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