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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
31#undef DEBUG
32
33/*
34 * This is the implementation for the generic read ahead framework.
35 *
36 * To trigger a readahead, btrfs_reada_add must be called. It will start
37 * a read ahead for the given range [start, end) on tree root. The returned
38 * handle can either be used to wait on the readahead to finish
39 * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
40 *
41 * The read ahead works as follows:
42 * On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
43 * reada_start_machine will then search for extents to prefetch and trigger
44 * some reads. When a read finishes for a node, all contained node/leaf
45 * pointers that lie in the given range will also be enqueued. The reads will
46 * be triggered in sequential order, thus giving a big win over a naive
47 * enumeration. It will also make use of multi-device layouts. Each disk
48 * will have its on read pointer and all disks will by utilized in parallel.
49 * Also will no two disks read both sides of a mirror simultaneously, as this
50 * would waste seeking capacity. Instead both disks will read different parts
51 * of the filesystem.
52 * Any number of readaheads can be started in parallel. The read order will be
53 * determined globally, i.e. 2 parallel readaheads will normally finish faster
54 * than the 2 started one after another.
55 */
56
57#define MAX_IN_FLIGHT 6
58
59struct reada_extctl {
60 struct list_head list;
61 struct reada_control *rc;
62 u64 generation;
63};
64
65struct reada_extent {
66 u64 logical;
67 struct btrfs_key top;
68 u32 blocksize;
69 int err;
70 struct list_head extctl;
71 struct kref refcnt;
72 spinlock_t lock;
73 struct reada_zone *zones[BTRFS_MAX_MIRRORS];
74 int nzones;
75 struct btrfs_device *scheduled_for;
76};
77
78struct reada_zone {
79 u64 start;
80 u64 end;
81 u64 elems;
82 struct list_head list;
83 spinlock_t lock;
84 int locked;
85 struct btrfs_device *device;
86 struct btrfs_device *devs[BTRFS_MAX_MIRRORS]; /* full list, incl
87 * self */
88 int ndevs;
89 struct kref refcnt;
90};
91
92struct reada_machine_work {
93 struct btrfs_work work;
94 struct btrfs_fs_info *fs_info;
95};
96
97static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
98static void reada_control_release(struct kref *kref);
99static void reada_zone_release(struct kref *kref);
100static void reada_start_machine(struct btrfs_fs_info *fs_info);
101static void __reada_start_machine(struct btrfs_fs_info *fs_info);
102
103static int reada_add_block(struct reada_control *rc, u64 logical,
104 struct btrfs_key *top, int level, u64 generation);
105
106/* recurses */
107/* in case of err, eb might be NULL */
108static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
109 u64 start, int err)
110{
111 int level = 0;
112 int nritems;
113 int i;
114 u64 bytenr;
115 u64 generation;
116 struct reada_extent *re;
117 struct btrfs_fs_info *fs_info = root->fs_info;
118 struct list_head list;
119 unsigned long index = start >> PAGE_CACHE_SHIFT;
120 struct btrfs_device *for_dev;
121
122 if (eb)
123 level = btrfs_header_level(eb);
124
125 /* find extent */
126 spin_lock(&fs_info->reada_lock);
127 re = radix_tree_lookup(&fs_info->reada_tree, index);
128 if (re)
129 kref_get(&re->refcnt);
130 spin_unlock(&fs_info->reada_lock);
131
132 if (!re)
133 return -1;
134
135 spin_lock(&re->lock);
136 /*
137 * just take the full list from the extent. afterwards we
138 * don't need the lock anymore
139 */
140 list_replace_init(&re->extctl, &list);
141 for_dev = re->scheduled_for;
142 re->scheduled_for = NULL;
143 spin_unlock(&re->lock);
144
145 if (err == 0) {
146 nritems = level ? btrfs_header_nritems(eb) : 0;
147 generation = btrfs_header_generation(eb);
148 /*
149 * FIXME: currently we just set nritems to 0 if this is a leaf,
150 * effectively ignoring the content. In a next step we could
151 * trigger more readahead depending from the content, e.g.
152 * fetch the checksums for the extents in the leaf.
