GNU Linux-libre 4.9.308-gnu1
[releases.git] / fs / btrfs / reada.c
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         int                     err;
70         struct list_head        extctl;
71         int                     refcnt;
72         spinlock_t              lock;
73         struct reada_zone       *zones[BTRFS_MAX_MIRRORS];
74         int                     nzones;
75         int                     scheduled;
76 };
77
78 struct 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
92 struct reada_machine_work {
93         struct btrfs_work       work;
94         struct btrfs_fs_info    *fs_info;
95 };
96
97 static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
98 static void reada_control_release(struct kref *kref);
99 static void reada_zone_release(struct kref *kref);
100 static void reada_start_machine(struct btrfs_fs_info *fs_info);
101 static void __reada_start_machine(struct btrfs_fs_info *fs_info);
102
103 static int reada_add_block(struct reada_control *rc, u64 logical,
104                            struct btrfs_key *top, u64 generation);
105
106 /* recurses */
107 /* in case of err, eb might be NULL */
108 static void __readahead_hook(struct btrfs_fs_info *fs_info,
109                              struct reada_extent *re, 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 list_head list;
118
119         if (eb)
120                 level = btrfs_header_level(eb);
121
122         spin_lock(&re->lock);
123         /*
124          * just take the full list from the extent. afterwards we
125          * don't need the lock anymore
126          */
127         list_replace_init(&re->extctl, &list);
128         re->scheduled = 0;
129         spin_unlock(&re->lock);
130
131         /*
132          * this is the error case, the extent buffer has not been
133          * read correctly. We won't access anything from it and
134          * just cleanup our data structures. Effectively this will
135          * cut the branch below this node from read ahead.
136          */
137         if (err)
138                 goto cleanup;
139
140         /*
141          * FIXME: currently we just set nritems to 0 if this is a leaf,
142          * effectively ignoring the content. In a next step we could
143          * trigger more readahead depending from the content, e.g.
144          * fetch the checksums for the extents in the leaf.
145          */
146         if (!level)
147                 goto cleanup;
148
149         nritems = btrfs_header_nritems(eb);
150         generation = btrfs_header_generation(eb);
151         for (i = 0; i < nritems; i++) {
152                 struct reada_extctl *rec;
153                 u64 n_gen;
154                 struct btrfs_key key;
155                 struct btrfs_key next_key;
156
157                 btrfs_node_key_to_cpu(eb, &key, i);
158                 if (i + 1 < nritems)
159                         btrfs_node_key_to_cpu(eb, &next_key, i + 1);
160                 else
161                         next_key = re->top;
162                 bytenr = btrfs_node_blockptr(eb, i);
163                 n_gen = btrfs_node_ptr_generation(eb, i);
164
165                 list_for_each_entry(rec, &list, list) {
166                         struct reada_control *rc = rec->rc;
167
168                         /*
169                          * if the generation doesn't match, just ignore this
170                          * extctl. This will probably cut off a branch from
171                          * prefetch. Alternatively one could start a new (sub-)
172                          * prefetch for this branch, starting again from root.
