;
351 goto end;
352 }
353 end:
354 return ret;
355 }
356
357 struct fd_tracker *fd_tracker_create(unsigned int capacity)
358 {
359 struct fd_tracker *tracker = zmalloc(sizeof(struct fd_tracker));
360
361 if (!tracker) {
362 goto end;
363 }
364
365 pthread_mutex_lock(&seed.lock);
366 if (!seed.initialized) {
367 seed.value = (unsigned long) time(NULL);
368 seed.initialized = true;
369 }
370 pthread_mutex_unlock(&seed.lock);
371
372 CDS_INIT_LIST_HEAD(&tracker->active_handles);
373 CDS_INIT_LIST_HEAD(&tracker->suspended_handles);
374 tracker->capacity = capacity;
375 tracker->unsuspendable_fds = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
376 CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
377 DBG("File descriptor tracker created with a limit of %u simultaneously-opened FDs",
378 capacity);
379 end:
380 return tracker;
381 }
382
383 void fd_tracker_log(struct fd_tracker *tracker)
384 {
385 struct fs_handle *handle;
386 struct unsuspendable_fd *unsuspendable_fd;
387 struct cds_lfht_iter iter;
388
389 pthread_mutex_lock(&tracker->lock);
390 DBG_NO_LOC("File descriptor tracker");
391 DBG_NO_LOC(" Stats:");
392 DBG_NO_LOC(" uses: %" PRIu64, tracker->stats.uses);
393 DBG_NO_LOC(" misses: %" PRIu64, tracker->stats.misses);
394 DBG_NO_LOC(" errors: %" PRIu64, tracker->stats.errors);
395 DBG_NO_LOC(" Tracked: %u", TRACKED_COUNT(tracker));
396 DBG_NO_LOC(" active: %u", ACTIVE_COUNT(tracker));
397 DBG_NO_LOC(" suspendable: %u", SUSPENDABLE_COUNT(tracker));
398 DBG_NO_LOC(" unsuspendable: %u", UNSUSPENDABLE_COUNT(tracker));
399 DBG_NO_LOC(" suspended: %u", SUSPENDED_COUNT(tracker));
400 DBG_NO_LOC(" capacity: %u", tracker->capacity);
401
402 DBG_NO_LOC(" Tracked suspendable file descriptors");
403 cds_list_for_each_entry(handle, &tracker->active_handles,
404 handles_list_node) {
405 fs_handle_log(handle);
406 }
407 cds_list_for_each_entry(handle, &tracker->suspended_handles,
408 handles_list_node) {
409 fs_handle_log(handle);
410 }
411 if (!SUSPENDABLE_COUNT(tracker)) {
412 DBG_NO_LOC(" None");
413 }
414
415 DBG_NO_LOC(" Tracked unsuspendable file descriptors");
416 rcu_read_lock();
417 cds_lfht_for_each_entry(tracker->unsuspendable_fds, &iter,
418 unsuspendable_fd, tracker_node) {
419 DBG_NO_LOC(" %s [active, fd %d]", unsuspendable_fd->name ? : "Unnamed",
420 unsuspendable_fd->fd);
421 }
422 rcu_read_unlock();
423 if (!UNSUSPENDABLE_COUNT(tracker)) {
424 DBG_NO_LOC(" None");
425 }
426
427 pthread_mutex_unlock(&tracker->lock);
428 }
429
430 int fd_tracker_destroy(struct fd_tracker *tracker)
431 {
432 int ret = 0;
433
434 /*
435 * Refuse to destroy the tracker as fs_handles may still old
436 * weak references to the tracker.
