session-descriptor: fix comment typos in session-descriptor.h
[lttng-tools.git] / src / common / fd-tracker / fd-tracker.c
1 /*
2 * Copyright (C) 2018-2020 Jérémie Galarneau <jeremie.galarneau@efficios.com>
3 *
4 * SPDX-License-Identifier: GPL-2.0-only
5 *
6 */
7
8 #include <urcu.h>
9 #include <urcu/list.h>
10 #include <urcu/rculfhash.h>
11
12 #include <fcntl.h>
13 #include <inttypes.h>
14 #include <pthread.h>
15 #include <stdbool.h>
16 #include <sys/stat.h>
17 #include <sys/types.h>
18
19 #include <common/defaults.h>
20 #include <common/error.h>
21 #include <common/fs-handle-internal.h>
22 #include <common/hashtable/hashtable.h>
23 #include <common/hashtable/utils.h>
24 #include <common/macros.h>
25 #include <common/optional.h>
26
27 #include "fd-tracker.h"
28 #include "inode.h"
29
30 /* Tracker lock must be taken by the user. */
31 #define TRACKED_COUNT(tracker) \
32 (tracker->count.suspendable.active + \
33 tracker->count.suspendable.suspended + \
34 tracker->count.unsuspendable)
35
36 /* Tracker lock must be taken by the user. */
37 #define ACTIVE_COUNT(tracker) \
38 (tracker->count.suspendable.active + tracker->count.unsuspendable)
39
40 /* Tracker lock must be taken by the user. */
41 #define SUSPENDED_COUNT(tracker) (tracker->count.suspendable.suspended)
42
43 /* Tracker lock must be taken by the user. */
44 #define SUSPENDABLE_COUNT(tracker) \
45 (tracker->count.suspendable.active + \
46 tracker->count.suspendable.suspended)
47
48 /* Tracker lock must be taken by the user. */
49 #define UNSUSPENDABLE_COUNT(tracker) (tracker->count.unsuspendable)
50
51 struct fd_tracker {
52 pthread_mutex_t lock;
53 struct {
54 struct {
55 unsigned int active;
56 unsigned int suspended;
57 } suspendable;
58 unsigned int unsuspendable;
59 } count;
60 unsigned int capacity;
61 struct {
62 uint64_t uses;
63 uint64_t misses;
64 /* Failures to suspend or restore fs handles. */
65 uint64_t errors;
66 } stats;
67 /*
68 * The head of the active_handles list is always the least recently
69 * used active handle. When an handle is used, it is removed from the
70 * list and added to the end. When a file has to be suspended, the
71 * first element in the list is "popped", suspended, and added to the
72 * list of suspended handles.
73 */
74 struct cds_list_head active_handles;
75 struct cds_list_head suspended_handles;
76 struct cds_lfht *unsuspendable_fds;
77 struct lttng_inode_registry *inode_registry;
78 /* Unlinked files are moved in this directory under a unique name. */
79 struct lttng_directory_handle *unlink_directory_handle;
80 struct lttng_unlinked_file_pool *unlinked_file_pool;
81 };
82
83 struct open_properties {
84 int flags;
85 LTTNG_OPTIONAL(mode_t) mode;
86 };
87
88 /*
89 * A fs_handle_tracked is not ref-counted. Therefore, it is assumed that a
90 * handle is never in-use while it is being reclaimed. It can be
91 * shared by multiple threads, but external synchronization is required
92 * to ensure it is not still being used when it is reclaimed (close method).
93 * In this respect, it is not different from a regular file descriptor.
94 *
95 * The fs_handle lock always nests _within_ the tracker's lock.
96 */
97 struct fs_handle_tracked {
98 struct fs_handle parent;
99 pthread_mutex_t lock;
100 /*
101 * Weak reference to the tracker. All fs_handles are assumed to have
102 * been closed at the moment of the destruction of the fd_tracker.
103 */
104 struct fd_tracker *tracker;
105 struct open_properties properties;
106 struct lttng_inode *inode;
107 int fd;
108 /* inode number of the file at the time of the handle's creation. */
109 uint64_t ino;
110 bool in_use;
111 /* Offset to which the file should be restored. */
112 off_t offset;
113 struct cds_list_head handles_list_node;
114 };
115
116 struct unsuspendable_fd {
117 /*
118 * Accesses are only performed through the tracker, which is protected
119 * by its own lock.
