2 * Copyright (C) 2011 STRATO. All rights reserved.
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.
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.
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.
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>
29 #include "transaction.h"
30 #include "dev-replace.h"
35 * This is the implementation for the generic read ahead framework.
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).
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
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.
58 #define MAX_IN_FLIGHT 6
61 struct list_head list;
62 struct reada_control *rc;
70 struct list_head extctl;
73 struct reada_zone *zones[BTRFS_MAX_MIRRORS];
82 struct list_head list;
85 struct btrfs_device *device;
86 struct btrfs_device *devs[BTRFS_MAX_MIRRORS]; /* full list, incl
92 struct reada_machine_work {
93 struct btrfs_work work;
94 struct btrfs_fs_info *fs_info;
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);
103 static int reada_add_block(struct reada_control *rc, u64 logical,
104 struct btrfs_key *top, u64 generation);
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,
117 struct list_head list;
120 level = btrfs_header_level(eb);
122 spin_lock(&re->lock);
124 * just take the full list from the extent. afterwards we
125 * don't need the lock anymore
127 list_replace_init(&re->extctl, &list);
129 spin_unlock(&re->lock);
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.
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.
149 nritems = btrfs_header_nritems(eb);
150 generation = btrfs_header_generation(eb);
151 for (i = 0; i < nritems; i++) {
152 struct reada_extctl *rec;
154 struct btrfs_key key;
155 struct btrfs_key next_key;
157 btrfs_node_key_to_cpu(eb, &key, i);
159 btrfs_node_key_to_cpu(eb, &next_key, i + 1);
162 bytenr = btrfs_node_blockptr(eb, i);
163 n_gen = btrfs_node_ptr_generation(eb, i);
165 list_for_each_entry(rec, &list, list) {
166 struct reada_control *rc = rec->rc;
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
176 if (rec->generation != generation) {
178 "generation mismatch for (%llu,%d,%llu) %llu != %llu",
179 key.objectid, key.type, key.offset,
180 rec->generation, generation);
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);
192 * free extctl records
194 while (!list_empty(&list)) {
195 struct reada_control *rc;
196 struct reada_extctl *rec;
198 rec = list_first_entry(&list, struct reada_extctl, list);
199 list_del(&rec->list);
203 kref_get(&rc->refcnt);
204 if (atomic_dec_and_test(&rc->elems)) {
205 kref_put(&rc->refcnt, reada_control_release);
208 kref_put(&rc->refcnt, reada_control_release);
210 reada_extent_put(fs_info, re); /* one ref for each entry */
217 * start is passed separately in case eb in NULL, which may be the case with
220 int btree_readahead_hook(struct btrfs_fs_info *fs_info,
221 struct extent_buffer *eb, u64 start, int err)
224 struct reada_extent *re;
227 spin_lock(&fs_info->reada_lock);
228 re = radix_tree_lookup(&fs_info->reada_tree,
229 start >> PAGE_CACHE_SHIFT);
232 spin_unlock(&fs_info->reada_lock);
238 __readahead_hook(fs_info, re, eb, start, err);
239 reada_extent_put(fs_info, re); /* our ref */
242 reada_start_machine(fs_info);
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)
251 struct reada_zone *zone;
252 struct btrfs_block_group_cache *cache = NULL;
258 spin_lock(&fs_info->reada_lock);
259 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
260 logical >> PAGE_CACHE_SHIFT, 1);