437 */
438 pthread_mutex_lock(&tracker->lock);
439 if (TRACKED_COUNT(tracker)) {
440 ERR("A file descriptor leak has been detected: %u tracked file descriptors are still being tracked",
441 TRACKED_COUNT(tracker));
442 pthread_mutex_unlock(&tracker->lock);
443 fd_tracker_log(tracker);
444 ret = -1;
445 goto end;
446 }
447 pthread_mutex_unlock(&tracker->lock);
448
449 ret = cds_lfht_destroy(tracker->unsuspendable_fds, NULL);
450 assert(!ret);
451 pthread_mutex_destroy(&tracker->lock);
452 free(tracker);
453 end:
454 return ret;
455 }
456
457 struct fs_handle *fd_tracker_open_fs_handle(struct fd_tracker *tracker,
458 const char *path, int flags, mode_t *mode)
459 {
460 int ret;
461 struct fs_handle *handle = NULL;
462 struct stat fd_stat;
463 struct open_properties properties = {
464 .path = strdup(path),
465 .flags = flags,
466 .mode.is_set = !!mode,
467 .mode.value = mode ? *mode : 0,
468 };
469
470 if (!properties.path) {
471 goto end;
472 }
473
474 pthread_mutex_lock(&tracker->lock);
475 if (ACTIVE_COUNT(tracker) == tracker->capacity) {
476 if (tracker->count.suspendable.active > 0) {
477 ret = fd_tracker_suspend_handles(tracker, 1);
478 if (ret) {
479 goto error_destroy;
480 }
481 } else {
482 /*
483 * There are not enough active suspendable file
484 * descriptors to open a new fd and still accomodate the
485 * tracker's capacity.
486 */
487 WARN("Cannot open file system handle, too many unsuspendable file descriptors are opened (%u)",
488 tracker->count.unsuspendable);
489 ret = -EMFILE;
490 goto error_destroy;
491 }
492 }
493
494 handle = zmalloc(sizeof(*handle));
495 if (!handle) {
496 goto end;
497 }
498
499 ret = pthread_mutex_init(&handle->lock, NULL);
500 if (ret) {
501 PERROR("Failed to initialize handle mutex while creating fs handle");
502 free(handle);
503 goto end;
504 }
505
506 handle->fd = open_from_properties(&properties);
507 if (handle->fd < 0) {
508 PERROR("Failed to open fs handle to %s, open() returned", path);
509 ret = -errno;
510 goto error_destroy;
511 }
512
513 handle->properties = properties;
514 properties.path = NULL;
515
516 if (fstat(handle->fd, &fd_stat)) {
517 PERROR("Failed to retrieve file descriptor inode while creating fs handle, fstat() returned");
518 ret = -errno;
519 goto error_destroy;
520 }
521 handle->ino = fd_stat.st_ino;
522
523 fd_tracker_track(tracker, handle);
524 handle->tracker = tracker;
525 pthread_mutex_unlock(&tracker->lock);
526 end:
527 free(properties.path);
528 return handle;
529 error_destroy:
530 pthread_mutex_unlock(&tracker->lock);
531 (void) fs_handle_close(handle);
532 handle = NULL;
533 goto end;
534 }
535
536 /* Caller must hold the tracker's lock. */
537 static
538 int fd_tracker_suspend_handles(struct fd_tracker *tracker,
539 unsigned int count)
540 {
541 unsigned int left_to_close = count;
542 struct fs_handle *handle, *tmp;
543
544 cds_list_for_each_entry_safe(handle, tmp, &tracker->active_handles,
545 handles_list_node) {
546 int ret;
547
548 fd_tracker_untrack(tracker, handle);
549 ret = fs_handle_suspend(handle);
550 fd_tracker_track(tracker, handle);
551 if (!ret) {
552 left_to_close--;
553 }
554
555 if (!left_to_close) {
556 break;
557 }
558 }
559 return left_to_close ? -EMFILE : 0;
560 }
561
562 int fd_tracker_open_unsuspendable_fd(struct fd_tracker *tracker,
563 int *out_fds, const char **names, unsigned int fd_count,
564 fd_open_cb open, void *user_data)
565 {
566 int ret, user_ret, i, fds_to_suspend;
567 unsigned int active_fds;
568 struct unsuspendable_fd *entries[fd_count];
569
570 memset(entries, 0, sizeof(entries));
571
572 pthread_mutex_lock(&tracker->lock);
573
574 active_fds = ACTIVE_COUNT(tracker);
575 fds_to_suspend = (int) active_fds + (int) fd_count - (int) tracker->capacity;
576 if (fds_to_suspend > 0) {
577 if (fds_to_suspend <= tracker->count.suspendable.active) {
578 ret = fd_tracker_suspend_handles(tracker, fds_to_suspend);
579 if (ret) {
580 goto end;
581 }
582 } else {
583 /*
584 * There are not enough active suspendable file
585 * descriptors to open a new fd and still accomodate the
586 * tracker's capacity.