120 */
121 int fd;
122 char *name;
123 struct cds_lfht_node tracker_node;
124 struct rcu_head rcu_head;
125 };
126
127 static struct {
128 pthread_mutex_t lock;
129 bool initialized;
130 unsigned long value;
131 } seed = {
132 .lock = PTHREAD_MUTEX_INITIALIZER,
133 };
134
135 static int match_fd(struct cds_lfht_node *node, const void *key);
136 static void unsuspendable_fd_destroy(struct unsuspendable_fd *entry);
137 static struct unsuspendable_fd *unsuspendable_fd_create(
138 const char *name, int fd);
139 static int open_from_properties(const struct lttng_directory_handle *dir_handle,
140 const char *path, struct open_properties *properties);
141
142 static void fs_handle_tracked_log(struct fs_handle_tracked *handle);
143 static int fs_handle_tracked_suspend(struct fs_handle_tracked *handle);
144 static int fs_handle_tracked_restore(struct fs_handle_tracked *handle);
145 static int fs_handle_tracked_get_fd(struct fs_handle *_handle);
146 static void fs_handle_tracked_put_fd(struct fs_handle *_handle);
147 static int fs_handle_tracked_unlink(struct fs_handle *_handle);
148 static int fs_handle_tracked_close(struct fs_handle *_handle);
149
150 static void fd_tracker_track(
151 struct fd_tracker *tracker, struct fs_handle_tracked *handle);
152 static void fd_tracker_untrack(
153 struct fd_tracker *tracker, struct fs_handle_tracked *handle);
154 static int fd_tracker_suspend_handles(
155 struct fd_tracker *tracker, unsigned int count);
156 static int fd_tracker_restore_handle(
157 struct fd_tracker *tracker, struct fs_handle_tracked *handle);
158
159 /* Match function of the tracker's unsuspendable_fds hash table. */
160 static int match_fd(struct cds_lfht_node *node, const void *key)
161 {
162 struct unsuspendable_fd *entry = caa_container_of(
163 node, struct unsuspendable_fd, tracker_node);
164
165 return hash_match_key_ulong(
166 (void *) (unsigned long) entry->fd, (void *) key);
167 }
168
169 static void delete_unsuspendable_fd(struct rcu_head *head)
170 {
171 struct unsuspendable_fd *fd = caa_container_of(
172 head, struct unsuspendable_fd, rcu_head);
173
174 free(fd->name);
175 free(fd);
176 }
177
178 static void unsuspendable_fd_destroy(struct unsuspendable_fd *entry)
179 {
180 if (!entry) {
181 return;
182 }
183 call_rcu(&entry->rcu_head, delete_unsuspendable_fd);
184 }
185
186 static struct unsuspendable_fd *unsuspendable_fd_create(
187 const char *name, int fd)
188 {
189 struct unsuspendable_fd *entry = zmalloc(sizeof(*entry));
190
191 if (!entry) {
192 goto error;
193 }
194 if (name) {
195 entry->name = strdup(name);
196 if (!entry->name) {
197 goto error;
198 }
199 }
200 cds_lfht_node_init(&entry->tracker_node);
201 entry->fd = fd;
202 return entry;
203 error:
204 unsuspendable_fd_destroy(entry);
205 return NULL;
206 }
207
208 static void fs_handle_tracked_log(struct fs_handle_tracked *handle)
209 {
210 const char *path;
211
212 pthread_mutex_lock(&handle->lock);
213 lttng_inode_borrow_location(handle->inode, NULL, &path);
214
215 if (handle->fd >= 0) {
216 DBG_NO_LOC(" %s [active, fd %d%s]", path, handle->fd,
217 handle->in_use ? ", in use" : "");
218 } else {
219 DBG_NO_LOC(" %s [suspended]", path);
220 }
221 pthread_mutex_unlock(&handle->lock);
222 }
223
224 /* Tracker lock must be held by the caller. */
225 static int fs_handle_tracked_suspend(struct fs_handle_tracked *handle)
226 {
227 int ret = 0;
228 struct stat fs_stat;
229 const char *path;
230 const struct lttng_directory_handle *node_directory_handle;
231
232 pthread_mutex_lock(&handle->lock);
233 lttng_inode_borrow_location(
