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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 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 = 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->start;
252 end = start + cache->length - 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 /* Insert extent in reada tree + all per-device trees, all or nothing */
381 down_read(&fs_info->dev_replace.rwsem);
382 ret = radix_tree_preload(GFP_KERNEL);
383 if (ret) {
384 up_read(&fs_info->dev_replace.rwsem);
385 goto error;
386 }
387
388 spin_lock(&fs_info->reada_lock);
389 ret = radix_tree_insert(&fs_info->reada_tree, index, re);
390 if (ret == -EEXIST) {
391 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
392 re_exist->refcnt++;
393 spin_unlock(&fs_info->reada_lock);
394 radix_tree_preload_end();
395 up_read(&fs_info->dev_replace.rwsem);
396 goto error;
397 }
398 if (ret) {
399 spin_unlock(&fs_info->reada_lock);
400 radix_tree_preload_end();
401 up_read(&fs_info->dev_replace.rwsem);
402 goto error;
403 }
404 radix_tree_preload_end();
405 prev_dev = NULL;
406 dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
407 &fs_info->dev_replace);
408 for (nzones = 0; nzones < re->nzones; ++nzones) {
409 dev = re->zones[nzones]->device;
410
411 if (dev == prev_dev) {
412 /*
413 * in case of DUP, just add the first zone. As both
414 * are on the same device, there's nothing to gain
415 * from adding both.
416 * Also, it wouldn't work, as the tree is per device
417 * and adding would fail with EEXIST
418 */
419 continue;
420 }
421 if (!dev->bdev)
422 continue;
423
424 if (dev_replace_is_ongoing &&
425 dev == fs_info->dev_replace.tgtdev) {
426 /*
427 * as this device is selected for reading only as
428 * a last resort, skip it for read ahead.
429 */
430 continue;
431 }
432 prev_dev = dev;
433 ret = radix_tree_insert(&dev->reada_extents, index, re);
434 if (ret) {
435 while (--nzones >= 0) {
436 dev = re->zones[nzones]->device;
437 BUG_ON(dev == NULL);
438 /* ignore whether the entry was inserted */
439 radix_tree_delete(&dev->reada_extents, index);
440 }
441 radix_tree_delete(&fs_info->reada_tree, index);
442 spin_unlock(&fs_info->reada_lock);
443 up_read(&fs_info->dev_replace.rwsem);
444 goto error;
445 }
446 have_zone = 1;
447 }
448 spin_unlock(&fs_info->reada_lock);
449 up_read(&fs_info->dev_replace.rwsem);
450
451 if (!have_zone)
452 goto error;
453
454 btrfs_put_bbio(bbio);
455 return re;
456
457error:
458 for (nzones = 0; nzones < re->nzones; ++nzones) {
459 struct reada_zone *zone;
460
461 zone = re->zones[nzones];
462 kref_get(&zone->refcnt);
463 spin_lock(&zone->lock);
464 --zone->elems;
465 if (zone->elems == 0) {
466 /*
467 * no fs_info->reada_lock needed, as this can't be
468 * the last ref
469 */
470 kref_put(&zone->refcnt, reada_zone_release);
471 }
472 spin_unlock(&zone->lock);
473
474 spin_lock(&fs_info->reada_lock);
475 kref_put(&zone->refcnt, reada_zone_release);
476 spin_unlock(&fs_info->reada_lock);
477 }
478 btrfs_put_bbio(bbio);
479 kfree(re);
480 return re_exist;
481}
482
483static void reada_extent_put(struct btrfs_fs_info *fs_info,
484 struct reada_extent *re)
485{
486 int i;
487 unsigned long index = re->logical >> PAGE_SHIFT;
488
489 spin_lock(&fs_info->reada_lock);
490 if (--re->refcnt) {
491 spin_unlock(&fs_info->reada_lock);