261 if (ret == 1 && logical >= zone->start && logical <= zone->end) {
262 kref_get(&zone->refcnt);
263 spin_unlock(&fs_info->reada_lock);
267 spin_unlock(&fs_info->reada_lock);
269 cache = btrfs_lookup_block_group(fs_info, logical);
273 start = cache->key.objectid;
274 end = start + cache->key.offset - 1;
275 btrfs_put_block_group(cache);
277 zone = kzalloc(sizeof(*zone), GFP_NOFS);
283 INIT_LIST_HEAD(&zone->list);
284 spin_lock_init(&zone->lock);
286 kref_init(&zone->refcnt);
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;
293 zone->ndevs = bbio->num_stripes;
295 spin_lock(&fs_info->reada_lock);
296 ret = radix_tree_insert(&dev->reada_zones,
297 (unsigned long)(zone->end >> PAGE_CACHE_SHIFT),
300 if (ret == -EEXIST) {
302 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
303 logical >> PAGE_CACHE_SHIFT, 1);
304 if (ret == 1 && logical >= zone->start && logical <= zone->end)
305 kref_get(&zone->refcnt);
309 spin_unlock(&fs_info->reada_lock);
314 static struct reada_extent *reada_find_extent(struct btrfs_root *root,
316 struct btrfs_key *top)
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;
329 unsigned long index = logical >> PAGE_CACHE_SHIFT;
330 int dev_replace_is_ongoing;
333 spin_lock(&fs_info->reada_lock);
334 re = radix_tree_lookup(&fs_info->reada_tree, index);
337 spin_unlock(&fs_info->reada_lock);
342 re = kzalloc(sizeof(*re), GFP_NOFS);
346 blocksize = root->nodesize;
347 re->logical = logical;
349 INIT_LIST_HEAD(&re->extctl);
350 spin_lock_init(&re->lock);
357 ret = btrfs_map_block(fs_info, REQ_GET_READ_MIRRORS, logical, &length,
359 if (ret || !bbio || length < blocksize)
362 if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
363 btrfs_err(root->fs_info,
364 "readahead: more than %d copies not supported",
369 real_stripes = bbio->num_stripes - bbio->num_tgtdevs;
370 for (nzones = 0; nzones < real_stripes; ++nzones) {
371 struct reada_zone *zone;
373 dev = bbio->stripes[nzones].dev;
374 zone = reada_find_zone(fs_info, dev, logical, bbio);
378 re->zones[re->nzones++] = zone;
379 spin_lock(&zone->lock);
381 kref_get(&zone->refcnt);
383 spin_unlock(&zone->lock);
384 spin_lock(&fs_info->reada_lock);
385 kref_put(&zone->refcnt, reada_zone_release);
386 spin_unlock(&fs_info->reada_lock);
388 if (re->nzones == 0) {
389 /* not a single zone found, error and out */
393 /* insert extent in reada_tree + all per-device trees, all or nothing */
394 btrfs_dev_replace_lock(&fs_info->dev_replace);
395 spin_lock(&fs_info->reada_lock);
396 ret = radix_tree_insert(&fs_info->reada_tree, index, re);
397 if (ret == -EEXIST) {
398 re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
401 spin_unlock(&fs_info->reada_lock);
402 btrfs_dev_replace_unlock(&fs_info->dev_replace);
406 spin_unlock(&fs_info->reada_lock);
407 btrfs_dev_replace_unlock(&fs_info->dev_replace);
411 dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
412 &fs_info->dev_replace);
413 for (nzones = 0; nzones < re->nzones; ++nzones) {
414 dev = re->zones[nzones]->device;
416 if (dev == prev_dev) {
418 * in case of DUP, just add the first zone. As both
419 * are on the same device, there's nothing to gain
421 * Also, it wouldn't work, as the tree is per device
422 * and adding would fail with EEXIST
428 * cannot read ahead on missing device, but for RAID5/6,
429 * REQ_GET_READ_MIRRORS return 1. So don't skip missing
430 * device for such case.
435 if (dev_replace_is_ongoing &&
436 dev == fs_info->dev_replace.tgtdev) {
438 * as this device is selected for reading only as
439 * a last resort, skip it for read ahead.