173                          * FIXME: move the generation check out of this loop
174                          */
175 #ifdef DEBUG
176                         if (rec->generation != generation) {
177                                 btrfs_debug(fs_info,
178                                             "generation mismatch for (%llu,%d,%llu) %llu != %llu",
179                                             key.objectid, key.type, key.offset,
180                                             rec->generation, generation);
181                         }
182 #endif
183                         if (rec->generation == generation &&
184                             btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 &&
185                             btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0)
186                                 reada_add_block(rc, bytenr, &next_key, n_gen);
187                 }
188         }
189
190 cleanup:
191         /*
192          * free extctl records
193          */
194         while (!list_empty(&list)) {
195                 struct reada_control *rc;
196                 struct reada_extctl *rec;
197
198                 rec = list_first_entry(&list, struct reada_extctl, list);
199                 list_del(&rec->list);
200                 rc = rec->rc;
201                 kfree(rec);
202
203                 kref_get(&rc->refcnt);
204                 if (atomic_dec_and_test(&rc->elems)) {
205                         kref_put(&rc->refcnt, reada_control_release);
206                         wake_up(&rc->wait);
207                 }
208                 kref_put(&rc->refcnt, reada_control_release);
209
210                 reada_extent_put(fs_info, re);  /* one ref for each entry */
211         }
212
213         return;
214 }
215
216 /*
217  * start is passed separately in case eb in NULL, which may be the case with
218  * failed I/O
219  */
220 int btree_readahead_hook(struct btrfs_fs_info *fs_info,
221                          struct extent_buffer *eb, u64 start, int err)
222 {
223         int ret = 0;
224         struct reada_extent *re;
225
226         /* find extent */
227         spin_lock(&fs_info->reada_lock);
228         re = radix_tree_lookup(&fs_info->reada_tree,
229                                start >> PAGE_SHIFT);
230         if (re)
231                 re->refcnt++;
232         spin_unlock(&fs_info->reada_lock);
233         if (!re) {
234                 ret = -1;
235                 goto start_machine;
236         }
237
238         __readahead_hook(fs_info, re, eb, start, err);
239         reada_extent_put(fs_info, re);  /* our ref */
240
241 start_machine:
242         reada_start_machine(fs_info);
243         return ret;
244 }
245
246 static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
247                                           struct btrfs_device *dev, u64 logical,
248                                           struct btrfs_bio *bbio)
249 {
250         int ret;
251         struct reada_zone *zone;
252         struct btrfs_block_group_cache *cache = NULL;
253         u64 start;
254         u64 end;
255         int i;
256
257         zone = NULL;
258         spin_lock(&fs_info->reada_lock);
259         ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
260                                      logical >> PAGE_SHIFT, 1);
261         if (ret == 1 && logical >= zone->start && logical <= zone->end) {
262                 kref_get(&zone->refcnt);
263                 spin_unlock(&fs_info->reada_lock);
264                 return zone;
265         }
266
267         spin_unlock(&fs_info->reada_lock);
268
269         cache = btrfs_lookup_block_group(fs_info, logical);
270         if (!cache)
271                 return NULL;
272
273         start = cache->key.objectid;
274         end = start + cache->key.offset - 1;
275         btrfs_put_block_group(cache);
276
277         zone = kzalloc(sizeof(*zone), GFP_KERNEL);
278         if (!zone)
279                 return NULL;
280
281         zone->start = start;
282         zone->end = end;
283         INIT_LIST_HEAD(&zone->list);
284         spin_lock_init(&zone->lock);
285         zone->locked = 0;
286         kref_init(&zone->refcnt);
287         zone->elems = 0;
288         zone->device = dev; /* our device always sits at index 0 */
289         for (i = 0; i < bbio->num_stripes; ++i) {
290                 /* bounds have already been checked */
291                 zone->devs[i] = bbio->stripes[i].dev;
292         }
293         zone->ndevs = bbio->num_stripes;
294
295         spin_lock(&fs_info->reada_lock);
296         ret = radix_tree_insert(&dev->reada_zones,
297                                 (unsigned long)(zone->end >> PAGE_SHIFT),
298                                 zone);
299
300         if (ret == -EEXIST) {
301                 kfree(zone);
302                 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
303                                              logical >> PAGE_SHIFT, 1);
304                 if (ret == 1 && logical >= zone->start && logical <= zone->end)
305                         kref_get(&zone->refcnt);
306                 else
307                         zone = NULL;
