1 /*
2 * Copyright (C) 2011 STRATO. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public
6 * License v2 as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public
14 * License along with this program; if not, write to the
15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16 * Boston, MA 021110-1307, USA.
17 */
18
19 #include <linux/sched.h>
20 #include <linux/pagemap.h>
21 #include <linux/writeback.h>
22 #include <linux/blkdev.h>
23 #include <linux/rbtree.h>
24 #include <linux/slab.h>
25 #include <linux/workqueue.h>
26 #include "ctree.h"
27 #include "volumes.h"
28 #include "disk-io.h"
29 #include "transaction.h"
30 #include "dev-replace.h"
31
32 #undef DEBUG
33
34 /*
35 * This is the implementation for the generic read ahead framework.
36 *
37 * To trigger a readahead, btrfs_reada_add must be called. It will start
38 * a read ahead for the given range [start, end) on tree root. The returned
39 * handle can either be used to wait on the readahead to finish
40 * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
41 *
42 * The read ahead works as follows:
43 * On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
44 * reada_start_machine will then search for extents to prefetch and trigger
45 * some reads. When a read finishes for a node, all contained node/leaf
46 * pointers that lie in the given range will also be enqueued. The reads will
47 * be triggered in sequential order, thus giving a big win over a naive
48 * enumeration. It will also make use of multi-device layouts. Each disk
49 * will have its on read pointer and all disks will by utilized in parallel.
50 * Also will no two disks read both sides of a mirror simultaneously, as this
51 * would waste seeking capacity. Instead both disks will read different parts
52 * of the filesystem.
53 * Any number of readaheads can be started in parallel. The read order will be
54 * determined globally, i.e. 2 parallel readaheads will normally finish faster
55 * than the 2 started one after another.
56 */
57
58 #define MAX_IN_FLIGHT 6
59
60 struct reada_extctl {
61 struct list_head list;
62 struct reada_control *rc;
63 u64 generation;
64 };
65
66 struct reada_extent {
67 u64 logical;
68 struct btrfs_key top;
69 u32 blocksize;
70 int err;
71 struct list_head extctl;
72 int refcnt;
73 spinlock_t lock;
74 struct reada_zone *zones[BTRFS_MAX_MIRRORS];
75 int nzones;
76 struct btrfs_device *scheduled_for;
77 };
78
79 struct reada_zone {
80 u64 start;
81 u64 end;
82 u64 elems;
83 struct list_head list;
84 spinlock_t lock;
85 int locked;
86 struct btrfs_device *device;
87 struct btrfs_device *devs[BTRFS_MAX_MIRRORS]; /* full list, incl
88 * self */
89 int ndevs;
90 struct kref refcnt;
91 };
92
93 struct reada_machine_work {
94 struct btrfs_work work;
95 struct btrfs_fs_info *fs_info;
96 };
97
98 static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
99 static void reada_control_release(struct kref *kref);
100 static void reada_zone_release(struct kref *kref);
101 static void reada_start_machine(struct btrfs_fs_info *fs_info);
102 static void __reada_start_machine(struct btrfs_fs_info *fs_info);
103
104 static int reada_add_block(struct reada_control *rc, u64 logical,
105 struct btrfs_key *top, int level, u64 generation);
106
107 /* recurses */
108 /* in case of err, eb might be NULL */
109 static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
110 u64 start, int err)
111 {
112 int level = 0;
113 int nritems;
114 int i;
115 u64 bytenr;
116 u64 generation;
117 struct reada_extent *re;
118 struct btrfs_fs_info *fs_info = root->fs_info;
119 struct list_head list;
120 unsigned long index = start >> PAGE_CACHE_SHIFT;
121 struct btrfs_device *for_dev;
122
123 if (eb)
124 level = btrfs_header_level(eb);
125
126 /* find extent */
127 spin_lock(&fs_info->reada_lock);
128 re = radix_tree_lookup(&fs_info->reada_tree, index);
129 if (re)
130 re->refcnt++;
131 spin_unlock(&fs_info->reada_lock);
132
133 if (!re)
134 return -1;
135
136 spin_lock(&re->lock);
137 /*
138 * just take the full list from the extent. afterwards we
139 * don't need the lock anymore
140 */
141 list_replace_init(&re->extctl, &list);
142 for_dev = re->scheduled_for;
143 re->scheduled_for = NULL;
144 spin_unlock(&re->lock);
145
146 if (err == 0) {
147 nritems = level ? btrfs_header_nritems(eb) : 0;
148 generation = btrfs_header_generation(eb);
149 /*
150 * FIXME: currently we just set nritems to 0 if this is a leaf,
151 * effectively ignoring the content. In a next step we could
152 * trigger more readahead depending from the content, e.g.