444 ret = radix_tree_insert(&dev->reada_extents, index, re);
446 while (--nzones >= 0) {
447 dev = re->zones[nzones]->device;
449 /* ignore whether the entry was inserted */
450 radix_tree_delete(&dev->reada_extents, index);
452 BUG_ON(fs_info == NULL);
453 radix_tree_delete(&fs_info->reada_tree, index);
454 spin_unlock(&fs_info->reada_lock);
455 btrfs_dev_replace_unlock(&fs_info->dev_replace);
460 spin_unlock(&fs_info->reada_lock);
461 btrfs_dev_replace_unlock(&fs_info->dev_replace);
466 btrfs_put_bbio(bbio);
470 for (nzones = 0; nzones < re->nzones; ++nzones) {
471 struct reada_zone *zone;
473 zone = re->zones[nzones];
474 kref_get(&zone->refcnt);
475 spin_lock(&zone->lock);
477 if (zone->elems == 0) {
479 * no fs_info->reada_lock needed, as this can't be
482 kref_put(&zone->refcnt, reada_zone_release);
484 spin_unlock(&zone->lock);
486 spin_lock(&fs_info->reada_lock);
487 kref_put(&zone->refcnt, reada_zone_release);
488 spin_unlock(&fs_info->reada_lock);
490 btrfs_put_bbio(bbio);
495 static void reada_extent_put(struct btrfs_fs_info *fs_info,
496 struct reada_extent *re)
499 unsigned long index = re->logical >> PAGE_CACHE_SHIFT;
501 spin_lock(&fs_info->reada_lock);
503 spin_unlock(&fs_info->reada_lock);
507 radix_tree_delete(&fs_info->reada_tree, index);
508 for (i = 0; i < re->nzones; ++i) {
509 struct reada_zone *zone = re->zones[i];
511 radix_tree_delete(&zone->device->reada_extents, index);
514 spin_unlock(&fs_info->reada_lock);
516 for (i = 0; i < re->nzones; ++i) {
517 struct reada_zone *zone = re->zones[i];
519 kref_get(&zone->refcnt);
520 spin_lock(&zone->lock);
522 if (zone->elems == 0) {
523 /* no fs_info->reada_lock needed, as this can't be
525 kref_put(&zone->refcnt, reada_zone_release);
527 spin_unlock(&zone->lock);
529 spin_lock(&fs_info->reada_lock);
530 kref_put(&zone->refcnt, reada_zone_release);
531 spin_unlock(&fs_info->reada_lock);
537 static void reada_zone_release(struct kref *kref)
539 struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt);
541 radix_tree_delete(&zone->device->reada_zones,
542 zone->end >> PAGE_CACHE_SHIFT);
547 static void reada_control_release(struct kref *kref)
549 struct reada_control *rc = container_of(kref, struct reada_control,
555 static int reada_add_block(struct reada_control *rc, u64 logical,
556 struct btrfs_key *top, u64 generation)
558 struct btrfs_root *root = rc->root;
559 struct reada_extent *re;
560 struct reada_extctl *rec;
562 re = reada_find_extent(root, logical, top); /* takes one ref */
566 rec = kzalloc(sizeof(*rec), GFP_NOFS);
568 reada_extent_put(root->fs_info, re);
573 rec->generation = generation;
574 atomic_inc(&rc->elems);
576 spin_lock(&re->lock);
577 list_add_tail(&rec->list, &re->extctl);
578 spin_unlock(&re->lock);
580 /* leave the ref on the extent */
586 * called with fs_info->reada_lock held
588 static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
591 unsigned long index = zone->end >> PAGE_CACHE_SHIFT;
593 for (i = 0; i < zone->ndevs; ++i) {
594 struct reada_zone *peer;
595 peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
596 if (peer && peer->device != zone->device)
602 * called with fs_info->reada_lock held
604 static int reada_pick_zone(struct btrfs_device *dev)
606 struct reada_zone *top_zone = NULL;
607 struct reada_zone *top_locked_zone = NULL;
609 u64 top_locked_elems = 0;
610 unsigned long index = 0;
613 if (dev->reada_curr_zone) {
614 reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
615 kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release);
616 dev->reada_curr_zone = NULL;
618 /* pick the zone with the most elements */
620 struct reada_zone *zone;
