diff options
Diffstat (limited to 'fs/btrfs/reada.c')
| -rw-r--r-- | fs/btrfs/reada.c | 1069 |
1 files changed, 1069 insertions, 0 deletions
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c new file mode 100644 index 000000000..d9a166eb3 --- /dev/null +++ b/fs/btrfs/reada.c @@ -0,0 +1,1069 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2011 STRATO. All rights reserved. + */ + +#include <linux/sched.h> +#include <linux/pagemap.h> +#include <linux/writeback.h> +#include <linux/blkdev.h> +#include <linux/slab.h> +#include <linux/workqueue.h> +#include "ctree.h" +#include "volumes.h" +#include "disk-io.h" +#include "transaction.h" +#include "dev-replace.h" +#include "block-group.h" + +#undef DEBUG + +/* + * This is the implementation for the generic read ahead framework. + * + * To trigger a readahead, btrfs_reada_add must be called. It will start + * a read ahead for the given range [start, end) on tree root. The returned + * handle can either be used to wait on the readahead to finish + * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach). + * + * The read ahead works as follows: + * On btrfs_reada_add, the root of the tree is inserted into a radix_tree. + * reada_start_machine will then search for extents to prefetch and trigger + * some reads. When a read finishes for a node, all contained node/leaf + * pointers that lie in the given range will also be enqueued. The reads will + * be triggered in sequential order, thus giving a big win over a naive + * enumeration. It will also make use of multi-device layouts. Each disk + * will have its on read pointer and all disks will by utilized in parallel. + * Also will no two disks read both sides of a mirror simultaneously, as this + * would waste seeking capacity. Instead both disks will read different parts + * of the filesystem. + * Any number of readaheads can be started in parallel. The read order will be + * determined globally, i.e. 2 parallel readaheads will normally finish faster + * than the 2 started one after another. + */ + +#define MAX_IN_FLIGHT 6 + +struct reada_extctl { + struct list_head list; + struct reada_control *rc; + u64 generation; +}; + +struct reada_extent { + u64 logical; + struct btrfs_key top; + struct list_head extctl; + int refcnt; + spinlock_t lock; + struct reada_zone *zones[BTRFS_MAX_MIRRORS]; + int nzones; + int scheduled; +}; + +struct reada_zone { + u64 start; + u64 end; + u64 elems; + struct list_head list; + spinlock_t lock; + int locked; + struct btrfs_device *device; + struct btrfs_device *devs[BTRFS_MAX_MIRRORS]; /* full list, incl + * self */ + int ndevs; + struct kref refcnt; +}; + +struct reada_machine_work { + struct btrfs_work work; + struct btrfs_fs_info *fs_info; +}; + +static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *); +static void reada_control_release(struct kref *kref); +static void reada_zone_release(struct kref *kref); +static void reada_start_machine(struct btrfs_fs_info *fs_info); +static void __reada_start_machine(struct btrfs_fs_info *fs_info); + +static int reada_add_block(struct reada_control *rc, u64 logical, + struct btrfs_key *top, u64 generation); + +/* recurses */ +/* in case of err, eb might be NULL */ +static void __readahead_hook(struct btrfs_fs_info *fs_info, + struct reada_extent *re, struct extent_buffer *eb, + int err) +{ + int nritems; + int i; + u64 bytenr; + u64 generation; + struct list_head list; + + spin_lock(&re->lock); + /* + * just take the full list from the extent. afterwards we + * don't need the lock anymore + */ + list_replace_init(&re->extctl, &list); + re->scheduled = 0; + spin_unlock(&re->lock); + + /* + * this is the error case, the extent buffer has not been + * read correctly. We won't access anything from it and + * just cleanup our data structures. Effectively this will + * cut the branch below this node from read ahead. + */ + if (err) + goto cleanup; + + /* + * FIXME: currently we just set nritems to 0 if this is a leaf, + * effectively ignoring the content. In a next step we could + * trigger more readahead depending from the content, e.g. + * fetch the checksums for the extents in the leaf. + */ + if (!btrfs_header_level(eb)) + goto cleanup; + + nritems = btrfs_header_nritems(eb); + generation = btrfs_header_generation(eb); + for (i = 0; i < nritems; i++) { + struct reada_extctl *rec; + u64 n_gen; + struct btrfs_key key; + struct btrfs_key next_key; + + btrfs_node_key_to_cpu(eb, &key, i); + if (i + 1 < nritems) + btrfs_node_key_to_cpu(eb, &next_key, i + 1); + else + next_key = re->top; + bytenr = btrfs_node_blockptr(eb, i); + n_gen = btrfs_node_ptr_generation(eb, i); + + list_for_each_entry(rec, &list, list) { + struct reada_control *rc = rec->rc; + + /* + * if the generation doesn't match, just ignore this + * extctl. This will probably cut off a branch from + * prefetch. Alternatively one could start a new (sub-) + * prefetch for this branch, starting again from root. + * FIXME: move the generation check out of this loop + */ +#ifdef DEBUG + if (rec->generation != generation) { + btrfs_debug(fs_info, + "generation mismatch for (%llu,%d,%llu) %llu != %llu", + key.objectid, key.type, key.offset, + rec->generation, generation); + } +#endif + if (rec->generation == generation && + btrfs_comp_cpu_keys(&key, &rc->key_end) < 0 && + btrfs_comp_cpu_keys(&next_key, &rc->key_start) > 0) + reada_add_block(rc, bytenr, &next_key, n_gen); + } + } + +cleanup: + /* + * free extctl records + */ + while (!list_empty(&list)) { + struct reada_control *rc; + struct reada_extctl *rec; + + rec = list_first_entry(&list, struct reada_extctl, list); + list_del(&rec->list); + rc = rec->rc; + kfree(rec); + + kref_get(&rc->refcnt); + if (atomic_dec_and_test(&rc->elems)) { + kref_put(&rc->refcnt, reada_control_release); + wake_up(&rc->wait); + } + kref_put(&rc->refcnt, reada_control_release); + + reada_extent_put(fs_info, re); /* one ref for each entry */ + } + + return; +} + +int btree_readahead_hook(struct extent_buffer *eb, int err) +{ + struct btrfs_fs_info *fs_info = eb->fs_info; + int ret = 0; + struct reada_extent *re; + + /* find extent */ + spin_lock(&fs_info->reada_lock); + re = radix_tree_lookup(&fs_info->reada_tree, + eb->start >> PAGE_SHIFT); + if (re) + re->refcnt++; + spin_unlock(&fs_info->reada_lock); + if (!re) { + ret = -1; + goto start_machine; + } + + __readahead_hook(fs_info, re, eb, err); + reada_extent_put(fs_info, re); /* our ref */ + +start_machine: + reada_start_machine(fs_info); + return ret; +} + +static struct reada_zone *reada_find_zone(struct btrfs_device *dev, u64 logical, + struct btrfs_bio *bbio) +{ + struct btrfs_fs_info *fs_info = dev->fs_info; + int ret; + struct reada_zone *zone; + struct btrfs_block_group *cache = NULL; + u64 start; + u64 end; + int i; + + zone = NULL; + spin_lock(&fs_info->reada_lock); + ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone, + logical >> PAGE_SHIFT, 1); + if (ret == 1 && logical >= zone->start && logical <= zone->end) { + kref_get(&zone->refcnt); + spin_unlock(&fs_info->reada_lock); + return zone; + } + + spin_unlock(&fs_info->reada_lock); + + cache = btrfs_lookup_block_group(fs_info, logical); + if (!cache) + return NULL; + + start = cache->start; + end = start + cache->length - 1; + btrfs_put_block_group(cache); + + zone = kzalloc(sizeof(*zone), GFP_KERNEL); + if (!zone) + return NULL; + + ret = radix_tree_preload(GFP_KERNEL); + if (ret) { + kfree(zone); + return NULL; + } + + zone->start = start; + zone->end = end; + INIT_LIST_HEAD(&zone->list); + spin_lock_init(&zone->lock); + zone->locked = 0; + kref_init(&zone->refcnt); + zone->elems = 0; + zone->device = dev; /* our device always sits at index 0 */ + for (i = 0; i < bbio->num_stripes; ++i) { + /* bounds have already been checked */ + zone->devs[i] = bbio->stripes[i].dev; + } + zone->ndevs = bbio->num_stripes; + + spin_lock(&fs_info->reada_lock); + ret = radix_tree_insert(&dev->reada_zones, + (unsigned long)(zone->end >> PAGE_SHIFT), + zone); + + if (ret == -EEXIST) { + kfree(zone); + ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone, + logical >> PAGE_SHIFT, 1); + if (ret == 1 && logical >= zone->start && logical <= zone->end) + kref_get(&zone->refcnt); + else + zone = NULL; + } + spin_unlock(&fs_info->reada_lock); + radix_tree_preload_end(); + + return zone; +} + +static struct reada_extent *reada_find_extent(struct btrfs_fs_info *fs_info, + u64 logical, + struct btrfs_key *top) +{ + int ret; + struct reada_extent *re = NULL; + struct reada_extent *re_exist = NULL; + struct btrfs_bio *bbio = NULL; + struct btrfs_device *dev; + struct btrfs_device *prev_dev; + u64 length; + int real_stripes; + int nzones = 0; + unsigned long index = logical >> PAGE_SHIFT; + int dev_replace_is_ongoing; + int have_zone = 0; + + spin_lock(&fs_info->reada_lock); + re = radix_tree_lookup(&fs_info->reada_tree, index); + if (re) + re->refcnt++; + spin_unlock(&fs_info->reada_lock); + + if (re) + return re; + + re = kzalloc(sizeof(*re), GFP_KERNEL); + if (!re) + return NULL; + + re->logical = logical; + re->top = *top; + INIT_LIST_HEAD(&re->extctl); + spin_lock_init(&re->lock); + re->refcnt = 1; + + /* + * map block + */ + length = fs_info->nodesize; + ret = btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical, + &length, &bbio, 0); + if (ret || !bbio || length < fs_info->nodesize) + goto error; + + if (bbio->num_stripes > BTRFS_MAX_MIRRORS) { + btrfs_err(fs_info, + "readahead: more than %d copies not supported", + BTRFS_MAX_MIRRORS); + goto error; + } + + real_stripes = bbio->num_stripes - bbio->num_tgtdevs; + for (nzones = 0; nzones < real_stripes; ++nzones) { + struct reada_zone *zone; + + dev = bbio->stripes[nzones].dev; + + /* cannot read ahead on missing device. */ + if (!dev->bdev) + continue; + + zone = reada_find_zone(dev, logical, bbio); + if (!zone) + continue; + + re->zones[re->nzones++] = zone; + spin_lock(&zone->lock); + if (!zone->elems) + kref_get(&zone->refcnt); + ++zone->elems; + spin_unlock(&zone->lock); + spin_lock(&fs_info->reada_lock); + kref_put(&zone->refcnt, reada_zone_release); + spin_unlock(&fs_info->reada_lock); + } + if (re->nzones == 0) { + /* not a single zone found, error and out */ + goto error; + } + + /* Insert extent in reada tree + all per-device trees, all or nothing */ + down_read(&fs_info->dev_replace.rwsem); + ret = radix_tree_preload(GFP_KERNEL); + if (ret) { + up_read(&fs_info->dev_replace.rwsem); + goto error; + } + + spin_lock(&fs_info->reada_lock); + ret = radix_tree_insert(&fs_info->reada_tree, index, re); + if (ret == -EEXIST) { + re_exist = radix_tree_lookup(&fs_info->reada_tree, index); + re_exist->refcnt++; + spin_unlock(&fs_info->reada_lock); + radix_tree_preload_end(); + up_read(&fs_info->dev_replace.rwsem); + goto error; + } + if (ret) { + spin_unlock(&fs_info->reada_lock); + radix_tree_preload_end(); + up_read(&fs_info->dev_replace.rwsem); + goto error; + } + radix_tree_preload_end(); + prev_dev = NULL; + dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing( + &fs_info->dev_replace); + for (nzones = 0; nzones < re->nzones; ++nzones) { + dev = re->zones[nzones]->device; + + if (dev == prev_dev) { + /* + * in case of DUP, just add the first zone. As both + * are on the same device, there's nothing to gain + * from adding both. + * Also, it wouldn't work, as the tree is per device + * and adding would fail with EEXIST + */ + continue; + } + if (!dev->bdev) + continue; + + if (test_bit(BTRFS_DEV_STATE_NO_READA, &dev->dev_state)) + continue; + + if (dev_replace_is_ongoing && + dev == fs_info->dev_replace.tgtdev) { + /* + * as this device is selected for reading only as + * a last resort, skip it for read ahead. + */ + continue; + } + prev_dev = dev; + ret = radix_tree_insert(&dev->reada_extents, index, re); + if (ret) { + while (--nzones >= 0) { + dev = re->zones[nzones]->device; + BUG_ON(dev == NULL); + /* ignore whether the entry was inserted */ + radix_tree_delete(&dev->reada_extents, index); + } + radix_tree_delete(&fs_info->reada_tree, index); + spin_unlock(&fs_info->reada_lock); + up_read(&fs_info->dev_replace.rwsem); + goto error; + } + have_zone = 1; + } + if (!have_zone) + radix_tree_delete(&fs_info->reada_tree, index); + spin_unlock(&fs_info->reada_lock); + up_read(&fs_info->dev_replace.rwsem); + + if (!have_zone) + goto error; + + btrfs_put_bbio(bbio); + return re; + +error: + for (nzones = 0; nzones < re->nzones; ++nzones) { + struct reada_zone *zone; + + zone = re->zones[nzones]; + kref_get(&zone->refcnt); + spin_lock(&zone->lock); + --zone->elems; + if (zone->elems == 0) { + /* + * no fs_info->reada_lock needed, as this can't be + * the last ref + */ + kref_put(&zone->refcnt, reada_zone_release); + } + spin_unlock(&zone->lock); + + spin_lock(&fs_info->reada_lock); + kref_put(&zone->refcnt, reada_zone_release); + spin_unlock(&fs_info->reada_lock); + } + btrfs_put_bbio(bbio); + kfree(re); + return re_exist; +} + +static void reada_extent_put(struct btrfs_fs_info *fs_info, + struct reada_extent *re) +{ + int i; + unsigned long index = re->logical >> PAGE_SHIFT; + + spin_lock(&fs_info->reada_lock); + if (--re->refcnt) { + spin_unlock(&fs_info->reada_lock); + return; + } + + radix_tree_delete(&fs_info->reada_tree, index); + for (i = 0; i < re->nzones; ++i) { + struct reada_zone *zone = re->zones[i]; + + radix_tree_delete(&zone->device->reada_extents, index); + } + + spin_unlock(&fs_info->reada_lock); + + for (i = 0; i < re->nzones; ++i) { + struct reada_zone *zone = re->zones[i]; + + kref_get(&zone->refcnt); + spin_lock(&zone->lock); + --zone->elems; + if (zone->elems == 0) { + /* no fs_info->reada_lock needed, as this can't be + * the last ref */ + kref_put(&zone->refcnt, reada_zone_release); + } + spin_unlock(&zone->lock); + + spin_lock(&fs_info->reada_lock); + kref_put(&zone->refcnt, reada_zone_release); + spin_unlock(&fs_info->reada_lock); + } + + kfree(re); +} + +static void reada_zone_release(struct kref *kref) +{ + struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt); + + radix_tree_delete(&zone->device->reada_zones, + zone->end >> PAGE_SHIFT); + + kfree(zone); +} + +static void reada_control_release(struct kref *kref) +{ + struct reada_control *rc = container_of(kref, struct reada_control, + refcnt); + + kfree(rc); +} + +static int reada_add_block(struct reada_control *rc, u64 logical, + struct btrfs_key *top, u64 generation) +{ + struct btrfs_fs_info *fs_info = rc->fs_info; + struct reada_extent *re; + struct reada_extctl *rec; + + /* takes one ref */ + re = reada_find_extent(fs_info, logical, top); + if (!re) + return -1; + + rec = kzalloc(sizeof(*rec), GFP_KERNEL); + if (!rec) { + reada_extent_put(fs_info, re); + return -ENOMEM; + } + + rec->rc = rc; + rec->generation = generation; + atomic_inc(&rc->elems); + + spin_lock(&re->lock); + list_add_tail(&rec->list, &re->extctl); + spin_unlock(&re->lock); + + /* leave the ref on the extent */ + + return 0; +} + +/* + * called with fs_info->reada_lock held + */ +static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock) +{ + int i; + unsigned long index = zone->end >> PAGE_SHIFT; + + for (i = 0; i < zone->ndevs; ++i) { + struct reada_zone *peer; + peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index); + if (peer && peer->device != zone->device) + peer->locked = lock; + } +} + +/* + * called with fs_info->reada_lock held + */ +static int reada_pick_zone(struct btrfs_device *dev) +{ + struct reada_zone *top_zone = NULL; + struct reada_zone *top_locked_zone = NULL; + u64 top_elems = 0; + u64 top_locked_elems = 0; + unsigned long index = 0; + int ret; + + if (dev->reada_curr_zone) { + reada_peer_zones_set_lock(dev->reada_curr_zone, 