153 * fetch the checksums for the extents in the leaf.
154 */
155 } else {
156 /*
157 * this is the error case, the extent buffer has not been
158 * read correctly. We won't access anything from it and
159 * just cleanup our data structures. Effectively this will
160 * cut the branch below this node from read ahead.
161 */
162 nritems = 0;
163 generation = 0;
164 }
165
166 for (i = 0; i < nritems; i++) {
167 struct reada_extctl *rec;
168 u64 n_gen;
169 struct btrfs_key key;
170 struct btrfs_key next_key;
171
172 btrfs_node_key_to_cpu(eb, &key, i);
173 if (i + 1 < nritems)
174 btrfs_node_key_to_cpu(eb, &next_key, i + 1);
175 else
176 next_key = re->top;
177 bytenr = btrfs_node_blockptr(eb, i);
178 n_gen = btrfs_node_ptr_generation(eb, i);
179
180 list_for_each_entry(rec, &list, list) {
181 struct reada_control *rc = rec->rc;
182
183 /*
184 * if the generation doesn't match, just ignore this
185 * extctl. This will probably cut off a branch from
186 * prefetch. Alternatively one could start a new (sub-)
187 * prefetch for this branch, starting again from root.
188 * FIXME: move the generation check out of this loop
189 */
190 #ifdef DEBUG
191 if (rec->generation != generation) {
192 printk(KERN_DEBUG "generation mismatch for "
193 "(%llu,%d,%llu) %llu != %llu\n",
194 key.objectid, key.type, key.offset,
195 rec->generation, generation);
196 }
197 #endif
198 if (rec->generation == generation &&
199 btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 &&
200 btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0)
201 reada_add_block(rc, bytenr, &next_key,
202 level - 1, n_gen);
203 }
204 }
205 /*
206 * free extctl records
207 */
208 while (!list_empty(&list)) {
209 struct reada_control *rc;
210 struct reada_extctl *rec;
211
212 rec = list_first_entry(&list, struct reada_extctl, list);
213 list_del(&rec->list);
214 rc = rec->rc;
215 kfree(rec);
216
217 kref_get(&rc->refcnt);
218 if (atomic_dec_and_test(&rc->elems)) {
219 kref_put(&rc->refcnt, reada_control_release);
220 wake_up(&rc->wait);
221 }
222 kref_put(&rc->refcnt, reada_control_release);
223
224 reada_extent_put(fs_info, re); /* one ref for each entry */
225 }
226 reada_extent_put(fs_info, re); /* our ref */
227 if (for_dev)
228 atomic_dec(&for_dev->reada_in_flight);
229
230 return 0;
231 }
232
233 /*
234 * start is passed separately in case eb in NULL, which may be the case with
235 * failed I/O
236 */
237 int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
238 u64 start, int err)
239 {
240 int ret;
241
242 ret = __readahead_hook(root, eb, start, err);
243
244 reada_start_machine(root->fs_info);
245
246 return ret;
247 }
248
249 static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
250 struct btrfs_device *dev, u64 logical,
251 struct btrfs_bio *bbio)
252 {
253 int ret;
254 struct reada_zone *zone;
255 struct btrfs_block_group_cache *cache = NULL;
256 u64 start;
257 u64 end;
258 int i;
259
260 zone = NULL;
261 spin_lock(&fs_info->reada_lock);
262 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
263 logical >> PAGE_CACHE_SHIFT, 1);
264 if (ret == 1)
265 kref_get(&zone->refcnt);
266 spin_unlock(&fs_info->reada_lock);
267
268 if (ret == 1) {
269 if (logical >= zone->start && logical < zone->end)
270 return zone;
271 spin_lock(&fs_info->reada_lock);
272 kref_put(&zone->refcnt, reada_zone_release);
273 spin_unlock(&fs_info->reada_lock);
274 }
275
276 cache = btrfs_lookup_block_group(fs_info, logical);
277 if (!cache)
278 return NULL;
279
280 start = cache->key.objectid;
281 end = start + cache->key.offset - 1;
282 btrfs_put_block_group(cache);
283
284 zone = kzalloc(sizeof(*zone), GFP_NOFS);
285 if (!zone)
286 return NULL;
287
288 zone->start = start;
289 zone->end = end;
290 INIT_LIST_HEAD(&zone->list);
291 spin_lock_init(&zone->lock);
292 zone->locked = 0;
