event-rule: introduce event-rule kprobe
[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 LTTNG_HIDDEN
364 struct fd_tracker *fd_tracker_create(const char *unlinked_file_path,
365 unsigned int capacity)
366 {
367 struct fd_tracker *tracker = zmalloc(sizeof(struct fd_tracker));
368
369 if (!tracker) {
370 goto end;
371 }
372
373 pthread_mutex_lock(&seed.lock);
374 if (!seed.initialized) {
375 seed.value = (unsigned long) time(NULL);
376 seed.initialized = true;
377 }
378 pthread_mutex_unlock(&seed.lock);
379
380 CDS_INIT_LIST_HEAD(&tracker->active_handles);
381 CDS_INIT_LIST_HEAD(&tracker->suspended_handles);
382 tracker->capacity = capacity;
383 tracker->unsuspendable_fds = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
384 CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
385 if (!tracker->unsuspendable_fds) {
386 ERR("Failed to create fd-tracker's unsuspendable_fds hash table");
387 goto error;
388 }
389 tracker->inode_registry = lttng_inode_registry_create();
390 if (!tracker->inode_registry) {
391 ERR("Failed to create fd-tracker's inode registry");
392 goto error;
393 }
394
395 tracker->unlinked_file_pool =
396 lttng_unlinked_file_pool_create(unlinked_file_path);
397 if (!tracker->unlinked_file_pool) {
398 goto error;
399 }
400 DBG("File descriptor tracker created with a limit of %u simultaneously-opened FDs",
401 capacity);
402 end:
403 return tracker;
404 error:
405 fd_tracker_destroy(tracker);
406 return NULL;
407 }
408
409 LTTNG_HIDDEN
410 void fd_tracker_log(struct fd_tracker *tracker)
411 {
412 struct fs_handle_tracked *handle;
413 struct unsuspendable_fd *unsuspendable_fd;
414 struct cds_lfht_iter iter;
415
416 pthread_mutex_lock(&tracker->lock);
417 DBG_NO_LOC("File descriptor tracker");
418 DBG_NO_LOC(" Stats:");
419 DBG_NO_LOC(" uses: %" PRIu64, tracker->stats.uses);
420 DBG_NO_LOC(" misses: %" PRIu64, tracker->stats.misses);
421 DBG_NO_LOC(" errors: %" PRIu64, tracker->stats.errors);
422 DBG_NO_LOC(" Tracked: %u", TRACKED_COUNT(tracker));
423 DBG_NO_LOC(" active: %u", ACTIVE_COUNT(tracker));
424 DBG_NO_LOC(" suspendable: %u", SUSPENDABLE_COUNT(tracker));
425 DBG_NO_LOC(" unsuspendable: %u", UNSUSPENDABLE_COUNT(tracker));
426 DBG_NO_LOC(" suspended: %u", SUSPENDED_COUNT(tracker));
427 DBG_NO_LOC(" capacity: %u", tracker->capacity);
428
429 DBG_NO_LOC(" Tracked suspendable file descriptors");
430 cds_list_for_each_entry(
431 handle, &tracker->active_handles, handles_list_node) {
432 fs_handle_tracked_log(handle);
433 }
434 cds_list_for_each_entry(handle, &tracker->suspended_handles,
435 handles_list_node) {
436 fs_handle_tracked_log(handle);
437 }
438 if (!SUSPENDABLE_COUNT(tracker)) {
439 DBG_NO_LOC(" None");
440 }
441
442 DBG_NO_LOC(" Tracked unsuspendable file descriptors");
443 rcu_read_lock();
444 cds_lfht_for_each_entry(tracker->unsuspendable_fds, &iter,
445 unsuspendable_fd, tracker_node) {
446 DBG_NO_LOC(" %s [active, fd %d]",
447 unsuspendable_fd->name ?: "Unnamed",
448 unsuspendable_fd->fd);
449 }
450 rcu_read_unlock();
451 if (!UNSUSPENDABLE_COUNT(tracker)) {
452 DBG_NO_LOC(" None");
453 }
454
455 pthread_mutex_unlock(&tracker->lock);
456 }
457
458 LTTNG_HIDDEN
459 int fd_tracker_destroy(struct fd_tracker *tracker)
460 {
461 int ret = 0;
462
463 if (!tracker) {
464 goto end;
465 }
466 /*
467 * Refuse to destroy the tracker as fs_handles may still old
468 * weak references to the tracker.