622 ret = radix_tree_gang_lookup(&dev->reada_zones,
623 (void **)&zone, index, 1);
626 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
628 if (zone->elems > top_locked_elems) {
629 top_locked_elems = zone->elems;
630 top_locked_zone = zone;
633 if (zone->elems > top_elems) {
634 top_elems = zone->elems;
640 dev->reada_curr_zone = top_zone;
641 else if (top_locked_zone)
642 dev->reada_curr_zone = top_locked_zone;
646 dev->reada_next = dev->reada_curr_zone->start;
647 kref_get(&dev->reada_curr_zone->refcnt);
648 reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
653 static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
654 struct btrfs_device *dev)
656 struct reada_extent *re = NULL;
658 struct extent_buffer *eb = NULL;
663 spin_lock(&fs_info->reada_lock);
664 if (dev->reada_curr_zone == NULL) {
665 ret = reada_pick_zone(dev);
667 spin_unlock(&fs_info->reada_lock);
672 * FIXME currently we issue the reads one extent at a time. If we have
673 * a contiguous block of extents, we could also coagulate them or use
674 * plugging to speed things up
676 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
677 dev->reada_next >> PAGE_CACHE_SHIFT, 1);
678 if (ret == 0 || re->logical > dev->reada_curr_zone->end) {
679 ret = reada_pick_zone(dev);
681 spin_unlock(&fs_info->reada_lock);
685 ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
686 dev->reada_next >> PAGE_CACHE_SHIFT, 1);
689 spin_unlock(&fs_info->reada_lock);
692 dev->reada_next = re->logical + fs_info->tree_root->nodesize;
695 spin_unlock(&fs_info->reada_lock);
697 spin_lock(&re->lock);
698 if (re->scheduled || list_empty(&re->extctl)) {
699 spin_unlock(&re->lock);
700 reada_extent_put(fs_info, re);
704 spin_unlock(&re->lock);
709 for (i = 0; i < re->nzones; ++i) {
710 if (re->zones[i]->device == dev) {
715 logical = re->logical;
717 atomic_inc(&dev->reada_in_flight);
718 ret = reada_tree_block_flagged(fs_info->extent_root, logical,
721 __readahead_hook(fs_info, re, NULL, logical, ret);
723 __readahead_hook(fs_info, re, eb, eb->start, ret);
726 free_extent_buffer(eb);
728 atomic_dec(&dev->reada_in_flight);
729 reada_extent_put(fs_info, re);
735 static void reada_start_machine_worker(struct btrfs_work *work)
737 struct reada_machine_work *rmw;
738 struct btrfs_fs_info *fs_info;
741 rmw = container_of(work, struct reada_machine_work, work);
742 fs_info = rmw->fs_info;
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);
752 atomic_dec(&fs_info->reada_works_cnt);
755 static void __reada_start_machine(struct btrfs_fs_info *fs_info)
757 struct btrfs_device *device;
758 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
765 list_for_each_entry(device, &fs_devices->devices, dev_list) {
766 if (atomic_read(&device->reada_in_flight) <
768 enqueued += reada_start_machine_dev(fs_info,
772 } while (enqueued && total < 10000);
778 * If everything is already in the cache, this is effectively single
779 * threaded. To a) not hold the caller for too long and b) to utilize
780 * more cores, we broke the loop above after 10000 iterations and now
781 * enqueue to workers to finish it. This will distribute the load to
784 for (i = 0; i < 2; ++i) {
785 reada_start_machine(fs_info);
786 if (atomic_read(&fs_info->reada_works_cnt) >
787 BTRFS_MAX_MIRRORS * 2)
792 static void reada_start_machine(struct btrfs_fs_info *fs_info)
794 struct reada_machine_work *rmw;
796 rmw = kzalloc(sizeof(*rmw), GFP_NOFS);
798 /* FIXME we cannot handle this properly right now */
801 btrfs_init_work(&rmw->work, btrfs_readahead_helper,
802 reada_start_machine_worker, NULL, NULL);
803 rmw->fs_info = fs_info;
805 btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