0); + kref_put(&dev->reada_curr_zone->refcnt, reada_zone_release); + dev->reada_curr_zone = NULL; + } + /* pick the zone with the most elements */ + while (1) { + struct reada_zone *zone; + + ret = radix_tree_gang_lookup(&dev->reada_zones, + (void **)&zone, index, 1); + if (ret == 0) + break; + index = (zone->end >> PAGE_SHIFT) + 1; + if (zone->locked) { + if (zone->elems > top_locked_elems) { + top_locked_elems = zone->elems; + top_locked_zone = zone; + } + } else { + if (zone->elems > top_elems) { + top_elems = zone->elems; + top_zone = zone; + } + } + } + if (top_zone) + dev->reada_curr_zone = top_zone; + else if (top_locked_zone) + dev->reada_curr_zone = top_locked_zone; + else + return 0; + + dev->reada_next = dev->reada_curr_zone->start; + kref_get(&dev->reada_curr_zone->refcnt); + reada_peer_zones_set_lock(dev->reada_curr_zone, 1); + + return 1; +} + +static int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr, + int mirror_num, struct extent_buffer **eb) +{ + struct extent_buffer *buf = NULL; + int ret; + + buf = btrfs_find_create_tree_block(fs_info, bytenr); + if (IS_ERR(buf)) + return 0; + + set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags); + + ret = read_extent_buffer_pages(buf, WAIT_PAGE_LOCK, mirror_num); + if (ret) { + free_extent_buffer_stale(buf); + return ret; + } + + if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) { + free_extent_buffer_stale(buf); + return -EIO; + } else if (extent_buffer_uptodate(buf)) { + *eb = buf; + } else { + free_extent_buffer(buf); + } + return 0; +} + +static int reada_start_machine_dev(struct btrfs_device *dev) +{ + struct btrfs_fs_info *fs_info = dev->fs_info; + struct reada_extent *re = NULL; + int mirror_num = 0; + struct extent_buffer *eb = NULL; + u64 logical; + int ret; + int i; + + spin_lock(&fs_info->reada_lock); + if (dev->reada_curr_zone == NULL) { + ret = reada_pick_zone(dev); + if (!ret) { + spin_unlock(&fs_info->reada_lock); + return 0; + } + } + /* + * FIXME currently we issue the reads one extent at a time. If we have + * a contiguous block of extents, we could also coagulate them or use + * plugging to speed things up + */ + ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re, + dev->reada_next >> PAGE_SHIFT, 1); + if (ret == 0 || re->logical > dev->reada_curr_zone->end) { + ret = reada_pick_zone(dev); + if (!ret) { + spin_unlock(&fs_info->reada_lock); + return 0; + } + re = NULL; + ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re, + dev->reada_next >> PAGE_SHIFT, 1); + } + if (ret == 0) { + spin_unlock(&fs_info->reada_lock); + return 0; + } + dev->reada_next = re->logical + fs_info->nodesize; + re->refcnt++; + + spin_unlock(&fs_info->reada_lock); + + spin_lock(&re->lock); + if (re->scheduled || list_empty(&re->extctl)) { + spin_unlock(&re->lock); + reada_extent_put(fs_info, re); + return 0; + } + re->scheduled = 1; + spin_unlock(&re->lock); + + /* + * find mirror num + */ + for (i = 0; i < re->nzones; ++i) { + if (re->zones[i]->device == dev) { + mirror_num = i + 1; + break; + } + } + logical = re->logical; + + atomic_inc(&dev->reada_in_flight); + ret = reada_tree_block_flagged(fs_info, logical, mirror_num, &eb); + if (ret) + __readahead_hook(fs_info, re, NULL, ret); + else if (eb) + __readahead_hook(fs_info, re, eb, ret); + + if (eb) + free_extent_buffer(eb); + + atomic_dec(&dev->reada_in_flight); + reada_extent_put(fs_info, re); + + return 1; + +} + +static void reada_start_machine_worker(struct btrfs_work *work) +{ + struct reada_machine_work *rmw; + int old_ioprio; + + rmw = container_of(work, struct reada_machine_work, work); + + old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current), + task_nice_ioprio(current)); + set_task_ioprio(current, BTRFS_IOPRIO_READA); + __reada_start_machine(rmw->fs_info); + set_task_ioprio(current, old_ioprio); + + atomic_dec(&rmw->fs_info->reada_works_cnt); + + kfree(rmw); +} + +/* Try to start