293 kref_init(&zone->refcnt);
294 zone->elems = 0;
295 zone->device = dev; /* our device always sits at index 0 */
296 for (i = 0; i < bbio->num_stripes; ++i) {
297 /* bounds have already been checked */
298 zone->devs[i] = bbio->stripes[i].dev;
299 }
300 zone->ndevs = bbio->num_stripes;
301
302 spin_lock(&fs_info->reada_lock);
303 ret = radix_tree_insert(&dev->reada_zones,
304 (unsigned long)(zone->end >> PAGE_CACHE_SHIFT),
305 zone);
306
307 if (ret == -EEXIST) {
308 kfree(zone);
309 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
310 logical >> PAGE_CACHE_SHIFT, 1);
311 if (ret == 1)
312 kref_get(&zone->refcnt);
313 }
314 spin_unlock(&fs_info->reada_lock);
315
316 return zone;
317 }
318
319 static struct reada_extent *reada_find_extent(struct btrfs_root *root,
320 u64 logical,
321 struct btrfs_key *top, int level)
322 {
323 int ret;
324 struct reada_extent *re = NULL;
325 struct reada_extent *re_exist = NULL;
326 struct btrfs_fs_info *fs_info = root->fs_info;
327 struct btrfs_bio *bbio = NULL;
328 struct btrfs_device *dev;
329 struct btrfs_device *prev_dev;
330 u32 blocksize;
331 u64 length;
332 int nzones = 0;
333 int i;
334 unsigned long index = logical >> PAGE_CACHE_SHIFT;
335 int dev_replace_is_ongoing;
336
337 spin_lock(&fs_info->reada_lock);
338 re = radix_tree_lookup(&fs_info->reada_tree, index);
339 if (re)
340 re->refcnt++;
341 spin_unlock(&fs_info->reada_lock);
342
343 if (re)
344 return re;
345
346 re = kzalloc(sizeof(*re), GFP_NOFS);
347 if (!re)
348 return NULL;
349
350 blocksize = btrfs_level_size(root, level);
351 re->logical = logical;
352 re->blocksize = blocksize;
353 re->top = *top;
354 INIT_LIST_HEAD(&re->extctl);
355 spin_lock_init(&re->lock);
356 re->refcnt = 1;
357
358 /*
359 * map block
360 */
361 length = blocksize;
362 ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, &length,
363 &bbio, 0);
364 if (ret || !bbio || length < blocksize)
365 goto error;
366
367 if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
368 printk(KERN_ERR "btrfs readahead: more than %d copies not "
369 "supported", BTRFS_MAX_MIRRORS);
370 goto error;
371 }
372
373 for (nzones = 0; nzones < bbio->num_stripes; ++nzones) {
374 struct reada_zone *zone;
375
376 dev = bbio->stripes[nzones].dev;
377 zone = reada_find_zone(fs_info, dev, logical, bbio);
378 if (!zone)
379 break;
380
381 re->zones[nzones] = zone;
382 spin_lock(&zone->lock);
383 if (!zone->elems)
384 kref_get(&zone->refcnt);
385 ++zone->elems;
386 spin_unlock(&zone->lock);
387 spin_lock(&fs_info->reada_lock);
388 kref_put(&zone->refcnt, reada_zone_release);
389 spin_unlock(&fs_info->reada_lock);
390 }
391 re->nzones = nzones;
392 if (nzones == 0) {
393 /* not a single zone found, error and out */
394 goto error;
395 }
396
397 /* insert extent in reada_tree + all per-device trees, all or nothing */
398 btrfs_dev_replace_lock(&fs_info->dev_replace);
399 spin_lock(&fs_info->reada_lock);
400 ret = radix_tree_insert(&fs_info->reada_tree, index, re);
401 if (ret == -EEXIST) {
402 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
403 BUG_ON(!re_exist);
404 re_exist->refcnt++;
405 spin_unlock(&fs_info->reada_lock);
406 btrfs_dev_replace_unlock(&fs_info->dev_replace);
407 goto error;
408 }
409 if (ret) {
410 spin_unlock(&fs_info->reada_lock);
411 btrfs_dev_replace_unlock(&fs_info->dev_replace);
412 goto error;
413 }
414 prev_dev = NULL;
415 dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
416 &fs_info->dev_replace);
417 for (i = 0; i < nzones; ++i) {
418 dev = bbio->stripes[i].dev;
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 /* cannot read ahead on missing device */
431 continue;
432 }
433 if (dev_replace_is_ongoing &&
434 dev == fs_info->dev_replace.tgtdev) {
435 /*
436 * as this device is selected for reading only as
437 * a last resort, skip it for read ahead.
