Loading...
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2011 STRATO. All rights reserved.
4 */
5
6#include <linux/sched.h>
7#include <linux/pagemap.h>
8#include <linux/writeback.h>
9#include <linux/blkdev.h>
10#include <linux/rbtree.h>
11#include <linux/slab.h>
12#include <linux/workqueue.h>
13#include "ctree.h"
14#include "volumes.h"
15#include "disk-io.h"
16#include "transaction.h"
17#include "dev-replace.h"
18
19#undef DEBUG
20
21/*
22 * This is the implementation for the generic read ahead framework.
23 *
24 * To trigger a readahead, btrfs_reada_add must be called. It will start
25 * a read ahead for the given range [start, end) on tree root. The returned
26 * handle can either be used to wait on the readahead to finish
27 * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
28 *
29 * The read ahead works as follows:
30 * On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
31 * reada_start_machine will then search for extents to prefetch and trigger
32 * some reads. When a read finishes for a node, all contained node/leaf
33 * pointers that lie in the given range will also be enqueued. The reads will
34 * be triggered in sequential order, thus giving a big win over a naive
35 * enumeration. It will also make use of multi-device layouts. Each disk
36 * will have its on read pointer and all disks will by utilized in parallel.
37 * Also will no two disks read both sides of a mirror simultaneously, as this
38 * would waste seeking capacity. Instead both disks will read different parts
39 * of the filesystem.
40 * Any number of readaheads can be started in parallel. The read order will be
41 * determined globally, i.e. 2 parallel readaheads will normally finish faster
42 * than the 2 started one after another.
43 */
44
45#define MAX_IN_FLIGHT 6
46
47struct reada_extctl {
48 struct list_head list;
49 struct reada_control *rc;
50 u64 generation;
51};
52
53struct reada_extent {
54 u64 logical;
55 struct btrfs_key top;
56 struct list_head extctl;
57 int refcnt;
58 spinlock_t lock;
59 struct reada_zone *zones[BTRFS_MAX_MIRRORS];
60 int nzones;
61 int scheduled;
62};
63
64struct reada_zone {
65 u64 start;
66 u64 end;
67 u64 elems;
68 struct list_head list;
69 spinlock_t lock;
70 int locked;
71 struct btrfs_device *device;
72 struct btrfs_device *devs[BTRFS_MAX_MIRRORS]; /* full list, incl
73 * self */
74 int ndevs;
75 struct kref refcnt;
76};
77
78struct reada_machine_work {
79 struct btrfs_work work;
80 struct btrfs_fs_info *fs_info;
81};
82
83static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
84static void reada_control_release(struct kref *kref);
85static void reada_zone_release(struct kref *kref);
86static void reada_start_machine(struct btrfs_fs_info *fs_info);
87static void __reada_start_machine(struct btrfs_fs_info *fs_info);
88
89static int reada_add_block(struct reada_control *rc, u64 logical,
90 struct btrfs_key *top, u64 generation);
91
92/* recurses */
93/* in case of err, eb might be NULL */
94static void __readahead_hook(struct btrfs_fs_info *fs_info,
95 struct reada_extent *re, struct extent_buffer *eb,
96 int err)
97{
98 int nritems;
99 int i;
100 u64 bytenr;
101 u64 generation;
102 struct list_head list;
103
104 spin_lock(&re->lock);
105 /*
106 * just take the full list from the extent. afterwards we
107 * don't need the lock anymore
108 */
109 list_replace_init(&re->extctl, &list);
110 re->scheduled = 0;
111 spin_unlock(&re->lock);
112
113 /*
114 * this is the error case, the extent buffer has not been
115 * read correctly. We won't access anything from it and
116 * just cleanup our data structures. Effectively this will
117 * cut the branch below this node from read ahead.
118 */
119 if (err)
120 goto cleanup;
121
122 /*
123 * FIXME: currently we just set nritems to 0 if this is a leaf,
124 * effectively ignoring the content. In a next step we could
125 * trigger more readahead depending from the content, e.g.
126 * fetch the checksums for the extents in the leaf.
127 */
128 if (!btrfs_header_level(eb))
129 goto cleanup;
130
131 nritems = btrfs_header_nritems(eb);
132 generation = btrfs_header_generation(eb);
133 for (i = 0; i < nritems; i++) {
134 struct reada_extctl *rec;
135 u64 n_gen;
136 struct btrfs_key key;
137 struct btrfs_key next_key;
138
139 btrfs_node_key_to_cpu(eb, &key, i);
140 if (i + 1 < nritems)
141 btrfs_node_key_to_cpu(eb, &next_key, i + 1);
142 else
143 next_key = re->top;
144 bytenr = btrfs_node_blockptr(eb, i);
145 n_gen = btrfs_node_ptr_generation(eb, i);
146
147 list_for_each_entry(rec, &list, list) {
148 struct reada_control *rc = rec->rc;
149
150 /*
151 * if the generation doesn't match, just ignore this
152 * extctl. This will probably cut off a branch from
153 * prefetch. Alternatively one could start a new (sub-)
154 * prefetch for this branch, starting again from root.
155 * FIXME: move the generation check out of this loop
156 */
157#ifdef DEBUG
158 if (rec->generation != generation) {
159 btrfs_debug(fs_info,
160 "generation mismatch for (%llu,%d,%llu) %llu != %llu",
161 key.objectid, key.type, key.offset,
162 rec->generation, generation);
163 }
164#endif
165 if (rec->generation == generation &&
166 btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 &&
167 btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0)
168 reada_add_block(rc, bytenr, &next_key, n_gen);
169 }
170 }
171
172cleanup:
173 /*
174 * free extctl records
175 */
176 while (!list_empty(&list)) {
177 struct reada_control *rc;
178 struct reada_extctl *rec;
179
180 rec = list_first_entry(&list, struct reada_extctl, list);
181 list_del(&rec->list);
182 rc = rec->rc;
183 kfree(rec);
184
185 kref_get(&rc->refcnt);
186 if (atomic_dec_and_test(&rc->elems)) {
187 kref_put(&rc->refcnt, reada_control_release);
188 wake_up(&rc->wait);
189 }
190 kref_put(&rc->refcnt, reada_control_release);
191
192 reada_extent_put(fs_info, re); /* one ref for each entry */
193 }
194
195 return;
196}
197
198int btree_readahead_hook(struct extent_buffer *eb, int err)
199{
200 struct btrfs_fs_info *fs_info = eb->fs_info;
201 int ret = 0;
202 struct reada_extent *re;
203
204 /* find extent */
205 spin_lock(&fs_info->reada_lock);
206 re = radix_tree_lookup(&fs_info->reada_tree,
207 eb->start >> PAGE_SHIFT);
208 if (re)
209 re->refcnt++;
210 spin_unlock(&fs_info->reada_lock);
211 if (!re) {
212 ret = -1;
213 goto start_machine;
214 }
215
216 __readahead_hook(fs_info, re, eb, err);
217 reada_extent_put(fs_info, re); /* our ref */
218
219start_machine:
220 reada_start_machine(fs_info);
221 return ret;
222}
223
224static struct reada_zone *reada_find_zone(struct btrfs_device *dev, u64 logical,
225 struct btrfs_bio *bbio)
226{
227 struct btrfs_fs_info *fs_info = dev->fs_info;
228 int ret;
229 struct reada_zone *zone;
230 struct btrfs_block_group_cache *cache = NULL;
231 u64 start;
232 u64 end;
233 int i;
234
235 zone = NULL;
236 spin_lock(&fs_info->reada_lock);
237 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