153 */
154 } else {
155 /*
156 * this is the error case, the extent buffer has not been
157 * read correctly. We won't access anything from it and
158 * just cleanup our data structures. Effectively this will
159 * cut the branch below this node from read ahead.
160 */
161 nritems = 0;
162 generation = 0;
163 }
164
165 for (i = 0; i < nritems; i++) {
166 struct reada_extctl *rec;
167 u64 n_gen;
168 struct btrfs_key key;
169 struct btrfs_key next_key;
170
171 btrfs_node_key_to_cpu(eb, &key, i);
172 if (i + 1 < nritems)
173 btrfs_node_key_to_cpu(eb, &next_key, i + 1);
174 else
175 next_key = re->top;
176 bytenr = btrfs_node_blockptr(eb, i);
177 n_gen = btrfs_node_ptr_generation(eb, i);
178
179 list_for_each_entry(rec, &list, list) {
180 struct reada_control *rc = rec->rc;
181
182 /*
183 * if the generation doesn't match, just ignore this
184 * extctl. This will probably cut off a branch from
185 * prefetch. Alternatively one could start a new (sub-)
186 * prefetch for this branch, starting again from root.
187 * FIXME: move the generation check out of this loop
188 */
189#ifdef DEBUG
190 if (rec->generation != generation) {
191 printk(KERN_DEBUG "generation mismatch for "
192 "(%llu,%d,%llu) %llu != %llu\n",
193 key.objectid, key.type, key.offset,
194 rec->generation, generation);
195 }
196#endif
197 if (rec->generation == generation &&
198 btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 &&
199 btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0)
200 reada_add_block(rc, bytenr, &next_key,
201 level - 1, n_gen);
202 }
203 }
204 /*
205 * free extctl records
206 */
207 while (!list_empty(&list)) {
208 struct reada_control *rc;
209 struct reada_extctl *rec;
210
211 rec = list_first_entry(&list, struct reada_extctl, list);
212 list_del(&rec->list);
213 rc = rec->rc;
214 kfree(rec);
215
216 kref_get(&rc->refcnt);
217 if (atomic_dec_and_test(&rc->elems)) {
218 kref_put(&rc->refcnt, reada_control_release);
219 wake_up(&rc->wait);
220 }
221 kref_put(&rc->refcnt, reada_control_release);
222
223 reada_extent_put(fs_info, re); /* one ref for each entry */
224 }
225 reada_extent_put(fs_info, re); /* our ref */
226 if (for_dev)
227 atomic_dec(&for_dev->reada_in_flight);
228
229 return 0;
230}
231
232/*
233 * start is passed separately in case eb in NULL, which may be the case with
234 * failed I/O
235 */
236int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
237 u64 start, int err)
238{
239 int ret;
240
241 ret = __readahead_hook(root, eb, start, err);
242
243 reada_start_machine(root->fs_info);
244
245 return ret;
246}
247
248static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
249 struct btrfs_device *dev, u64 logical,
250 struct btrfs_bio *bbio)
251{
252 int ret;
253 struct reada_zone *zone;
254 struct btrfs_block_group_cache *cache = NULL;
255 u64 start;
256 u64 end;
257 int i;
258
259 zone = NULL;
260 spin_lock(&fs_info->reada_lock);
261 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
262 logical >> PAGE_CACHE_SHIFT, 1);
263 if (ret == 1)
264 kref_get(&zone->refcnt);
265 spin_unlock(&fs_info->reada_lock);
266
267 if (ret == 1) {
268 if (logical >= zone->start && logical < zone->end)
269 return zone;
270 spin_lock(&fs_info->reada_lock);
271 kref_put(&zone->refcnt, reada_zone_release);
272 spin_unlock(&fs_info->reada_lock);
273 }
274
275 cache = btrfs_lookup_block_group(fs_info, logical);
276 if (!cache)
277 return NULL;
278
279 start = cache->key.objectid;
