3 files changed, 141 insertions, 137 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 6af1211d4ee9..e2a5cc0d4a14 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1825,6 +1825,9 @@ struct btrfs_fs_info {
         spinlock_t reada_lock;
         struct radix_tree_root reada_tree;
 
+        /* readahead works cnt */
+        atomic_t reada_works_cnt;
+
         /* Extent buffer radix tree */
         spinlock_t buffer_lock;
         struct radix_tree_root buffer_radix;
@@ -4563,8 +4566,8 @@ struct reada_control *btrfs_reada_add(struct btrfs_root *root,
                               struct btrfs_key *start, struct btrfs_key *end);
 int btrfs_reada_wait(void *handle);
 void btrfs_reada_detach(void *handle);
-int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
-                         u64 start, int err);
+int btree_readahead_hook(struct btrfs_fs_info *fs_info,
+                         struct extent_buffer *eb, u64 start, int err);
 
 static inline int is_fstree(u64 rootid)
 {
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 294c77729df3..de68b8b61fd2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -612,6 +612,7 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
         int found_level;
         struct extent_buffer *eb;
         struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
+        struct btrfs_fs_info *fs_info = root->fs_info;
         int ret = 0;
         int reads_done;
 
@@ -637,21 +638,21 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 
         found_start = btrfs_header_bytenr(eb);
         if (found_start != eb->start) {
-                btrfs_err_rl(eb->fs_info, "bad tree block start %llu %llu",
-                               found_start, eb->start);
+                btrfs_err_rl(fs_info, "bad tree block start %llu %llu",
+                             found_start, eb->start);
                 ret = -EIO;
                 goto err;
         }
-        if (check_tree_block_fsid(root->fs_info, eb)) {
-                btrfs_err_rl(eb->fs_info, "bad fsid on block %llu",
-                               eb->start);
+        if (check_tree_block_fsid(fs_info, eb)) {
+                btrfs_err_rl(fs_info, "bad fsid on block %llu",
+                             eb->start);
                 ret = -EIO;
                 goto err;
         }
         found_level = btrfs_header_level(eb);
         if (found_level >= BTRFS_MAX_LEVEL) {
-                btrfs_err(root->fs_info, "bad tree block level %d",
-                           (int)btrfs_header_level(eb));
+                btrfs_err(fs_info, "bad tree block level %d",
+                          (int)btrfs_header_level(eb));
                 ret = -EIO;
                 goto err;
         }
@@ -659,7 +660,7 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
         btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb),
                                        eb, found_level);
 
-        ret = csum_tree_block(root->fs_info, eb, 1);
+        ret = csum_tree_block(fs_info, eb, 1);
         if (ret) {
                 ret = -EIO;
                 goto err;
@@ -680,7 +681,7 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 err:
         if (reads_done &&
             test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
-                btree_readahead_hook(root, eb, eb->start, ret);
+                btree_readahead_hook(fs_info, eb, eb->start, ret);
 
         if (ret) {
                 /*
@@ -699,14 +700,13 @@ out:
 static int btree_io_failed_hook(struct page *page, int failed_mirror)
 {
         struct extent_buffer *eb;
-        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
 
         eb = (struct extent_buffer *)page->private;
         set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
         eb->read_mirror = failed_mirror;
         atomic_dec(&eb->io_pages);
         if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
-                btree_readahead_hook(root, eb, eb->start, -EIO);
+                btree_readahead_hook(eb->fs_info, eb, eb->start, -EIO);
         return -EIO;    /* we fixed nothing */
 }
 
@@ -2604,6 +2604,7 @@ int open_ctree(struct super_block *sb,
         atomic_set(&fs_info->nr_async_bios, 0);
         atomic_set(&fs_info->defrag_running, 0);
         atomic_set(&fs_info->qgroup_op_seq, 0);
+        atomic_set(&fs_info->reada_works_cnt, 0);
         atomic64_set(&fs_info->tree_mod_seq, 0);
         fs_info->sb = sb;
         fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE;
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index c5f1773c4794..bf69c008249c 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -72,7 +72,7 @@ struct reada_extent {
         spinlock_t              lock;
         struct reada_zone       *zones[BTRFS_MAX_MIRRORS];
         int                     nzones;
-        struct btrfs_device     *scheduled_for;
+        int                     scheduled;
 };
 
 struct reada_zone {
@@ -101,67 +101,53 @@ 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, int level, u64 generation);
+                           struct btrfs_key *top, u64 generation);
 