238 logical >> PAGE_SHIFT, 1);
239 if (ret == 1 && logical >= zone->start && logical <= zone->end) {
240 kref_get(&zone->refcnt);
241 spin_unlock(&fs_info->reada_lock);
242 return zone;
243 }
244
245 spin_unlock(&fs_info->reada_lock);
246
247 cache = btrfs_lookup_block_group(fs_info, logical);
248 if (!cache)
249 return NULL;
250
251 start = cache->key.objectid;
252 end = start + cache->key.offset - 1;
253 btrfs_put_block_group(cache);
254
255 zone = kzalloc(sizeof(*zone), GFP_KERNEL);
256 if (!zone)
257 return NULL;
258
259 ret = radix_tree_preload(GFP_KERNEL);
260 if (ret) {
261 kfree(zone);
262 return NULL;
263 }
264
265 zone->start = start;
266 zone->end = end;
267 INIT_LIST_HEAD(&zone->list);
268 spin_lock_init(&zone->lock);
269 zone->locked = 0;
270 kref_init(&zone->refcnt);
271 zone->elems = 0;
272 zone->device = dev; /* our device always sits at index 0 */
273 for (i = 0; i < bbio->num_stripes; ++i) {
274 /* bounds have already been checked */
275 zone->devs[i] = bbio->stripes[i].dev;
276 }
277 zone->ndevs = bbio->num_stripes;
278
279 spin_lock(&fs_info->reada_lock);
280 ret = radix_tree_insert(&dev->reada_zones,
281 (unsigned long)(zone->end >> PAGE_SHIFT),
282 zone);
283
284 if (ret == -EEXIST) {
285 kfree(zone);
286 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
287 logical >> PAGE_SHIFT, 1);
288 if (ret == 1 && logical >= zone->start && logical <= zone->end)
289 kref_get(&zone->refcnt);
290 else
291 zone = NULL;
292 }
293 spin_unlock(&fs_info->reada_lock);
294 radix_tree_preload_end();
295
296 return zone;
297}
298
299static struct reada_extent *reada_find_extent(struct btrfs_fs_info *fs_info,
300 u64 logical,
301 struct btrfs_key *top)
302{
303 int ret;
304 struct reada_extent *re = NULL;
305 struct reada_extent *re_exist = NULL;
306 struct btrfs_bio *bbio = NULL;
307 struct btrfs_device *dev;
308 struct btrfs_device *prev_dev;
309 u64 length;
310 int real_stripes;
311 int nzones = 0;
312 unsigned long index = logical >> PAGE_SHIFT;
313 int dev_replace_is_ongoing;
314 int have_zone = 0;
315
316 spin_lock(&fs_info->reada_lock);
317 re = radix_tree_lookup(&fs_info->reada_tree, index);
318 if (re)
319 re->refcnt++;
320 spin_unlock(&fs_info->reada_lock);
321
322 if (re)
323 return re;
324
325 re = kzalloc(sizeof(*re), GFP_KERNEL);
326 if (!re)
327 return NULL;
328
329 re->logical = logical;
330 re->top = *top;
331 INIT_LIST_HEAD(&re->extctl);
332 spin_lock_init(&re->lock);
333 re->refcnt = 1;
334
335 /*
336 * map block
337 */
338 length = fs_info->nodesize;
339 ret = btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical,
340 &length, &bbio, 0);
341 if (ret || !bbio || length < fs_info->nodesize)
342 goto error;
343
344 if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
345 btrfs_err(fs_info,
346 "readahead: more than %d copies not supported",
347 BTRFS_MAX_MIRRORS);
348 goto error;
349 }
350
351 real_stripes = bbio->num_stripes - bbio->num_tgtdevs;
352 for (nzones = 0; nzones < real_stripes; ++nzones) {
353 struct reada_zone *zone;
354
355 dev = bbio->stripes[nzones].dev;
356
357 /* cannot read ahead on missing device. */
358 if (!dev->bdev)
359 continue;
360
361 zone = reada_find_zone(dev, logical, bbio);
362 if (!zone)
363 continue;
364
365 re->zones[re->nzones++] = zone;
366 spin_lock(&zone->lock);
367 if (!zone->elems)
368 kref_get(&zone->refcnt);
369 ++zone->elems;
370 spin_unlock(&zone->lock);
371 spin_lock(&fs_info->reada_lock);
372 kref_put(&zone->refcnt, reada_zone_release);
373 spin_unlock(&fs_info->reada_lock);
374 }
375 if (re->nzones == 0) {
376 /* not a single zone found, error and out */
377 goto error;
378 }
379
380 ret = radix_tree_preload(GFP_KERNEL);
381 if (ret)
382 goto error;
383
384 /* insert extent in reada_tree + all per-device trees, all or nothing */
385 btrfs_dev_replace_read_lock(&fs_info->dev_replace);
386 spin_lock(&fs_info->reada_lock);
387 ret = radix_tree_insert(&fs_info->reada_tree, index, re);
388 if (ret == -EEXIST) {
389 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
390 re_exist->refcnt++;
391 spin_unlock(&fs_info->reada_lock);
392 btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
393 radix_tree_preload_end();
394 goto error;
395 }
396 if (ret) {
397 spin_unlock(&fs_info->reada_lock);
398 btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
399 radix_tree_preload_end();
400 goto error;
401 }
402 radix_tree_preload_end();
403 prev_dev = NULL;
404 dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
405 &fs_info->dev_replace);
406 for (nzones = 0; nzones < re->nzones; ++nzones) {
407 dev = re->zones[nzones]->device;
408
409 if (dev == prev_dev) {
410 /*
411 * in case of DUP, just add the first zone. As both
412 * are on the same device, there's nothing to gain
413 * from adding both.
414 * Also, it wouldn't work, as the tree is per device
415 * and adding would fail with EEXIST
416 */
417 continue;
418 }
419 if (!dev->bdev)
420 continue;
421
422 if (dev_replace_is_ongoing &&
423 dev == fs_info->dev_replace.tgtdev) {
424 /*
425 * as this device is selected for reading only as
426 * a last resort, skip it for read ahead.
427 */
428 continue;
429 }
430 prev_dev = dev;
431 ret = radix_tree_insert(&dev->reada_extents, index, re);
432 if (ret) {
433 while (--nzones >= 0) {
434 dev = re->zones[nzones]->device;
435 BUG_ON(dev == NULL);
436 /* ignore whether the entry was inserted */
437 radix_tree_delete(&dev->reada_extents, index);
438 }
439 radix_tree_delete(&fs_info->reada_tree, index);
440 spin_unlock(&fs_info->reada_lock);
441 btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
442 goto error;
443 }
444 have_zone = 1;
445 }
446 spin_unlock(&fs_info->reada_lock);
447 btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
448
449 if (!have_zone)
450 goto error;
451
452 btrfs_put_bbio(bbio);
453 return re;
454
455error:
456 for (nzones = 0; nzones < re->nzones; ++nzones) {
457 struct reada_zone *zone;
458
459 zone = re->zones[nzones];
460 kref_get(&zone->refcnt);
461 spin_lock(&zone->lock);
462 --zone->elems;
463 if (zone->elems == 0) {
464 /*
465 * no fs_info->reada_lock needed, as this can't be
466 * the last ref
467 */
468 kref_put(&zone->refcnt, reada_zone_release);
469 }
470 spin_unlock(&zone->lock);
471
472 spin_lock(&fs_info->reada_lock);
473 kref_put(&zone->refcnt, reada_zone_release);
474 spin_unlock(&fs_info->reada_lock);
475 }
476 btrfs_put_bbio(bbio);
477 kfree(re);
478 return re_exist;
479}
480
481static void reada_extent_put(struct btrfs_fs_info *fs_info,
482 struct reada_extent *re)
483{
484 int i;
485 unsigned long index = re->logical >> PAGE_SHIFT;
486
487 spin_lock(&fs_info->reada_lock);
488 if (--re->refcnt) {
489 spin_unlock(&fs_info->reada_lock);
490 return;
491 }
492
493 radix_tree_delete(&fs_info->reada_tree, index);
494 for (i = 0; i < re->nzones; ++i) {
495 struct reada_zone *zone = re->zones[i];
496
497 radix_tree_delete(&zone->device->reada_extents, index);
498 }
499
