Clean-up: coverity warns of uncaught exception during logging
[lttng-tools.git] / src / common / fd-tracker / fd-tracker.cpp
CommitLineData
df038819 1/*
ab5be9fa 2 * Copyright (C) 2018-2020 Jérémie Galarneau <jeremie.galarneau@efficios.com>
df038819 3 *
ab5be9fa 4 * SPDX-License-Identifier: GPL-2.0-only
df038819 5 *
df038819
JG
6 */
7
8#include <urcu.h>
9#include <urcu/list.h>
10#include <urcu/rculfhash.h>
11
df038819 12#include <fcntl.h>
df038819 13#include <inttypes.h>
5c1f54d1
JG
14#include <pthread.h>
15#include <stdbool.h>
16#include <sys/stat.h>
17#include <sys/types.h>
df038819 18
c9e313bc
SM
19#include <common/defaults.hpp>
20#include <common/error.hpp>
21#include <common/fs-handle-internal.hpp>
22#include <common/hashtable/hashtable.hpp>
23#include <common/hashtable/utils.hpp>
24#include <common/macros.hpp>
25#include <common/optional.hpp>
26
27#include "fd-tracker.hpp"
28#include "inode.hpp"
df038819
JG
29
30/* Tracker lock must be taken by the user. */
5c1f54d1
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31#define TRACKED_COUNT(tracker) \
32 (tracker->count.suspendable.active + \
33 tracker->count.suspendable.suspended + \
34 tracker->count.unsuspendable)
df038819
JG
35
36/* Tracker lock must be taken by the user. */
5c1f54d1
JG
37#define ACTIVE_COUNT(tracker) \
38 (tracker->count.suspendable.active + tracker->count.unsuspendable)
df038819
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39
40/* Tracker lock must be taken by the user. */
5c1f54d1 41#define SUSPENDED_COUNT(tracker) (tracker->count.suspendable.suspended)
df038819
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42
43/* Tracker lock must be taken by the user. */
5c1f54d1
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44#define SUSPENDABLE_COUNT(tracker) \
45 (tracker->count.suspendable.active + \
46 tracker->count.suspendable.suspended)
df038819
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47
48/* Tracker lock must be taken by the user. */
5c1f54d1 49#define UNSUSPENDABLE_COUNT(tracker) (tracker->count.unsuspendable)
df038819
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50
51struct fd_tracker {
52 pthread_mutex_t lock;
53 struct {
5c1f54d1 54 struct {
df038819
JG
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;
874a3441 77 struct lttng_inode_registry *inode_registry;
f7c3ffd7
JG
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;
df038819
JG
81};
82
f1494934 83namespace {
df038819 84struct open_properties {
df038819 85 int flags;
1e4f5625 86 LTTNG_OPTIONAL(mode_t) mode;
df038819
JG
87};
88
89/*
f5ea0241 90 * A fs_handle_tracked is not ref-counted. Therefore, it is assumed that a
df038819
JG
91 * handle is never in-use while it is being reclaimed. It can be
92 * shared by multiple threads, but external synchronization is required
93 * to ensure it is not still being used when it is reclaimed (close method).
94 * In this respect, it is not different from a regular file descriptor.
95 *
96 * The fs_handle lock always nests _within_ the tracker's lock.
97 */
f5ea0241
JG
98struct fs_handle_tracked {
99 struct fs_handle parent;
df038819
JG
100 pthread_mutex_t lock;
101 /*
102 * Weak reference to the tracker. All fs_handles are assumed to have
103 * been closed at the moment of the destruction of the fd_tracker.
104 */
105 struct fd_tracker *tracker;
106 struct open_properties properties;
874a3441 107 struct lttng_inode *inode;
df038819
JG
108 int fd;
109 /* inode number of the file at the time of the handle's creation. */
110 uint64_t ino;
111 bool in_use;
112 /* Offset to which the file should be restored. */
113 off_t offset;
114 struct cds_list_head handles_list_node;
115};
116
117struct unsuspendable_fd {
118 /*
119 * Accesses are only performed through the tracker, which is protected
120 * by its own lock.