234 handle->inode, &node_directory_handle, &path);
235 assert(handle->fd >= 0);
236 if (handle->in_use) {
237 /* This handle can't be suspended as it is currently in use. */
238 ret = -EAGAIN;
239 goto end;
240 }
241
242 ret = lttng_directory_handle_stat(
243 node_directory_handle, path, &fs_stat);
244 if (ret) {
245 PERROR("Filesystem handle to %s cannot be suspended as stat() failed",
246 path);
247 ret = -errno;
248 goto end;
249 }
250
251 if (fs_stat.st_ino != handle->ino) {
252 /* Don't suspend as the handle would not be restorable. */
253 WARN("Filesystem handle to %s cannot be suspended as its inode changed",
254 path);
255 ret = -ENOENT;
256 goto end;
257 }
258
259 handle->offset = lseek(handle->fd, 0, SEEK_CUR);
260 if (handle->offset == -1) {
261 WARN("Filesystem handle to %s cannot be suspended as lseek() failed to sample its current position",
262 path);
263 ret = -errno;
264 goto end;
265 }
266
267 ret = close(handle->fd);
268 if (ret) {
269 PERROR("Filesystem handle to %s cannot be suspended as close() failed",
270 path);
271 ret = -errno;
272 goto end;
273 }
274 DBG("Suspended filesystem handle to %s (fd %i) at position %" PRId64,
275 path, handle->fd, handle->offset);
276 handle->fd = -1;
277 end:
278 if (ret) {
279 handle->tracker->stats.errors++;
280 }
281 pthread_mutex_unlock(&handle->lock);
282 return ret;
283 }
284
285 /* Caller must hold the tracker and handle's locks. */
286 static int fs_handle_tracked_restore(struct fs_handle_tracked *handle)
287 {
288 int ret, fd = -1;
289 const char *path;
290 const struct lttng_directory_handle *node_directory_handle;
291
292 lttng_inode_borrow_location(
293 handle->inode, &node_directory_handle, &path);
294
295 assert(handle->fd == -1);
296 assert(path);
297 ret = open_from_properties(
298 node_directory_handle, path, &handle->properties);
299 if (ret < 0) {
300 PERROR("Failed to restore filesystem handle to %s, open() failed",
301 path);
302 ret = -errno;
303 goto end;
304 }
305 fd = ret;
306
307 ret = lseek(fd, handle->offset, SEEK_SET);
308 if (ret < 0) {
309 PERROR("Failed to restore filesystem handle to %s, lseek() failed",
310 path);
311 ret = -errno;
312 goto end;
313 }
314 DBG("Restored filesystem handle to %s (fd %i) at position %" PRId64,
315 path, fd, handle->offset);
316 ret = 0;
317 handle->fd = fd;
318 fd = -1;
319 end:
320 if (fd >= 0) {
321 (void) close(fd);
322 }
323 return ret;
324 }
325
326 static int open_from_properties(const struct lttng_directory_handle *dir_handle,
327 const char *path, struct open_properties *properties)
328 {
329 int ret;
330
331 /*
332 * open() ignores the 'flags' parameter unless the O_CREAT or O_TMPFILE
333 * flags are set. O_TMPFILE would not make sense in the context of a
334 * suspendable fs_handle as it would not be restorable (see OPEN(2)),
335 * thus it is ignored here.
336 */
337 if ((properties->flags & O_CREAT) && properties->mode.is_set) {
338 ret = lttng_directory_handle_open_file(dir_handle, path,
339 properties->flags, properties->mode.value);
340 } else {
341 ret = lttng_directory_handle_open_file(dir_handle, path,
342 properties->flags, 0);
343 }
344 /*
345 * Some flags should not be used beyond the initial open() of a
346 * restorable file system handle. O_CREAT and O_TRUNC must
347 * be cleared since it would be unexpected to re-use them
348 * when the handle is retored:
349 * - O_CREAT should not be needed as the file has been created
350 * on the initial call to open(),
351 * - O_TRUNC would destroy the file's contents by truncating it
352 * to length 0.