280 end = start + cache->key.offset - 1;
281 btrfs_put_block_group(cache);
282
283 zone = kzalloc(sizeof(*zone), GFP_NOFS);
284 if (!zone)
285 return NULL;
286
287 zone->start = start;
288 zone->end = end;
289 INIT_LIST_HEAD(&zone->list);
290 spin_lock_init(&zone->lock);
291 zone->locked = 0;
292 kref_init(&zone->refcnt);
293 zone->elems = 0;
294 zone->device = dev; /* our device always sits at index 0 */
295 for (i = 0; i < bbio->num_stripes; ++i) {
296 /* bounds have already been checked */
297 zone->devs[i] = bbio->stripes[i].dev;
298 }
299 zone->ndevs = bbio->num_stripes;
300
301 spin_lock(&fs_info->reada_lock);
302 ret = radix_tree_insert(&dev->reada_zones,
303 (unsigned long)(zone->end >> PAGE_CACHE_SHIFT),
304 zone);
305
306 if (ret == -EEXIST) {
307 kfree(zone);
308 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
309 logical >> PAGE_CACHE_SHIFT, 1);
310 if (ret == 1)
311 kref_get(&zone->refcnt);
312 }
313 spin_unlock(&fs_info->reada_lock);
314
315 return zone;
316}
317
318static struct reada_extent *reada_find_extent(struct btrfs_root *root,
319 u64 logical,
320 struct btrfs_key *top, int level)
321{
322 int ret;
323 struct reada_extent *re = NULL;
324 struct reada_extent *re_exist = NULL;
325 struct btrfs_fs_info *fs_info = root->fs_info;
326 struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
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
336 spin_lock(&fs_info->reada_lock);
337 re = radix_tree_lookup(&fs_info->reada_tree, index);
338 if (re)
339 kref_get(&re->refcnt);
340 spin_unlock(&fs_info->reada_lock);
341
342 if (re)
343 return re;
344
345 re = kzalloc(sizeof(*re), GFP_NOFS);
346 if (!re)
347 return NULL;
348
349 blocksize = btrfs_level_size(root, level);
350 re->logical = logical;
351 re->blocksize = blocksize;
352 re->top = *top;
353 INIT_LIST_HEAD(&re->extctl);
354 spin_lock_init(&re->lock);
355 kref_init(&re->refcnt);
356
357 /*
358 * map block
359 */
360 length = blocksize;
361 ret = btrfs_map_block(map_tree, REQ_WRITE, logical, &length, &bbio, 0);
362 if (ret || !bbio || length < blocksize)
363 goto error;
364
365 if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
366 printk(KERN_ERR "btrfs readahead: more than %d copies not "
367 "supported", BTRFS_MAX_MIRRORS);
368 goto error;
369 }
370
371 for (nzones = 0; nzones < bbio->num_stripes; ++nzones) {
372 struct reada_zone *zone;
373
374 dev = bbio->stripes[nzones].dev;
375 zone = reada_find_zone(fs_info, dev, logical, bbio);
376 if (!zone)
377 break;
378
379 re->zones[nzones] = zone;
380 spin_lock(&zone->lock);
381 if (!zone->elems)
382 kref_get(&zone->refcnt);
383 ++zone->elems;
384 spin_unlock(&zone->lock);
385 spin_lock(&fs_info->reada_lock);
386 kref_put(&zone->refcnt, reada_zone_release);
387 spin_unlock(&fs_info->reada_lock);
388 }
389 re->nzones = nzones;
390 if (nzones == 0) {
391 /* not a single zone found, error and out */
392 goto error;
393 }
394
395 /* insert extent in reada_tree + all per-device trees, all or nothing */
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 BUG_ON(!re_exist);
401 kref_get(&re_exist->refcnt);
402 spin_unlock(&fs_info->reada_lock);
403 goto error;
404 }
405 if (ret) {
406 spin_unlock(&fs_info->reada_lock);
407 goto error;
408 }
409 prev_dev = NULL;
410 for (i = 0; i < nzones; ++i) {
411 dev = bbio->stripes[i].dev;
412 if (dev == prev_dev) {
413 /*
414 * in case of DUP, just add the first zone. As both
415 * are on the same device, there's nothing to gain
416 * from adding both.