308         }
309         spin_unlock(&fs_info->reada_lock);
310
311         return zone;
312 }
313
314 static struct reada_extent *reada_find_extent(struct btrfs_root *root,
315                                               u64 logical,
316                                               struct btrfs_key *top)
317 {
318         int ret;
319         struct reada_extent *re = NULL;
320         struct reada_extent *re_exist = NULL;
321         struct btrfs_fs_info *fs_info = root->fs_info;
322         struct btrfs_bio *bbio = NULL;
323         struct btrfs_device *dev;
324         struct btrfs_device *prev_dev;
325         u32 blocksize;
326         u64 length;
327         int real_stripes;
328         int nzones = 0;
329         unsigned long index = logical >> PAGE_SHIFT;
330         int dev_replace_is_ongoing;
331         int have_zone = 0;
332
333         spin_lock(&fs_info->reada_lock);
334         re = radix_tree_lookup(&fs_info->reada_tree, index);
335         if (re)
336                 re->refcnt++;
337         spin_unlock(&fs_info->reada_lock);
338
339         if (re)
340                 return re;
341
342         re = kzalloc(sizeof(*re), GFP_KERNEL);
343         if (!re)
344                 return NULL;
345
346         blocksize = root->nodesize;
347         re->logical = logical;
348         re->top = *top;
349         INIT_LIST_HEAD(&re->extctl);
350         spin_lock_init(&re->lock);
351         re->refcnt = 1;
352
353         /*
354          * map block
355          */
356         length = blocksize;
357         ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, &length,
358                               &bbio, 0);
359         if (ret || !bbio || length < blocksize)
360                 goto error;
361
362         if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
363                 btrfs_err(root->fs_info,
364                            "readahead: more than %d copies not supported",
365                            BTRFS_MAX_MIRRORS);
366                 goto error;
367         }
368
369         real_stripes = bbio->num_stripes - bbio->num_tgtdevs;
370         for (nzones = 0; nzones < real_stripes; ++nzones) {
371                 struct reada_zone *zone;
372
373                 dev = bbio->stripes[nzones].dev;
374
375                 /* cannot read ahead on missing device. */
376                  if (!dev->bdev)
377                         continue;
378
379                 zone = reada_find_zone(fs_info, dev, logical, bbio);
380                 if (!zone)
381                         continue;
382
383                 re->zones[re->nzones++] = zone;
384                 spin_lock(&zone->lock);
385                 if (!zone->elems)
386                         kref_get(&zone->refcnt);
387                 ++zone->elems;
388                 spin_unlock(&zone->lock);
389                 spin_lock(&fs_info->reada_lock);
390                 kref_put(&zone->refcnt, reada_zone_release);
391                 spin_unlock(&fs_info->reada_lock);
392         }
393         if (re->nzones == 0) {
394                 /* not a single zone found, error and out */
395                 goto error;
396         }
397
398         /* insert extent in reada_tree + all per-device trees, all or nothing */
399         btrfs_dev_replace_lock(&fs_info->dev_replace, 0);
400         spin_lock(&fs_info->reada_lock);
401         ret = radix_tree_insert(&fs_info->reada_tree, index, re);
402         if (ret == -EEXIST) {
403                 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
404                 BUG_ON(!re_exist);
405                 re_exist->refcnt++;
406                 spin_unlock(&fs_info->reada_lock);
407                 btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
408                 goto error;
409         }
410         if (ret) {
411                 spin_unlock(&fs_info->reada_lock);
412                 btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
413                 goto error;
414         }
415         prev_dev = NULL;
416         dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
417                         &fs_info->dev_replace);
418         for (nzones = 0; nzones < re->nzones; ++nzones) {
419                 dev = re->zones[nzones]->device;
420
421                 if (dev == prev_dev) {
422                         /*
423                          * in case of DUP, just add the first zone. As both
424                          * are on the same device, there's nothing to gain
425                          * from adding both.
426                          * Also, it wouldn't work, as the tree is per device
427                          * and adding would fail with EEXIST
428                          */
429                         continue;
430                 }
431                 if (!dev->bdev)
432                         continue;
433
434                 if (dev_replace_is_ongoing &&
435                     dev == fs_info->dev_replace.tgtdev) {
436                         /*
437                          * as this device is selected for reading only as
438                          * a last resort, skip it for read ahead.
