1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/jiffies.h>
4 #include <linux/kernel.h>
5 #include <linux/ktime.h>
6 #include <linux/list.h>
7 #include <linux/math64.h>
8 #include <linux/sizes.h>
9 #include <linux/workqueue.h>
10 #include "ctree.h"
11 #include "block-group.h"
12 #include "discard.h"
13 #include "free-space-cache.h"
14 #include "fs.h"
15
16 /*
17 * This contains the logic to handle async discard.
18 *
19 * Async discard manages trimming of free space outside of transaction commit.
20 * Discarding is done by managing the block_groups on a LRU list based on free
21 * space recency. Two passes are used to first prioritize discarding extents
22 * and then allow for trimming in the bitmap the best opportunity to coalesce.
23 * The block_groups are maintained on multiple lists to allow for multiple
24 * passes with different discard filter requirements. A delayed work item is
25 * used to manage discarding with timeout determined by a max of the delay
26 * incurred by the iops rate limit, the byte rate limit, and the max delay of
27 * BTRFS_DISCARD_MAX_DELAY.
28 *
29 * Note, this only keeps track of block_groups that are explicitly for data.
30 * Mixed block_groups are not supported.
31 *
32 * The first list is special to manage discarding of fully free block groups.
33 * This is necessary because we issue a final trim for a full free block group
34 * after forgetting it. When a block group becomes unused, instead of directly
35 * being added to the unused_bgs list, we add it to this first list. Then
36 * from there, if it becomes fully discarded, we place it onto the unused_bgs
37 * list.
38 *
39 * The in-memory free space cache serves as the backing state for discard.
40 * Consequently this means there is no persistence. We opt to load all the
41 * block groups in as not discarded, so the mount case degenerates to the
42 * crashing case.
43 *
44 * As the free space cache uses bitmaps, there exists a tradeoff between
45 * ease/efficiency for find_free_extent() and the accuracy of discard state.
46 * Here we opt to let untrimmed regions merge with everything while only letting
47 * trimmed regions merge with other trimmed regions. This can cause
48 * overtrimming, but the coalescing benefit seems to be worth it. Additionally,
49 * bitmap state is tracked as a whole. If we're able to fully trim a bitmap,
50 * the trimmed flag is set on the bitmap. Otherwise, if an allocation comes in,
51 * this resets the state and we will retry trimming the whole bitmap. This is a
52 * tradeoff between discard state accuracy and the cost of accounting.
53 */
54
55 /* This is an initial delay to give some chance for block reuse */
56 #define BTRFS_DISCARD_DELAY (120ULL * NSEC_PER_SEC)
57 #define BTRFS_DISCARD_UNUSED_DELAY (10ULL * NSEC_PER_SEC)
58
59 #define BTRFS_DISCARD_MIN_DELAY_MSEC (1UL)
60 #define BTRFS_DISCARD_MAX_DELAY_MSEC (1000UL)
61 #define BTRFS_DISCARD_MAX_IOPS (1000U)
62
63 /* Monotonically decreasing minimum length filters after index 0 */
64 static int discard_minlen[BTRFS_NR_DISCARD_LISTS] = {
65 0,
66 BTRFS_ASYNC_DISCARD_MAX_FILTER,
67 BTRFS_ASYNC_DISCARD_MIN_FILTER
68 };
69
70 static struct list_head *get_discard_list(struct btrfs_discard_ctl *discard_ctl,
71 struct btrfs_block_group *block_group)
72 {
73 return &discard_ctl->discard_list[block_group->discard_index];
74 }
75
76 /*
77 * Determine if async discard should be running.
78 *
79 * @discard_ctl: discard control
80 *
81 * Check if the file system is writeable and BTRFS_FS_DISCARD_RUNNING is set.