417 * Also, it wouldn't work, as the tree is per device
418 * and adding would fail with EEXIST
419 */
420 continue;
421 }
422 prev_dev = dev;
423 ret = radix_tree_insert(&dev->reada_extents, index, re);
424 if (ret) {
425 while (--i >= 0) {
426 dev = bbio->stripes[i].dev;
427 BUG_ON(dev == NULL);
428 radix_tree_delete(&dev->reada_extents, index);
429 }
430 BUG_ON(fs_info == NULL);
431 radix_tree_delete(&fs_info->reada_tree, index);
432 spin_unlock(&fs_info->reada_lock);
433 goto error;
434 }
435 }
436 spin_unlock(&fs_info->reada_lock);
437
438 kfree(bbio);
439 return re;
440
441error:
442 while (nzones) {
443 struct reada_zone *zone;
444
445 --nzones;
446 zone = re->zones[nzones];
447 kref_get(&zone->refcnt);
448 spin_lock(&zone->lock);
449 --zone->elems;
450 if (zone->elems == 0) {
451 /*
452 * no fs_info->reada_lock needed, as this can't be
453 * the last ref
454 */
455 kref_put(&zone->refcnt, reada_zone_release);
456 }
457 spin_unlock(&zone->lock);
458
459 spin_lock(&fs_info->reada_lock);
460 kref_put(&zone->refcnt, reada_zone_release);
461 spin_unlock(&fs_info->reada_lock);
462 }
463 kfree(bbio);
464 kfree(re);
465 return re_exist;
466}
467
468static void reada_kref_dummy(struct kref *kr)
469{
470}
471
472static void reada_extent_put(struct btrfs_fs_info *fs_info,
473 struct reada_extent *re)
474{
475 int i;
476 unsigned long index = re->logical >> PAGE_CACHE_SHIFT;
477
478 spin_lock(&fs_info->reada_lock);
479 if (!kref_put(&re->refcnt, reada_kref_dummy)) {
480 spin_unlock(&fs_info->reada_lock);
481 return;
482 }
483
484 radix_tree_delete(&fs_info->reada_tree, index);
485 for (i = 0; i < re->nzones; ++i) {
486 struct reada_zone *zone = re->zones[i];
487
488 radix_tree_delete(&zone->device->reada_extents, index);
489 }
490
491 spin_unlock(&fs_info->reada_lock);
492
493 for (i = 0; i < re->nzones; ++i) {
494 struct reada_zone *zone = re->zones[i];
495
496 kref_get(&zone->refcnt);
497 spin_lock(&zone->lock);
498 --zone->elems;
499 if (zone->elems == 0) {
500 /* no fs_info->reada_lock needed, as this can't be
501 * the last ref */
502 kref_put(&zone->refcnt, reada_zone_release);
503 }
504 spin_unlock(&zone->lock);
505
506 spin_lock(&fs_info->reada_lock);
507 kref_put(&zone->refcnt, reada_zone_release);
508 spin_unlock(&fs_info->reada_lock);
509 }
510 if (re->scheduled_for)
511 atomic_dec(&re->scheduled_for->reada_in_flight);
512
513 kfree(re);
514}
515
516static void reada_zone_release(struct kref *kref)
517{
518 struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
519
520 radix_tree_delete(&zone->device->reada_zones,
521 zone->end >> PAGE_CACHE_SHIFT);
522
523 kfree(zone);
524}
525
526static void reada_control_release(struct kref *kref)
527{
528 struct reada_control *rc = container_of(kref, struct reada_control,
529 refcnt);
530
531 kfree(rc);
532}
533
534static int reada_add_block(struct reada_control *rc, u64 logical,
535 struct btrfs_key *top, int level, u64 generation)
536{
537 struct btrfs_root *root = rc->root;
538 struct reada_extent *re;
539 struct reada_extctl *rec;
540
541 re = reada_find_extent(root, logical, top, level); /* takes one ref */
542 if (!re)
543 return -1;
544
545 rec = kzalloc(sizeof(*rec), GFP_NOFS);
546 if (!rec) {
547 reada_extent_put(root->fs_info, re);
548 return -1;
549 }
550
551 rec->rc = rc;
552 rec->generation = generation;
553 atomic_inc(&rc->elems);
554
555 spin_lock(&re->lock);
556 list_add_tail(&rec->list, &re->extctl);
557 spin_unlock(&re->lock);
558
559 /* leave the ref on the extent */
560
561 return 0;
562}
563
564/*
565 * called with fs_info->reada_lock held