121 */
122 int fd;
123 char *name;
124 struct cds_lfht_node tracker_node;
125 struct rcu_head rcu_head;
126};
127
f1494934 128struct {
df038819
JG
129 pthread_mutex_t lock;
130 bool initialized;
131 unsigned long value;
132} seed = {
133 .lock = PTHREAD_MUTEX_INITIALIZER,
1c9a0b0e
MJ
134 .initialized = false,
135 .value = 0,
df038819 136};
f1494934 137} /* namespace */
df038819
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138
139static int match_fd(struct cds_lfht_node *node, const void *key);
140static void unsuspendable_fd_destroy(struct unsuspendable_fd *entry);
5c1f54d1
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141static struct unsuspendable_fd *unsuspendable_fd_create(
142 const char *name, int fd);
f7c3ffd7 143static int open_from_properties(const struct lttng_directory_handle *dir_handle,
5c1f54d1 144 const char *path, struct open_properties *properties);
df038819 145
f5ea0241
JG
146static void fs_handle_tracked_log(struct fs_handle_tracked *handle);
147static int fs_handle_tracked_suspend(struct fs_handle_tracked *handle);
148static int fs_handle_tracked_restore(struct fs_handle_tracked *handle);
149static int fs_handle_tracked_get_fd(struct fs_handle *_handle);
150static void fs_handle_tracked_put_fd(struct fs_handle *_handle);
151static int fs_handle_tracked_unlink(struct fs_handle *_handle);
152static int fs_handle_tracked_close(struct fs_handle *_handle);
df038819 153
5c1f54d1 154static void fd_tracker_track(
f5ea0241 155 struct fd_tracker *tracker, struct fs_handle_tracked *handle);
5c1f54d1 156static void fd_tracker_untrack(
f5ea0241 157 struct fd_tracker *tracker, struct fs_handle_tracked *handle);
5c1f54d1
JG
158static int fd_tracker_suspend_handles(
159 struct fd_tracker *tracker, unsigned int count);
160static int fd_tracker_restore_handle(
f5ea0241
JG
161 struct fd_tracker *tracker, struct fs_handle_tracked *handle);
162
df038819 163/* Match function of the tracker's unsuspendable_fds hash table. */
5c1f54d1 164static int match_fd(struct cds_lfht_node *node, const void *key)
df038819 165{
0114db0e
JG
166 struct unsuspendable_fd *entry = lttng::utils::container_of(
167 node, &unsuspendable_fd::tracker_node);
df038819 168
5c1f54d1
JG
169 return hash_match_key_ulong(
170 (void *) (unsigned long) entry->fd, (void *) key);
df038819
JG
171}
172
5c1f54d1 173static void delete_unsuspendable_fd(struct rcu_head *head)
df038819 174{
5c1f54d1
JG
175 struct unsuspendable_fd *fd = caa_container_of(
176 head, struct unsuspendable_fd, rcu_head);
df038819
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177
178 free(fd->name);
179 free(fd);
180}
181
5c1f54d1 182static void unsuspendable_fd_destroy(struct unsuspendable_fd *entry)
df038819
JG
183{
184 if (!entry) {
185 return;
186 }
187 call_rcu(&entry->rcu_head, delete_unsuspendable_fd);
188}
189
5c1f54d1
JG
190static struct unsuspendable_fd *unsuspendable_fd_create(
191 const char *name, int fd)
df038819 192{
64803277 193 struct unsuspendable_fd *entry = zmalloc<unsuspendable_fd>();
df038819
JG
194
195 if (!entry) {
196 goto error;
197 }
198 if (name) {
199 entry->name = strdup(name);
200 if (!entry->name) {
201 goto error;
202 }
203 }
204 cds_lfht_node_init(&entry->tracker_node);
205 entry->fd = fd;
206 return entry;
207error:
208 unsuspendable_fd_destroy(entry);
209 return NULL;
210}
211
f5ea0241 212static void fs_handle_tracked_log(struct fs_handle_tracked *handle)
df038819 213{
874a3441
JG
214 const char *path;
215
df038819 216 pthread_mutex_lock(&handle->lock);
dd95933f 217 lttng_inode_borrow_location(handle->inode, NULL, &path);
874a3441 218
df038819 219 if (handle->fd >= 0) {
5c1f54d1 220 DBG_NO_LOC(" %s [active, fd %d%s]", path, handle->fd,
df038819
JG
221 handle->in_use ? ", in use" : "");
222 } else {
874a3441 223 DBG_NO_LOC(" %s [suspended]", path);