469 */
470 pthread_mutex_lock(&tracker->lock);
471 if (TRACKED_COUNT(tracker)) {
472 ERR("A file descriptor leak has been detected: %u tracked file descriptors are still being tracked",
473 TRACKED_COUNT(tracker));
474 pthread_mutex_unlock(&tracker->lock);
475 fd_tracker_log(tracker);
476 ret = -1;
477 goto end;
478 }
479 pthread_mutex_unlock(&tracker->lock);
480
481 if (tracker->unsuspendable_fds) {
482 ret = cds_lfht_destroy(tracker->unsuspendable_fds, NULL);
483 assert(!ret);
484 }
485
486 lttng_inode_registry_destroy(tracker->inode_registry);
487 lttng_unlinked_file_pool_destroy(tracker->unlinked_file_pool);
488 pthread_mutex_destroy(&tracker->lock);
489 free(tracker);
490 end:
491 return ret;
492 }
493
494 LTTNG_HIDDEN
495 struct fs_handle *fd_tracker_open_fs_handle(struct fd_tracker *tracker,
496 struct lttng_directory_handle *directory,
497 const char *path,
498 int flags,
499 mode_t *mode)
500 {
501 int ret;
502 struct fs_handle_tracked *handle = NULL;
503 struct stat fd_stat;
504 struct open_properties properties = {
505 .flags = flags,
506 .mode.is_set = !!mode,
507 .mode.value = mode ? *mode : 0,
508 };
509
510 pthread_mutex_lock(&tracker->lock);
511 if (ACTIVE_COUNT(tracker) == tracker->capacity) {
512 if (tracker->count.suspendable.active > 0) {
513 ret = fd_tracker_suspend_handles(tracker, 1);
514 if (ret) {
515 goto end;
516 }
517 } else {
518 /*
519 * There are not enough active suspendable file
520 * descriptors to open a new fd and still accommodate
521 * the tracker's capacity.
522 */
523 WARN("Cannot open file system handle, too many unsuspendable file descriptors are opened (%u)",
524 tracker->count.unsuspendable);
525 goto end;
526 }
527 }
528
529 handle = zmalloc(sizeof(*handle));
530 if (!handle) {
531 goto end;
532 }
533 handle->parent = (typeof(handle->parent)) {
534 .get_fd = fs_handle_tracked_get_fd,
535 .put_fd = fs_handle_tracked_put_fd,
536 .unlink = fs_handle_tracked_unlink,
537 .close = fs_handle_tracked_close,
538 };
539
540 handle->tracker = tracker;
541
542 ret = pthread_mutex_init(&handle->lock, NULL);
543 if (ret) {
544 PERROR("Failed to initialize handle mutex while creating fs handle");
545 goto error_mutex_init;
546 }
547
548 handle->fd = open_from_properties(directory, path, &properties);
549 if (handle->fd < 0) {
550 PERROR("Failed to open fs handle to %s, open() returned", path);
551 goto error;
552 }
553
554 handle->properties = properties;
555
556 handle->inode = lttng_inode_registry_get_inode(tracker->inode_registry,
557 directory, path, handle->fd,
558 tracker->unlinked_file_pool);
559 if (!handle->inode) {
560 ERR("Failed to get lttng_inode corresponding to file %s", path);
561 goto error;
562 }
563
564 if (fstat(handle->fd, &fd_stat)) {
565 PERROR("Failed to retrieve file descriptor inode while creating fs handle, fstat() returned");
566 goto error;
567 }
568 handle->ino = fd_stat.st_ino;
569
570 fd_tracker_track(tracker, handle);
571 end:
572 pthread_mutex_unlock(&tracker->lock);
573 return handle ? &handle->parent : NULL;
574 error:
575 if (handle->inode) {
576 lttng_inode_put(handle->inode);
577 }
578 pthread_mutex_destroy(&handle->lock);
579 error_mutex_init:
580 free(handle);
581 handle = NULL;
582 goto end;
583 }
584
585 /* Caller must hold the tracker's lock. */
586 static int fd_tracker_suspend_handles(
587 struct fd_tracker *tracker, unsigned int count)
588 {