353 */
354 properties->flags &= ~(O_CREAT | O_TRUNC);
355 if (ret < 0) {
356 ret = -errno;
357 goto end;
358 }
359 end:
360 return ret;
361 }
362
363 struct fd_tracker *fd_tracker_create(const char *unlinked_file_path,
364 unsigned int capacity)
365 {
366 struct fd_tracker *tracker = zmalloc(sizeof(struct fd_tracker));
367
368 if (!tracker) {
369 goto end;
370 }
371
372 pthread_mutex_lock(&seed.lock);
373 if (!seed.initialized) {
374 seed.value = (unsigned long) time(NULL);
375 seed.initialized = true;
376 }
377 pthread_mutex_unlock(&seed.lock);
378
379 CDS_INIT_LIST_HEAD(&tracker->active_handles);
380 CDS_INIT_LIST_HEAD(&tracker->suspended_handles);
381 tracker->capacity = capacity;
382 tracker->unsuspendable_fds = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
383 CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
384 if (!tracker->unsuspendable_fds) {
385 ERR("Failed to create fd-tracker's unsuspendable_fds hash table");
386 goto error;
387 }
388 tracker->inode_registry = lttng_inode_registry_create();
389 if (!tracker->inode_registry) {
390 ERR("Failed to create fd-tracker's inode registry");
391 goto error;
392 }
393
394 tracker->unlinked_file_pool =
395 lttng_unlinked_file_pool_create(unlinked_file_path);
396 if (!tracker->unlinked_file_pool) {
397 goto error;
398 }
399 DBG("File descriptor tracker created with a limit of %u simultaneously-opened FDs",
400 capacity);
401 end:
402 return tracker;
403 error:
404 fd_tracker_destroy(tracker);
405 return NULL;
406 }
407
408 void fd_tracker_log(struct fd_tracker *tracker)
409 {
410 struct fs_handle_tracked *handle;
411 struct unsuspendable_fd *unsuspendable_fd;
412 struct cds_lfht_iter iter;
413
414 pthread_mutex_lock(&tracker->lock);
415 DBG_NO_LOC("File descriptor tracker");
416 DBG_NO_LOC(" Stats:");
417 DBG_NO_LOC(" uses: %" PRIu64, tracker->stats.uses);
418 DBG_NO_LOC(" misses: %" PRIu64, tracker->stats.misses);
419 DBG_NO_LOC(" errors: %" PRIu64, tracker->stats.errors);
420 DBG_NO_LOC(" Tracked: %u", TRACKED_COUNT(tracker));
421 DBG_NO_LOC(" active: %u", ACTIVE_COUNT(tracker));
422 DBG_NO_LOC(" suspendable: %u", SUSPENDABLE_COUNT(tracker));
423 DBG_NO_LOC(" unsuspendable: %u", UNSUSPENDABLE_COUNT(tracker));
424 DBG_NO_LOC(" suspended: %u", SUSPENDED_COUNT(tracker));
425 DBG_NO_LOC(" capacity: %u", tracker->capacity);
426
427 DBG_NO_LOC(" Tracked suspendable file descriptors");
428 cds_list_for_each_entry(
429 handle, &tracker->active_handles, handles_list_node) {
430 fs_handle_tracked_log(handle);
431 }
432 cds_list_for_each_entry(handle, &tracker->suspended_handles,
433 handles_list_node) {
434 fs_handle_tracked_log(handle);
435 }
436 if (!SUSPENDABLE_COUNT(tracker)) {
437 DBG_NO_LOC(" None");
438 }
439
440 DBG_NO_LOC(" Tracked unsuspendable file descriptors");
441 rcu_read_lock();
442 cds_lfht_for_each_entry(tracker->unsuspendable_fds, &iter,
443 unsuspendable_fd, tracker_node) {
444 DBG_NO_LOC(" %s [active, fd %d]",
445 unsuspendable_fd->name ?: "Unnamed",
446 unsuspendable_fd->fd);
447 }
448 rcu_read_unlock();
449 if (!UNSUSPENDABLE_COUNT(tracker)) {
450 DBG_NO_LOC(" None");
451 }
452
453 pthread_mutex_unlock(&tracker->lock);
454 }
455
456 int fd_tracker_destroy(struct fd_tracker *tracker)
457 {
458 int ret = 0;
459
460 /*
461 * Refuse to destroy the tracker as fs_handles may still old
462 * weak references to the tracker.