df038819
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224 }
225 pthread_mutex_unlock(&handle->lock);
226}
227
874a3441 228/* Tracker lock must be held by the caller. */
f5ea0241 229static int fs_handle_tracked_suspend(struct fs_handle_tracked *handle)
df038819
JG
230{
231 int ret = 0;
232 struct stat fs_stat;
874a3441 233 const char *path;
f7c3ffd7 234 const struct lttng_directory_handle *node_directory_handle;
df038819
JG
235
236 pthread_mutex_lock(&handle->lock);
dd95933f
JG
237 lttng_inode_borrow_location(
238 handle->inode, &node_directory_handle, &path);
a0377dfe 239 LTTNG_ASSERT(handle->fd >= 0);
df038819
JG
240 if (handle->in_use) {
241 /* This handle can't be suspended as it is currently in use. */
242 ret = -EAGAIN;
243 goto end;
244 }
245
f7c3ffd7
JG
246 ret = lttng_directory_handle_stat(
247 node_directory_handle, path, &fs_stat);
df038819 248 if (ret) {
5c1f54d1 249 PERROR("Filesystem handle to %s cannot be suspended as stat() failed",
874a3441 250 path);
df038819
JG
251 ret = -errno;
252 goto end;
253 }
254
255 if (fs_stat.st_ino != handle->ino) {
256 /* Don't suspend as the handle would not be restorable. */
257 WARN("Filesystem handle to %s cannot be suspended as its inode changed",
874a3441 258 path);
df038819
JG
259 ret = -ENOENT;
260 goto end;
261 }
262
5c1f54d1 263 handle->offset = lseek(handle->fd, 0, SEEK_CUR);
df038819
JG
264 if (handle->offset == -1) {
265 WARN("Filesystem handle to %s cannot be suspended as lseek() failed to sample its current position",
874a3441 266 path);
df038819
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267 ret = -errno;
268 goto end;
269 }
270
271 ret = close(handle->fd);
272 if (ret) {
5c1f54d1 273 PERROR("Filesystem handle to %s cannot be suspended as close() failed",
874a3441 274 path);
df038819
JG
275 ret = -errno;
276 goto end;
277 }
278 DBG("Suspended filesystem handle to %s (fd %i) at position %" PRId64,
874a3441 279 path, handle->fd, handle->offset);
df038819
JG
280 handle->fd = -1;
281end:
282 if (ret) {
283 handle->tracker->stats.errors++;
284 }
285 pthread_mutex_unlock(&handle->lock);
286 return ret;
287}
288
289/* Caller must hold the tracker and handle's locks. */
f5ea0241 290static int fs_handle_tracked_restore(struct fs_handle_tracked *handle)
df038819
JG
291{
292 int ret, fd = -1;
f7c3ffd7
JG
293 const char *path;
294 const struct lttng_directory_handle *node_directory_handle;
295
dd95933f
JG
296 lttng_inode_borrow_location(
297 handle->inode, &node_directory_handle, &path);
df038819 298
a0377dfe
FD
299 LTTNG_ASSERT(handle->fd == -1);
300 LTTNG_ASSERT(path);
f7c3ffd7
JG
301 ret = open_from_properties(
302 node_directory_handle, path, &handle->properties);
df038819 303 if (ret < 0) {
5c1f54d1 304 PERROR("Failed to restore filesystem handle to %s, open() failed",
874a3441 305 path);
df038819
JG
306 ret = -errno;
307 goto end;
308 }
309 fd = ret;
310
311 ret = lseek(fd, handle->offset, SEEK_SET);
312 if (ret < 0) {
5c1f54d1 313 PERROR("Failed to restore filesystem handle to %s, lseek() failed",
874a3441 314 path);
df038819
JG
315 ret = -errno;
316 goto end;
317 }
318 DBG("Restored filesystem handle to %s (fd %i) at position %" PRId64,
874a3441 319 path, fd, handle->offset);
df038819
JG
320 ret = 0;
321 handle->fd = fd;
322 fd = -1;
323end:
324 if (fd >= 0) {
325 (void) close(fd);
326 }
327 return ret;
328}
329
f7c3ffd7 330static int open_from_properties(const struct lttng_directory_handle *dir_handle,
5c1f54d1 331 const char *path, struct open_properties *properties)
df038819
JG
332{
333 int ret;
334
335 /*
336 * open() ignores the 'flags' parameter unless the O_CREAT or O_TMPFILE
337 * flags are set. O_TMPFILE would not make sense in the context of a
338 * suspendable fs_handle as it would not be restorable (see OPEN(2)),
339 * thus it is ignored here.