589 unsigned int left_to_close = count;
590 unsigned int attempts_left = tracker->count.suspendable.active;
591 struct fs_handle_tracked *handle, *tmp;
592
593 cds_list_for_each_entry_safe(handle, tmp, &tracker->active_handles,
594 handles_list_node) {
595 int ret;
596
597 fd_tracker_untrack(tracker, handle);
598 ret = fs_handle_tracked_suspend(handle);
599 fd_tracker_track(tracker, handle);
600 if (!ret) {
601 left_to_close--;
602 }
603 attempts_left--;
604
605 if (left_to_close == 0 || attempts_left == 0) {
606 break;
607 }
608 }
609 return left_to_close ? -EMFILE : 0;
610 }
611
612 LTTNG_HIDDEN
613 int fd_tracker_open_unsuspendable_fd(struct fd_tracker *tracker,
614 int *out_fds,
615 const char **names,
616 unsigned int fd_count,
617 fd_open_cb open,
618 void *user_data)
619 {
620 int ret, user_ret, i, fds_to_suspend;
621 unsigned int active_fds;
622 struct unsuspendable_fd **entries;
623
624 entries = zmalloc(fd_count * sizeof(*entries));
625 if (!entries) {
626 ret = -1;
627 goto end;
628 }
629
630 pthread_mutex_lock(&tracker->lock);
631
632 active_fds = ACTIVE_COUNT(tracker);
633 fds_to_suspend = (int) active_fds + (int) fd_count -
634 (int) tracker->capacity;
635 if (fds_to_suspend > 0) {
636 if (fds_to_suspend <= tracker->count.suspendable.active) {
637 ret = fd_tracker_suspend_handles(
638 tracker, fds_to_suspend);
639 if (ret) {
640 goto end_unlock;
641 }
642 } else {
643 /*
644 * There are not enough active suspendable file
645 * descriptors to open a new fd and still accommodates the
646 * tracker's capacity.
647 */
648 WARN("Cannot open unsuspendable fd, too many unsuspendable file descriptors are opened (%u)",
649 tracker->count.unsuspendable);
650 ret = -EMFILE;
651 goto end_unlock;
652 }
653 }
654
655 user_ret = open(user_data, out_fds);
656 if (user_ret) {
657 ret = user_ret;
658 goto end_unlock;
659 }
660
661 /*
662 * Add the fds returned by the user's callback to the hashtable
663 * of unsuspendable fds.
664 */
665 for (i = 0; i < fd_count; i++) {
666 struct unsuspendable_fd *entry = unsuspendable_fd_create(
667 names ? names[i] : NULL, out_fds[i]);
668
669 if (!entry) {
670 ret = -1;
671 goto end_free_entries;
672 }
673 entries[i] = entry;
674 }
675
676 rcu_read_lock();
677 for (i = 0; i < fd_count; i++) {
678 struct cds_lfht_node *node;
679 struct unsuspendable_fd *entry = entries[i];
680
681 node = cds_lfht_add_unique(tracker->unsuspendable_fds,
682 hash_key_ulong((void *) (unsigned long)
683 out_fds[i],
684 seed.value),
685 match_fd, (void *) (unsigned long) out_fds[i],
686 &entry->tracker_node);
687
688 if (node != &entry->tracker_node) {
689 ret = -EEXIST;
690 rcu_read_unlock();
691 goto end_free_entries;
692 }
693 entries[i] = NULL;
694 }
695 tracker->count.unsuspendable += fd_count;
696 rcu_read_unlock();
697 ret = user_ret;
698 end_unlock:
699 pthread_mutex_unlock(&tracker->lock);
700 end:
701 free(entries);
702 return ret;
703 end_free_entries:
704 for (i = 0; i < fd_count; i++) {
705 unsuspendable_fd_destroy(entries[i]);
706 }
707 goto end_unlock;
708 }
709
710 LTTNG_HIDDEN
711 int fd_tracker_close_unsuspendable_fd(struct fd_tracker *tracker,
712 int *fds_in,
713 unsigned int fd_count,
714 fd_close_cb close,
715 void *user_data)
716 {
717 int i, ret, user_ret;
718 int *fds = NULL;
719
720 /*
721 * Maintain a local copy of fds_in as the user's callback may modify its
722 * contents (e.g. setting the fd(s) to -1 after close).