463 */
464 pthread_mutex_lock(&tracker->lock);
465 if (TRACKED_COUNT(tracker)) {
466 ERR("A file descriptor leak has been detected: %u tracked file descriptors are still being tracked",
467 TRACKED_COUNT(tracker));
468 pthread_mutex_unlock(&tracker->lock);
469 fd_tracker_log(tracker);
470 ret = -1;
471 goto end;
472 }
473 pthread_mutex_unlock(&tracker->lock);
474
475 if (tracker->unsuspendable_fds) {
476 ret = cds_lfht_destroy(tracker->unsuspendable_fds, NULL);
477 assert(!ret);
478 }
479
480 lttng_inode_registry_destroy(tracker->inode_registry);
481 lttng_unlinked_file_pool_destroy(tracker->unlinked_file_pool);
482 pthread_mutex_destroy(&tracker->lock);
483 free(tracker);
484 end:
485 return ret;
486 }
487
488 struct fs_handle *fd_tracker_open_fs_handle(struct fd_tracker *tracker,
489 struct lttng_directory_handle *directory,
490 const char *path,
491 int flags,
492 mode_t *mode)
493 {
494 int ret;
495 struct fs_handle_tracked *handle = NULL;
496 struct stat fd_stat;
497 struct open_properties properties = {
498 .flags = flags,
499 .mode.is_set = !!mode,
500 .mode.value = mode ? *mode : 0,
501 };
502
503 pthread_mutex_lock(&tracker->lock);
504 if (ACTIVE_COUNT(tracker) == tracker->capacity) {
505 if (tracker->count.suspendable.active > 0) {
506 ret = fd_tracker_suspend_handles(tracker, 1);
507 if (ret) {
508 goto end;
509 }
510 } else {
511 /*
512 * There are not enough active suspendable file
513 * descriptors to open a new fd and still accommodate
514 * the tracker's capacity.
515 */
516 WARN("Cannot open file system handle, too many unsuspendable file descriptors are opened (%u)",
517 tracker->count.unsuspendable);
518 goto end;
519 }
520 }
521
522 handle = zmalloc(sizeof(*handle));
523 if (!handle) {
524 goto end;
525 }
526 handle->parent = (typeof(handle->parent)) {
527 .get_fd = fs_handle_tracked_get_fd,
528 .put_fd = fs_handle_tracked_put_fd,
529 .unlink = fs_handle_tracked_unlink,
530 .close = fs_handle_tracked_close,
531 };
532
533 handle->tracker = tracker;
534
535 ret = pthread_mutex_init(&handle->lock, NULL);
536 if (ret) {
537 PERROR("Failed to initialize handle mutex while creating fs handle");
538 goto error_mutex_init;
539 }
540
541 handle->fd = open_from_properties(directory, path, &properties);
542 if (handle->fd < 0) {
543 PERROR("Failed to open fs handle to %s, open() returned", path);
544 goto error;
545 }
546
547 handle->properties = properties;
548
549 handle->inode = lttng_inode_registry_get_inode(tracker->inode_registry,
550 directory, path, handle->fd,
551 tracker->unlinked_file_pool);
552 if (!handle->inode) {
553 ERR("Failed to get lttng_inode corresponding to file %s", path);
554 goto error;
555 }
556
557 if (fstat(handle->fd, &fd_stat)) {
558 PERROR("Failed to retrieve file descriptor inode while creating fs handle, fstat() returned");
559 goto error;
560 }
561 handle->ino = fd_stat.st_ino;
562
563 fd_tracker_track(tracker, handle);
564 end:
565 pthread_mutex_unlock(&tracker->lock);
566 return handle ? &handle->parent : NULL;
567 error:
568 if (handle->inode) {
569 lttng_inode_put(handle->inode);
570 }
571 pthread_mutex_destroy(&handle->lock);
572 error_mutex_init:
573 free(handle);
574 handle = NULL;
575 goto end;
576 }
577
578 /* Caller must hold the tracker's lock. */
579 static int fd_tracker_suspend_handles(
580 struct fd_tracker *tracker, unsigned int count)
581 {