566 */
567static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
568{
569 int i;
570 unsigned long index = zone->end >> PAGE_CACHE_SHIFT;
571
572 for (i = 0; i < zone->ndevs; ++i) {
573 struct reada_zone *peer;
574 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
575 if (peer && peer->device != zone->device)
576 peer->locked = lock;
577 }
578}
579
580/*
581 * called with fs_info->reada_lock held
582 */
583static int reada_pick_zone(struct btrfs_device *dev)
584{
585 struct reada_zone *top_zone = NULL;
586 struct reada_zone *top_locked_zone = NULL;
587 u64 top_elems = 0;
588 u64 top_locked_elems = 0;
589 unsigned long index = 0;
590 int ret;
591
592 if (dev->reada_curr_zone) {
593 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
594 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
595 dev->reada_curr_zone = NULL;
596 }
597 /* pick the zone with the most elements */
598 while (1) {
599 struct reada_zone *zone;
600
601 ret = radix_tree_gang_lookup(&dev->reada_zones,
602 (void **)&zone, index, 1);
603 if (ret == 0)
604 break;
605 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
606 if (zone->locked) {
607 if (zone->elems > top_locked_elems) {
608 top_locked_elems = zone->elems;
609 top_locked_zone = zone;
610 }
611 } else {
612 if (zone->elems > top_elems) {
613 top_elems = zone->elems;
614 top_zone = zone;
615 }
616 }
617 }
618 if (top_zone)
619 dev->reada_curr_zone = top_zone;
620 else if (top_locked_zone)
621 dev->reada_curr_zone = top_locked_zone;
622 else
623 return 0;
624
625 dev->reada_next = dev->reada_curr_zone->start;
626 kref_get(&dev->reada_curr_zone->refcnt);
627 reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
628
629 return 1;
630}
631
632static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
633 struct btrfs_device *dev)
634{
635 struct reada_extent *re = NULL;
636 int mirror_num = 0;
637 struct extent_buffer *eb = NULL;
638 u64 logical;
639 u32 blocksize;
640 int ret;
641 int i;
642 int need_kick = 0;
643
644 spin_lock(&fs_info->reada_lock);
645 if (dev->reada_curr_zone == NULL) {
646 ret = reada_pick_zone(dev);
647 if (!ret) {
648 spin_unlock(&fs_info->reada_lock);
649 return 0;
650 }
651 }
652 /*
653 * FIXME currently we issue the reads one extent at a time. If we have
654 * a contiguous block of extents, we could also coagulate them or use
655 * plugging to speed things up
656 */
657 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
658 dev->reada_next >> PAGE_CACHE_SHIFT, 1);
659 if (ret == 0 || re->logical >= dev->reada_curr_zone->end) {
660 ret = reada_pick_zone(dev);
661 if (!ret) {
662 spin_unlock(&fs_info->reada_lock);
663 return 0;
664 }
665 re = NULL;
666 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
667 dev->reada_next >> PAGE_CACHE_SHIFT, 1);
668 }
669 if (ret == 0) {
670 spin_unlock(&fs_info->reada_lock);
671 return 0;
672 }
673 dev->reada_next = re->logical + re->blocksize;
674 kref_get(&re->refcnt);
675
676 spin_unlock(&fs_info->reada_lock);
677
678 /*
679 * find mirror num
680 */
681 for (i = 0; i < re->nzones; ++i) {
682 if (re->zones[i]->device == dev) {
683 mirror_num = i + 1;
684 break;
685 }
686 }
687 logical = re->logical;
688 blocksize = re->blocksize;
689
690 spin_lock(&re->lock);
691 if (re->scheduled_for == NULL) {
692 re->scheduled_for = dev;
693 need_kick = 1;
694 }
695 spin_unlock(&re->lock);
696
697 reada_extent_put(fs_info, re);
698
699 if (!need_kick)
700 return 0;
701
702 atomic_inc(&dev->reada_in_flight);
703 ret = reada_tree_block_flagged(fs_info->extent_root, logical, blocksize,