439                          */
440                         continue;
441                 }
442                 prev_dev = dev;
443                 ret = radix_tree_insert(&dev->reada_extents, index, re);
444                 if (ret) {
445                         while (--nzones >= 0) {
446                                 dev = re->zones[nzones]->device;
447                                 BUG_ON(dev == NULL);
448                                 /* ignore whether the entry was inserted */
449                                 radix_tree_delete(&dev->reada_extents, index);
450                         }
451                         BUG_ON(fs_info == NULL);
452                         radix_tree_delete(&fs_info->reada_tree, index);
453                         spin_unlock(&fs_info->reada_lock);
454                         btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
455                         goto error;
456                 }
457                 have_zone = 1;
458         }
459         if (!have_zone)
460                 radix_tree_delete(&fs_info->reada_tree, index);
461         spin_unlock(&fs_info->reada_lock);
462         btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
463
464         if (!have_zone)
465                 goto error;
466
467         btrfs_put_bbio(bbio);
468         return re;
469
470 error:
471         for (nzones = 0; nzones < re->nzones; ++nzones) {
472                 struct reada_zone *zone;
473
474                 zone = re->zones[nzones];
475                 kref_get(&zone->refcnt);
476                 spin_lock(&zone->lock);
477                 --zone->elems;
478                 if (zone->elems == 0) {
479                         /*
480                          * no fs_info->reada_lock needed, as this can't be
481                          * the last ref
482                          */
483                         kref_put(&zone->refcnt, reada_zone_release);
484                 }
485                 spin_unlock(&zone->lock);
486
487                 spin_lock(&fs_info->reada_lock);
488                 kref_put(&zone->refcnt, reada_zone_release);
489                 spin_unlock(&fs_info->reada_lock);
490         }
491         btrfs_put_bbio(bbio);
492         kfree(re);
493         return re_exist;
494 }
495
496 static void reada_extent_put(struct btrfs_fs_info *fs_info,
497                              struct reada_extent *re)
498 {
499         int i;
500         unsigned long index = re->logical >> PAGE_SHIFT;
501
502         spin_lock(&fs_info->reada_lock);
503         if (--re->refcnt) {
504                 spin_unlock(&fs_info->reada_lock);
505                 return;
506         }
507
508         radix_tree_delete(&fs_info->reada_tree, index);
509         for (i = 0; i < re->nzones; ++i) {
510                 struct reada_zone *zone = re->zones[i];
511
512                 radix_tree_delete(&zone->device->reada_extents, index);
513         }
514
515         spin_unlock(&fs_info->reada_lock);
516
517         for (i = 0; i < re->nzones; ++i) {
518                 struct reada_zone *zone = re->zones[i];
519
520                 kref_get(&zone->refcnt);
521                 spin_lock(&zone->lock);
522                 --zone->elems;
523                 if (zone->elems == 0) {
524                         /* no fs_info->reada_lock needed, as this can't be
525                          * the last ref */
526                         kref_put(&zone->refcnt, reada_zone_release);
527                 }
528                 spin_unlock(&zone->lock);
529
530                 spin_lock(&fs_info->reada_lock);
531                 kref_put(&zone->refcnt, reada_zone_release);
532                 spin_unlock(&fs_info->reada_lock);
533         }
534
535         kfree(re);
536 }
537
538 static void reada_zone_release(struct kref *kref)
539 {
540         struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
541
542         radix_tree_delete(&zone->device->reada_zones,
543                           zone->end >> PAGE_SHIFT);
544
545         kfree(zone);
546 }
547
548 static void reada_control_release(struct kref *kref)
549 {
550         struct reada_control *rc = container_of(kref, struct reada_control,
551                                                 refcnt);
552
553         kfree(rc);
554 }
555
556 static int reada_add_block(struct reada_control *rc, u64 logical,
557                            struct btrfs_key *top, u64 generation)
558 {
559         struct btrfs_root *root = rc->root;
560         struct reada_extent *re;
561         struct reada_extctl *rec;
562
563         re = reada_find_extent(root, logical, top); /* takes one ref */
564         if (!re)
565                 return -1;
566
567         rec = kzalloc(sizeof(*rec), GFP_KERNEL);
568         if (!rec) {
569                 reada_extent_put(root->fs_info, re);
570                 return -ENOMEM;
571         }
572
573         rec->rc = rc;
574         rec->generation = generation;
575         atomic_inc(&rc->elems);
576
577         spin_lock(&re->lock);
578         list_add_tail(&rec->list, &re->extctl);
579         spin_unlock(&re->lock);
580
581         /* leave the ref on the extent */
582
583         return 0;
584 }
585
586 /*
587  * called with fs_info->reada_lock held
588  */