438 */
439 continue;
440 }
441 prev_dev = dev;
442 ret = radix_tree_insert(&dev->reada_extents, index, re);
443 if (ret) {
444 while (--i >= 0) {
445 dev = bbio->stripes[i].dev;
446 BUG_ON(dev == NULL);
447 /* ignore whether the entry was inserted */
448 radix_tree_delete(&dev->reada_extents, index);
449 }
450 BUG_ON(fs_info == NULL);
451 radix_tree_delete(&fs_info->reada_tree, index);
452 spin_unlock(&fs_info->reada_lock);
453 btrfs_dev_replace_unlock(&fs_info->dev_replace);
454 goto error;
455 }
456 }
457 spin_unlock(&fs_info->reada_lock);
458 btrfs_dev_replace_unlock(&fs_info->dev_replace);
459
460 kfree(bbio);
461 return re;
462
463 error:
464 while (nzones) {
465 struct reada_zone *zone;
466
467 --nzones;
468 zone = re->zones[nzones];
469 kref_get(&zone->refcnt);
470 spin_lock(&zone->lock);
471 --zone->elems;
472 if (zone->elems == 0) {
473 /*
474 * no fs_info->reada_lock needed, as this can't be
475 * the last ref
476 */
477 kref_put(&zone->refcnt, reada_zone_release);
478 }
479 spin_unlock(&zone->lock);
480
481 spin_lock(&fs_info->reada_lock);
482 kref_put(&zone->refcnt, reada_zone_release);
483 spin_unlock(&fs_info->reada_lock);
484 }
485 kfree(bbio);
486 kfree(re);
487 return re_exist;
488 }
489
490 static void reada_extent_put(struct btrfs_fs_info *fs_info,
491 struct reada_extent *re)
492 {
493 int i;
494 unsigned long index = re->logical >> PAGE_CACHE_SHIFT;
495
496 spin_lock(&fs_info->reada_lock);
497 if (--re->refcnt) {
498 spin_unlock(&fs_info->reada_lock);
499 return;
500 }
501
502 radix_tree_delete(&fs_info->reada_tree, index);
503 for (i = 0; i < re->nzones; ++i) {
504 struct reada_zone *zone = re->zones[i];
505
506 radix_tree_delete(&zone->device->reada_extents, index);
507 }
508
509 spin_unlock(&fs_info->reada_lock);
510
511 for (i = 0; i < re->nzones; ++i) {
512 struct reada_zone *zone = re->zones[i];
513
514 kref_get(&zone->refcnt);
515 spin_lock(&zone->lock);
516 --zone->elems;
517 if (zone->elems == 0) {
518 /* no fs_info->reada_lock needed, as this can't be
519 * the last ref */
520 kref_put(&zone->refcnt, reada_zone_release);
521 }
522 spin_unlock(&zone->lock);
523
524 spin_lock(&fs_info->reada_lock);
525 kref_put(&zone->refcnt, reada_zone_release);
526 spin_unlock(&fs_info->reada_lock);
527 }
528 if (re->scheduled_for)
529 atomic_dec(&re->scheduled_for->reada_in_flight);
530
531 kfree(re);
532 }
533
534 static void reada_zone_release(struct kref *kref)
535 {
536 struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
537
538 radix_tree_delete(&zone->device->reada_zones,
539 zone->end >> PAGE_CACHE_SHIFT);
540
541 kfree(zone);
542 }
543
544 static void reada_control_release(struct kref *kref)
545 {
546 struct reada_control *rc = container_of(kref, struct reada_control,
547 refcnt);
548
549 kfree(rc);
550 }
551
552 static int reada_add_block(struct reada_control *rc, u64 logical,
553 struct btrfs_key *top, int level, u64 generation)
554 {
555 struct btrfs_root *root = rc->root;
556 struct reada_extent *re;
557 struct reada_extctl *rec;
558
559 re = reada_find_extent(root, logical, top, level); /* takes one ref */
560 if (!re)
561 return -1;
562
563 rec = kzalloc(sizeof(*rec), GFP_NOFS);
564 if (!rec) {
565 reada_extent_put(root->fs_info, re);
566 return -1;
567 }
568
569 rec->rc = rc;
570 rec->generation = generation;
571 atomic_inc(&rc->elems);
572
573 spin_lock(&re->lock);
574 list_add_tail(&rec->list, &re->extctl);
575 spin_unlock(&re->lock);
576
577 /* leave the ref on the extent */
578
579 return 0;
580 }
581
582 /*
583 * called with fs_info->reada_lock held