500 spin_unlock(&fs_info->reada_lock);
501
502 for (i = 0; i < re->nzones; ++i) {
503 struct reada_zone *zone = re->zones[i];
504
505 kref_get(&zone->refcnt);
506 spin_lock(&zone->lock);
507 --zone->elems;
508 if (zone->elems == 0) {
509 /* no fs_info->reada_lock needed, as this can't be
510 * the last ref */
511 kref_put(&zone->refcnt, reada_zone_release);
512 }
513 spin_unlock(&zone->lock);
514
515 spin_lock(&fs_info->reada_lock);
516 kref_put(&zone->refcnt, reada_zone_release);
517 spin_unlock(&fs_info->reada_lock);
518 }
519
520 kfree(re);
521}
522
523static void reada_zone_release(struct kref *kref)
524{
525 struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
526
527 radix_tree_delete(&zone->device->reada_zones,
528 zone->end >> PAGE_SHIFT);
529
530 kfree(zone);
531}
532
533static void reada_control_release(struct kref *kref)
534{
535 struct reada_control *rc = container_of(kref, struct reada_control,
536 refcnt);
537
538 kfree(rc);
539}
540
541static int reada_add_block(struct reada_control *rc, u64 logical,
542 struct btrfs_key *top, u64 generation)
543{
544 struct btrfs_fs_info *fs_info = rc->fs_info;
545 struct reada_extent *re;
546 struct reada_extctl *rec;
547
548 /* takes one ref */
549 re = reada_find_extent(fs_info, logical, top);
550 if (!re)
551 return -1;
552
553 rec = kzalloc(sizeof(*rec), GFP_KERNEL);
554 if (!rec) {
555 reada_extent_put(fs_info, re);
556 return -ENOMEM;
557 }
558
559 rec->rc = rc;
560 rec->generation = generation;
561 atomic_inc(&rc->elems);
562
563 spin_lock(&re->lock);
564 list_add_tail(&rec->list, &re->extctl);
565 spin_unlock(&re->lock);
566
567 /* leave the ref on the extent */
568
569 return 0;
570}
571
572/*
573 * called with fs_info->reada_lock held
574 */
575static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
576{
577 int i;
578 unsigned long index = zone->end >> PAGE_SHIFT;
579
580 for (i = 0; i < zone->ndevs; ++i) {
581 struct reada_zone *peer;
582 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
583 if (peer && peer->device != zone->device)
584 peer->locked = lock;
585 }
586}
587
588/*
589 * called with fs_info->reada_lock held
590 */
591static int reada_pick_zone(struct btrfs_device *dev)
592{
593 struct reada_zone *top_zone = NULL;
594 struct reada_zone *top_locked_zone = NULL;
595 u64 top_elems = 0;
596 u64 top_locked_elems = 0;
597 unsigned long index = 0;
598 int ret;
599
600 if (dev->reada_curr_zone) {
601 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
602 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
603 dev->reada_curr_zone = NULL;
604 }
605 /* pick the zone with the most elements */
606 while (1) {
607 struct reada_zone *zone;
608
609 ret = radix_tree_gang_lookup(&dev->reada_zones,
610 (void **)&zone, index, 1);
611 if (ret == 0)
612 break;
613 index = (zone->end >> PAGE_SHIFT) + 1;
614 if (zone->locked) {
615 if (zone->elems > top_locked_elems) {
616 top_locked_elems = zone->elems;
617 top_locked_zone = zone;
618 }
619 } else {
620 if (zone->elems > top_elems) {
621 top_elems = zone->elems;
622 top_zone = zone;
623 }
624 }
625 }
626 if (top_zone)
627 dev->reada_curr_zone = top_zone;
628 else if (top_locked_zone)
629 dev->reada_curr_zone = top_locked_zone;
630 else
631 return 0;
632
633 dev->reada_next = dev->reada_curr_zone->start;
634 kref_get(&dev->reada_curr_zone->refcnt);
635 reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
636
637 return 1;
638}
639
640static int reada_start_machine_dev(struct btrfs_device *dev)
641{
642 struct btrfs_fs_info *fs_info = dev->fs_info;
643 struct reada_extent *re = NULL;
644 int mirror_num = 0;
645 struct extent_buffer *eb = NULL;
646 u64 logical;
647 int ret;
648 int i;
649
650 spin_lock(&fs_info->reada_lock);
651 if (dev->reada_curr_zone == NULL) {
652 ret = reada_pick_zone(dev);
653 if (!ret) {
654 spin_unlock(&fs_info->reada_lock);
655 return 0;
656 }
657 }
658 /*
659 * FIXME currently we issue the reads one extent at a time. If we have
660 * a contiguous block of extents, we could also coagulate them or use
661 * plugging to speed things up
662 */
663 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
664 dev->reada_next >> PAGE_SHIFT, 1);
665 if (ret == 0 || re->logical > dev->reada_curr_zone->end) {
666 ret = reada_pick_zone(dev);
667 if (!ret) {
668 spin_unlock(&fs_info->reada_lock);
669 return 0;
670 }
671 re = NULL;
672 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
673 dev->reada_next >> PAGE_SHIFT, 1);
674 }
675 if (ret == 0) {
676 spin_unlock(&fs_info->reada_lock);
677 return 0;
678 }
679 dev->reada_next = re->logical + fs_info->nodesize;
680 re->refcnt++;
681
682 spin_unlock(&fs_info->reada_lock);
683
684 spin_lock(&re->lock);
685 if (re->scheduled || list_empty(&re->extctl)) {
686 spin_unlock(&re->lock);
687 reada_extent_put(fs_info, re);
688 return 0;
689 }
690 re->scheduled = 1;
691 spin_unlock(&re->lock);
692
693 /*
694 * find mirror num
695 */
696 for (i = 0; i < re->nzones; ++i) {
697 if (re->zones[i]->device == dev) {
698 mirror_num = i + 1;
699 break;
700 }
701 }
702 logical = re->logical;
703
704 atomic_inc(&dev->reada_in_flight);
705 ret = reada_tree_block_flagged(fs_info, logical, mirror_num, &eb);
706 if (ret)
707 __readahead_hook(fs_info, re, NULL, ret);
708 else if (eb)
709 __readahead_hook(fs_info, re, eb, ret);
710
711 if (eb)
712 free_extent_buffer(eb);
713
714 atomic_dec(&dev->reada_in_flight);
715 reada_extent_put(fs_info, re);
716
717 return 1;
718
719}
720
721static void reada_start_machine_worker(struct btrfs_work *work)
722{
723 struct reada_machine_work *rmw;
724 struct btrfs_fs_info *fs_info;
725 int old_ioprio;
726
727 rmw = container_of(work, struct reada_machine_work, work);
728 fs_info = rmw->fs_info;
729
730 kfree(rmw);
731
732 old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
733 task_nice_ioprio(current));
734 set_task_ioprio(current, BTRFS_IOPRIO_READA);
735 __reada_start_machine(fs_info);
736 set_task_ioprio(current, old_ioprio);
737
738 atomic_dec(&fs_info->reada_works_cnt);
739}
740
741static void __reada_start_machine(struct btrfs_fs_info *fs_info)
742{
743 struct btrfs_device *device;
744 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
745 u64 enqueued;
746 u64 total = 0;
747 int i;
748
749 do {
750 enqueued = 0;
751 mutex_lock(&fs_devices->device_list_mutex);
752 list_for_each_entry(device, &fs_devices->devices, dev_list) {
753 if (atomic_read(&device->reada_in_flight) <
754 MAX_IN_FLIGHT)
755 enqueued += reada_start_machine_dev(device);
756 }
757 mutex_unlock(&fs_devices->device_list_mutex);
758 total += enqueued;
759 } while (enqueued && total < 10000);
760
761 if (enqueued == 0)
762 return;
763
764 /*
765 * If everything is already in the cache, this is effectively single
766 * threaded. To a) not hold the caller for too long and b) to utilize
767 * more cores, we broke the loop above after 10000 iterations and now
768 * enqueue to workers to finish it. This will distribute the load to
769 * the cores.