582 unsigned int left_to_close = count;
583 unsigned int attempts_left = tracker->count.suspendable.active;
584 struct fs_handle_tracked *handle, *tmp;
585
586 cds_list_for_each_entry_safe(handle, tmp, &tracker->active_handles,
587 handles_list_node) {
588 int ret;
589
590 fd_tracker_untrack(tracker, handle);
591 ret = fs_handle_tracked_suspend(handle);
592 fd_tracker_track(tracker, handle);
593 if (!ret) {
594 left_to_close--;
595 }
596 attempts_left--;
597
598 if (left_to_close == 0 || attempts_left == 0) {
599 break;
600 }
601 }
602 return left_to_close ? -EMFILE : 0;
603 }
604
605 int fd_tracker_open_unsuspendable_fd(struct fd_tracker *tracker,
606 int *out_fds,
607 const char **names,
608 unsigned int fd_count,
609 fd_open_cb open,
610 void *user_data)
611 {
612 int ret, user_ret, i, fds_to_suspend;
613 unsigned int active_fds;
614 struct unsuspendable_fd **entries;
615
616 entries = zmalloc(fd_count * sizeof(*entries));
617 if (!entries) {
618 ret = -1;
619 goto end;
620 }
621
622 pthread_mutex_lock(&tracker->lock);
623
624 active_fds = ACTIVE_COUNT(tracker);
625 fds_to_suspend = (int) active_fds + (int) fd_count -
626 (int) tracker->capacity;
627 if (fds_to_suspend > 0) {
628 if (fds_to_suspend <= tracker->count.suspendable.active) {
629 ret = fd_tracker_suspend_handles(
630 tracker, fds_to_suspend);
631 if (ret) {
632 goto end_unlock;
633 }
634 } else {
635 /*
636 * There are not enough active suspendable file
637 * descriptors to open a new fd and still accomodate the
638 * tracker's capacity.
639 */
640 WARN("Cannot open unsuspendable fd, too many unsuspendable file descriptors are opened (%u)",
641 tracker->count.unsuspendable);
642 ret = -EMFILE;
643 goto end_unlock;
644 }
645 }
646
647 user_ret = open(user_data, out_fds);
648 if (user_ret) {
649 ret = user_ret;
650 goto end_unlock;
651 }
652
653 /*
654 * Add the fds returned by the user's callback to the hashtable
655 * of unsuspendable fds.
656 */
657 for (i = 0; i < fd_count; i++) {
658 struct unsuspendable_fd *entry = unsuspendable_fd_create(
659 names ? names[i] : NULL, out_fds[i]);
660
661 if (!entry) {
662 ret = -1;
663 goto end_free_entries;
664 }
665 entries[i] = entry;
666 }
667
668 rcu_read_lock();
669 for (i = 0; i < fd_count; i++) {
670 struct cds_lfht_node *node;
671 struct unsuspendable_fd *entry = entries[i];
672
673 node = cds_lfht_add_unique(tracker->unsuspendable_fds,
674 hash_key_ulong((void *) (unsigned long)
675 out_fds[i],
676 seed.value),
677 match_fd, (void *) (unsigned long) out_fds[i],
678 &entry->tracker_node);
679
680 if (node != &entry->tracker_node) {
681 ret = -EEXIST;
682 rcu_read_unlock();
683 goto end_free_entries;
684 }
685 entries[i] = NULL;
686 }
687 tracker->count.unsuspendable += fd_count;
688 rcu_read_unlock();
689 ret = user_ret;
690 end_unlock:
691 pthread_mutex_unlock(&tracker->lock);
692 end:
693 free(entries);
694 return ret;
695 end_free_entries:
696 for (i = 0; i < fd_count; i++) {
697 unsuspendable_fd_destroy(entries[i]);
698 }
699 goto end_unlock;
700 }
701
702 int fd_tracker_close_unsuspendable_fd(struct fd_tracker *tracker,
703 int *fds_in,
704 unsigned int fd_count,
705 fd_close_cb close,
706 void *user_data)
707 {
708 int i, ret, user_ret;
709 int *fds = NULL;
710
711 /*
712 * Maintain a local copy of fds_in as the user's callback may modify its
713 * contents (e.g. setting the fd(s) to -1 after close).