584 */
585 static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
586 {
587 int i;
588 unsigned long index = zone->end >> PAGE_CACHE_SHIFT;
589
590 for (i = 0; i < zone->ndevs; ++i) {
591 struct reada_zone *peer;
592 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
593 if (peer && peer->device != zone->device)
594 peer->locked = lock;
595 }
596 }
597
598 /*
599 * called with fs_info->reada_lock held
600 */
601 static int reada_pick_zone(struct btrfs_device *dev)
602 {
603 struct reada_zone *top_zone = NULL;
604 struct reada_zone *top_locked_zone = NULL;
605 u64 top_elems = 0;
606 u64 top_locked_elems = 0;
607 unsigned long index = 0;
608 int ret;
609
610 if (dev->reada_curr_zone) {
611 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
612 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
613 dev->reada_curr_zone = NULL;
614 }
615 /* pick the zone with the most elements */
616 while (1) {
617 struct reada_zone *zone;
618
619 ret = radix_tree_gang_lookup(&dev->reada_zones,
620 (void **)&zone, index, 1);
621 if (ret == 0)
622 break;
623 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
624 if (zone->locked) {
625 if (zone->elems > top_locked_elems) {
626 top_locked_elems = zone->elems;
627 top_locked_zone = zone;
628 }
629 } else {
630 if (zone->elems > top_elems) {
631 top_elems = zone->elems;
632 top_zone = zone;
633 }
634 }
635 }
636 if (top_zone)
637 dev->reada_curr_zone = top_zone;
638 else if (top_locked_zone)
639 dev->reada_curr_zone = top_locked_zone;
640 else
641 return 0;
642
643 dev->reada_next = dev->reada_curr_zone->start;
644 kref_get(&dev->reada_curr_zone->refcnt);
645 reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
646
647 return 1;
648 }
649
650 static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
651 struct btrfs_device *dev)
652 {
653 struct reada_extent *re = NULL;
654 int mirror_num = 0;
655 struct extent_buffer *eb = NULL;
656 u64 logical;
657 u32 blocksize;
658 int ret;
659 int i;
660 int need_kick = 0;
661
662 spin_lock(&fs_info->reada_lock);
663 if (dev->reada_curr_zone == NULL) {
664 ret = reada_pick_zone(dev);
665 if (!ret) {
666 spin_unlock(&fs_info->reada_lock);
667 return 0;
668 }
669 }
670 /*
671 * FIXME currently we issue the reads one extent at a time. If we have
672 * a contiguous block of extents, we could also coagulate them or use
673 * plugging to speed things up
674 */
675 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
676 dev->reada_next >> PAGE_CACHE_SHIFT, 1);
677 if (ret == 0 || re->logical >= dev->reada_curr_zone->end) {
678 ret = reada_pick_zone(dev);
679 if (!ret) {
680 spin_unlock(&fs_info->reada_lock);
681 return 0;
682 }
683 re = NULL;
684 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
685 dev->reada_next >> PAGE_CACHE_SHIFT, 1);
686 }
687 if (ret == 0) {
688 spin_unlock(&fs_info->reada_lock);
689 return 0;
690 }
691 dev->reada_next = re->logical + re->blocksize;
692 re->refcnt++;
693
694 spin_unlock(&fs_info->reada_lock);
695
696 /*
697 * find mirror num
698 */
699 for (i = 0; i < re->nzones; ++i) {
700 if (re->zones[i]->device == dev) {
701 mirror_num = i + 1;
702 break;
703 }
704 }
705 logical = re->logical;
706 blocksize = re->blocksize;
707
708 spin_lock(&re->lock);
709 if (re->scheduled_for == NULL) {
710 re->scheduled_for = dev;
711 need_kick = 1;
712 }
713 spin_unlock(&re->lock);
714
715 reada_extent_put(fs_info, re);
716
717 if (!need_kick)
718 return 0;
719
720 atomic_inc(&dev->reada_in_flight);
721 ret = reada_tree_block_flagged(fs_info->extent_root, logical, blocksize,
722 mirror_num, &eb);