340 */
341 if ((properties->flags & O_CREAT) && properties->mode.is_set) {
f7c3ffd7
JG
342 ret = lttng_directory_handle_open_file(dir_handle, path,
343 properties->flags, properties->mode.value);
df038819 344 } else {
f7c3ffd7
JG
345 ret = lttng_directory_handle_open_file(dir_handle, path,
346 properties->flags, 0);
df038819
JG
347 }
348 /*
349 * Some flags should not be used beyond the initial open() of a
350 * restorable file system handle. O_CREAT and O_TRUNC must
351 * be cleared since it would be unexpected to re-use them
352 * when the handle is retored:
353 * - O_CREAT should not be needed as the file has been created
354 * on the initial call to open(),
355 * - O_TRUNC would destroy the file's contents by truncating it
356 * to length 0.
357 */
358 properties->flags &= ~(O_CREAT | O_TRUNC);
359 if (ret < 0) {
360 ret = -errno;
361 goto end;
362 }
363end:
364 return ret;
365}
366
f7c3ffd7
JG
367struct fd_tracker *fd_tracker_create(const char *unlinked_file_path,
368 unsigned int capacity)
df038819 369{
64803277 370 struct fd_tracker *tracker = zmalloc<fd_tracker>();
df038819
JG
371
372 if (!tracker) {
373 goto end;
374 }
375
376 pthread_mutex_lock(&seed.lock);
377 if (!seed.initialized) {
378 seed.value = (unsigned long) time(NULL);
379 seed.initialized = true;
380 }
381 pthread_mutex_unlock(&seed.lock);
382
383 CDS_INIT_LIST_HEAD(&tracker->active_handles);
384 CDS_INIT_LIST_HEAD(&tracker->suspended_handles);
385 tracker->capacity = capacity;
386 tracker->unsuspendable_fds = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
387 CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
874a3441
JG
388 if (!tracker->unsuspendable_fds) {
389 ERR("Failed to create fd-tracker's unsuspendable_fds hash table");
390 goto error;
391 }
392 tracker->inode_registry = lttng_inode_registry_create();
393 if (!tracker->inode_registry) {
394 ERR("Failed to create fd-tracker's inode registry");
395 goto error;
396 }
f7c3ffd7
JG
397
398 tracker->unlinked_file_pool =
399 lttng_unlinked_file_pool_create(unlinked_file_path);
400 if (!tracker->unlinked_file_pool) {
401 goto error;
402 }
df038819
JG
403 DBG("File descriptor tracker created with a limit of %u simultaneously-opened FDs",
404 capacity);
405end:
406 return tracker;
874a3441
JG
407error:
408 fd_tracker_destroy(tracker);
409 return NULL;
df038819
JG
410}
411
412void fd_tracker_log(struct fd_tracker *tracker)
413{
f5ea0241 414 struct fs_handle_tracked *handle;
df038819
JG
415 struct unsuspendable_fd *unsuspendable_fd;
416 struct cds_lfht_iter iter;
417
418 pthread_mutex_lock(&tracker->lock);
419 DBG_NO_LOC("File descriptor tracker");
420 DBG_NO_LOC(" Stats:");
421 DBG_NO_LOC(" uses: %" PRIu64, tracker->stats.uses);
422 DBG_NO_LOC(" misses: %" PRIu64, tracker->stats.misses);
423 DBG_NO_LOC(" errors: %" PRIu64, tracker->stats.errors);
424 DBG_NO_LOC(" Tracked: %u", TRACKED_COUNT(tracker));
425 DBG_NO_LOC(" active: %u", ACTIVE_COUNT(tracker));
426 DBG_NO_LOC(" suspendable: %u", SUSPENDABLE_COUNT(tracker));
427 DBG_NO_LOC(" unsuspendable: %u", UNSUSPENDABLE_COUNT(tracker));