714 */
715 fds = malloc(sizeof(*fds) * fd_count);
716 if (!fds) {
717 ret = -1;
718 goto end;
719 }
720 memcpy(fds, fds_in, sizeof(*fds) * fd_count);
721
722 pthread_mutex_lock(&tracker->lock);
723 rcu_read_lock();
724
725 /* Let the user close the file descriptors. */
726 user_ret = close(user_data, fds_in);
727 if (user_ret) {
728 ret = user_ret;
729 goto end_unlock;
730 }
731
732 /* Untrack the fds that were just closed by the user's callback. */
733 for (i = 0; i < fd_count; i++) {
734 struct cds_lfht_node *node;
735 struct cds_lfht_iter iter;
736 struct unsuspendable_fd *entry;
737
738 cds_lfht_lookup(tracker->unsuspendable_fds,
739 hash_key_ulong((void *) (unsigned long) fds[i],
740 seed.value),
741 match_fd, (void *) (unsigned long) fds[i],
742 &iter);
743 node = cds_lfht_iter_get_node(&iter);
744 if (!node) {
745 /* Unknown file descriptor. */
746 WARN("Untracked file descriptor %d passed to fd_tracker_close_unsuspendable_fd()",
747 fds[i]);
748 ret = -EINVAL;
749 goto end_unlock;
750 }
751 entry = caa_container_of(
752 node, struct unsuspendable_fd, tracker_node);
753
754 cds_lfht_del(tracker->unsuspendable_fds, node);
755 unsuspendable_fd_destroy(entry);
756 fds[i] = -1;
757 }
758
759 tracker->count.unsuspendable -= fd_count;
760 ret = 0;
761 end_unlock:
762 rcu_read_unlock();
763 pthread_mutex_unlock(&tracker->lock);
764 free(fds);
765 end:
766 return ret;
767 }
768
769 /* Caller must have taken the tracker's and handle's locks. */
770 static void fd_tracker_track(
771 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
772 {
773 if (handle->fd >= 0) {
774 tracker->count.suspendable.active++;
775 cds_list_add_tail(&handle->handles_list_node,
776 &tracker->active_handles);
777 } else {
778 tracker->count.suspendable.suspended++;
779 cds_list_add_tail(&handle->handles_list_node,
780 &tracker->suspended_handles);
781 }
782 }
783
784 /* Caller must have taken the tracker's and handle's locks. */
785 static void fd_tracker_untrack(
786 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
787 {
788 if (handle->fd >= 0) {
789 tracker->count.suspendable.active--;
790 } else {
791 tracker->count.suspendable.suspended--;
792 }
793 cds_list_del(&handle->handles_list_node);
794 }
795
796 /* Caller must have taken the tracker's and handle's locks. */
797 static int fd_tracker_restore_handle(
798 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
799 {
800 int ret;
801
802 fd_tracker_untrack(tracker, handle);
803 if (ACTIVE_COUNT(tracker) >= tracker->capacity) {
804 ret = fd_tracker_suspend_handles(tracker, 1);
805 if (ret) {
806 goto end;
807 }
808 }
809 ret = fs_handle_tracked_restore(handle);
810 end:
811 fd_tracker_track(tracker, handle);
812 return ret ? ret : handle->fd;
813 }
814
815 static int fs_handle_tracked_get_fd(struct fs_handle *_handle)
816 {
817 int ret;
818 struct fs_handle_tracked *handle =
819 container_of(_handle, struct fs_handle_tracked, parent);
820
821 /*
822 * TODO This should be optimized as it is a fairly hot path.
823 * The fd-tracker's lock should only be taken when a fs_handle is
824 * restored (slow path). On the fast path (fs_handle is active),
825 * the only effect on the fd_tracker is marking the handle as the
826 * most recently used. Currently, it is done by a call to the
827 * track/untrack helpers, but it should be done atomically.
