v4.19.13 snapshot.
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
new file mode 100644
index 0000000..dec14b7
--- /dev/null
+++ b/fs/btrfs/reada.c
@@ -0,0 +1,980 @@
+// 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"
+
+#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 *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->key.objectid;
+ end = start + cache->key.offset - 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;
+ }
+
+ ret = radix_tree_preload(GFP_KERNEL);
+ if (ret)
+ goto error;
+
+ /* insert extent in reada_tree + all per-device trees, all or nothing */
+ btrfs_dev_replace_read_lock(&fs_info->dev_replace);
+ 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);
+ btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+ radix_tree_preload_end();
+ goto error;
+ }
+ if (ret) {
+ spin_unlock(&fs_info->reada_lock);
+ btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+ radix_tree_preload_end();
+ 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 (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);
+ btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+ goto error;
+ }
+ have_zone = 1;
+ }
+ spin_unlock(&fs_info->reada_lock);
+ btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+
+ 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_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;
+ struct btrfs_fs_info *fs_info;
+ int old_ioprio;
+
+ rmw = container_of(work, struct reada_machine_work, work);
+ fs_info = rmw->fs_info;
+
+ kfree(rmw);
+
+ old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
+ task_nice_ioprio(current));
+ set_task_ioprio(current, BTRFS_IOPRIO_READA);
+ __reada_start_machine(fs_info);
+ set_task_ioprio(current, old_ioprio);
+
+ atomic_dec(&fs_info->reada_works_cnt);
+}
+
+static void __reada_start_machine(struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_device *device;
+ struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+ u64 enqueued;
+ u64 total = 0;
+ int i;
+
+ do {
+ enqueued = 0;
+ mutex_lock(&fs_devices->device_list_mutex);
+ 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);
+ }
+ mutex_unlock(&fs_devices->device_list_mutex);
+ total += enqueued;
+ } while (enqueued && total < 10000);
+
+ 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, btrfs_readahead_helper,
+ 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);
+}