428 DBG_NO_LOC(" suspended: %u", SUSPENDED_COUNT(tracker));
429 DBG_NO_LOC(" capacity: %u", tracker->capacity);
430
431 DBG_NO_LOC(" Tracked suspendable file descriptors");
f5ea0241 432 cds_list_for_each_entry(
5c1f54d1 433 handle, &tracker->active_handles, handles_list_node) {
f5ea0241 434 fs_handle_tracked_log(handle);
df038819 435 }
f5ea0241 436 cds_list_for_each_entry(handle, &tracker->suspended_handles,
df038819 437 handles_list_node) {
f5ea0241 438 fs_handle_tracked_log(handle);
df038819
JG
439 }
440 if (!SUSPENDABLE_COUNT(tracker)) {
441 DBG_NO_LOC(" None");
442 }
443
444 DBG_NO_LOC(" Tracked unsuspendable file descriptors");
445 rcu_read_lock();
f5ea0241 446 cds_lfht_for_each_entry(tracker->unsuspendable_fds, &iter,
df038819 447 unsuspendable_fd, tracker_node) {
5c1f54d1
JG
448 DBG_NO_LOC(" %s [active, fd %d]",
449 unsuspendable_fd->name ?: "Unnamed",
df038819
JG
450 unsuspendable_fd->fd);
451 }
452 rcu_read_unlock();
453 if (!UNSUSPENDABLE_COUNT(tracker)) {
454 DBG_NO_LOC(" None");
455 }
456
457 pthread_mutex_unlock(&tracker->lock);
458}
459
460int fd_tracker_destroy(struct fd_tracker *tracker)
461{
462 int ret = 0;
463
f6bef966
JG
464 if (!tracker) {
465 goto end;
466 }
df038819
JG
467 /*
468 * Refuse to destroy the tracker as fs_handles may still old
469 * weak references to the tracker.
470 */
471 pthread_mutex_lock(&tracker->lock);
472 if (TRACKED_COUNT(tracker)) {
473 ERR("A file descriptor leak has been detected: %u tracked file descriptors are still being tracked",
474 TRACKED_COUNT(tracker));
475 pthread_mutex_unlock(&tracker->lock);
476 fd_tracker_log(tracker);
477 ret = -1;
478 goto end;
479 }
480 pthread_mutex_unlock(&tracker->lock);
481
874a3441
JG
482 if (tracker->unsuspendable_fds) {
483 ret = cds_lfht_destroy(tracker->unsuspendable_fds, NULL);
a0377dfe 484 LTTNG_ASSERT(!ret);
874a3441 485 }
660a216c
JG
486
487 lttng_inode_registry_destroy(tracker->inode_registry);
f7c3ffd7 488 lttng_unlinked_file_pool_destroy(tracker->unlinked_file_pool);
df038819
JG
489 pthread_mutex_destroy(&tracker->lock);
490 free(tracker);
491end:
492 return ret;
493}
494
495struct fs_handle *fd_tracker_open_fs_handle(struct fd_tracker *tracker,
f7c3ffd7 496 struct lttng_directory_handle *directory,
5c1f54d1
JG
497 const char *path,
498 int flags,
499 mode_t *mode)
df038819
JG
500{
501 int ret;
f5ea0241 502 struct fs_handle_tracked *handle = NULL;
df038819
JG
503 struct stat fd_stat;
504 struct open_properties properties = {
df038819 505 .flags = flags,
e032c6fd
SM
506 .mode = {
507 .is_set = !!mode,
9730eb85 508 .value = static_cast<mode_t>(mode ? *mode : 0),
e032c6fd 509 }
df038819
JG
510 };
511
df038819
JG
512 pthread_mutex_lock(&tracker->lock);
513 if (ACTIVE_COUNT(tracker) == tracker->capacity) {
514 if (tracker->count.suspendable.active > 0) {
515 ret = fd_tracker_suspend_handles(tracker, 1);
516 if (ret) {
19380ea8 517 goto end;
df038819
JG
518 }
519 } else {
520 /*
521 * There are not enough active suspendable file
19380ea8
JG
522 * descriptors to open a new fd and still accommodate
523 * the tracker's capacity.