770 */
771 for (i = 0; i < 2; ++i) {
772 reada_start_machine(fs_info);
773 if (atomic_read(&fs_info->reada_works_cnt) >
774 BTRFS_MAX_MIRRORS * 2)
775 break;
776 }
777}
778
779static void reada_start_machine(struct btrfs_fs_info *fs_info)
780{
781 struct reada_machine_work *rmw;
782
783 rmw = kzalloc(sizeof(*rmw), GFP_KERNEL);
784 if (!rmw) {
785 /* FIXME we cannot handle this properly right now */
786 BUG();
787 }
788 btrfs_init_work(&rmw->work, btrfs_readahead_helper,
789 reada_start_machine_worker, NULL, NULL);
790 rmw->fs_info = fs_info;
791
792 btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
793 atomic_inc(&fs_info->reada_works_cnt);
794}
795
796#ifdef DEBUG
797static void dump_devs(struct btrfs_fs_info *fs_info, int all)
798{
799 struct btrfs_device *device;
800 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
801 unsigned long index;
802 int ret;
803 int i;
804 int j;
805 int cnt;
806
807 spin_lock(&fs_info->reada_lock);
808 list_for_each_entry(device, &fs_devices->devices, dev_list) {
809 btrfs_debug(fs_info, "dev %lld has %d in flight", device->devid,
810 atomic_read(&device->reada_in_flight));
811 index = 0;
812 while (1) {
813 struct reada_zone *zone;
814 ret = radix_tree_gang_lookup(&device->reada_zones,
815 (void **)&zone, index, 1);
816 if (ret == 0)
817 break;
818 pr_debug(" zone %llu-%llu elems %llu locked %d devs",
819 zone->start, zone->end, zone->elems,
820 zone->locked);
821 for (j = 0; j < zone->ndevs; ++j) {
822 pr_cont(" %lld",
823 zone->devs[j]->devid);
824 }
825 if (device->reada_curr_zone == zone)
826 pr_cont(" curr off %llu",
827 device->reada_next - zone->start);
828 pr_cont("\n");
829 index = (zone->end >> PAGE_SHIFT) + 1;
830 }
831 cnt = 0;
832 index = 0;
833 while (all) {
834 struct reada_extent *re = NULL;
835
836 ret = radix_tree_gang_lookup(&device->reada_extents,
837 (void **)&re, index, 1);
838 if (ret == 0)
839 break;
840 pr_debug(" re: logical %llu size %u empty %d scheduled %d",
841 re->logical, fs_info->nodesize,
842 list_empty(&re->extctl), re->scheduled);
843
844 for (i = 0; i < re->nzones; ++i) {
845 pr_cont(" zone %llu-%llu devs",
846 re->zones[i]->start,
847 re->zones[i]->end);
848 for (j = 0; j < re->zones[i]->ndevs; ++j) {
849 pr_cont(" %lld",
850 re->zones[i]->devs[j]->devid);
851 }
852 }
853 pr_cont("\n");
854 index = (re->logical >> PAGE_SHIFT) + 1;
855 if (++cnt > 15)
856 break;
857 }
858 }
859
860 index = 0;
861 cnt = 0;
862 while (all) {
863 struct reada_extent *re = NULL;
864
865 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
866 index, 1);
867 if (ret == 0)
868 break;
869 if (!re->scheduled) {
870 index = (re->logical >> PAGE_SHIFT) + 1;
871 continue;
872 }
873 pr_debug("re: logical %llu size %u list empty %d scheduled %d",
874 re->logical, fs_info->nodesize,
875 list_empty(&re->extctl), re->scheduled);
876 for (i = 0; i < re->nzones; ++i) {
877 pr_cont(" zone %llu-%llu devs",
878 re->zones[i]->start,
879 re->zones[i]->end);
880 for (j = 0; j < re->zones[i]->ndevs; ++j) {
881 pr_cont(" %lld",
882 re->zones[i]->devs[j]->devid);
883 }
884 }
885 pr_cont("\n");
886 index = (re->logical >> PAGE_SHIFT) + 1;
887 }
888 spin_unlock(&fs_info->reada_lock);
889}
890#endif
891
892/*
893 * interface
894 */
895struct reada_control *btrfs_reada_add(struct btrfs_root *root,
896 struct btrfs_key *key_start, struct btrfs_key *key_end)
897{
898 struct reada_control *rc;
899 u64 start;
900 u64 generation;
901 int ret;
902 struct extent_buffer *node;
903 static struct btrfs_key max_key = {
904 .objectid = (u64)-1,
905 .type = (u8)-1,
906 .offset = (u64)-1
907 };
908
909 rc = kzalloc(sizeof(*rc), GFP_KERNEL);
910 if (!rc)
911 return ERR_PTR(-ENOMEM);
912
913 rc->fs_info = root->fs_info;
914 rc->key_start = *key_start;
915 rc->key_end = *key_end;
916 atomic_set(&rc->elems, 0);
917 init_waitqueue_head(&rc->wait);
918 kref_init(&rc->refcnt);
919 kref_get(&rc->refcnt); /* one ref for having elements */
920
921 node = btrfs_root_node(root);
922 start = node->start;
923 generation = btrfs_header_generation(node);
924 free_extent_buffer(node);
925
926 ret = reada_add_block(rc, start, &max_key, generation);
927 if (ret) {
928 kfree(rc);
929 return ERR_PTR(ret);
930 }
931
932 reada_start_machine(root->fs_info);
933
934 return rc;
935}
936
937#ifdef DEBUG
938int btrfs_reada_wait(void *handle)
939{
940 struct reada_control *rc = handle;
941 struct btrfs_fs_info *fs_info = rc->fs_info;
942
943 while (atomic_read(&rc->elems)) {
944 if (!atomic_read(&fs_info->reada_works_cnt))
945 reada_start_machine(fs_info);
946 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
947 5 * HZ);
948 dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
949 }
950
951 dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
952
953 kref_put(&rc->refcnt, reada_control_release);
954
955 return 0;
956}
957#else
958int btrfs_reada_wait(void *handle)
959{
960 struct reada_control *rc = handle;
961 struct btrfs_fs_info *fs_info = rc->fs_info;
962
963 while (atomic_read(&rc->elems)) {
964 if (!atomic_read(&fs_info->reada_works_cnt))
965 reada_start_machine(fs_info);
966 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
967 (HZ + 9) / 10);
968 }
969
970 kref_put(&rc->refcnt, reada_control_release);
971
972 return 0;
973}
974#endif
975
976void btrfs_reada_detach(void *handle)
977{
978 struct reada_control *rc = handle;
979
980 kref_put(&rc->refcnt, reada_control_release);
981}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2011 STRATO. All rights reserved.
4 */
5
6#include <linux/sched.h>
7#include <linux/pagemap.h>
8#include <linux/writeback.h>
9#include <linux/blkdev.h>
10#include <linux/slab.h>
11#include <linux/workqueue.h>
12#include "ctree.h"
13#include "volumes.h"
14#include "disk-io.h"
15#include "transaction.h"
16#include "dev-replace.h"
17#include "block-group.h"
18
19#undef DEBUG
20
21/*
22 * This is the implementation for the generic read ahead framework.
23 *
24 * To trigger a readahead, btrfs_reada_add must be called. It will start
25 * a read ahead for the given range [start, end) on tree root. The returned
26 * handle can either be used to wait on the readahead to finish
27 * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
28 *
29 * The read ahead works as follows:
30 * On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
31 * reada_start_machine will then search for extents to prefetch and trigger
32 * some reads. When a read finishes for a node, all contained node/leaf
33 * pointers that lie in the given range will also be enqueued. The reads will
34 * be triggered in sequential order, thus giving a big win over a naive
35 * enumeration. It will also make use of multi-device layouts. Each disk
36 * will have its on read pointer and all disks will by utilized in parallel.
37 * Also will no two disks read both sides of a mirror simultaneously, as this
38 * would waste seeking capacity. Instead both disks will read different parts
39 * of the filesystem.
40 * Any number of readaheads can be started in parallel. The read order will be
41 * determined globally, i.e. 2 parallel readaheads will normally finish faster
42 * than the 2 started one after another.