704 mirror_num, &eb);
705 if (ret)
706 __readahead_hook(fs_info->extent_root, NULL, logical, ret);
707 else if (eb)
708 __readahead_hook(fs_info->extent_root, eb, eb->start, ret);
709
710 if (eb)
711 free_extent_buffer(eb);
712
713 return 1;
714
715}
716
717static void reada_start_machine_worker(struct btrfs_work *work)
718{
719 struct reada_machine_work *rmw;
720 struct btrfs_fs_info *fs_info;
721 int old_ioprio;
722
723 rmw = container_of(work, struct reada_machine_work, work);
724 fs_info = rmw->fs_info;
725
726 kfree(rmw);
727
728 old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
729 task_nice_ioprio(current));
730 set_task_ioprio(current, BTRFS_IOPRIO_READA);
731 __reada_start_machine(fs_info);
732 set_task_ioprio(current, old_ioprio);
733}
734
735static void __reada_start_machine(struct btrfs_fs_info *fs_info)
736{
737 struct btrfs_device *device;
738 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
739 u64 enqueued;
740 u64 total = 0;
741 int i;
742
743 do {
744 enqueued = 0;
745 list_for_each_entry(device, &fs_devices->devices, dev_list) {
746 if (atomic_read(&device->reada_in_flight) <
747 MAX_IN_FLIGHT)
748 enqueued += reada_start_machine_dev(fs_info,
749 device);
750 }
751 total += enqueued;
752 } while (enqueued && total < 10000);
753
754 if (enqueued == 0)
755 return;
756
757 /*
758 * If everything is already in the cache, this is effectively single
759 * threaded. To a) not hold the caller for too long and b) to utilize
760 * more cores, we broke the loop above after 10000 iterations and now
761 * enqueue to workers to finish it. This will distribute the load to
762 * the cores.
763 */
764 for (i = 0; i < 2; ++i)
765 reada_start_machine(fs_info);
766}
767
768static void reada_start_machine(struct btrfs_fs_info *fs_info)
769{
770 struct reada_machine_work *rmw;
771
772 rmw = kzalloc(sizeof(*rmw), GFP_NOFS);
773 if (!rmw) {
774 /* FIXME we cannot handle this properly right now */
775 BUG();
776 }
777 rmw->work.func = reada_start_machine_worker;
778 rmw->fs_info = fs_info;
779
780 btrfs_queue_worker(&fs_info->readahead_workers, &rmw->work);
781}
782
783#ifdef DEBUG
784static void dump_devs(struct btrfs_fs_info *fs_info, int all)
785{
786 struct btrfs_device *device;
787 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
788 unsigned long index;
789 int ret;
790 int i;
791 int j;
792 int cnt;
793
794 spin_lock(&fs_info->reada_lock);
795 list_for_each_entry(device, &fs_devices->devices, dev_list) {
796 printk(KERN_DEBUG "dev %lld has %d in flight\n", device->devid,
797 atomic_read(&device->reada_in_flight));
798 index = 0;
799 while (1) {
800 struct reada_zone *zone;
801 ret = radix_tree_gang_lookup(&device->reada_zones,
802 (void **)&zone, index, 1);
803 if (ret == 0)
804 break;
805 printk(KERN_DEBUG " zone %llu-%llu elems %llu locked "
806 "%d devs", zone->start, zone->end, zone->elems,
807 zone->locked);
808 for (j = 0; j < zone->ndevs; ++j) {
809 printk(KERN_CONT " %lld",
810 zone->devs[j]->devid);
811 }
812 if (device->reada_curr_zone == zone)
813 printk(KERN_CONT " curr off %llu",
814 device->reada_next - zone->start);
815 printk(KERN_CONT "\n");
816 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
817 }
818 cnt = 0;
819 index = 0;
820 while (all) {
821 struct reada_extent *re = NULL;
822
823 ret = radix_tree_gang_lookup(&device->reada_extents,
824 (void **)&re, index, 1);
825 if (ret == 0)
826 break;
827 printk(KERN_DEBUG
828 " re: logical %llu size %u empty %d for %lld",
829 re->logical, re->blocksize,
830 list_empty(&re->extctl), re->scheduled_for ?