82 */
83 static bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
84 {
85 struct btrfs_fs_info *fs_info = container_of(discard_ctl,
86 struct btrfs_fs_info,
87 discard_ctl);
88
89 return (!(fs_info->sb->s_flags & SB_RDONLY) &&
90 test_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags));
91 }
92
93 static void __add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
94 struct btrfs_block_group *block_group)
95 {
96 lockdep_assert_held(&discard_ctl->lock);
97 if (!btrfs_run_discard_work(discard_ctl))
98 return;
99
100 if (list_empty(&block_group->discard_list) ||
101 block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED) {
102 if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED)
103 block_group->discard_index = BTRFS_DISCARD_INDEX_START;
104 block_group->discard_eligible_time = (ktime_get_ns() +
105 BTRFS_DISCARD_DELAY);
106 block_group->discard_state = BTRFS_DISCARD_RESET_CURSOR;
107 }
108 if (list_empty(&block_group->discard_list))
109 btrfs_get_block_group(block_group);
110
111 list_move_tail(&block_group->discard_list,
112 get_discard_list(discard_ctl, block_group));
113 }
114
115 static void add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
116 struct btrfs_block_group *block_group)
117 {
118 if (!btrfs_is_block_group_data_only(block_group))
119 return;
120
121 spin_lock(&discard_ctl->lock);
122 __add_to_discard_list(discard_ctl, block_group);
123 spin_unlock(&discard_ctl->lock);
124 }
125
126 static void add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
127 struct btrfs_block_group *block_group)
128 {
129 bool queued;
130
131 spin_lock(&discard_ctl->lock);
132
133 queued = !list_empty(&block_group->discard_list);
134
135 if (!btrfs_run_discard_work(discard_ctl)) {
136 spin_unlock(&discard_ctl->lock);
137 return;
138 }
139
140 list_del_init(&block_group->discard_list);
141
142 block_group->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
143 block_group->discard_eligible_time = (ktime_get_ns() +
144 BTRFS_DISCARD_UNUSED_DELAY);
145 block_group->discard_state = BTRFS_DISCARD_RESET_CURSOR;
146 if (!queued)
147 btrfs_get_block_group(block_group);
148 list_add_tail(&block_group->discard_list,
149 &discard_ctl->discard_list[BTRFS_DISCARD_INDEX_UNUSED]);
150
151 spin_unlock(&discard_ctl->lock);
152 }
153
154 static bool remove_from_discard_list(struct btrfs_discard_ctl *discard_ctl,
155 struct btrfs_block_group *block_group)
156 {
157 bool running = false;
158 bool queued = false;
159
160 spin_lock(&discard_ctl->lock);
161
162 if (block_group == discard_ctl->block_group) {
163 running = true;
164 discard_ctl->block_group = NULL;
165 }
166
167 block_group->discard_eligible_time = 0;
168 queued = !list_empty(&block_group->discard_list);
169 list_del_init(&block_group->discard_list);
170 /*
171 * If the block group is currently running in the discard workfn, we
172 * don't want to deref it, since it's still being used by the workfn.
173 * The workfn will notice this case and deref the block group when it is
174 * finished.
175 */
176 if (queued && !running)
177 btrfs_put_block_group(block_group);
178
179 spin_unlock(&discard_ctl->lock);
180
181 return running;
182 }
183
184 /*
185 * Find block_group that's up next for discarding.
186 *
187 * @discard_ctl: discard control
188 * @now: current time
189 *
190 * Iterate over the discard lists to find the next block_group up for
191 * discarding checking the discard_eligible_time of block_group.
192 */
193 static struct btrfs_block_group *find_next_block_group(
194 struct btrfs_discard_ctl *discard_ctl,
195 u64 now)
196 {
197 struct btrfs_block_group *ret_block_group = NULL, *block_group;
198 int i;
199
200 for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++) {
201 struct list_head *discard_list = &discard_ctl->discard_list[i];
202
203 if (!list_empty(discard_list)) {
204 block_group = list_first_entry(discard_list,
205 struct btrfs_block_group,
206 discard_list);
207
208 if (!ret_block_group)
209 ret_block_group = block_group;
210
211 if (ret_block_group->discard_eligible_time < now)
212 break;
213
214 if (ret_block_group->discard_eligible_time >
215 block_group->discard_eligible_time)
216 ret_block_group = block_group;
217 }
218 }
219
220 return ret_block_group;
221 }
222
223 /*
224 * Look up next block group and set it for use.