723 */
724 fds = malloc(sizeof(*fds) * fd_count);
725 if (!fds) {
726 ret = -1;
727 goto end;
728 }
729 memcpy(fds, fds_in, sizeof(*fds) * fd_count);
730
731 pthread_mutex_lock(&tracker->lock);
732 rcu_read_lock();
733
734 /* Let the user close the file descriptors. */
735 user_ret = close(user_data, fds_in);
736 if (user_ret) {
737 ret = user_ret;
738 goto end_unlock;
739 }
740
741 /* Untrack the fds that were just closed by the user's callback. */
742 for (i = 0; i < fd_count; i++) {
743 struct cds_lfht_node *node;
744 struct cds_lfht_iter iter;
745 struct unsuspendable_fd *entry;
746
747 cds_lfht_lookup(tracker->unsuspendable_fds,
748 hash_key_ulong((void *) (unsigned long) fds[i],
749 seed.value),
750 match_fd, (void *) (unsigned long) fds[i],
751 &iter);
752 node = cds_lfht_iter_get_node(&iter);
753 if (!node) {
754 /* Unknown file descriptor. */
755 WARN("Untracked file descriptor %d passed to fd_tracker_close_unsuspendable_fd()",
756 fds[i]);
757 ret = -EINVAL;
758 goto end_unlock;
759 }
760 entry = caa_container_of(
761 node, struct unsuspendable_fd, tracker_node);
762
763 cds_lfht_del(tracker->unsuspendable_fds, node);
764 unsuspendable_fd_destroy(entry);
765 fds[i] = -1;
766 }
767
768 tracker->count.unsuspendable -= fd_count;
769 ret = 0;
770 end_unlock:
771 rcu_read_unlock();
772 pthread_mutex_unlock(&tracker->lock);
773 free(fds);
774 end:
775 return ret;
776 }
777
778 /* Caller must have taken the tracker's and handle's locks. */
779 static void fd_tracker_track(
780 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
781 {
782 if (handle->fd >= 0) {
783 tracker->count.suspendable.active++;
784 cds_list_add_tail(&handle->handles_list_node,
785 &tracker->active_handles);
786 } else {
787 tracker->count.suspendable.suspended++;
788 cds_list_add_tail(&handle->handles_list_node,
789 &tracker->suspended_handles);
790 }
791 }
792
793 /* Caller must have taken the tracker's and handle's locks. */
794 static void fd_tracker_untrack(
795 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
796 {
797 if (handle->fd >= 0) {
798 tracker->count.suspendable.active--;
799 } else {
800 tracker->count.suspendable.suspended--;
801 }
802 cds_list_del(&handle->handles_list_node);
803 }
804
805 /* Caller must have taken the tracker's and handle's locks. */
806 static int fd_tracker_restore_handle(
807 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
808 {
809 int ret;
810
811 fd_tracker_untrack(tracker, handle);
812 if (ACTIVE_COUNT(tracker) >= tracker->capacity) {
813 ret = fd_tracker_suspend_handles(tracker, 1);
814 if (ret) {
815 goto end;
816 }
817 }
818 ret = fs_handle_tracked_restore(handle);
819 end:
820 fd_tracker_track(tracker, handle);
821 return ret ? ret : handle->fd;
822 }
823
824 static int fs_handle_tracked_get_fd(struct fs_handle *_handle)
825 {
826 int ret;
827 struct fs_handle_tracked *handle =
828 container_of(_handle, struct fs_handle_tracked, parent);
829
830 /*
831 * TODO This should be optimized as it is a fairly hot path.
832 * The fd-tracker's lock should only be taken when a fs_handle is
833 * restored (slow path). On the fast path (fs_handle is active),
834 * the only effect on the fd_tracker is marking the handle as the
835 * most recently used. Currently, it is done by a call to the
836 * track/untrack helpers, but it should be done atomically.