43 */
44
45#define MAX_IN_FLIGHT 6
46
47struct reada_extctl {
48 struct list_head list;
49 struct reada_control *rc;
50 u64 generation;
51};
52
53struct reada_extent {
54 u64 logical;
55 u64 owner_root;
56 struct btrfs_key top;
57 struct list_head extctl;
58 int refcnt;
59 spinlock_t lock;
60 struct reada_zone *zones[BTRFS_MAX_MIRRORS];
61 int nzones;
62 int scheduled;
63 int level;
64};
65
66struct reada_zone {
67 u64 start;
68 u64 end;
69 u64 elems;
70 struct list_head list;
71 spinlock_t lock;
72 int locked;
73 struct btrfs_device *device;
74 struct btrfs_device *devs[BTRFS_MAX_MIRRORS]; /* full list, incl
75 * self */
76 int ndevs;
77 struct kref refcnt;
78};
79
80struct reada_machine_work {
81 struct btrfs_work work;
82 struct btrfs_fs_info *fs_info;
83};
84
85static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
86static void reada_control_release(struct kref *kref);
87static void reada_zone_release(struct kref *kref);
88static void reada_start_machine(struct btrfs_fs_info *fs_info);
89static void __reada_start_machine(struct btrfs_fs_info *fs_info);
90
91static int reada_add_block(struct reada_control *rc, u64 logical,
92 struct btrfs_key *top, u64 owner_root,
93 u64 generation, int level);
94
95/* recurses */
96/* in case of err, eb might be NULL */
97static void __readahead_hook(struct btrfs_fs_info *fs_info,
98 struct reada_extent *re, struct extent_buffer *eb,
99 int err)
100{
101 int nritems;
102 int i;
103 u64 bytenr;
104 u64 generation;
105 struct list_head list;
106
107 spin_lock(&re->lock);
108 /*
109 * just take the full list from the extent. afterwards we
110 * don't need the lock anymore
111 */
112 list_replace_init(&re->extctl, &list);
113 re->scheduled = 0;
114 spin_unlock(&re->lock);
115
116 /*
117 * this is the error case, the extent buffer has not been
118 * read correctly. We won't access anything from it and
119 * just cleanup our data structures. Effectively this will
120 * cut the branch below this node from read ahead.
121 */
122 if (err)
123 goto cleanup;
124
125 /*
126 * FIXME: currently we just set nritems to 0 if this is a leaf,
127 * effectively ignoring the content. In a next step we could
128 * trigger more readahead depending from the content, e.g.
129 * fetch the checksums for the extents in the leaf.
130 */
131 if (!btrfs_header_level(eb))
132 goto cleanup;
133
134 nritems = btrfs_header_nritems(eb);
135 generation = btrfs_header_generation(eb);
136 for (i = 0; i < nritems; i++) {
137 struct reada_extctl *rec;
138 u64 n_gen;
139 struct btrfs_key key;
140 struct btrfs_key next_key;
141
142 btrfs_node_key_to_cpu(eb, &key, i);
143 if (i + 1 < nritems)
144 btrfs_node_key_to_cpu(eb, &next_key, i + 1);
145 else
146 next_key = re->top;
147 bytenr = btrfs_node_blockptr(eb, i);
148 n_gen = btrfs_node_ptr_generation(eb, i);
149
150 list_for_each_entry(rec, &list, list) {
151 struct reada_control *rc = rec->rc;
152
153 /*
154 * if the generation doesn't match, just ignore this
155 * extctl. This will probably cut off a branch from
156 * prefetch. Alternatively one could start a new (sub-)
157 * prefetch for this branch, starting again from root.
158 * FIXME: move the generation check out of this loop
159 */
160#ifdef DEBUG
161 if (rec->generation != generation) {
162 btrfs_debug(fs_info,
163 "generation mismatch for (%llu,%d,%llu) %llu != %llu",
164 key.objectid, key.type, key.offset,
165 rec->generation, generation);
166 }
167#endif
168 if (rec->generation == generation &&
169 btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 &&
170 btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0)
171 reada_add_block(rc, bytenr, &next_key,
172 btrfs_header_owner(eb), n_gen,
173 btrfs_header_level(eb) - 1);
174 }
175 }
176
177cleanup:
178 /*
179 * free extctl records
180 */
181 while (!list_empty(&list)) {
182 struct reada_control *rc;
183 struct reada_extctl *rec;
184
185 rec = list_first_entry(&list, struct reada_extctl, list);
186 list_del(&rec->list);
187 rc = rec->rc;
188 kfree(rec);
189
190 kref_get(&rc->refcnt);
191 if (atomic_dec_and_test(&rc->elems)) {
192 kref_put(&rc->refcnt, reada_control_release);
193 wake_up(&rc->wait);
194 }
195 kref_put(&rc->refcnt, reada_control_release);
196
197 reada_extent_put(fs_info, re); /* one ref for each entry */
198 }
199
200 return;
201}
202
203int btree_readahead_hook(struct extent_buffer *eb, int err)
204{
205 struct btrfs_fs_info *fs_info = eb->fs_info;
206 int ret = 0;
207 struct reada_extent *re;
208
209 /* find extent */
210 spin_lock(&fs_info->reada_lock);
211 re = radix_tree_lookup(&fs_info->reada_tree,
212 eb->start >> fs_info->sectorsize_bits);
213 if (re)
214 re->refcnt++;
215 spin_unlock(&fs_info->reada_lock);
216 if (!re) {
217 ret = -1;
218 goto start_machine;
219 }
220
221 __readahead_hook(fs_info, re, eb, err);
222 reada_extent_put(fs_info, re); /* our ref */
223
224start_machine:
225 reada_start_machine(fs_info);
226 return ret;
227}
228
229static struct reada_zone *reada_find_zone(struct btrfs_device *dev, u64 logical,
230 struct btrfs_bio *bbio)
231{
232 struct btrfs_fs_info *fs_info = dev->fs_info;
233 int ret;
234 struct reada_zone *zone;
235 struct btrfs_block_group *cache = NULL;
236 u64 start;
237 u64 end;
238 int i;
239
240 zone = NULL;
241 spin_lock(&fs_info->reada_lock);
242 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
243 logical >> fs_info->sectorsize_bits, 1);
244 if (ret == 1 && logical >= zone->start && logical <= zone->end) {
245 kref_get(&zone->refcnt);
246 spin_unlock(&fs_info->reada_lock);
247 return zone;
248 }
249
250 spin_unlock(&fs_info->reada_lock);
251
252 cache = btrfs_lookup_block_group(fs_info, logical);
253 if (!cache)
254 return NULL;
255
256 start = cache->start;
257 end = start + cache->length - 1;
258 btrfs_put_block_group(cache);
259
260 zone = kzalloc(sizeof(*zone), GFP_KERNEL);
261 if (!zone)
262 return NULL;
263
264 ret = radix_tree_preload(GFP_KERNEL);
265 if (ret) {
266 kfree(zone);
267 return NULL;
268 }
269
270 zone->start = start;
271 zone->end = end;
272 INIT_LIST_HEAD(&zone->list);
273 spin_lock_init(&zone->lock);
274 zone->locked = 0;
275 kref_init(&zone->refcnt);
276 zone->elems = 0;
277 zone->device = dev; /* our device always sits at index 0 */
278 for (i = 0; i < bbio->num_stripes; ++i) {
279 /* bounds have already been checked */
280 zone->devs[i] = bbio->stripes[i].dev;
281 }
282 zone->ndevs = bbio->num_stripes;
283
284 spin_lock(&fs_info->reada_lock);
285 ret = radix_tree_insert(&dev->reada_zones,
286 (unsigned long)(zone->end >> fs_info->sectorsize_bits),
287 zone);
288
289 if (ret == -EEXIST) {
290 kfree(zone);
291 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
292 logical >> fs_info->sectorsize_bits, 1);
293 if (ret == 1 && logical >= zone->start && logical <= zone->end)
294 kref_get(&zone->refcnt);
295 else
296 zone = NULL;
297 }
298 spin_unlock(&fs_info->reada_lock);
299 radix_tree_preload_end();
300
301 return zone;
302}
303