 /* recurses */
 /* in case of err, eb might be NULL */
-static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
-                            u64 start, int err)
+static void __readahead_hook(struct btrfs_fs_info *fs_info,
+                             struct reada_extent *re, struct extent_buffer *eb,
+                             u64 start, int err)
 {
         int level = 0;
         int nritems;
         int i;
         u64 bytenr;
         u64 generation;
-        struct reada_extent *re;
-        struct btrfs_fs_info *fs_info = root->fs_info;
         struct list_head list;
-        unsigned long index = start >> PAGE_CACHE_SHIFT;
-        struct btrfs_device *for_dev;
 
         if (eb)
                 level = btrfs_header_level(eb);
 
-        /* find extent */
-        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 -1;
-
         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);
-        for_dev = re->scheduled_for;
-        re->scheduled_for = NULL;
+        re->scheduled = 0;
         spin_unlock(&re->lock);
 
-        if (err == 0) {
-                nritems = level ? btrfs_header_nritems(eb) : 0;
-                generation = btrfs_header_generation(eb);
-                /*
-                 * 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.
-                 */
-        } else {
-                /*
-                 * 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.
-                 */
-                nritems = 0;
-                generation = 0;
-        }
+        /*
+         * 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 (!level)
+                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;
@@ -188,19 +174,20 @@ static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
                          */
 #ifdef DEBUG
                         if (rec->generation != generation) {
-                                btrfs_debug(root->fs_info,
-                                           "generation mismatch for (%llu,%d,%llu) %llu != %llu",
-                                       key.objectid, key.type, key.offset,
-                                       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,
-                                                level - 1, n_gen);
+                                reada_add_block(rc, bytenr, &next_key, n_gen);
                 }
         }
+
+cleanup:
         /*
          * free extctl records
          */
@@ -222,26 +209,37 @@ static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
 
                 reada_extent_put(fs_info, re);  /* one ref for each entry */
         }
-        reada_extent_put(fs_info, re);  /* our ref */
-        if (for_dev)
-                atomic_dec(&for_dev->reada_in_flight);
 
-        return 0;
+        return;
 }
 
 /*
  * start is passed separately in case eb in NULL, which may be the case with
  * failed I/O
  */
-int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
-                         u64 start, int err)
+int btree_readahead_hook(struct btrfs_fs_info *fs_info,
+                         struct extent_buffer *eb, u64 start, int err)
 {
-        int ret;
+        int ret = 0;
+        struct reada_extent *re;
 
-        ret = __readahead_hook(root, eb, start, err);
+        /* find extent */
+        spin_lock(&fs_info->reada_lock);
+        re = radix_tree_lookup(&fs_info->reada_tree,
+                               start >> PAGE_CACHE_SHIFT);
+        if (re)
+                re->refcnt++;
+        spin_unlock(&fs_info->reada_lock);
+        if (!re) {
+                ret = -1;
+                goto start_machine;
+        }
 
-        reada_start_machine(root->fs_info);
+        __readahead_hook(fs_info, re, eb, start, err);
+        reada_extent_put(fs_info, re);  /* our ref */
 
+start_machine:
+        reada_start_machine(fs_info);
         return ret;
 }
 
@@ -260,18 +258,14 @@ static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
         spin_lock(&fs_info->reada_lock);
         ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
                                      logical >> PAGE_CACHE_SHIFT, 1);
-        if (ret == 1)
+        if (ret == 1 && logical >= zone->start && logical <= zone->end) {
                 kref_get(&zone->refcnt);
-        spin_unlock(&fs_info->reada_lock);
-
-        if (ret == 1) {
-                if (logical >= zone->start && logical < zone->end)
-                        return zone;
-                spin_lock(&fs_info->reada_lock);
-                kref_put(&zone->refcnt, reada_zone_release);
                 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;
@@ -307,8 +301,10 @@ static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
                 kfree(zone);
                 ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
                                              logical >> PAGE_CACHE_SHIFT, 1);
-                if (ret == 1)
+                if (ret == 1 && logical >= zone->start && logical <= zone->end)
                         kref_get(&zone->refcnt);
+                else
+                        zone = NULL;
         }
         spin_unlock(&fs_info->reada_lock);
 