225 *
226 * @discard_ctl: discard control
227 * @discard_state: the discard_state of the block_group after state management
228 * @discard_index: the discard_index of the block_group after state management
229 * @now: time when discard was invoked, in ns
230 *
231 * Wrap find_next_block_group() and set the block_group to be in use.
232 * @discard_state's control flow is managed here. Variables related to
233 * @discard_state are reset here as needed (eg. @discard_cursor). @discard_state
234 * and @discard_index are remembered as it may change while we're discarding,
235 * but we want the discard to execute in the context determined here.
236 */
237 static struct btrfs_block_group *peek_discard_list(
238 struct btrfs_discard_ctl *discard_ctl,
239 enum btrfs_discard_state *discard_state,
240 int *discard_index, u64 now)
241 {
242 struct btrfs_block_group *block_group;
243
244 spin_lock(&discard_ctl->lock);
245 again:
246 block_group = find_next_block_group(discard_ctl, now);
247
248 if (block_group && now >= block_group->discard_eligible_time) {
249 if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&
250 block_group->used != 0) {
251 if (btrfs_is_block_group_data_only(block_group)) {
252 __add_to_discard_list(discard_ctl, block_group);
253 } else {
254 list_del_init(&block_group->discard_list);
255 btrfs_put_block_group(block_group);
256 }
257 goto again;
258 }
259 if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
260 block_group->discard_cursor = block_group->start;
261 block_group->discard_state = BTRFS_DISCARD_EXTENTS;
262 }
263 discard_ctl->block_group = block_group;
264 }
265 if (block_group) {
266 *discard_state = block_group->discard_state;
267 *discard_index = block_group->discard_index;
268 }
269 spin_unlock(&discard_ctl->lock);
270
271 return block_group;
272 }
273
274 /*
275 * Update a block group's filters.
276 *
277 * @block_group: block group of interest
278 * @bytes: recently freed region size after coalescing
279 *
280 * Async discard maintains multiple lists with progressively smaller filters
281 * to prioritize discarding based on size. Should a free space that matches
282 * a larger filter be returned to the free_space_cache, prioritize that discard
283 * by moving @block_group to the proper filter.
284 */
285 void btrfs_discard_check_filter(struct btrfs_block_group *block_group,
286 u64 bytes)
287 {
288 struct btrfs_discard_ctl *discard_ctl;
289
290 if (!block_group ||
291 !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
292 return;
293
294 discard_ctl = &block_group->fs_info->discard_ctl;
295
296 if (block_group->discard_index > BTRFS_DISCARD_INDEX_START &&
297 bytes >= discard_minlen[block_group->discard_index - 1]) {
298 int i;
299
300 remove_from_discard_list(discard_ctl, block_group);
301
302 for (i = BTRFS_DISCARD_INDEX_START; i < BTRFS_NR_DISCARD_LISTS;
303 i++) {
304 if (bytes >= discard_minlen[i]) {
305 block_group->discard_index = i;
306 add_to_discard_list(discard_ctl, block_group);
307 break;
308 }
309 }
310 }
311 }
312
313 /*
314 * Move a block group along the discard lists.
315 *
316 * @discard_ctl: discard control
317 * @block_group: block_group of interest
318 *
319 * Increment @block_group's discard_index. If it falls of the list, let it be.
320 * Otherwise add it back to the appropriate list.
321 */
322 static void btrfs_update_discard_index(struct btrfs_discard_ctl *discard_ctl,
323 struct btrfs_block_group *block_group)
324 {
325 block_group->discard_index++;
326 if (block_group->discard_index == BTRFS_NR_DISCARD_LISTS) {
327 block_group->discard_index = 1;
328 return;
329 }
330
331 add_to_discard_list(discard_ctl, block_group);
332 }
333
334 /*
335 * Remove a block_group from the discard lists.