837 *
838 * Note that the lock's nesting order must still be respected here.
839 * The handle's lock nests inside the tracker's lock.
840 */
841 pthread_mutex_lock(&handle->tracker->lock);
842 pthread_mutex_lock(&handle->lock);
843 assert(!handle->in_use);
844
845 handle->tracker->stats.uses++;
846 if (handle->fd >= 0) {
847 ret = handle->fd;
848 /* Mark as most recently used. */
849 fd_tracker_untrack(handle->tracker, handle);
850 fd_tracker_track(handle->tracker, handle);
851 } else {
852 handle->tracker->stats.misses++;
853 ret = fd_tracker_restore_handle(handle->tracker, handle);
854 if (ret < 0) {
855 handle->tracker->stats.errors++;
856 goto end;
857 }
858 }
859 handle->in_use = true;
860 end:
861 pthread_mutex_unlock(&handle->lock);
862 pthread_mutex_unlock(&handle->tracker->lock);
863 return ret;
864 }
865
866 static void fs_handle_tracked_put_fd(struct fs_handle *_handle)
867 {
868 struct fs_handle_tracked *handle =
869 container_of(_handle, struct fs_handle_tracked, parent);
870
871 pthread_mutex_lock(&handle->lock);
872 handle->in_use = false;
873 pthread_mutex_unlock(&handle->lock);
874 }
875
876 static int fs_handle_tracked_unlink(struct fs_handle *_handle)
877 {
878 int ret;
879 struct fs_handle_tracked *handle =
880 container_of(_handle, struct fs_handle_tracked, parent);
881
882 pthread_mutex_lock(&handle->tracker->lock);
883 pthread_mutex_lock(&handle->lock);
884 ret = lttng_inode_unlink(handle->inode);
885 pthread_mutex_unlock(&handle->lock);
886 pthread_mutex_unlock(&handle->tracker->lock);
887 return ret;
888 }
889
890 static int fs_handle_tracked_close(struct fs_handle *_handle)
891 {
892 int ret = 0;
893 const char *path = NULL;
894 struct fs_handle_tracked *handle =
895 container_of(_handle, struct fs_handle_tracked, parent);
896 struct lttng_directory_handle *inode_directory_handle = NULL;
897
898 if (!handle) {
899 ret = -EINVAL;
900 goto end;
901 }
902
903 pthread_mutex_lock(&handle->tracker->lock);
904 pthread_mutex_lock(&handle->lock);
905 if (handle->inode) {
906 lttng_inode_borrow_location(handle->inode, NULL, &path);
907 /*
908 * Here a reference to the inode's directory handle is acquired
909 * to prevent the last reference to it from being released while
910 * the tracker's lock is taken.
911 *
912 * If this wasn't done, the directory handle could attempt to
913 * close its underlying directory file descriptor, which would
914 * attempt to lock the tracker's lock, resulting in a deadlock.
915 *
916 * Since a new reference to the directory handle is taken within
917 * the scope of this function, it is not possible for the last
918 * reference to the inode's location directory handle to be
919 * released during the call to lttng_inode_put().
920 *
921 * We wait until the tracker's lock is released to release the
922 * reference. Hence, the call to the tracker is delayed just
923 * enough to not attempt to recursively acquire the tracker's
924 * lock twice.
925 */
926 inode_directory_handle =
927 lttng_inode_get_location_directory_handle(
928 handle->inode);
929 }
930 fd_tracker_untrack(handle->tracker, handle);
931 if (handle->fd >= 0) {
932 /*
933 * The return value of close() is not propagated as there
934 * isn't much the user can do about it.
935 */
936 if (close(handle->fd)) {
937 PERROR("Failed to close the file descriptor (%d) of fs handle to %s, close() returned",
938 handle->fd, path ? path : "Unknown");
939 }
940 handle->fd = -1;
941 }
942 if (handle->inode) {
943 lttng_inode_put(handle->inode);
944 }
945 pthread_mutex_unlock(&handle->lock);
946 pthread_mutex_destroy(&handle->lock);
947 pthread_mutex_unlock(&handle->tracker->lock);
948 free(handle);
949 lttng_directory_handle_put(inode_directory_handle);
950 end:
951 return ret;
952 }
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