828 *
829 * Note that the lock's nesting order must still be respected here.
830 * The handle's lock nests inside the tracker's lock.
831 */
832 pthread_mutex_lock(&handle->tracker->lock);
833 pthread_mutex_lock(&handle->lock);
834 assert(!handle->in_use);
835
836 handle->tracker->stats.uses++;
837 if (handle->fd >= 0) {
838 ret = handle->fd;
839 /* Mark as most recently used. */
840 fd_tracker_untrack(handle->tracker, handle);
841 fd_tracker_track(handle->tracker, handle);
842 } else {
843 handle->tracker->stats.misses++;
844 ret = fd_tracker_restore_handle(handle->tracker, handle);
845 if (ret < 0) {
846 handle->tracker->stats.errors++;
847 goto end;
848 }
849 }
850 handle->in_use = true;
851 end:
852 pthread_mutex_unlock(&handle->lock);
853 pthread_mutex_unlock(&handle->tracker->lock);
854 return ret;
855 }
856
857 static void fs_handle_tracked_put_fd(struct fs_handle *_handle)
858 {
859 struct fs_handle_tracked *handle =
860 container_of(_handle, struct fs_handle_tracked, parent);
861
862 pthread_mutex_lock(&handle->lock);
863 handle->in_use = false;
864 pthread_mutex_unlock(&handle->lock);
865 }
866
867 static int fs_handle_tracked_unlink(struct fs_handle *_handle)
868 {
869 int ret;
870 struct fs_handle_tracked *handle =
871 container_of(_handle, struct fs_handle_tracked, parent);
872
873 pthread_mutex_lock(&handle->tracker->lock);
874 pthread_mutex_lock(&handle->lock);
875 ret = lttng_inode_unlink(handle->inode);
876 pthread_mutex_unlock(&handle->lock);
877 pthread_mutex_unlock(&handle->tracker->lock);
878 return ret;
879 }
880
881 static int fs_handle_tracked_close(struct fs_handle *_handle)
882 {
883 int ret = 0;
884 const char *path = NULL;
885 struct fs_handle_tracked *handle =
886 container_of(_handle, struct fs_handle_tracked, parent);
887 struct lttng_directory_handle *inode_directory_handle = NULL;
888
889 if (!handle) {
890 ret = -EINVAL;
891 goto end;
892 }
893
894 pthread_mutex_lock(&handle->tracker->lock);
895 pthread_mutex_lock(&handle->lock);
896 if (handle->inode) {
897 lttng_inode_borrow_location(handle->inode, NULL, &path);
898 /*
899 * Here a reference to the inode's directory handle is acquired
900 * to prevent the last reference to it from being released while
901 * the tracker's lock is taken.
902 *
903 * If this wasn't done, the directory handle could attempt to
904 * close its underlying directory file descriptor, which would
905 * attempt to lock the tracker's lock, resulting in a deadlock.
906 *
907 * Since a new reference to the directory handle is taken within
908 * the scope of this function, it is not possible for the last
909 * reference to the inode's location directory handle to be
910 * released during the call to lttng_inode_put().
911 *
912 * We wait until the tracker's lock is released to release the
913 * reference. Hence, the call to the tracker is delayed just
914 * enough to not attempt to recursively acquire the tracker's
915 * lock twice.
916 */
917 inode_directory_handle =
918 lttng_inode_get_location_directory_handle(
919 handle->inode);
920 }
921 fd_tracker_untrack(handle->tracker, handle);
922 if (handle->fd >= 0) {
923 /*
924 * The return value of close() is not propagated as there
925 * isn't much the user can do about it.
926 */
927 if (close(handle->fd)) {
928 PERROR("Failed to close the file descritptor (%d) of fs handle to %s, close() returned",
929 handle->fd, path ? path : "Unknown");
930 }
931 handle->fd = -1;
932 }
933 if (handle->inode) {
934 lttng_inode_put(handle->inode);
935 }
936 pthread_mutex_unlock(&handle->lock);
937 pthread_mutex_destroy(&handle->lock);
938 pthread_mutex_unlock(&handle->tracker->lock);
939 free(handle);
940 lttng_directory_handle_put(inode_directory_handle);
941 end:
942 return ret;
943 }
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