492 return;
493 }
494
495 radix_tree_delete(&fs_info->reada_tree, index);
496 for (i = 0; i < re->nzones; ++i) {
497 struct reada_zone *zone = re->zones[i];
498
499 radix_tree_delete(&zone->device->reada_extents, index);
500 }
501
502 spin_unlock(&fs_info->reada_lock);
503
504 for (i = 0; i < re->nzones; ++i) {
505 struct reada_zone *zone = re->zones[i];
506
507 kref_get(&zone->refcnt);
508 spin_lock(&zone->lock);
509 --zone->elems;
510 if (zone->elems == 0) {
511 /* no fs_info->reada_lock needed, as this can't be
512 * the last ref */
513 kref_put(&zone->refcnt, reada_zone_release);
514 }
515 spin_unlock(&zone->lock);
516
517 spin_lock(&fs_info->reada_lock);
518 kref_put(&zone->refcnt, reada_zone_release);
519 spin_unlock(&fs_info->reada_lock);
520 }
521
522 kfree(re);
523}
524
525static void reada_zone_release(struct kref *kref)
526{
527 struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
528
529 radix_tree_delete(&zone->device->reada_zones,
530 zone->end >> PAGE_SHIFT);
531
532 kfree(zone);
533}
534
535static void reada_control_release(struct kref *kref)
536{
537 struct reada_control *rc = container_of(kref, struct reada_control,
538 refcnt);
539
540 kfree(rc);
541}
542
543static int reada_add_block(struct reada_control *rc, u64 logical,
544 struct btrfs_key *top, u64 generation)
545{
546 struct btrfs_fs_info *fs_info = rc->fs_info;
547 struct reada_extent *re;
548 struct reada_extctl *rec;
549
550 /* takes one ref */
551 re = reada_find_extent(fs_info, logical, top);
552 if (!re)
553 return -1;
554
555 rec = kzalloc(sizeof(*rec), GFP_KERNEL);
556 if (!rec) {
557 reada_extent_put(fs_info, re);
558 return -ENOMEM;
559 }
560
561 rec->rc = rc;
562 rec->generation = generation;
563 atomic_inc(&rc->elems);
564
565 spin_lock(&re->lock);
566 list_add_tail(&rec->list, &re->extctl);
567 spin_unlock(&re->lock);
568
569 /* leave the ref on the extent */
570
571 return 0;
572}
573
574/*
575 * called with fs_info->reada_lock held
576 */
577static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
578{
579 int i;
580 unsigned long index = zone->end >> PAGE_SHIFT;
581
582 for (i = 0; i < zone->ndevs; ++i) {
583 struct reada_zone *peer;
584 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
585 if (peer && peer->device != zone->device)
586 peer->locked = lock;
587 }
588}
589
590/*
591 * called with fs_info->reada_lock held
592 */
593static int reada_pick_zone(struct btrfs_device *dev)
594{
595 struct reada_zone *top_zone = NULL;
596 struct reada_zone *top_locked_zone = NULL;
597 u64 top_elems = 0;
598 u64 top_locked_elems = 0;
599 unsigned long index = 0;
600 int ret;
601
602 if (dev->reada_curr_zone) {
603 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
604 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
605 dev->reada_curr_zone = NULL;
606 }
607 /* pick the zone with the most elements */
608 while (1) {
609 struct reada_zone *zone;
610
611 ret = radix_tree_gang_lookup(&dev->reada_zones,
612 (void **)&zone, index, 1);
613 if (ret == 0)
614 break;
615 index = (zone->end >> PAGE_SHIFT) + 1;
616 if (zone->locked) {
617 if (zone->elems > top_locked_elems) {
618 top_locked_elems = zone->elems;
619 top_locked_zone = zone;
620 }
621 } else {
622 if (zone->elems > top_elems) {
623 top_elems = zone->elems;
624 top_zone = zone;
625 }
626 }
627 }
628 if (top_zone)