df038819
JG
524 */
525 WARN("Cannot open file system handle, too many unsuspendable file descriptors are opened (%u)",
526 tracker->count.unsuspendable);
19380ea8 527 goto end;
df038819
JG
528 }
529 }
530
64803277 531 handle = zmalloc<fs_handle_tracked>();
df038819
JG
532 if (!handle) {
533 goto end;
534 }
f7c3ffd7
JG
535 handle->parent = (typeof(handle->parent)) {
536 .get_fd = fs_handle_tracked_get_fd,
537 .put_fd = fs_handle_tracked_put_fd,
538 .unlink = fs_handle_tracked_unlink,
539 .close = fs_handle_tracked_close,
540 };
541
660a216c 542 handle->tracker = tracker;
df038819
JG
543
544 ret = pthread_mutex_init(&handle->lock, NULL);
545 if (ret) {
546 PERROR("Failed to initialize handle mutex while creating fs handle");
19380ea8 547 goto error_mutex_init;
df038819
JG
548 }
549
f7c3ffd7 550 handle->fd = open_from_properties(directory, path, &properties);
df038819
JG
551 if (handle->fd < 0) {
552 PERROR("Failed to open fs handle to %s, open() returned", path);
19380ea8 553 goto error;
df038819
JG
554 }
555
556 handle->properties = properties;
874a3441 557
f7c3ffd7
JG
558 handle->inode = lttng_inode_registry_get_inode(tracker->inode_registry,
559 directory, path, handle->fd,
560 tracker->unlinked_file_pool);
874a3441 561 if (!handle->inode) {
5c1f54d1 562 ERR("Failed to get lttng_inode corresponding to file %s", path);
19380ea8 563 goto error;
874a3441 564 }
df038819
JG
565
566 if (fstat(handle->fd, &fd_stat)) {
567 PERROR("Failed to retrieve file descriptor inode while creating fs handle, fstat() returned");
19380ea8 568 goto error;
df038819
JG
569 }
570 handle->ino = fd_stat.st_ino;
571
572 fd_tracker_track(tracker, handle);
df038819 573end:
19380ea8 574 pthread_mutex_unlock(&tracker->lock);
f5ea0241 575 return handle ? &handle->parent : NULL;
19380ea8 576error:
660a216c
JG
577 if (handle->inode) {
578 lttng_inode_put(handle->inode);
579 }
19380ea8
JG
580 pthread_mutex_destroy(&handle->lock);
581error_mutex_init:
660a216c 582 free(handle);
df038819
JG
583 handle = NULL;
584 goto end;
585}
586
587/* Caller must hold the tracker's lock. */
5c1f54d1
JG
588static int fd_tracker_suspend_handles(
589 struct fd_tracker *tracker, unsigned int count)
df038819
JG
590{
591 unsigned int left_to_close = count;
f7c3ffd7 592 unsigned int attempts_left = tracker->count.suspendable.active;
f5ea0241 593 struct fs_handle_tracked *handle, *tmp;
df038819 594
f5ea0241 595 cds_list_for_each_entry_safe(handle, tmp, &tracker->active_handles,
df038819
JG
596 handles_list_node) {
597 int ret;
598
599 fd_tracker_untrack(tracker, handle);
f5ea0241 600 ret = fs_handle_tracked_suspend(handle);
df038819
JG
601 fd_tracker_track(tracker, handle);
602 if (!ret) {
603 left_to_close--;
604 }
f7c3ffd7 605 attempts_left--;
df038819 606
f7c3ffd7 607 if (left_to_close == 0 || attempts_left == 0) {
df038819
JG
608 break;
609 }
610 }
611 return left_to_close ? -EMFILE : 0;
612}
613
614int fd_tracker_open_unsuspendable_fd(struct fd_tracker *tracker,
5c1f54d1
JG
615 int *out_fds,
616 const char **names,
617 unsigned int fd_count,
618 fd_open_cb open,
619 void *user_data)
df038819
JG
620{
621 int ret, user_ret, i, fds_to_suspend;
622 unsigned int active_fds;
b13a2b17 623 struct unsuspendable_fd **entries;
df038819 624
64803277 625 entries = calloc<unsuspendable_fd *>(fd_count);
b13a2b17
JG
626 if (!entries) {
627 ret = -1;
628 goto end;
629 }
df038819
JG
630
631 pthread_mutex_lock(&tracker->lock);
632
633 active_fds = ACTIVE_COUNT(tracker);
5c1f54d1
JG
634 fds_to_suspend = (int) active_fds + (int) fd_count -
635 (int) tracker->capacity;
df038819
JG
636 if (fds_to_suspend > 0) {
637 if (fds_to_suspend <= tracker->count.suspendable.active) {
5c1f54d1
JG
638 ret = fd_tracker_suspend_handles(
639 tracker, fds_to_suspend);
df038819 640 if (ret) {
b13a2b17 641 goto end_unlock;
df038819
JG
642 }
643 } else {
644 /*
645 * There are not enough active suspendable file
d49487dc 646 * descriptors to open a new fd and still accommodates the
df038819
JG
647 * tracker's capacity.