336 *
337 * @discard_ctl: discard control
338 * @block_group: block_group of interest
339 *
340 * Remove @block_group from the discard lists. If necessary, wait on the
341 * current work and then reschedule the delayed work.
342 */
343 void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
344 struct btrfs_block_group *block_group)
345 {
346 if (remove_from_discard_list(discard_ctl, block_group)) {
347 cancel_delayed_work_sync(&discard_ctl->work);
348 btrfs_discard_schedule_work(discard_ctl, true);
349 }
350 }
351
352 /*
353 * Handles queuing the block_groups.
354 *
355 * @discard_ctl: discard control
356 * @block_group: block_group of interest
357 *
358 * Maintain the LRU order of the discard lists.
359 */
360 void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
361 struct btrfs_block_group *block_group)
362 {
363 if (!block_group || !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
364 return;
365
366 if (block_group->used == 0)
367 add_to_discard_unused_list(discard_ctl, block_group);
368 else
369 add_to_discard_list(discard_ctl, block_group);
370
371 if (!delayed_work_pending(&discard_ctl->work))
372 btrfs_discard_schedule_work(discard_ctl, false);
373 }
374
375 static void __btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
376 u64 now, bool override)
377 {
378 struct btrfs_block_group *block_group;
379
380 if (!btrfs_run_discard_work(discard_ctl))
381 return;
382 if (!override && delayed_work_pending(&discard_ctl->work))
383 return;
384
385 block_group = find_next_block_group(discard_ctl, now);
386 if (block_group) {
387 u64 delay = discard_ctl->delay_ms * NSEC_PER_MSEC;
388 u32 kbps_limit = READ_ONCE(discard_ctl->kbps_limit);
389
390 /*
391 * A single delayed workqueue item is responsible for
392 * discarding, so we can manage the bytes rate limit by keeping
393 * track of the previous discard.
394 */
395 if (kbps_limit && discard_ctl->prev_discard) {
396 u64 bps_limit = ((u64)kbps_limit) * SZ_1K;
397 u64 bps_delay = div64_u64(discard_ctl->prev_discard *
398 NSEC_PER_SEC, bps_limit);
399
400 delay = max(delay, bps_delay);
401 }
402
403 /*
404 * This timeout is to hopefully prevent immediate discarding
405 * in a recently allocated block group.
406 */
407 if (now < block_group->discard_eligible_time) {
408 u64 bg_timeout = block_group->discard_eligible_time - now;
409
410 delay = max(delay, bg_timeout);
411 }
412
413 if (override && discard_ctl->prev_discard) {
414 u64 elapsed = now - discard_ctl->prev_discard_time;
415
416 if (delay > elapsed)
417 delay -= elapsed;
418 else
419 delay = 0;
420 }
421
422 mod_delayed_work(discard_ctl->discard_workers,
423 &discard_ctl->work, nsecs_to_jiffies(delay));
424 }
425 }
426
427 /*
428 * Responsible for scheduling the discard work.
429 *
430 * @discard_ctl: discard control
431 * @override: override the current timer
432 *
433 * Discards are issued by a delayed workqueue item. @override is used to
434 * update the current delay as the baseline delay interval is reevaluated on
435 * transaction commit. This is also maxed with any other rate limit.
436 */
437 void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
438 bool override)
439 {
440 const u64 now = ktime_get_ns();
441
442 spin_lock(&discard_ctl->lock);
443 __btrfs_discard_schedule_work(discard_ctl, now, override);
444 spin_unlock(&discard_ctl->lock);
445 }
446
447 /*
448 * Determine next step of a block_group.
449 *
450 * @discard_ctl: discard control
451 * @block_group: block_group of interest
452 *
453 * Determine the next step for a block group after it's finished going through
454 * a pass on a discard list. If it is unused and fully trimmed, we can mark it
455 * unused and send it to the unused_bgs path. Otherwise, pass it onto the
456 * appropriate filter list or let it fall off.