587 */
588 WARN("Cannot open unsuspendable fd, too many unsuspendable file descriptors are opened (%u)",
589 tracker->count.unsuspendable);
590 ret = -EMFILE;
591 goto end;
592 }
593 }
594
595 user_ret = open(user_data, out_fds);
596 if (user_ret) {
597 ret = user_ret;
598 goto end;
599 }
600
601 /*
602 * Add the fds returned by the user's callback to the hashtable
603 * of unsuspendable fds.
604 */
605 for (i = 0; i < fd_count; i++) {
606 struct unsuspendable_fd *entry =
607 unsuspendable_fd_create(names ? names[i] : NULL,
608 out_fds[i]);
609
610 if (!entry) {
611 ret = -1;
612 goto end_free_entries;
613 }
614 entries[i] = entry;
615 }
616
617 rcu_read_lock();
618 for (i = 0; i < fd_count; i++) {
619 struct cds_lfht_node *node;
620 struct unsuspendable_fd *entry = entries[i];
621
622 node = cds_lfht_add_unique(
623 tracker->unsuspendable_fds,
624 hash_key_ulong((void *) (unsigned long) out_fds[i],
625 seed.value),
626 match_fd,
627 (void *) (unsigned long) out_fds[i],
628 &entry->tracker_node);
629
630 if (node != &entry->tracker_node) {
631 ret = -EEXIST;
632 rcu_read_unlock();
633 goto end_free_entries;
634 }
635 entries[i] = NULL;
636 }
637 tracker->count.unsuspendable += fd_count;
638 rcu_read_unlock();
639 ret = user_ret;
640 end:
641 pthread_mutex_unlock(&tracker->lock);
642 return ret;
643 end_free_entries:
644 for (i = 0; i < fd_count; i++) {
645 unsuspendable_fd_destroy(entries[i]);
646 }
647 goto end;
648 }
649
650 int fd_tracker_close_unsuspendable_fd(struct fd_tracker *tracker,
651 int *fds_in, unsigned int fd_count, fd_close_cb close,
652 void *user_data)
653 {
654 int i, ret, user_ret;
655 int fds[fd_count];
656
657 /*
658 * Maintain a local copy of fds_in as the user's callback may modify its
659 * contents (e.g. setting the fd(s) to -1 after close).
660 */
661 memcpy(fds, fds_in, sizeof(*fds) * fd_count);
662
663 pthread_mutex_lock(&tracker->lock);
664 rcu_read_lock();
665
666 /* Let the user close the file descriptors. */
667 user_ret = close(user_data, fds_in);
668 if (user_ret) {
669 ret = user_ret;
670 goto end;
671 }
672
673 /* Untrack the fds that were just closed by the user's callback. */
674 for (i = 0; i < fd_count; i++) {
675 struct cds_lfht_node *node;
676 struct cds_lfht_iter iter;
677 struct unsuspendable_fd *entry;
678
679 cds_lfht_lookup(tracker->unsuspendable_fds,
680 hash_key_ulong((void *) (unsigned long) fds[i],
681 seed.value),
682 match_fd,
683 (void *) (unsigned long) fds[i],
684 &iter);
685 node = cds_lfht_iter_get_node(&iter);
686 if (!node) {
687 /* Unknown file descriptor. */
688 WARN("Untracked file descriptor %d passed to fd_tracker_close_unsuspendable_fd()",
689 fds[i]);
690 ret = -EINVAL;
691 goto end;
692 }
693 entry = caa_container_of(node,
694 struct unsuspendable_fd,
695 tracker_node);
696
697 cds_lfht_del(tracker->unsuspendable_fds, node);
698 unsuspendable_fd_destroy(entry);
699 fds[i] = -1;
700 }
701
702 tracker->count.unsuspendable -= fd_count;
703 ret = 0;
704 end:
705 rcu_read_unlock();
706 pthread_mutex_unlock(&tracker->lock);
707 return ret;
708 }
709
710 /* Caller must have taken the tracker's and handle's locks. */
711 static
712 void fd_tracker_track(struct fd_tracker *tracker, struct fs_handle *handle)
713 {
714 if (handle->fd >= 0) {
715 tracker->count.suspendable.active++;
716 cds_list_add_tail(&handle->handles_list_node,
717 &tracker->active_handles);
718 } else {
719 tracker->count.suspendable.suspended++;
720 cds_list_add_tail(&handle->handles_list_node,
721 &tracker->suspended_handles);
722 }
723 }
724