@@ -317,7 +313,7 @@ static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
 
 static struct reada_extent *reada_find_extent(struct btrfs_root *root,
                                               u64 logical,
-                                              struct btrfs_key *top, int level)
+                                              struct btrfs_key *top)
 {
         int ret;
         struct reada_extent *re = NULL;
@@ -330,9 +326,9 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
         u64 length;
         int real_stripes;
         int nzones = 0;
-        int i;
         unsigned long index = logical >> PAGE_CACHE_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);
@@ -375,11 +371,16 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
                 struct reada_zone *zone;
 
                 dev = bbio->stripes[nzones].dev;
+
+                /* cannot read ahead on missing device. */
+                 if (!dev->bdev)
+                        continue;
+
                 zone = reada_find_zone(fs_info, dev, logical, bbio);
                 if (!zone)
-                        break;
+                        continue;
 
-                re->zones[nzones] = zone;
+                re->zones[re->nzones++] = zone;
                 spin_lock(&zone->lock);
                 if (!zone->elems)
                         kref_get(&zone->refcnt);
@@ -389,8 +390,7 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
                 kref_put(&zone->refcnt, reada_zone_release);
                 spin_unlock(&fs_info->reada_lock);
         }
-        re->nzones = nzones;
-        if (nzones == 0) {
+        if (re->nzones == 0) {
                 /* not a single zone found, error and out */
                 goto error;
         }
@@ -415,8 +415,9 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
         prev_dev = NULL;
         dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(
                         &fs_info->dev_replace);
-        for (i = 0; i < nzones; ++i) {
-                dev = bbio->stripes[i].dev;
+        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
@@ -427,15 +428,9 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
                          */
                         continue;
                 }
-                if (!dev->bdev) {
-                        /*
-                         * cannot read ahead on missing device, but for RAID5/6,
-                         * REQ_GET_READ_MIRRORS return 1. So don't skip missing
-                         * device for such case.
-                         */
-                        if (nzones > 1)
-                                continue;
-                }
+                if (!dev->bdev)
+                        continue;
+
                 if (dev_replace_is_ongoing &&
                     dev == fs_info->dev_replace.tgtdev) {
                         /*
@@ -447,8 +442,8 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
                 prev_dev = dev;
                 ret = radix_tree_insert(&dev->reada_extents, index, re);
                 if (ret) {
-                        while (--i >= 0) {
-                                dev = bbio->stripes[i].dev;
+                        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);
@@ -459,18 +454,21 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root,
                         btrfs_dev_replace_unlock(&fs_info->dev_replace);
                         goto error;
                 }
+                have_zone = 1;
         }
         spin_unlock(&fs_info->reada_lock);
         btrfs_dev_replace_unlock(&fs_info->dev_replace);
 
+        if (!have_zone)
+                goto error;
+
         btrfs_put_bbio(bbio);
         return re;
 
 error:
-        while (nzones) {
+        for (nzones = 0; nzones < re->nzones; ++nzones) {
                 struct reada_zone *zone;
 
-                --nzones;
                 zone = re->zones[nzones];
                 kref_get(&zone->refcnt);
                 spin_lock(&zone->lock);
@@ -531,8 +529,6 @@ static void reada_extent_put(struct btrfs_fs_info *fs_info,
                 kref_put(&zone->refcnt, reada_zone_release);
                 spin_unlock(&fs_info->reada_lock);
         }
-        if (re->scheduled_for)
-                atomic_dec(&re->scheduled_for->reada_in_flight);
 
         kfree(re);
 }
@@ -556,13 +552,13 @@ static void reada_control_release(struct kref *kref)
 }
 
 static int reada_add_block(struct reada_control *rc, u64 logical,
-                           struct btrfs_key *top, int level, u64 generation)
+                           struct btrfs_key *top, u64 generation)
 {
         struct btrfs_root *root = rc->root;
         struct reada_extent *re;
         struct reada_extctl *rec;
 
-        re = reada_find_extent(root, logical, top, level); /* takes one ref */
+        re = reada_find_extent(root, logical, top); /* takes one ref */
         if (!re)
                 return -1;
 
@@ -662,7 +658,6 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
         u64 logical;
         int ret;
         int i;
-        int need_kick = 0;
 
         spin_lock(&fs_info->reada_lock);
         if (dev->reada_curr_zone == NULL) {
@@ -679,7 +674,7 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
          */
         ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
                                      dev->reada_next >> PAGE_CACHE_SHIFT, 1);
-        if (ret == 0 || re->logical >= dev->reada_curr_zone->end) {
+        if (ret == 0 || re->logical > dev->reada_curr_zone->end) {
                 ret = reada_pick_zone(dev);
                 if (!ret) {
                         spin_unlock(&fs_info->reada_lock);
@@ -698,6 +693,15 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
 
         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
          */
@@ -709,29 +713,20 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
         }
         logical = re->logical;
 