457 */
458 static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
459 struct btrfs_block_group *block_group)
460 {
461 remove_from_discard_list(discard_ctl, block_group);
462
463 if (block_group->used == 0) {
464 if (btrfs_is_free_space_trimmed(block_group))
465 btrfs_mark_bg_unused(block_group);
466 else
467 add_to_discard_unused_list(discard_ctl, block_group);
468 } else {
469 btrfs_update_discard_index(discard_ctl, block_group);
470 }
471 }
472
473 /*
474 * Discard work queue callback
475 *
476 * @work: work
477 *
478 * Find the next block_group to start discarding and then discard a single
479 * region. It does this in a two-pass fashion: first extents and second
480 * bitmaps. Completely discarded block groups are sent to the unused_bgs path.
481 */
482 static void btrfs_discard_workfn(struct work_struct *work)
483 {
484 struct btrfs_discard_ctl *discard_ctl;
485 struct btrfs_block_group *block_group;
486 enum btrfs_discard_state discard_state;
487 int discard_index = 0;
488 u64 trimmed = 0;
489 u64 minlen = 0;
490 u64 now = ktime_get_ns();
491
492 discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work);
493
494 block_group = peek_discard_list(discard_ctl, &discard_state,
495 &discard_index, now);
496 if (!block_group || !btrfs_run_discard_work(discard_ctl))
497 return;
498 if (now < block_group->discard_eligible_time) {
499 btrfs_discard_schedule_work(discard_ctl, false);
500 return;
501 }
502
503 /* Perform discarding */
504 minlen = discard_minlen[discard_index];
505
506 if (discard_state == BTRFS_DISCARD_BITMAPS) {
507 u64 maxlen = 0;
508
509 /*
510 * Use the previous levels minimum discard length as the max
511 * length filter. In the case something is added to make a
512 * region go beyond the max filter, the entire bitmap is set
513 * back to BTRFS_TRIM_STATE_UNTRIMMED.
514 */
515 if (discard_index != BTRFS_DISCARD_INDEX_UNUSED)
516 maxlen = discard_minlen[discard_index - 1];
517
518 btrfs_trim_block_group_bitmaps(block_group, &trimmed,
519 block_group->discard_cursor,
520 btrfs_block_group_end(block_group),
521 minlen, maxlen, true);
522 discard_ctl->discard_bitmap_bytes += trimmed;
523 } else {
524 btrfs_trim_block_group_extents(block_group, &trimmed,
525 block_group->discard_cursor,
526 btrfs_block_group_end(block_group),
527 minlen, true);
528 discard_ctl->discard_extent_bytes += trimmed;
529 }
530
531 /* Determine next steps for a block_group */
532 if (block_group->discard_cursor >= btrfs_block_group_end(block_group)) {
533 if (discard_state == BTRFS_DISCARD_BITMAPS) {
534 btrfs_finish_discard_pass(discard_ctl, block_group);
535 } else {
536 block_group->discard_cursor = block_group->start;
537 spin_lock(&discard_ctl->lock);
538 if (block_group->discard_state !=
539 BTRFS_DISCARD_RESET_CURSOR)
540 block_group->discard_state =
541 BTRFS_DISCARD_BITMAPS;
542 spin_unlock(&discard_ctl->lock);
543 }
544 }
545
546 now = ktime_get_ns();
547 spin_lock(&discard_ctl->lock);
548 discard_ctl->prev_discard = trimmed;
549 discard_ctl->prev_discard_time = now;
550 /*
551 * If the block group was removed from the discard list while it was
552 * running in this workfn, then we didn't deref it, since this function
553 * still owned that reference. But we set the discard_ctl->block_group
554 * back to NULL, so we can use that condition to know that now we need
555 * to deref the block_group.
556 */
557 if (discard_ctl->block_group == NULL)
558 btrfs_put_block_group(block_group);
559 discard_ctl->block_group = NULL;
560 __btrfs_discard_schedule_work(discard_ctl, now, false);
561 spin_unlock(&discard_ctl->lock);
562 }
563
564 /*
565 * Recalculate the base delay.