304static struct reada_extent *reada_find_extent(struct btrfs_fs_info *fs_info,
305 u64 logical,
306 struct btrfs_key *top,
307 u64 owner_root, int level)
308{
309 int ret;
310 struct reada_extent *re = NULL;
311 struct reada_extent *re_exist = NULL;
312 struct btrfs_bio *bbio = NULL;
313 struct btrfs_device *dev;
314 struct btrfs_device *prev_dev;
315 u64 length;
316 int real_stripes;
317 int nzones = 0;
318 unsigned long index = logical >> fs_info->sectorsize_bits;
319 int dev_replace_is_ongoing;
320 int have_zone = 0;
321
322 spin_lock(&fs_info->reada_lock);
323 re = radix_tree_lookup(&fs_info->reada_tree, index);
324 if (re)
325 re->refcnt++;
326 spin_unlock(&fs_info->reada_lock);
327
328 if (re)
329 return re;
330
331 re = kzalloc(sizeof(*re), GFP_KERNEL);
332 if (!re)
333 return NULL;
334
335 re->logical = logical;
336 re->top = *top;
337 INIT_LIST_HEAD(&re->extctl);
338 spin_lock_init(&re->lock);
339 re->refcnt = 1;
340 re->owner_root = owner_root;
341 re->level = level;
342
343 /*
344 * map block
345 */
346 length = fs_info->nodesize;
347 ret = btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical,
348 &length, &bbio, 0);
349 if (ret || !bbio || length < fs_info->nodesize)
350 goto error;
351
352 if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
353 btrfs_err(fs_info,
354 "readahead: more than %d copies not supported",
355 BTRFS_MAX_MIRRORS);
356 goto error;
357 }
358
359 real_stripes = bbio->num_stripes - bbio->num_tgtdevs;
360 for (nzones = 0; nzones < real_stripes; ++nzones) {
361 struct reada_zone *zone;
362
363 dev = bbio->stripes[nzones].dev;
364
365 /* cannot read ahead on missing device. */
366 if (!dev->bdev)
367 continue;
368
369 zone = reada_find_zone(dev, logical, bbio);
370 if (!zone)
371 continue;
372
373 re->zones[re->nzones++] = zone;
374 spin_lock(&zone->lock);
375 if (!zone->elems)
376 kref_get(&zone->refcnt);
377 ++zone->elems;
378 spin_unlock(&zone->lock);
379 spin_lock(&fs_info->reada_lock);
380 kref_put(&zone->refcnt, reada_zone_release);
381 spin_unlock(&fs_info->reada_lock);
382 }
383 if (re->nzones == 0) {
384 /* not a single zone found, error and out */
385 goto error;
386 }
387
388 /* Insert extent in reada tree + all per-device trees, all or nothing */
389 down_read(&fs_info->dev_replace.rwsem);
390 ret = radix_tree_preload(GFP_KERNEL);
391 if (ret) {
392 up_read(&fs_info->dev_replace.rwsem);
393 goto error;
394 }
395
396 spin_lock(&fs_info->reada_lock);
397 ret = radix_tree_insert(&fs_info->reada_tree, index, re);
398 if (ret == -EEXIST) {
399 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
400 re_exist->refcnt++;
401 spin_unlock(&fs_info->reada_lock);
402 radix_tree_preload_end();
403 up_read(&fs_info->dev_replace.rwsem);
404 goto error;
405 }
406 if (ret) {
407 spin_unlock(&fs_info->reada_lock);
408 radix_tree_preload_end();
409 up_read(&fs_info->dev_replace.rwsem);
410 goto error;
411 }
412 radix_tree_preload_end();
413 prev_dev = NULL;
414 dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
415 &fs_info->dev_replace);
416 for (nzones = 0; nzones < re->nzones; ++nzones) {
417 dev = re->zones[nzones]->device;
418
419 if (dev == prev_dev) {
420 /*
421 * in case of DUP, just add the first zone. As both
422 * are on the same device, there's nothing to gain
423 * from adding both.
424 * Also, it wouldn't work, as the tree is per device
425 * and adding would fail with EEXIST
426 */
427 continue;
428 }
429 if (!dev->bdev)
430 continue;
431
432 if (test_bit(BTRFS_DEV_STATE_NO_READA, &dev->dev_state))
433 continue;
434
435 if (dev_replace_is_ongoing &&
436 dev == fs_info->dev_replace.tgtdev) {
437 /*
438 * as this device is selected for reading only as
439 * a last resort, skip it for read ahead.
440 */
441 continue;
442 }
443 prev_dev = dev;
444 ret = radix_tree_insert(&dev->reada_extents, index, re);
445 if (ret) {
446 while (--nzones >= 0) {
447 dev = re->zones[nzones]->device;
448 BUG_ON(dev == NULL);
449 /* ignore whether the entry was inserted */
450 radix_tree_delete(&dev->reada_extents, index);
451 }
452 radix_tree_delete(&fs_info->reada_tree, index);
453 spin_unlock(&fs_info->reada_lock);
454 up_read(&fs_info->dev_replace.rwsem);
455 goto error;
456 }
457 have_zone = 1;
458 }
459 if (!have_zone)
460 radix_tree_delete(&fs_info->reada_tree, index);
461 spin_unlock(&fs_info->reada_lock);
462 up_read(&fs_info->dev_replace.rwsem);
463
464 if (!have_zone)
465 goto error;
466
467 btrfs_put_bbio(bbio);
468 return re;
469
470error:
471 for (nzones = 0; nzones < re->nzones; ++nzones) {
472 struct reada_zone *zone;
473
474 zone = re->zones[nzones];
475 kref_get(&zone->refcnt);
476 spin_lock(&zone->lock);
477 --zone->elems;
478 if (zone->elems == 0) {
479 /*
480 * no fs_info->reada_lock needed, as this can't be
481 * the last ref
482 */
483 kref_put(&zone->refcnt, reada_zone_release);
484 }
485 spin_unlock(&zone->lock);
486
487 spin_lock(&fs_info->reada_lock);
488 kref_put(&zone->refcnt, reada_zone_release);
489 spin_unlock(&fs_info->reada_lock);
490 }
491 btrfs_put_bbio(bbio);
492 kfree(re);
493 return re_exist;
494}
495
496static void reada_extent_put(struct btrfs_fs_info *fs_info,
497 struct reada_extent *re)
498{
499 int i;
500 unsigned long index = re->logical >> fs_info->sectorsize_bits;
501
502 spin_lock(&fs_info->reada_lock);
503 if (--re->refcnt) {
504 spin_unlock(&fs_info->reada_lock);
505 return;
506 }
507
508 radix_tree_delete(&fs_info->reada_tree, index);
509 for (i = 0; i < re->nzones; ++i) {
510 struct reada_zone *zone = re->zones[i];
511
512 radix_tree_delete(&zone->device->reada_extents, index);
513 }
514
515 spin_unlock(&fs_info->reada_lock);
516
517 for (i = 0; i < re->nzones; ++i) {
518 struct reada_zone *zone = re->zones[i];
519
520 kref_get(&zone->refcnt);
521 spin_lock(&zone->lock);
522 --zone->elems;
523 if (zone->elems == 0) {
524 /* no fs_info->reada_lock needed, as this can't be
525 * the last ref */
526 kref_put(&zone->refcnt, reada_zone_release);
527 }
528 spin_unlock(&zone->lock);
529
530 spin_lock(&fs_info->reada_lock);
531 kref_put(&zone->refcnt, reada_zone_release);
532 spin_unlock(&fs_info->reada_lock);
533 }
534
535 kfree(re);
536}
537
538static void reada_zone_release(struct kref *kref)
539{
540 struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
541 struct btrfs_fs_info *fs_info = zone->device->fs_info;
542
543 lockdep_assert_held(&fs_info->reada_lock);
544
545 radix_tree_delete(&zone->device->reada_zones,
546 zone->end >> fs_info->sectorsize_bits);
547
548 kfree(zone);
549}
550
551static void reada_control_release(struct kref *kref)
552{
553 struct reada_control *rc = container_of(kref, struct reada_control,
554 refcnt);
555
556 kfree(rc);
557}
558
559static int reada_add_block(struct reada_control *rc, u64 logical,
560 struct btrfs_key *top, u64 owner_root,
561 u64 generation, int level)
562{
563 struct btrfs_fs_info *fs_info = rc->fs_info;
564 struct reada_extent *re;
565 struct reada_extctl *rec;
566
567 /* takes one ref */