723 if (ret)
724 __readahead_hook(fs_info->extent_root, NULL, logical, ret);
725 else if (eb)
726 __readahead_hook(fs_info->extent_root, eb, eb->start, ret);
727
728 if (eb)
729 free_extent_buffer(eb);
730
731 return 1;
732
733 }
734
735 static void reada_start_machine_worker(struct btrfs_work *work)
736 {
737 struct reada_machine_work *rmw;
738 struct btrfs_fs_info *fs_info;
739 int old_ioprio;
740
741 rmw = container_of(work, struct reada_machine_work, work);
742 fs_info = rmw->fs_info;
743
744 kfree(rmw);
745
746 old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
747 task_nice_ioprio(current));
748 set_task_ioprio(current, BTRFS_IOPRIO_READA);
749 __reada_start_machine(fs_info);
750 set_task_ioprio(current, old_ioprio);
751 }
752
753 static void __reada_start_machine(struct btrfs_fs_info *fs_info)
754 {
755 struct btrfs_device *device;
756 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
757 u64 enqueued;
758 u64 total = 0;
759 int i;
760
761 do {
762 enqueued = 0;
763 list_for_each_entry(device, &fs_devices->devices, dev_list) {
764 if (atomic_read(&device->reada_in_flight) <
765 MAX_IN_FLIGHT)
766 enqueued += reada_start_machine_dev(fs_info,
767 device);
768 }
769 total += enqueued;
770 } while (enqueued && total < 10000);
771
772 if (enqueued == 0)
773 return;
774
775 /*
776 * If everything is already in the cache, this is effectively single
777 * threaded. To a) not hold the caller for too long and b) to utilize
778 * more cores, we broke the loop above after 10000 iterations and now
779 * enqueue to workers to finish it. This will distribute the load to
780 * the cores.
781 */
782 for (i = 0; i < 2; ++i)
783 reada_start_machine(fs_info);
784 }
785
786 static void reada_start_machine(struct btrfs_fs_info *fs_info)
787 {
788 struct reada_machine_work *rmw;
789
790 rmw = kzalloc(sizeof(*rmw), GFP_NOFS);
791 if (!rmw) {
792 /* FIXME we cannot handle this properly right now */
793 BUG();
794 }
795 rmw->work.func = reada_start_machine_worker;
796 rmw->fs_info = fs_info;
797
798 btrfs_queue_worker(&fs_info->readahead_workers, &rmw->work);
799 }
800
801 #ifdef DEBUG
802 static void dump_devs(struct btrfs_fs_info *fs_info, int all)
803 {
804 struct btrfs_device *device;
805 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
806 unsigned long index;
807 int ret;
808 int i;
809 int j;
810 int cnt;
811
812 spin_lock(&fs_info->reada_lock);
813 list_for_each_entry(device, &fs_devices->devices, dev_list) {
814 printk(KERN_DEBUG "dev %lld has %d in flight\n", device->devid,
815 atomic_read(&device->reada_in_flight));
816 index = 0;
817 while (1) {
818 struct reada_zone *zone;
819 ret = radix_tree_gang_lookup(&device->reada_zones,
820 (void **)&zone, index, 1);
821 if (ret == 0)
822 break;
823 printk(KERN_DEBUG " zone %llu-%llu elems %llu locked "
824 "%d devs", zone->start, zone->end, zone->elems,
825 zone->locked);
826 for (j = 0; j < zone->ndevs; ++j) {
827 printk(KERN_CONT " %lld",
828 zone->devs[j]->devid);
829 }
830 if (device->reada_curr_zone == zone)
831 printk(KERN_CONT " curr off %llu",
832 device->reada_next - zone->start);
833 printk(KERN_CONT "\n");
834 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
835 }
836 cnt = 0;
837 index = 0;
838 while (all) {
839 struct reada_extent *re = NULL;
840
841 ret = radix_tree_gang_lookup(&device->reada_extents,
842 (void **)&re, index, 1);
843 if (ret == 0)
844 break;
845 printk(KERN_DEBUG
846 " re: logical %llu size %u empty %d for %lld",
847 re->logical, re->blocksize,
848 list_empty(&re->extctl), re->scheduled_for ?