725 /* Caller must have taken the tracker's and handle's locks. */
726 static
727 void fd_tracker_untrack(struct fd_tracker *tracker, struct fs_handle *handle)
728 {
729 if (handle->fd >= 0) {
730 tracker->count.suspendable.active--;
731 } else {
732 tracker->count.suspendable.suspended--;
733 }
734 cds_list_del(&handle->handles_list_node);
735 }
736
737 /* Caller must have taken the tracker's and handle's locks. */
738 static
739 int fd_tracker_restore_handle(struct fd_tracker *tracker,
740 struct fs_handle *handle)
741 {
742 int ret;
743
744 fd_tracker_untrack(tracker, handle);
745 if (ACTIVE_COUNT(tracker) >= tracker->capacity) {
746 ret = fd_tracker_suspend_handles(tracker, 1);
747 if (ret) {
748 goto end;
749 }
750 }
751 ret = fs_handle_restore(handle);
752 end:
753 fd_tracker_track(tracker, handle);
754 return ret ? ret : handle->fd;
755 }
756
757 int fs_handle_get_fd(struct fs_handle *handle)
758 {
759 int ret;
760
761 /*
762 * TODO This should be optimized as it is a fairly hot path.
763 * The fd-tracker's lock should only be taken when a fs_handle is
764 * restored (slow path). On the fast path (fs_handle is active),
765 * the only effect on the fd_tracker is marking the handle as the
766 * most recently used. Currently, it is done by a call to the
767 * track/untrack helpers, but it should be done atomically.
768 *
769 * Note that the lock's nesting order must still be respected here.
770 * The handle's lock nests inside the tracker's lock.
771 */
772 pthread_mutex_lock(&handle->tracker->lock);
773 pthread_mutex_lock(&handle->lock);
774 assert(!handle->in_use);
775
776 handle->tracker->stats.uses++;
777 if (handle->fd >= 0) {
778 ret = handle->fd;
779 /* Mark as most recently used. */
780 fd_tracker_untrack(handle->tracker, handle);
781 fd_tracker_track(handle->tracker, handle);
782 } else {
783 handle->tracker->stats.misses++;
784 ret = fd_tracker_restore_handle(handle->tracker, handle);
785 if (ret < 0) {
786 handle->tracker->stats.errors++;
787 goto end;
788 }
789 }
790 handle->in_use = true;
791 end:
792 pthread_mutex_unlock(&handle->lock);
793 pthread_mutex_unlock(&handle->tracker->lock);
794 return ret;
795 }
796
797 void fs_handle_put_fd(struct fs_handle *handle)
798 {
799 pthread_mutex_lock(&handle->lock);
800 handle->in_use = false;
801 pthread_mutex_unlock(&handle->lock);
802 }
803
804 int fs_handle_unlink(struct fs_handle *handle)
805 {
806 int ret;
807
808 pthread_mutex_lock(&handle->tracker->lock);
809 pthread_mutex_lock(&handle->lock);
810 ret = lttng_inode_defer_unlink(handle->inode);
811 pthread_mutex_unlock(&handle->lock);
812 pthread_mutex_unlock(&handle->tracker->lock);
813 return ret;
814 }
815
816 int fs_handle_close(struct fs_handle *handle)
817 {
818 int ret = 0;
819
820 if (!handle) {
821 ret = -EINVAL;
822 goto end;
823 }
824
825 pthread_mutex_lock(&handle->tracker->lock);
826 pthread_mutex_lock(&handle->lock);
827 fd_tracker_untrack(handle->tracker, handle);
828 if (handle->fd >= 0) {
829 /*
830 * The return value of close() is not propagated as there
831 * isn't much the user can do about it.
832 */
833 if (close(handle->fd)) {
834 PERROR("Failed to close the file descritptor (%d) of fs handle to %s, close() returned",
835 handle->fd, handle->properties.path);
836 }
837 handle->fd = -1;
838 }
839 pthread_mutex_unlock(&handle->lock);
840 pthread_mutex_destroy(&handle->lock);
841 pthread_mutex_unlock(&handle->tracker->lock);
842 free(handle->properties.path);
843 free(handle);
844 end:
845 return ret;
846 }
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