568 re = reada_find_extent(fs_info, logical, top, owner_root, level);
569 if (!re)
570 return -1;
571
572 rec = kzalloc(sizeof(*rec), GFP_KERNEL);
573 if (!rec) {
574 reada_extent_put(fs_info, re);
575 return -ENOMEM;
576 }
577
578 rec->rc = rc;
579 rec->generation = generation;
580 atomic_inc(&rc->elems);
581
582 spin_lock(&re->lock);
583 list_add_tail(&rec->list, &re->extctl);
584 spin_unlock(&re->lock);
585
586 /* leave the ref on the extent */
587
588 return 0;
589}
590
591/*
592 * called with fs_info->reada_lock held
593 */
594static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
595{
596 int i;
597 unsigned long index = zone->end >> zone->device->fs_info->sectorsize_bits;
598
599 for (i = 0; i < zone->ndevs; ++i) {
600 struct reada_zone *peer;
601 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
602 if (peer && peer->device != zone->device)
603 peer->locked = lock;
604 }
605}
606
607/*
608 * called with fs_info->reada_lock held
609 */
610static int reada_pick_zone(struct btrfs_device *dev)
611{
612 struct reada_zone *top_zone = NULL;
613 struct reada_zone *top_locked_zone = NULL;
614 u64 top_elems = 0;
615 u64 top_locked_elems = 0;
616 unsigned long index = 0;
617 int ret;
618
619 if (dev->reada_curr_zone) {
620 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
621 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
622 dev->reada_curr_zone = NULL;
623 }
624 /* pick the zone with the most elements */
625 while (1) {
626 struct reada_zone *zone;
627
628 ret = radix_tree_gang_lookup(&dev->reada_zones,
629 (void **)&zone, index, 1);
630 if (ret == 0)
631 break;
632 index = (zone->end >> dev->fs_info->sectorsize_bits) + 1;
633 if (zone->locked) {
634 if (zone->elems > top_locked_elems) {
635 top_locked_elems = zone->elems;
636 top_locked_zone = zone;
637 }
638 } else {
639 if (zone->elems > top_elems) {
640 top_elems = zone->elems;
641 top_zone = zone;
642 }
643 }
644 }
645 if (top_zone)
646 dev->reada_curr_zone = top_zone;
647 else if (top_locked_zone)
648 dev->reada_curr_zone = top_locked_zone;
649 else
650 return 0;
651
652 dev->reada_next = dev->reada_curr_zone->start;
653 kref_get(&dev->reada_curr_zone->refcnt);
654 reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
655
656 return 1;
657}
658
659static int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr,
660 u64 owner_root, int level, int mirror_num,
661 struct extent_buffer **eb)
662{
663 struct extent_buffer *buf = NULL;
664 int ret;
665
666 buf = btrfs_find_create_tree_block(fs_info, bytenr, owner_root, level);
667 if (IS_ERR(buf))
668 return 0;
669
670 set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);
671
672 ret = read_extent_buffer_pages(buf, WAIT_PAGE_LOCK, mirror_num);
673 if (ret) {
674 free_extent_buffer_stale(buf);
675 return ret;
676 }
677
678 if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) {
679 free_extent_buffer_stale(buf);
680 return -EIO;
681 } else if (extent_buffer_uptodate(buf)) {
682 *eb = buf;
683 } else {
684 free_extent_buffer(buf);
685 }
686 return 0;
687}
688
689static int reada_start_machine_dev(struct btrfs_device *dev)
690{
691 struct btrfs_fs_info *fs_info = dev->fs_info;
692 struct reada_extent *re = NULL;
693 int mirror_num = 0;
694 struct extent_buffer *eb = NULL;
695 u64 logical;
696 int ret;
697 int i;
698
699 spin_lock(&fs_info->reada_lock);
700 if (dev->reada_curr_zone == NULL) {
701 ret = reada_pick_zone(dev);
702 if (!ret) {
703 spin_unlock(&fs_info->reada_lock);
704 return 0;
705 }
706 }
707 /*
708 * FIXME currently we issue the reads one extent at a time. If we have
709 * a contiguous block of extents, we could also coagulate them or use
710 * plugging to speed things up
711 */
712 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
713 dev->reada_next >> fs_info->sectorsize_bits, 1);
714 if (ret == 0 || re->logical > dev->reada_curr_zone->end) {
715 ret = reada_pick_zone(dev);
716 if (!ret) {
717 spin_unlock(&fs_info->reada_lock);
718 return 0;
719 }
720 re = NULL;
721 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
722 dev->reada_next >> fs_info->sectorsize_bits, 1);
723 }
724 if (ret == 0) {
725 spin_unlock(&fs_info->reada_lock);
726 return 0;
727 }
728 dev->reada_next = re->logical + fs_info->nodesize;
729 re->refcnt++;
730
731 spin_unlock(&fs_info->reada_lock);
732
733 spin_lock(&re->lock);
734 if (re->scheduled || list_empty(&re->extctl)) {
735 spin_unlock(&re->lock);
736 reada_extent_put(fs_info, re);
737 return 0;
738 }
739 re->scheduled = 1;
740 spin_unlock(&re->lock);
741
742 /*
743 * find mirror num
744 */
745 for (i = 0; i < re->nzones; ++i) {
746 if (re->zones[i]->device == dev) {
747 mirror_num = i + 1;
748 break;
749 }
750 }
751 logical = re->logical;
752
753 atomic_inc(&dev->reada_in_flight);
754 ret = reada_tree_block_flagged(fs_info, logical, re->owner_root,
755 re->level, mirror_num, &eb);
756 if (ret)
757 __readahead_hook(fs_info, re, NULL, ret);
758 else if (eb)
759 __readahead_hook(fs_info, re, eb, ret);
760
761 if (eb)
762 free_extent_buffer(eb);
763
764 atomic_dec(&dev->reada_in_flight);
765 reada_extent_put(fs_info, re);
766
767 return 1;
768
769}
770
771static void reada_start_machine_worker(struct btrfs_work *work)
772{
773 struct reada_machine_work *rmw;
774 int old_ioprio;
775
776 rmw = container_of(work, struct reada_machine_work, work);
777
778 old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
779 task_nice_ioprio(current));
780 set_task_ioprio(current, BTRFS_IOPRIO_READA);
781 __reada_start_machine(rmw->fs_info);
782 set_task_ioprio(current, old_ioprio);
783
784 atomic_dec(&rmw->fs_info->reada_works_cnt);
785
786 kfree(rmw);
787}
788
789/* Try to start up to 10k READA requests for a group of devices */
790static int reada_start_for_fsdevs(struct btrfs_fs_devices *fs_devices)
791{
792 u64 enqueued;
793 u64 total = 0;
794 struct btrfs_device *device;
795
796 do {
797 enqueued = 0;
798 list_for_each_entry(device, &fs_devices->devices, dev_list) {
799 if (atomic_read(&device->reada_in_flight) <
800 MAX_IN_FLIGHT)
801 enqueued += reada_start_machine_dev(device);
802 }
803 total += enqueued;
804 } while (enqueued && total < 10000);
805
806 return total;
807}
808
809static void __reada_start_machine(struct btrfs_fs_info *fs_info)
810{
811 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
812 int i;
813 u64 enqueued = 0;
814
815 mutex_lock(&fs_devices->device_list_mutex);
816
817 enqueued += reada_start_for_fsdevs(fs_devices);
818 list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list)
819 enqueued += reada_start_for_fsdevs(seed_devs);
820
821 mutex_unlock(&fs_devices->device_list_mutex);
822 if (enqueued == 0)
823 return;
824
825 /*
826 * If everything is already in the cache, this is effectively single
827 * threaded. To a) not hold the caller for too long and b) to utilize
828 * more cores, we broke the loop above after 10000 iterations and now
829 * enqueue to workers to finish it. This will distribute the load to
830 * the cores.