629 dev->reada_curr_zone = top_zone;
630 else if (top_locked_zone)
631 dev->reada_curr_zone = top_locked_zone;
632 else
633 return 0;
634
635 dev->reada_next = dev->reada_curr_zone->start;
636 kref_get(&dev->reada_curr_zone->refcnt);
637 reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
638
639 return 1;
640}
641
642static int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr,
643 int mirror_num, struct extent_buffer **eb)
644{
645 struct extent_buffer *buf = NULL;
646 int ret;
647
648 buf = btrfs_find_create_tree_block(fs_info, bytenr);
649 if (IS_ERR(buf))
650 return 0;
651
652 set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);
653
654 ret = read_extent_buffer_pages(buf, WAIT_PAGE_LOCK, mirror_num);
655 if (ret) {
656 free_extent_buffer_stale(buf);
657 return ret;
658 }
659
660 if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) {
661 free_extent_buffer_stale(buf);
662 return -EIO;
663 } else if (extent_buffer_uptodate(buf)) {
664 *eb = buf;
665 } else {
666 free_extent_buffer(buf);
667 }
668 return 0;
669}
670
671static int reada_start_machine_dev(struct btrfs_device *dev)
672{
673 struct btrfs_fs_info *fs_info = dev->fs_info;
674 struct reada_extent *re = NULL;
675 int mirror_num = 0;
676 struct extent_buffer *eb = NULL;
677 u64 logical;
678 int ret;
679 int i;
680
681 spin_lock(&fs_info->reada_lock);
682 if (dev->reada_curr_zone == NULL) {
683 ret = reada_pick_zone(dev);
684 if (!ret) {
685 spin_unlock(&fs_info->reada_lock);
686 return 0;
687 }
688 }
689 /*
690 * FIXME currently we issue the reads one extent at a time. If we have
691 * a contiguous block of extents, we could also coagulate them or use
692 * plugging to speed things up
693 */
694 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
695 dev->reada_next >> PAGE_SHIFT, 1);
696 if (ret == 0 || re->logical > dev->reada_curr_zone->end) {
697 ret = reada_pick_zone(dev);
698 if (!ret) {
699 spin_unlock(&fs_info->reada_lock);
700 return 0;
701 }
702 re = NULL;
703 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
704 dev->reada_next >> PAGE_SHIFT, 1);
705 }
706 if (ret == 0) {
707 spin_unlock(&fs_info->reada_lock);
708 return 0;
709 }
710 dev->reada_next = re->logical + fs_info->nodesize;
711 re->refcnt++;
712
713 spin_unlock(&fs_info->reada_lock);
714
715 spin_lock(&re->lock);
716 if (re->scheduled || list_empty(&re->extctl)) {
717 spin_unlock(&re->lock);
718 reada_extent_put(fs_info, re);
719 return 0;
720 }
721 re->scheduled = 1;
722 spin_unlock(&re->lock);
723
724 /*
725 * find mirror num
726 */
727 for (i = 0; i < re->nzones; ++i) {
728 if (re->zones[i]->device == dev) {
729 mirror_num = i + 1;
730 break;
731 }
732 }
733 logical = re->logical;
734
735 atomic_inc(&dev->reada_in_flight);
736 ret = reada_tree_block_flagged(fs_info, logical, mirror_num, &eb);
737 if (ret)
738 __readahead_hook(fs_info, re, NULL, ret);
739 else if (eb)
740 __readahead_hook(fs_info, re, eb, ret);
741
742 if (eb)
743 free_extent_buffer(eb);
744
745 atomic_dec(&dev->reada_in_flight);
746 reada_extent_put(fs_info, re);
747
748 return 1;
749
750}
751
752static void reada_start_machine_worker(struct btrfs_work *work)
753{
754 struct reada_machine_work *rmw;
755 int old_ioprio;
756
757 rmw = container_of(work, struct reada_machine_work, work);
758
759 old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