up to 10k READA requests for a group of devices */ +static int reada_start_for_fsdevs(struct btrfs_fs_devices *fs_devices) +{ + u64 enqueued; + u64 total = 0; + struct btrfs_device *device; + + do { + enqueued = 0; + list_for_each_entry(device, &fs_devices->devices, dev_list) { + if (atomic_read(&device->reada_in_flight) < + MAX_IN_FLIGHT) + enqueued += reada_start_machine_dev(device); + } + total += enqueued; + } while (enqueued && total < 10000); + + return total; +} + +static void __reada_start_machine(struct btrfs_fs_info *fs_info) +{ + struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs; + int i; + u64 enqueued = 0; + + mutex_lock(&fs_devices->device_list_mutex); + + enqueued += reada_start_for_fsdevs(fs_devices); + list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) + enqueued += reada_start_for_fsdevs(seed_devs); + + mutex_unlock(&fs_devices->device_list_mutex); + if (enqueued == 0) + return; + + /* + * If everything is already in the cache, this is effectively single + * threaded. To a) not hold the caller for too long and b) to utilize + * more cores, we broke the loop above after 10000 iterations and now + * enqueue to workers to finish it. This will distribute the load to + * the cores. + */ + for (i = 0; i < 2; ++i) { + reada_start_machine(fs_info); + if (atomic_read(&fs_info->reada_works_cnt) > + BTRFS_MAX_MIRRORS * 2) + break; + } +} + +static void reada_start_machine(struct btrfs_fs_info *fs_info) +{ + struct reada_machine_work *rmw; + + rmw = kzalloc(sizeof(*rmw), GFP_KERNEL); + if (!rmw) { + /* FIXME we cannot handle this properly right now */ + BUG(); + } + btrfs_init_work(&rmw->work, reada_start_machine_worker, NULL, NULL); + rmw->fs_info = fs_info; + + btrfs_queue_work(fs_info->readahead_workers, &rmw->work); + atomic_inc(&fs_info->reada_works_cnt); +} + +#ifdef DEBUG +static void dump_devs(struct btrfs_fs_info *fs_info, int all) +{ + struct btrfs_device *device; + struct btrfs_fs_devices *fs_devices = fs_info->fs_devices; + unsigned long index; + int ret; + int i; + int j; + int cnt; + + spin_lock(&fs_info->reada_lock); + list_for_each_entry(device, &fs_devices->devices, dev_list) { + btrfs_debug(fs_info, "dev %lld has %d in flight", device->devid, + atomic_read(&device->reada_in_flight)); + index = 0; + while (1) { + struct reada_zone *zone; + ret = radix_tree_gang_lookup(&device->reada_zones, + (void **)&zone, index, 1); + if (ret == 0) + break; + pr_debug(" zone %llu-%llu elems %llu locked %d devs", + zone->start, zone->end, zone->elems, + zone->locked); + for (j = 0; j < zone->ndevs; ++j) { + pr_cont(" %lld", + zone->devs[j]->devid); + } + if (device->reada_curr_zone == zone) + pr_cont(" curr off %llu", + device->reada_next - zone->start); + pr_cont("\n"); + index = (zone->end >> PAGE_SHIFT) + 1; + } + cnt = 0; + index = 0; + while (all) { + struct reada_extent *re = NULL; + + ret = radix_tree_gang_lookup(&device->reada_extents, + (void **)&re, index, 1); + if (ret == 0) + break; + pr_debug(" re: logical %llu size %u empty %d scheduled %d", + re->logical, fs_info->nodesize, + list_empty(&re->extctl), re->scheduled); + + for (i = 0; i < re->nzones; ++i) { + pr_cont(" zone %llu-%llu devs", + re->zones[i]->start, + re->zones[i]->end); + for (j = 0; j < re->zones[i]->ndevs; ++j) { + pr_cont(" %lld", + re->zones[i]->devs[j]->devid); + } + } + pr_cont("\n"); + index = (re->logical >> PAGE_SHIFT) + 1; + if (++cnt > 15) + break; + } + } + + index = 0; + cnt = 0; + while (all) { + struct reada_extent *re = NULL; + + ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re, + index, 1); + if (ret == 0) + break; + if (!re->scheduled) { + index = (re->logical >> PAGE_SHIFT) + 1; + continue; + } + pr_debug("re: logical %llu size %u list empty %d scheduled %d", + re->logical, fs_info->nodesize, + list_empty(&re->extctl), re->scheduled); + for (i = 0; i < re->nzones; ++i) { + pr_cont(" zone %llu-%llu