648 */
649 WARN("Cannot open unsuspendable fd, too many unsuspendable file descriptors are opened (%u)",
650 tracker->count.unsuspendable);
651 ret = -EMFILE;
b13a2b17 652 goto end_unlock;
df038819
JG
653 }
654 }
655
656 user_ret = open(user_data, out_fds);
657 if (user_ret) {
658 ret = user_ret;
b13a2b17 659 goto end_unlock;
df038819
JG
660 }
661
662 /*
663 * Add the fds returned by the user's callback to the hashtable
664 * of unsuspendable fds.
665 */
666 for (i = 0; i < fd_count; i++) {
5c1f54d1
JG
667 struct unsuspendable_fd *entry = unsuspendable_fd_create(
668 names ? names[i] : NULL, out_fds[i]);
df038819
JG
669
670 if (!entry) {
671 ret = -1;
672 goto end_free_entries;
673 }
674 entries[i] = entry;
675 }
676
677 rcu_read_lock();
678 for (i = 0; i < fd_count; i++) {
679 struct cds_lfht_node *node;
680 struct unsuspendable_fd *entry = entries[i];
681
5c1f54d1
JG
682 node = cds_lfht_add_unique(tracker->unsuspendable_fds,
683 hash_key_ulong((void *) (unsigned long)
684 out_fds[i],
df038819 685 seed.value),
5c1f54d1 686 match_fd, (void *) (unsigned long) out_fds[i],
df038819
JG
687 &entry->tracker_node);
688
689 if (node != &entry->tracker_node) {
690 ret = -EEXIST;
691 rcu_read_unlock();
692 goto end_free_entries;
693 }
694 entries[i] = NULL;
695 }
696 tracker->count.unsuspendable += fd_count;
697 rcu_read_unlock();
698 ret = user_ret;
b13a2b17 699end_unlock:
df038819 700 pthread_mutex_unlock(&tracker->lock);
b13a2b17
JG
701end:
702 free(entries);
df038819
JG
703 return ret;
704end_free_entries:
705 for (i = 0; i < fd_count; i++) {
706 unsuspendable_fd_destroy(entries[i]);
707 }
b13a2b17 708 goto end_unlock;
df038819
JG
709}
710
711int fd_tracker_close_unsuspendable_fd(struct fd_tracker *tracker,
5c1f54d1
JG
712 int *fds_in,
713 unsigned int fd_count,
714 fd_close_cb close,
df038819
JG
715 void *user_data)
716{
717 int i, ret, user_ret;
b13a2b17 718 int *fds = NULL;
df038819
JG
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 */
64803277 724 fds = malloc<int>(sizeof(*fds) * fd_count);
b13a2b17
JG
725 if (!fds) {
726 ret = -1;
727 goto end;
728 }
df038819
JG
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;
b13a2b17 738 goto end_unlock;
df038819
JG
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),
5c1f54d1 750 match_fd, (void *) (unsigned long) fds[i],
df038819
JG
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;
b13a2b17 758 goto end_unlock;
df038819 759 }
0114db0e
JG
760 entry = lttng::utils::container_of(
761 node, &unsuspendable_fd::tracker_node);
df038819
JG
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;
b13a2b17 770end_unlock:
df038819
JG
771 rcu_read_unlock();
772 pthread_mutex_unlock(&tracker->lock);
b13a2b17
JG
773 free(fds);
774end:
df038819
JG
775 return ret;
776}
777
778/* Caller must have taken the tracker's and handle's locks. */
5c1f54d1 779static void fd_tracker_track(
f5ea0241 780 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
df038819
JG
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. */
5c1f54d1 794static void fd_tracker_untrack(