760 task_nice_ioprio(current));
761 set_task_ioprio(current, BTRFS_IOPRIO_READA);
762 __reada_start_machine(rmw->fs_info);
763 set_task_ioprio(current, old_ioprio);
764
765 atomic_dec(&rmw->fs_info->reada_works_cnt);
766
767 kfree(rmw);
768}
769
770static void __reada_start_machine(struct btrfs_fs_info *fs_info)
771{
772 struct btrfs_device *device;
773 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
774 u64 enqueued;
775 u64 total = 0;
776 int i;
777
778again:
779 do {
780 enqueued = 0;
781 mutex_lock(&fs_devices->device_list_mutex);
782 list_for_each_entry(device, &fs_devices->devices, dev_list) {
783 if (atomic_read(&device->reada_in_flight) <
784 MAX_IN_FLIGHT)
785 enqueued += reada_start_machine_dev(device);
786 }
787 mutex_unlock(&fs_devices->device_list_mutex);
788 total += enqueued;
789 } while (enqueued && total < 10000);
790 if (fs_devices->seed) {
791 fs_devices = fs_devices->seed;
792 goto again;
793 }
794
795 if (enqueued == 0)
796 return;
797
798 /*
799 * If everything is already in the cache, this is effectively single
800 * threaded. To a) not hold the caller for too long and b) to utilize
801 * more cores, we broke the loop above after 10000 iterations and now
802 * enqueue to workers to finish it. This will distribute the load to
803 * the cores.
804 */
805 for (i = 0; i < 2; ++i) {
806 reada_start_machine(fs_info);
807 if (atomic_read(&fs_info->reada_works_cnt) >
808 BTRFS_MAX_MIRRORS * 2)
809 break;
810 }
811}
812
813static void reada_start_machine(struct btrfs_fs_info *fs_info)
814{
815 struct reada_machine_work *rmw;
816
817 rmw = kzalloc(sizeof(*rmw), GFP_KERNEL);
818 if (!rmw) {
819 /* FIXME we cannot handle this properly right now */
820 BUG();
821 }
822 btrfs_init_work(&rmw->work, reada_start_machine_worker, NULL, NULL);
823 rmw->fs_info = fs_info;
824
825 btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
826 atomic_inc(&fs_info->reada_works_cnt);
827}
828
829#ifdef DEBUG
830static void dump_devs(struct btrfs_fs_info *fs_info, int all)
831{
832 struct btrfs_device *device;
833 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
834 unsigned long index;
835 int ret;
836 int i;
837 int j;
838 int cnt;
839
840 spin_lock(&fs_info->reada_lock);
841 list_for_each_entry(device, &fs_devices->devices, dev_list) {
842 btrfs_debug(fs_info, "dev %lld has %d in flight", device->devid,
843 atomic_read(&device->reada_in_flight));
844 index = 0;
845 while (1) {
846 struct reada_zone *zone;
847 ret = radix_tree_gang_lookup(&device->reada_zones,
848 (void **)&zone, index, 1);
849 if (ret == 0)
850 break;
851 pr_debug(" zone %llu-%llu elems %llu locked %d devs",
852 zone->start, zone->end, zone->elems,
853 zone->locked);
854 for (j = 0; j < zone->ndevs; ++j) {
855 pr_cont(" %lld",
856 zone->devs[j]->devid);
857 }
858 if (device->reada_curr_zone == zone)
859 pr_cont(" curr off %llu",
860 device->reada_next - zone->start);
861 pr_cont("\n");
862 index = (zone->end >> PAGE_SHIFT) + 1;
863 }
864 cnt = 0;
865 index = 0;
866 while (all) {
867 struct reada_extent *re = NULL;
868
869 ret = radix_tree_gang_lookup(&device->reada_extents,
870 (void **)&re, index, 1);
871 if (ret == 0)
872 break;
873 pr_debug(" re: logical %llu size %u empty %d scheduled %d",
874 re->logical, fs_info->nodesize,
875 list_empty(&re->extctl), re->scheduled);
876
877 for (i = 0; i < re->nzones; ++i) {