devs", + re->zones[i]->start, + re->zones[i]->end); + for (j = 0; j < re->zones[i]->ndevs; ++j) { + pr_cont(" %lld", + re->zones[i]->devs[j]->devid); + } + } + pr_cont("\n"); + index = (re->logical >> PAGE_SHIFT) + 1; + } + spin_unlock(&fs_info->reada_lock); +} +#endif + +/* + * interface + */ +struct reada_control *btrfs_reada_add(struct btrfs_root *root, + struct btrfs_key *key_start, struct btrfs_key *key_end) +{ + struct reada_control *rc; + u64 start; + u64 generation; + int ret; + struct extent_buffer *node; + static struct btrfs_key max_key = { + .objectid = (u64)-1, + .type = (u8)-1, + .offset = (u64)-1 + }; + + rc = kzalloc(sizeof(*rc), GFP_KERNEL); + if (!rc) + return ERR_PTR(-ENOMEM); + + rc->fs_info = root->fs_info; + rc->key_start = *key_start; + rc->key_end = *key_end; + atomic_set(&rc->elems, 0); + init_waitqueue_head(&rc->wait); + kref_init(&rc->refcnt); + kref_get(&rc->refcnt); /* one ref for having elements */ + + node = btrfs_root_node(root); + start = node->start; + generation = btrfs_header_generation(node); + free_extent_buffer(node); + + ret = reada_add_block(rc, start, &max_key, generation); + if (ret) { + kfree(rc); + return ERR_PTR(ret); + } + + reada_start_machine(root->fs_info); + + return rc; +} + +#ifdef DEBUG +int btrfs_reada_wait(void *handle) +{ + struct reada_control *rc = handle; + struct btrfs_fs_info *fs_info = rc->fs_info; + + while (atomic_read(&rc->elems)) { + if (!atomic_read(&fs_info->reada_works_cnt)) + reada_start_machine(fs_info); + wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0, + 5 * HZ); + dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0); + } + + dump_devs(fs_info, atomic_read(&rc->elems) < 10 ? 1 : 0); + + kref_put(&rc->refcnt, reada_control_release); + + return 0; +} +#else +int btrfs_reada_wait(void *handle) +{ + struct reada_control *rc = handle; + struct btrfs_fs_info *fs_info = rc->fs_info; + + while (atomic_read(&rc->elems)) { + if (!atomic_read(&fs_info->reada_works_cnt)) + reada_start_machine(fs_info); + wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0, + (HZ + 9) / 10); + } + + kref_put(&rc->refcnt, reada_control_release); + + return 0; +} +#endif + +void btrfs_reada_detach(void *handle) +{ + struct reada_control *rc = handle; + + kref_put(&rc->refcnt, reada_control_release); +} + +/* + * Before removing a device (device replace or device remove ioctls), call this + * function to wait for all existing readahead requests on the device and to + * make sure no one queues more readahead requests for the device. + * + * Must be called without holding neither the device list mutex nor the device + * replace semaphore, otherwise it will deadlock. + */ +void btrfs_reada_remove_dev(struct btrfs_device *dev) +{ + struct btrfs_fs_info *fs_info = dev->fs_info; + + /* Serialize with readahead extent creation at reada_find_extent(). */ + spin_lock(&fs_info->reada_lock); + set_bit(BTRFS_DEV_STATE_NO_READA, &dev->dev_state); + spin_unlock(&fs_info->reada_lock); + + /* + * There might be readahead requests added to the radix trees which + * were not yet added to the readahead work queue. We need to start + * them and wait for their completion, otherwise we can end up with + * use-after-free problems when dropping the last reference on the + * readahead extents and their zones, as they need to access the + * device structure. + */ + reada_start_machine(fs_info); + btrfs_flush_workqueue(fs_info->readahead_workers); +} + +/* + * If when removing a device (device replace or device remove ioctls) an error + * happens after calling btrfs_reada_remove_dev(), call this to undo what that + * function did. This is safe to call even if btrfs_reada_remove_dev() was not + * called before. + */ +void btrfs_reada_undo_remove_dev(struct btrfs_device *dev) +{ + spin_lock(&dev->fs_info->reada_lock); + clear_bit(BTRFS_DEV_STATE_NO_READA, &dev->dev_state); + spin_unlock(&dev->fs_info->reada_lock); +} |