806 atomic_inc(&fs_info->reada_works_cnt);
810 static void dump_devs(struct btrfs_fs_info *fs_info, int all)
812 struct btrfs_device *device;
813 struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
820 spin_lock(&fs_info->reada_lock);
821 list_for_each_entry(device, &fs_devices->devices, dev_list) {
822 printk(KERN_DEBUG "dev %lld has %d in flight\n", device->devid,
823 atomic_read(&device->reada_in_flight));
826 struct reada_zone *zone;
827 ret = radix_tree_gang_lookup(&device->reada_zones,
828 (void **)&zone, index, 1);
831 printk(KERN_DEBUG " zone %llu-%llu elems %llu locked "
832 "%d devs", zone->start, zone->end, zone->elems,
834 for (j = 0; j < zone->ndevs; ++j) {
835 printk(KERN_CONT " %lld",
836 zone->devs[j]->devid);
838 if (device->reada_curr_zone == zone)
839 printk(KERN_CONT " curr off %llu",
840 device->reada_next - zone->start);
841 printk(KERN_CONT "\n");
842 index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
847 struct reada_extent *re = NULL;
849 ret = radix_tree_gang_lookup(&device->reada_extents,
850 (void **)&re, index, 1);
854 " re: logical %llu size %u empty %d scheduled %d",
855 re->logical, fs_info->tree_root->nodesize,
856 list_empty(&re->extctl), re->scheduled);
858 for (i = 0; i < re->nzones; ++i) {
859 printk(KERN_CONT " zone %llu-%llu devs",
862 for (j = 0; j < re->zones[i]->ndevs; ++j) {
863 printk(KERN_CONT " %lld",
864 re->zones[i]->devs[j]->devid);
867 printk(KERN_CONT "\n");
868 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
877 struct reada_extent *re = NULL;
879 ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
883 if (!re->scheduled) {
884 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
888 "re: logical %llu size %u list empty %d scheduled %d",
889 re->logical, fs_info->tree_root->nodesize,
890 list_empty(&re->extctl), re->scheduled);
891 for (i = 0; i < re->nzones; ++i) {
892 printk(KERN_CONT " zone %llu-%llu devs",
895 for (j = 0; j < re->zones[i]->ndevs; ++j) {
896 printk(KERN_CONT " %lld",
897 re->zones[i]->devs[j]->devid);
900 printk(KERN_CONT "\n");
901 index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
903 spin_unlock(&fs_info->reada_lock);
910 struct reada_control *btrfs_reada_add(struct btrfs_root *root,
911 struct btrfs_key *key_start, struct btrfs_key *key_end)
913 struct reada_control *rc;
917 struct extent_buffer *node;
918 static struct btrfs_key max_key = {
924 rc = kzalloc(sizeof(*rc), GFP_NOFS);
926 return ERR_PTR(-ENOMEM);
929 rc->key_start = *key_start;
930 rc->key_end = *key_end;
931 atomic_set(&rc->elems, 0);
932 init_waitqueue_head(&rc->wait);
933 kref_init(&rc->refcnt);
934 kref_get(&rc->refcnt); /* one ref for having elements */
936 node = btrfs_root_node(root);
938 generation = btrfs_header_generation(node);
939 free_extent_buffer(node);
941 ret = reada_add_block(rc, start, &max_key, generation);
947 reada_start_machine(root->fs_info);
953 int btrfs_reada_wait(void *handle)
955 struct reada_control *rc = handle;
957 while (atomic_read(&rc->elems)) {
958 wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0,
960 dump_devs(rc->root->fs_info,
961 atomic_read(&rc->elems) < 10 ? 1 : 0);
964 dump_devs(rc->root->fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0);
966 kref_put(&rc->refcnt, reada_control_release);
971 int btrfs_reada_wait(void *handle)
973 struct reada_control *rc = handle;
975 while (atomic_read(&rc->elems)) {
976 wait_event(rc->wait, atomic_read(&rc->elems) == 0);
979 kref_put(&rc->refcnt, reada_control_release);
985 void btrfs_reada_detach(void *handle)
987 struct reada_control *rc = handle;
989 kref_put(&rc->refcnt, reada_control_release);