566 *
567 * @discard_ctl: discard control
568 *
569 * Recalculate the base delay which is based off the total number of
570 * discardable_extents. Clamp this between the lower_limit (iops_limit or 1ms)
571 * and the upper_limit (BTRFS_DISCARD_MAX_DELAY_MSEC).
572 */
573 void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl)
574 {
575 s32 discardable_extents;
576 s64 discardable_bytes;
577 u32 iops_limit;
578 unsigned long min_delay = BTRFS_DISCARD_MIN_DELAY_MSEC;
579 unsigned long delay;
580
581 discardable_extents = atomic_read(&discard_ctl->discardable_extents);
582 if (!discardable_extents)
583 return;
584
585 spin_lock(&discard_ctl->lock);
586
587 /*
588 * The following is to fix a potential -1 discrepancy that we're not
589 * sure how to reproduce. But given that this is the only place that
590 * utilizes these numbers and this is only called by from
591 * btrfs_finish_extent_commit() which is synchronized, we can correct
592 * here.
593 */
594 if (discardable_extents < 0)
595 atomic_add(-discardable_extents,
596 &discard_ctl->discardable_extents);
597
598 discardable_bytes = atomic64_read(&discard_ctl->discardable_bytes);
599 if (discardable_bytes < 0)
600 atomic64_add(-discardable_bytes,
601 &discard_ctl->discardable_bytes);
602
603 if (discardable_extents <= 0) {
604 spin_unlock(&discard_ctl->lock);
605 return;
606 }
607
608 iops_limit = READ_ONCE(discard_ctl->iops_limit);
609
610 if (iops_limit) {
611 delay = MSEC_PER_SEC / iops_limit;
612 } else {
613 /*
614 * Unset iops_limit means go as fast as possible, so allow a
615 * delay of 0.
616 */
617 delay = 0;
618 min_delay = 0;
619 }
620
621 delay = clamp(delay, min_delay, BTRFS_DISCARD_MAX_DELAY_MSEC);
622 discard_ctl->delay_ms = delay;
623
624 spin_unlock(&discard_ctl->lock);
625 }
626
627 /*
628 * Propagate discard counters.
629 *
630 * @block_group: block_group of interest
631 *
632 * Propagate deltas of counters up to the discard_ctl. It maintains a current
633 * counter and a previous counter passing the delta up to the global stat.
634 * Then the current counter value becomes the previous counter value.
635 */
636 void btrfs_discard_update_discardable(struct btrfs_block_group *block_group)
637 {
638 struct btrfs_free_space_ctl *ctl;
639 struct btrfs_discard_ctl *discard_ctl;
640 s32 extents_delta;
641 s64 bytes_delta;
642
643 if (!block_group ||
644 !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC) ||
645 !btrfs_is_block_group_data_only(block_group))
646 return;
647
648 ctl = block_group->free_space_ctl;
649 discard_ctl = &block_group->fs_info->discard_ctl;
650
651 lockdep_assert_held(&ctl->tree_lock);
652 extents_delta = ctl->discardable_extents[BTRFS_STAT_CURR] -
653 ctl->discardable_extents[BTRFS_STAT_PREV];
654 if (extents_delta) {
655 atomic_add(extents_delta, &discard_ctl->discardable_extents);
656 ctl->discardable_extents[BTRFS_STAT_PREV] =
657 ctl->discardable_extents[BTRFS_STAT_CURR];
658 }
659
660 bytes_delta = ctl->discardable_bytes[BTRFS_STAT_CURR] -
661 ctl->discardable_bytes[BTRFS_STAT_PREV];
662 if (bytes_delta) {
663 atomic64_add(bytes_delta, &discard_ctl->discardable_bytes);
664 ctl->discardable_bytes[BTRFS_STAT_PREV] =
665 ctl->discardable_bytes[BTRFS_STAT_CURR];
666 }
667 }
668
669 /*
670 * Punt unused_bgs list to discard lists.