831 */
832 for (i = 0; i < 2; ++i) {
833 reada_start_machine(fs_info);
834 if (atomic_read(&fs_info->reada_works_cnt) >
835 BTRFS_MAX_MIRRORS * 2)
836 break;
837 }
838}
839
840static void reada_start_machine(struct btrfs_fs_info *fs_info)
841{
842 struct reada_machine_work *rmw;
843
844 rmw = kzalloc(sizeof(*rmw), GFP_KERNEL);
845 if (!rmw) {
846 /* FIXME we cannot handle this properly right now */
847 BUG();
848 }
849 btrfs_init_work(&rmw->work, reada_start_machine_worker, NULL, NULL);
850 rmw->fs_info = fs_info;
851
852 btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
853 atomic_inc(&fs_info->reada_works_cnt);
854}
855
856#ifdef DEBUG
857static void dump_devs(struct btrfs_fs_info *fs_info, int all)
858{
859 struct btrfs_device *device;
860 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
861 unsigned long index;
862 int ret;
863 int i;
864 int j;
865 int cnt;
866
867 spin_lock(&fs_info->reada_lock);
868 list_for_each_entry(device, &fs_devices->devices, dev_list) {
869 btrfs_debug(fs_info, "dev %lld has %d in flight", device->devid,
870 atomic_read(&device->reada_in_flight));
871 index = 0;
872 while (1) {
873 struct reada_zone *zone;
874 ret = radix_tree_gang_lookup(&device->reada_zones,
875 (void **)&zone, index, 1);
876 if (ret == 0)
877 break;
878 pr_debug(" zone %llu-%llu elems %llu locked %d devs",
879 zone->start, zone->end, zone->elems,
880 zone->locked);
881 for (j = 0; j < zone->ndevs; ++j) {
882 pr_cont(" %lld",
883 zone->devs[j]->devid);
884 }
885 if (device->reada_curr_zone == zone)
886 pr_cont(" curr off %llu",
887 device->reada_next - zone->start);
888 pr_cont("\n");
889 index = (zone->end >> fs_info->sectorsize_bits) + 1;
890 }
891 cnt = 0;
892 index = 0;
893 while (all) {
894 struct reada_extent *re = NULL;
895
896 ret = radix_tree_gang_lookup(&device->reada_extents,
897 (void **)&re, index, 1);
898 if (ret == 0)
899 break;
900 pr_debug(" re: logical %llu size %u empty %d scheduled %d",
901 re->logical, fs_info->nodesize,
902 list_empty(&re->extctl), re->scheduled);
903
904 for (i = 0; i < re->nzones; ++i) {
905 pr_cont(" zone %llu-%llu devs",
906 re->zones[i]->start,
907 re->zones[i]->end);
908 for (j = 0; j < re->zones[i]->ndevs; ++j) {
909 pr_cont(" %lld",
910 re->zones[i]->devs[j]->devid);
911 }
912 }
913 pr_cont("\n");
914 index = (re->logical >> fs_info->sectorsize_bits) + 1;
915 if (++cnt > 15)
916 break;
917 }
918 }
919
920 index = 0;
921 cnt = 0;
922 while (all) {
923 struct reada_extent *re = NULL;
924
925 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
926 index, 1);
927 if (ret == 0)
928 break;
929 if (!re->scheduled) {
930 index = (re->logical >> fs_info->sectorsize_bits) + 1;
931 continue;
932 }
933 pr_debug("re: logical %llu size %u list empty %d scheduled %d",
934 re->logical, fs_info->nodesize,
935 list_empty(&re->extctl), re->scheduled);
936 for (i = 0; i < re->nzones; ++i) {
937 pr_cont(" zone %llu-%llu devs",
938 re->zones[i]->start,
939 re->zones[i]->end);
940 for (j = 0; j < re->zones[i]->ndevs; ++j) {
941 pr_cont(" %lld",
942 re->zones[i]->devs[j]->devid);
943 }
944 }
945 pr_cont("\n");
946 index = (re->logical >> fs_info->sectorsize_bits) + 1;
947 }
948 spin_unlock(&fs_info->reada_lock);
949}
950#endif
951
952/*
953 * interface
954 */
955struct reada_control *btrfs_reada_add(struct btrfs_root *root,
956 struct btrfs_key *key_start, struct btrfs_key *key_end)
957{
958 struct reada_control *rc;
959 u64 start;
960 u64 generation;
961 int ret;
962 int level;
963 struct extent_buffer *node;
964 static struct btrfs_key max_key = {
965 .objectid = (u64)-1,
966 .type = (u8)-1,
967 .offset = (u64)-1
968 };
969
970 rc = kzalloc(sizeof(*rc), GFP_KERNEL);
971 if (!rc)
972 return ERR_PTR(-ENOMEM);
973
974 rc->fs_info = root->fs_info;
975 rc->key_start = *key_start;
976 rc->key_end = *key_end;
977 atomic_set(&rc->elems, 0);
978 init_waitqueue_head(&rc->wait);
979 kref_init(&rc->refcnt);
980 kref_get(&rc->refcnt); /* one ref for having elements */
981
982 node = btrfs_root_node(root);
983 start = node->start;
984 generation = btrfs_header_generation(node);
985 level = btrfs_header_level(node);
986 free_extent_buffer(node);
987
988 ret = reada_add_block(rc, start, &max_key, root->root_key.objectid,
989 generation, level);
990 if (ret) {
991 kfree(rc);
992 return ERR_PTR(ret);
993 }
994
995 reada_start_machine(root->fs_info);
996
997 return rc;
998}
999
1000#ifdef DEBUG
1001int btrfs_reada_wait(void *handle)
1002{
1003 struct reada_control *rc = handle;
1004 struct btrfs_fs_info *fs_info = rc->fs_info;
1005
1006 while (atomic_read(&rc->elems)) {
1007 if (!atomic_read(&fs_info->reada_works_cnt))
1008 reada_start_machine(fs_info);
1009 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
1010 5 * HZ);
1011 dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
1012 }
1013
1014 dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
1015
1016 kref_put(&rc->refcnt, reada_control_release);
1017
1018 return 0;
1019}
1020#else
1021int btrfs_reada_wait(void *handle)
1022{
1023 struct reada_control *rc = handle;
1024 struct btrfs_fs_info *fs_info = rc->fs_info;
1025
1026 while (atomic_read(&rc->elems)) {
1027 if (!atomic_read(&fs_info->reada_works_cnt))
1028 reada_start_machine(fs_info);
1029 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
1030 (HZ + 9) / 10);
1031 }
1032
1033 kref_put(&rc->refcnt, reada_control_release);
1034
1035 return 0;
1036}
1037#endif
1038
1039void btrfs_reada_detach(void *handle)
1040{
1041 struct reada_control *rc = handle;
1042
1043 kref_put(&rc->refcnt, reada_control_release);
1044}
1045
1046/*
1047 * Before removing a device (device replace or device remove ioctls), call this
1048 * function to wait for all existing readahead requests on the device and to
1049 * make sure no one queues more readahead requests for the device.
1050 *
1051 * Must be called without holding neither the device list mutex nor the device
1052 * replace semaphore, otherwise it will deadlock.
1053 */
1054void btrfs_reada_remove_dev(struct btrfs_device *dev)
1055{
1056 struct btrfs_fs_info *fs_info = dev->fs_info;
1057
1058 /* Serialize with readahead extent creation at reada_find_extent(). */
1059 spin_lock(&fs_info->reada_lock);
1060 set_bit(BTRFS_DEV_STATE_NO_READA, &dev->dev_state);
1061 spin_unlock(&fs_info->reada_lock);
1062
1063 /*
1064 * There might be readahead requests added to the radix trees which
1065 * were not yet added to the readahead work queue. We need to start
1066 * them and wait for their completion, otherwise we can end up with
1067 * use-after-free problems when dropping the last reference on the
1068 * readahead extents and their zones, as they need to access the
1069 * device structure.
1070 */
1071 reada_start_machine(fs_info);
1072 btrfs_flush_workqueue(fs_info->readahead_workers);
1073}
1074
1075/*
1076 * If when removing a device (device replace or device remove ioctls) an error
1077 * happens after calling btrfs_reada_remove_dev(), call this to undo what that
1078 * function did. This is safe to call even if btrfs_reada_remove_dev() was not
1079 * called before.
1080 */
1081void btrfs_reada_undo_remove_dev(struct btrfs_device *dev)
1082{
1083 spin_lock(&dev->fs_info->reada_lock);
1084 clear_bit(BTRFS_DEV_STATE_NO_READA, &dev->dev_state);
1085 spin_unlock(&dev->fs_info->reada_lock);
1086}