878 pr_cont(" zone %llu-%llu devs",
879 re->zones[i]->start,
880 re->zones[i]->end);
881 for (j = 0; j < re->zones[i]->ndevs; ++j) {
882 pr_cont(" %lld",
883 re->zones[i]->devs[j]->devid);
884 }
885 }
886 pr_cont("\n");
887 index = (re->logical >> PAGE_SHIFT) + 1;
888 if (++cnt > 15)
889 break;
890 }
891 }
892
893 index = 0;
894 cnt = 0;
895 while (all) {
896 struct reada_extent *re = NULL;
897
898 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
899 index, 1);
900 if (ret == 0)
901 break;
902 if (!re->scheduled) {
903 index = (re->logical >> PAGE_SHIFT) + 1;
904 continue;
905 }
906 pr_debug("re: logical %llu size %u list empty %d scheduled %d",
907 re->logical, fs_info->nodesize,
908 list_empty(&re->extctl), re->scheduled);
909 for (i = 0; i < re->nzones; ++i) {
910 pr_cont(" zone %llu-%llu devs",
911 re->zones[i]->start,
912 re->zones[i]->end);
913 for (j = 0; j < re->zones[i]->ndevs; ++j) {
914 pr_cont(" %lld",
915 re->zones[i]->devs[j]->devid);
916 }
917 }
918 pr_cont("\n");
919 index = (re->logical >> PAGE_SHIFT) + 1;
920 }
921 spin_unlock(&fs_info->reada_lock);
922}
923#endif
924
925/*
926 * interface
927 */
928struct reada_control *btrfs_reada_add(struct btrfs_root *root,
929 struct btrfs_key *key_start, struct btrfs_key *key_end)
930{
931 struct reada_control *rc;
932 u64 start;
933 u64 generation;
934 int ret;
935 struct extent_buffer *node;
936 static struct btrfs_key max_key = {
937 .objectid = (u64)-1,
938 .type = (u8)-1,
939 .offset = (u64)-1
940 };
941
942 rc = kzalloc(sizeof(*rc), GFP_KERNEL);
943 if (!rc)
944 return ERR_PTR(-ENOMEM);
945
946 rc->fs_info = root->fs_info;
947 rc->key_start = *key_start;
948 rc->key_end = *key_end;
949 atomic_set(&rc->elems, 0);
950 init_waitqueue_head(&rc->wait);
951 kref_init(&rc->refcnt);
952 kref_get(&rc->refcnt); /* one ref for having elements */
953
954 node = btrfs_root_node(root);
955 start = node->start;
956 generation = btrfs_header_generation(node);
957 free_extent_buffer(node);
958
959 ret = reada_add_block(rc, start, &max_key, generation);
960 if (ret) {
961 kfree(rc);
962 return ERR_PTR(ret);
963 }
964
965 reada_start_machine(root->fs_info);
966
967 return rc;
968}
969
970#ifdef DEBUG
971int btrfs_reada_wait(void *handle)
972{
973 struct reada_control *rc = handle;
974 struct btrfs_fs_info *fs_info = rc->fs_info;
975
976 while (atomic_read(&rc->elems)) {
977 if (!atomic_read(&fs_info->reada_works_cnt))
978 reada_start_machine(fs_info);
979 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
980 5 * HZ);
981 dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
982 }
983
984 dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
985
986 kref_put(&rc->refcnt, reada_control_release);
987
988 return 0;
989}
990#else
991int btrfs_reada_wait(void *handle)
992{
993 struct reada_control *rc = handle;
994 struct btrfs_fs_info *fs_info = rc->fs_info;
995
996 while (atomic_read(&rc->elems)) {
997 if (!atomic_read(&fs_info->reada_works_cnt))
998 reada_start_machine(fs_info);
999 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
1000 (HZ + 9) / 10);
1001 }
1002
1003 kref_put(&rc->refcnt, reada_control_release);
1004
1005 return 0;
1006}
1007#endif
1008
1009void btrfs_reada_detach(void *handle)
1010{
1011 struct reada_control *rc = handle;
1012
1013 kref_put(&rc->refcnt, reada_control_release);
1014}