589 static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
590 {
591         int i;
592         unsigned long index = zone->end >> PAGE_SHIFT;
593
594         for (i = 0; i < zone->ndevs; ++i) {
595                 struct reada_zone *peer;
596                 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
597                 if (peer && peer->device != zone->device)
598                         peer->locked = lock;
599         }
600 }
601
602 /*
603  * called with fs_info->reada_lock held
604  */
605 static int reada_pick_zone(struct btrfs_device *dev)
606 {
607         struct reada_zone *top_zone = NULL;
608         struct reada_zone *top_locked_zone = NULL;
609         u64 top_elems = 0;
610         u64 top_locked_elems = 0;
611         unsigned long index = 0;
612         int ret;
613
614         if (dev->reada_curr_zone) {
615                 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
616                 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
617                 dev->reada_curr_zone = NULL;
618         }
619         /* pick the zone with the most elements */
620         while (1) {
621                 struct reada_zone *zone;
622
623                 ret = radix_tree_gang_lookup(&dev->reada_zones,
624                                              (void **)&zone, index, 1);
625                 if (ret == 0)
626                         break;
627                 index = (zone->end >> PAGE_SHIFT) + 1;
628                 if (zone->locked) {
629                         if (zone->elems > top_locked_elems) {
630                                 top_locked_elems = zone->elems;
631                                 top_locked_zone = zone;
632                         }
633                 } else {
634                         if (zone->elems > top_elems) {
635                                 top_elems = zone->elems;
636                                 top_zone = zone;
637                         }
638                 }
639         }
640         if (top_zone)
641                 dev->reada_curr_zone = top_zone;
642         else if (top_locked_zone)
643                 dev->reada_curr_zone = top_locked_zone;
644         else
645                 return 0;
646
647         dev->reada_next = dev->reada_curr_zone->start;
648         kref_get(&dev->reada_curr_zone->refcnt);
649         reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
650
651         return 1;
652 }
653
654 static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
655                                    struct btrfs_device *dev)
656 {
657         struct reada_extent *re = NULL;
658         int mirror_num = 0;
659         struct extent_buffer *eb = NULL;
660         u64 logical;
661         int ret;
662         int i;
663
664         spin_lock(&fs_info->reada_lock);
665         if (dev->reada_curr_zone == NULL) {
666                 ret = reada_pick_zone(dev);
667                 if (!ret) {
668                         spin_unlock(&fs_info->reada_lock);
669                         return 0;
670                 }
671         }
672         /*
673          * FIXME currently we issue the reads one extent at a time. If we have
674          * a contiguous block of extents, we could also coagulate them or use
675          * plugging to speed things up
676          */
677         ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
678                                      dev->reada_next >> PAGE_SHIFT, 1);
679         if (ret == 0 || re->logical > dev->reada_curr_zone->end) {
680                 ret = reada_pick_zone(dev);
681                 if (!ret) {
682                         spin_unlock(&fs_info->reada_lock);
683                         return 0;
684                 }
685                 re = NULL;
686                 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
687                                         dev->reada_next >> PAGE_SHIFT, 1);
688         }
689         if (ret == 0) {
690                 spin_unlock(&fs_info->reada_lock);
691                 return 0;
692         }
693         dev->reada_next = re->logical + fs_info->tree_root->nodesize;
694         re->refcnt++;
695
696         spin_unlock(&fs_info->reada_lock);
697
698         spin_lock(&re->lock);
699         if (re->scheduled || list_empty(&re->extctl)) {
700                 spin_unlock(&re->lock);
701                 reada_extent_put(fs_info, re);
702                 return 0;
703         }
704         re->scheduled = 1;
705         spin_unlock(&re->lock);
706
707         /*
708          * find mirror num
709          */
710         for (i = 0; i < re->nzones; ++i) {
711                 if (re->zones[i]->device == dev) {
712                         mirror_num = i + 1;
713                         break;
714                 }
715         }
716         logical = re->logical;
717
718         atomic_inc(&dev->reada_in_flight);
719         ret = reada_tree_block_flagged(fs_info->extent_root, logical,
720                         mirror_num, &eb);
721         if (ret)
722                 __readahead_hook(fs_info, re, NULL, logical, ret);
723         else if (eb)
724                 __readahead_hook(fs_info, re, eb, eb->start, ret);
725
726         if (eb)
727                 free_extent_buffer(eb);
728
729         atomic_dec(&dev->reada_in_flight);