671 *
672 * @fs_info: fs_info of interest
673 *
674 * The unused_bgs list needs to be punted to the discard lists because the
675 * order of operations is changed. In the normal synchronous discard path, the
676 * block groups are trimmed via a single large trim in transaction commit. This
677 * is ultimately what we are trying to avoid with asynchronous discard. Thus,
678 * it must be done before going down the unused_bgs path.
679 */
680 void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info)
681 {
682 struct btrfs_block_group *block_group, *next;
683
684 spin_lock(&fs_info->unused_bgs_lock);
685 /* We enabled async discard, so punt all to the queue */
686 list_for_each_entry_safe(block_group, next, &fs_info->unused_bgs,
687 bg_list) {
688 list_del_init(&block_group->bg_list);
689 btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
690 /*
691 * This put is for the get done by btrfs_mark_bg_unused.
692 * Queueing discard incremented it for discard's reference.
693 */
694 btrfs_put_block_group(block_group);
695 }
696 spin_unlock(&fs_info->unused_bgs_lock);
697 }
698
699 /*
700 * Purge discard lists.
701 *
702 * @discard_ctl: discard control
703 *
704 * If we are disabling async discard, we may have intercepted block groups that
705 * are completely free and ready for the unused_bgs path. As discarding will
706 * now happen in transaction commit or not at all, we can safely mark the
707 * corresponding block groups as unused and they will be sent on their merry
708 * way to the unused_bgs list.
709 */
710 static void btrfs_discard_purge_list(struct btrfs_discard_ctl *discard_ctl)
711 {
712 struct btrfs_block_group *block_group, *next;
713 int i;
714
715 spin_lock(&discard_ctl->lock);
716 for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++) {
717 list_for_each_entry_safe(block_group, next,
718 &discard_ctl->discard_list[i],
719 discard_list) {
720 list_del_init(&block_group->discard_list);
721 spin_unlock(&discard_ctl->lock);
722 if (block_group->used == 0)
723 btrfs_mark_bg_unused(block_group);
724 spin_lock(&discard_ctl->lock);
725 btrfs_put_block_group(block_group);
726 }
727 }
728 spin_unlock(&discard_ctl->lock);
729 }
730
731 void btrfs_discard_resume(struct btrfs_fs_info *fs_info)
732 {
733 if (!btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
734 btrfs_discard_cleanup(fs_info);
735 return;
736 }
737
738 btrfs_discard_punt_unused_bgs_list(fs_info);
739
740 set_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
741 }
742
743 void btrfs_discard_stop(struct btrfs_fs_info *fs_info)
744 {
745 clear_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
746 }
747
748 void btrfs_discard_init(struct btrfs_fs_info *fs_info)
749 {
750 struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
751 int i;
752
753 spin_lock_init(&discard_ctl->lock);
754 INIT_DELAYED_WORK(&discard_ctl->work, btrfs_discard_workfn);
755
756 for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
757 INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
758
759 discard_ctl->prev_discard = 0;
760 discard_ctl->prev_discard_time = 0;
761 atomic_set(&discard_ctl->discardable_extents, 0);
762 atomic64_set(&discard_ctl->discardable_bytes, 0);
763 discard_ctl->max_discard_size = BTRFS_ASYNC_DISCARD_DEFAULT_MAX_SIZE;
764 discard_ctl->delay_ms = BTRFS_DISCARD_MAX_DELAY_MSEC;
765 discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
766 discard_ctl->kbps_limit = 0;
767 discard_ctl->discard_extent_bytes = 0;
768 discard_ctl->discard_bitmap_bytes = 0;
769 atomic64_set(&discard_ctl->discard_bytes_saved, 0);
770 }
771
772 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
773 {
774 btrfs_discard_stop(fs_info);
775 cancel_delayed_work_sync(&fs_info->discard_ctl.work);
776 btrfs_discard_purge_list(&fs_info->discard_ctl);
777 }
778
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