f5ea0241 795 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
df038819
JG
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. */
5c1f54d1 806static int fd_tracker_restore_handle(
f5ea0241 807 struct fd_tracker *tracker, struct fs_handle_tracked *handle)
df038819
JG
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 }
f5ea0241 818 ret = fs_handle_tracked_restore(handle);
df038819
JG
819end:
820 fd_tracker_track(tracker, handle);
821 return ret ? ret : handle->fd;
822}
823
f5ea0241 824static int fs_handle_tracked_get_fd(struct fs_handle *_handle)
df038819
JG
825{
826 int ret;
f5ea0241 827 struct fs_handle_tracked *handle =
0114db0e 828 lttng::utils::container_of(_handle, &fs_handle_tracked::parent);
df038819
JG
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);
a0377dfe 843 LTTNG_ASSERT(!handle->in_use);
df038819
JG
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;
860end:
861 pthread_mutex_unlock(&handle->lock);
862 pthread_mutex_unlock(&handle->tracker->lock);
863 return ret;
864}
865
f5ea0241 866static void fs_handle_tracked_put_fd(struct fs_handle *_handle)
df038819 867{
f5ea0241 868 struct fs_handle_tracked *handle =
0114db0e 869 lttng::utils::container_of(_handle, &fs_handle_tracked::parent);
f5ea0241 870
df038819
JG
871 pthread_mutex_lock(&handle->lock);
872 handle->in_use = false;
873 pthread_mutex_unlock(&handle->lock);
874}
875
f5ea0241 876static int fs_handle_tracked_unlink(struct fs_handle *_handle)
9d16fc7f
JG
877{
878 int ret;
f5ea0241 879 struct fs_handle_tracked *handle =
0114db0e 880 lttng::utils::container_of(_handle, &fs_handle_tracked::parent);
9d16fc7f
JG
881
882 pthread_mutex_lock(&handle->tracker->lock);
883 pthread_mutex_lock(&handle->lock);
f7c3ffd7 884 ret = lttng_inode_unlink(handle->inode);
9d16fc7f
JG
885 pthread_mutex_unlock(&handle->lock);
886 pthread_mutex_unlock(&handle->tracker->lock);
887 return ret;
888}
889
f5ea0241 890static int fs_handle_tracked_close(struct fs_handle *_handle)
df038819
JG
891{
892 int ret = 0;
660a216c 893 const char *path = NULL;
f5ea0241 894 struct fs_handle_tracked *handle =
0114db0e 895 lttng::utils::container_of(_handle, &fs_handle_tracked::parent);
dd95933f 896 struct lttng_directory_handle *inode_directory_handle = NULL;
df038819
JG
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);
660a216c 905 if (handle->inode) {
dd95933f
JG
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);
660a216c 929 }
df038819
JG
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)) {
ea05fafd 937 PERROR("Failed to close the file descriptor (%d) of fs handle to %s, close() returned",
660a216c 938 handle->fd, path ? path : "Unknown");
df038819
JG
939 }
940 handle->fd = -1;
941 }
4c372c54
JG
942 if (handle->inode) {
943 lttng_inode_put(handle->inode);
944 }
df038819
JG
945 pthread_mutex_unlock(&handle->lock);
946 pthread_mutex_destroy(&handle->lock);
947 pthread_mutex_unlock(&handle->tracker->lock);
df038819 948 free(handle);
dd95933f 949 lttng_directory_handle_put(inode_directory_handle);
df038819
JG
950end:
951 return ret;
952}
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