730         reada_extent_put(fs_info, re);
731
732         return 1;
733
734 }
735
736 static void reada_start_machine_worker(struct btrfs_work *work)
737 {
738         struct reada_machine_work *rmw;
739         int old_ioprio;
740
741         rmw = container_of(work, struct reada_machine_work, work);
742
743         old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
744                                        task_nice_ioprio(current));
745         set_task_ioprio(current, BTRFS_IOPRIO_READA);
746         __reada_start_machine(rmw->fs_info);
747         set_task_ioprio(current, old_ioprio);
748
749         atomic_dec(&rmw->fs_info->reada_works_cnt);
750
751         kfree(rmw);
752 }
753
754 static void __reada_start_machine(struct btrfs_fs_info *fs_info)
755 {
756         struct btrfs_device *device;
757         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
758         u64 enqueued;
759         u64 total = 0;
760         int i;
761
762 again:
763         do {
764                 enqueued = 0;
765                 mutex_lock(&fs_devices->device_list_mutex);
766                 list_for_each_entry(device, &fs_devices->devices, dev_list) {
767                         if (atomic_read(&device->reada_in_flight) <
768                             MAX_IN_FLIGHT)
769                                 enqueued += reada_start_machine_dev(fs_info,
770                                                                     device);
771                 }
772                 mutex_unlock(&fs_devices->device_list_mutex);
773                 total += enqueued;
774         } while (enqueued && total < 10000);
775         if (fs_devices->seed) {
776                 fs_devices = fs_devices->seed;
777                 goto again;
778         }
779
780         if (enqueued == 0)
781                 return;
782
783         /*
784          * If everything is already in the cache, this is effectively single
785          * threaded. To a) not hold the caller for too long and b) to utilize
786          * more cores, we broke the loop above after 10000 iterations and now
787          * enqueue to workers to finish it. This will distribute the load to
788          * the cores.
789          */
790         for (i = 0; i < 2; ++i) {
791                 reada_start_machine(fs_info);
792                 if (atomic_read(&fs_info->reada_works_cnt) >
793                     BTRFS_MAX_MIRRORS * 2)
794                         break;
795         }
796 }
797
798 static void reada_start_machine(struct btrfs_fs_info *fs_info)
799 {
800         struct reada_machine_work *rmw;
801
802         rmw = kzalloc(sizeof(*rmw), GFP_KERNEL);
803         if (!rmw) {
804                 /* FIXME we cannot handle this properly right now */
805                 BUG();
806         }
807         btrfs_init_work(&rmw->work, btrfs_readahead_helper,
808                         reada_start_machine_worker, NULL, NULL);
809         rmw->fs_info = fs_info;
810
811         btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
812         atomic_inc(&fs_info->reada_works_cnt);
813 }
814
815 #ifdef DEBUG
816 static void dump_devs(struct btrfs_fs_info *fs_info, int all)
817 {
818         struct btrfs_device *device;
819         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
820         unsigned long index;
821         int ret;
822         int i;
823         int j;
824         int cnt;
825
826         spin_lock(&fs_info->reada_lock);
827         list_for_each_entry(device, &fs_devices->devices, dev_list) {
828                 btrfs_debug(fs_info, "dev %lld has %d in flight", device->devid,
829                         atomic_read(&device->reada_in_flight));
830                 index = 0;
831                 while (1) {
832                         struct reada_zone *zone;
833                         ret = radix_tree_gang_lookup(&device->reada_zones,
834                                                      (void **)&zone, index, 1);
835                         if (ret == 0)
836                                 break;
837                         pr_debug("  zone %llu-%llu elems %llu locked %d devs",
838                                     zone->start, zone->end, zone->elems,
839                                     zone->locked);
840                         for (j = 0; j < zone->ndevs; ++j) {
841                                 pr_cont(" %lld",
842                                         zone->devs[j]->devid);
843                         }
844                         if (device->reada_curr_zone == zone)
845                                 pr_cont(" curr off %llu",
846                                         device->reada_next - zone->start);
847                         pr_cont("\n");
848                         index = (zone->end >> PAGE_SHIFT) + 1;
849                 }
850                 cnt = 0;
851                 index = 0;
852                 while (all) {
853                         struct reada_extent *re = NULL;
854
855                         ret = radix_tree_gang_lookup(&device->reada_extents,
856                                                      (void **)&re, index, 1);
857                         if (ret == 0)
858                                 break;
859                         pr_debug("  re: logical %llu size %u empty %d scheduled %d",