849 re->scheduled_for->devid : -1);
850
851 for (i = 0; i < re->nzones; ++i) {
852 printk(KERN_CONT " zone %llu-%llu devs",
853 re->zones[i]->start,
854 re->zones[i]->end);
855 for (j = 0; j < re->zones[i]->ndevs; ++j) {
856 printk(KERN_CONT " %lld",
857 re->zones[i]->devs[j]->devid);
858 }
859 }
860 printk(KERN_CONT "\n");
861 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
862 if (++cnt > 15)
863 break;
864 }
865 }
866
867 index = 0;
868 cnt = 0;
869 while (all) {
870 struct reada_extent *re = NULL;
871
872 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
873 index, 1);
874 if (ret == 0)
875 break;
876 if (!re->scheduled_for) {
877 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
878 continue;
879 }
880 printk(KERN_DEBUG
881 "re: logical %llu size %u list empty %d for %lld",
882 re->logical, re->blocksize, list_empty(&re->extctl),
883 re->scheduled_for ? re->scheduled_for->devid : -1);
884 for (i = 0; i < re->nzones; ++i) {
885 printk(KERN_CONT " zone %llu-%llu devs",
886 re->zones[i]->start,
887 re->zones[i]->end);
888 for (i = 0; i < re->nzones; ++i) {
889 printk(KERN_CONT " zone %llu-%llu devs",
890 re->zones[i]->start,
891 re->zones[i]->end);
892 for (j = 0; j < re->zones[i]->ndevs; ++j) {
893 printk(KERN_CONT " %lld",
894 re->zones[i]->devs[j]->devid);
895 }
896 }
897 }
898 printk(KERN_CONT "\n");
899 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
900 }
901 spin_unlock(&fs_info->reada_lock);
902 }
903 #endif
904
905 /*
906 * interface
907 */
908 struct reada_control *btrfs_reada_add(struct btrfs_root *root,
909 struct btrfs_key *key_start, struct btrfs_key *key_end)
910 {
911 struct reada_control *rc;
912 u64 start;
913 u64 generation;
914 int level;
915 struct extent_buffer *node;
916 static struct btrfs_key max_key = {
917 .objectid = (u64)-1,
918 .type = (u8)-1,
919 .offset = (u64)-1
920 };
921
922 rc = kzalloc(sizeof(*rc), GFP_NOFS);
923 if (!rc)
924 return ERR_PTR(-ENOMEM);
925
926 rc->root = root;
927 rc->key_start = *key_start;
928 rc->key_end = *key_end;
929 atomic_set(&rc->elems, 0);
930 init_waitqueue_head(&rc->wait);
931 kref_init(&rc->refcnt);
932 kref_get(&rc->refcnt); /* one ref for having elements */
933
934 node = btrfs_root_node(root);
935 start = node->start;
936 level = btrfs_header_level(node);
937 generation = btrfs_header_generation(node);
938 free_extent_buffer(node);
939
940 if (reada_add_block(rc, start, &max_key, level, generation)) {
941 kfree(rc);
942 return ERR_PTR(-ENOMEM);
943 }
944
945 reada_start_machine(root->fs_info);
946
947 return rc;
948 }
949
950 #ifdef DEBUG
951 int btrfs_reada_wait(void *handle)
952 {
953 struct reada_control *rc = handle;
954
955 while (atomic_read(&rc->elems)) {
956 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
957 5 * HZ);
958 dump_devs(rc->root->fs_info,
959 atomic_read(&rc->elems) < 10 ? 1 : 0);
960 }
961
962 dump_devs(rc->root->fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
963
964 kref_put(&rc->refcnt, reada_control_release);
965
966 return 0;
967 }
968 #else
969 int btrfs_reada_wait(void *handle)
970 {
971 struct reada_control *rc = handle;
972
973 while (atomic_read(&rc->elems)) {
974 wait_event(rc->wait, atomic_read(&rc->elems) == 0);
975 }
976
977 kref_put(&rc->refcnt, reada_control_release);
978
979 return 0;
980 }
981 #endif
982
983 void btrfs_reada_detach(void *handle)
984 {
985 struct reada_control *rc = handle;
986
987 kref_put(&rc->refcnt, reada_control_release);
988 }
989
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