831 re->scheduled_for->devid : -1);
832
833 for (i = 0; i < re->nzones; ++i) {
834 printk(KERN_CONT " zone %llu-%llu devs",
835 re->zones[i]->start,
836 re->zones[i]->end);
837 for (j = 0; j < re->zones[i]->ndevs; ++j) {
838 printk(KERN_CONT " %lld",
839 re->zones[i]->devs[j]->devid);
840 }
841 }
842 printk(KERN_CONT "\n");
843 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
844 if (++cnt > 15)
845 break;
846 }
847 }
848
849 index = 0;
850 cnt = 0;
851 while (all) {
852 struct reada_extent *re = NULL;
853
854 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
855 index, 1);
856 if (ret == 0)
857 break;
858 if (!re->scheduled_for) {
859 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
860 continue;
861 }
862 printk(KERN_DEBUG
863 "re: logical %llu size %u list empty %d for %lld",
864 re->logical, re->blocksize, list_empty(&re->extctl),
865 re->scheduled_for ? re->scheduled_for->devid : -1);
866 for (i = 0; i < re->nzones; ++i) {
867 printk(KERN_CONT " zone %llu-%llu devs",
868 re->zones[i]->start,
869 re->zones[i]->end);
870 for (i = 0; i < re->nzones; ++i) {
871 printk(KERN_CONT " zone %llu-%llu devs",
872 re->zones[i]->start,
873 re->zones[i]->end);
874 for (j = 0; j < re->zones[i]->ndevs; ++j) {
875 printk(KERN_CONT " %lld",
876 re->zones[i]->devs[j]->devid);
877 }
878 }
879 }
880 printk(KERN_CONT "\n");
881 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
882 }
883 spin_unlock(&fs_info->reada_lock);
884}
885#endif
886
887/*
888 * interface
889 */
890struct reada_control *btrfs_reada_add(struct btrfs_root *root,
891 struct btrfs_key *key_start, struct btrfs_key *key_end)
892{
893 struct reada_control *rc;
894 u64 start;
895 u64 generation;
896 int level;
897 struct extent_buffer *node;
898 static struct btrfs_key max_key = {
899 .objectid = (u64)-1,
900 .type = (u8)-1,
901 .offset = (u64)-1
902 };
903
904 rc = kzalloc(sizeof(*rc), GFP_NOFS);
905 if (!rc)
906 return ERR_PTR(-ENOMEM);
907
908 rc->root = root;
909 rc->key_start = *key_start;
910 rc->key_end = *key_end;
911 atomic_set(&rc->elems, 0);
912 init_waitqueue_head(&rc->wait);
913 kref_init(&rc->refcnt);
914 kref_get(&rc->refcnt); /* one ref for having elements */
915
916 node = btrfs_root_node(root);
917 start = node->start;
918 level = btrfs_header_level(node);
919 generation = btrfs_header_generation(node);
920 free_extent_buffer(node);
921
922 reada_add_block(rc, start, &max_key, level, generation);
923
924 reada_start_machine(root->fs_info);
925
926 return rc;
927}
928
929#ifdef DEBUG
930int btrfs_reada_wait(void *handle)
931{
932 struct reada_control *rc = handle;
933
934 while (atomic_read(&rc->elems)) {
935 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
936 5 * HZ);
937 dump_devs(rc->root->fs_info, rc->elems < 10 ? 1 : 0);
938 }
939
940 dump_devs(rc->root->fs_info, rc->elems < 10 ? 1 : 0);
941
942 kref_put(&rc->refcnt, reada_control_release);
943
944 return 0;
945}
946#else
947int btrfs_reada_wait(void *handle)
948{
949 struct reada_control *rc = handle;
950
951 while (atomic_read(&rc->elems)) {
952 wait_event(rc->wait, atomic_read(&rc->elems) == 0);
953 }
954
955 kref_put(&rc->refcnt, reada_control_release);
956
957 return 0;
958}
959#endif
960
961void btrfs_reada_detach(void *handle)
962{
963 struct reada_control *rc = handle;
964
965 kref_put(&rc->refcnt, reada_control_release);
966}