860                                 re->logical, fs_info->tree_root->nodesize,
861                                 list_empty(&re->extctl), re->scheduled);
862
863                         for (i = 0; i < re->nzones; ++i) {
864                                 pr_cont(" zone %llu-%llu devs",
865                                         re->zones[i]->start,
866                                         re->zones[i]->end);
867                                 for (j = 0; j < re->zones[i]->ndevs; ++j) {
868                                         pr_cont(" %lld",
869                                                 re->zones[i]->devs[j]->devid);
870                                 }
871                         }
872                         pr_cont("\n");
873                         index = (re->logical >> PAGE_SHIFT) + 1;
874                         if (++cnt > 15)
875                                 break;
876                 }
877         }
878
879         index = 0;
880         cnt = 0;
881         while (all) {
882                 struct reada_extent *re = NULL;
883
884                 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
885                                              index, 1);
886                 if (ret == 0)
887                         break;
888                 if (!re->scheduled) {
889                         index = (re->logical >> PAGE_SHIFT) + 1;
890                         continue;
891                 }
892                 pr_debug("re: logical %llu size %u list empty %d scheduled %d",
893                         re->logical, fs_info->tree_root->nodesize,
894                         list_empty(&re->extctl), re->scheduled);
895                 for (i = 0; i < re->nzones; ++i) {
896                         pr_cont(" zone %llu-%llu devs",
897                                 re->zones[i]->start,
898                                 re->zones[i]->end);
899                         for (j = 0; j < re->zones[i]->ndevs; ++j) {
900                                 pr_cont(" %lld",
901                                        re->zones[i]->devs[j]->devid);
902                         }
903                 }
904                 pr_cont("\n");
905                 index = (re->logical >> PAGE_SHIFT) + 1;
906         }
907         spin_unlock(&fs_info->reada_lock);
908 }
909 #endif
910
911 /*
912  * interface
913  */
914 struct reada_control *btrfs_reada_add(struct btrfs_root *root,
915                         struct btrfs_key *key_start, struct btrfs_key *key_end)
916 {
917         struct reada_control *rc;
918         u64 start;
919         u64 generation;
920         int ret;
921         struct extent_buffer *node;
922         static struct btrfs_key max_key = {
923                 .objectid = (u64)-1,
924                 .type = (u8)-1,
925                 .offset = (u64)-1
926         };
927
928         rc = kzalloc(sizeof(*rc), GFP_KERNEL);
929         if (!rc)
930                 return ERR_PTR(-ENOMEM);
931
932         rc->root = root;
933         rc->key_start = *key_start;
934         rc->key_end = *key_end;
935         atomic_set(&rc->elems, 0);
936         init_waitqueue_head(&rc->wait);
937         kref_init(&rc->refcnt);
938         kref_get(&rc->refcnt); /* one ref for having elements */
939
940         node = btrfs_root_node(root);
941         start = node->start;
942         generation = btrfs_header_generation(node);
943         free_extent_buffer(node);
944
945         ret = reada_add_block(rc, start, &max_key, generation);
946         if (ret) {
947                 kfree(rc);
948                 return ERR_PTR(ret);
949         }
950
951         reada_start_machine(root->fs_info);
952
953         return rc;
954 }
955
956 #ifdef DEBUG
957 int btrfs_reada_wait(void *handle)
958 {
959         struct reada_control *rc = handle;
960         struct btrfs_fs_info *fs_info = rc->root->fs_info;
961
962         while (atomic_read(&rc->elems)) {
963                 if (!atomic_read(&fs_info->reada_works_cnt))
964                         reada_start_machine(fs_info);
965                 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
966                                    5 * HZ);
967                 dump_devs(rc->root->fs_info,
968                           atomic_read(&rc->elems) < 10 ? 1 : 0);
969         }
970
971         dump_devs(rc->root->fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
972
973         kref_put(&rc->refcnt, reada_control_release);
974
975         return 0;
976 }
977 #else
978 int btrfs_reada_wait(void *handle)
979 {
980         struct reada_control *rc = handle;
981         struct btrfs_fs_info *fs_info = rc->root->fs_info;
982
983         while (atomic_read(&rc->elems)) {
984                 if (!atomic_read(&fs_info->reada_works_cnt))
985                         reada_start_machine(fs_info);
986                 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
987                                    (HZ + 9) / 10);
988         }
989
990         kref_put(&rc->refcnt, reada_control_release);
991
992         return 0;
993 }
994 #endif
995
996 void btrfs_reada_detach(void *handle)
997 {
998         struct reada_control *rc = handle;
999
1000         kref_put(&rc->refcnt, reada_control_release);
1001 }