-        spin_lock(&re->lock);
-        if (re->scheduled_for == NULL) {
-                re->scheduled_for = dev;
-                need_kick = 1;
-        }
-        spin_unlock(&re->lock);
-
-        reada_extent_put(fs_info, re);
-
-        if (!need_kick)
-                return 0;
-
         atomic_inc(&dev->reada_in_flight);
         ret = reada_tree_block_flagged(fs_info->extent_root, logical,
                         mirror_num, &eb);
         if (ret)
-                __readahead_hook(fs_info->extent_root, NULL, logical, ret);
+                __readahead_hook(fs_info, re, NULL, logical, ret);
         else if (eb)
-                __readahead_hook(fs_info->extent_root, eb, eb->start, ret);
+                __readahead_hook(fs_info, re, eb, eb->start, ret);
 
         if (eb)
                 free_extent_buffer(eb);
 
+        atomic_dec(&dev->reada_in_flight);
+        reada_extent_put(fs_info, re);
+
         return 1;
 
 }
@@ -752,6 +747,8 @@ static void reada_start_machine_worker(struct btrfs_work *work)
         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)
@@ -783,8 +780,12 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info)
          * enqueue to workers to finish it. This will distribute the load to
          * the cores.
          */
-        for (i = 0; i < 2; ++i)
+        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)
@@ -801,6 +802,7 @@ static void reada_start_machine(struct btrfs_fs_info *fs_info)
         rmw->fs_info = fs_info;
 
         btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
+        atomic_inc(&fs_info->reada_works_cnt);
 }
 
 #ifdef DEBUG
@@ -848,10 +850,9 @@ static void dump_devs(struct btrfs_fs_info *fs_info, int all)
                         if (ret == 0)
                                 break;
                         printk(KERN_DEBUG
-                                "  re: logical %llu size %u empty %d for %lld",
+                                "  re: logical %llu size %u empty %d scheduled %d",
                                 re->logical, fs_info->tree_root->nodesize,
-                                list_empty(&re->extctl), re->scheduled_for ?
-                                re->scheduled_for->devid : -1);
+                                list_empty(&re->extctl), re->scheduled);
 
                         for (i = 0; i < re->nzones; ++i) {
                                 printk(KERN_CONT " zone %llu-%llu devs",
@@ -878,27 +879,21 @@ static void dump_devs(struct btrfs_fs_info *fs_info, int all)
                                              index, 1);
                 if (ret == 0)
                         break;
-                if (!re->scheduled_for) {
+                if (!re->scheduled) {
                         index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
                         continue;
                 }
                 printk(KERN_DEBUG
-                        "re: logical %llu size %u list empty %d for %lld",
+                        "re: logical %llu size %u list empty %d scheduled %d",
                         re->logical, fs_info->tree_root->nodesize,
-                        list_empty(&re->extctl),
-                        re->scheduled_for ? re->scheduled_for->devid : -1);
+                        list_empty(&re->extctl), re->scheduled);
                 for (i = 0; i < re->nzones; ++i) {
                         printk(KERN_CONT " zone %llu-%llu devs",
                                 re->zones[i]->start,
                                 re->zones[i]->end);
-                        for (i = 0; i < re->nzones; ++i) {
-                                printk(KERN_CONT " zone %llu-%llu devs",
-                                        re->zones[i]->start,
-                                        re->zones[i]->end);
-                                for (j = 0; j < re->zones[i]->ndevs; ++j) {
-                                        printk(KERN_CONT " %lld",
-                                                re->zones[i]->devs[j]->devid);
-                                }
+                        for (j = 0; j < re->zones[i]->ndevs; ++j) {
+                                printk(KERN_CONT " %lld",
+                                       re->zones[i]->devs[j]->devid);
                         }
                 }
                 printk(KERN_CONT "\n");
@@ -917,7 +912,6 @@ struct reada_control *btrfs_reada_add(struct btrfs_root *root,
         struct reada_control *rc;
         u64 start;
         u64 generation;
-        int level;
         int ret;
         struct extent_buffer *node;
         static struct btrfs_key max_key = {
@@ -940,11 +934,10 @@ struct reada_control *btrfs_reada_add(struct btrfs_root *root,
 
         node = btrfs_root_node(root);
         start = node->start;
-        level = btrfs_header_level(node);
         generation = btrfs_header_generation(node);
         free_extent_buffer(node);
 
-        ret = reada_add_block(rc, start, &max_key, level, generation);
+        ret = reada_add_block(rc, start, &max_key, generation);
         if (ret) {
                 kfree(rc);
                 return ERR_PTR(ret);
@@ -959,8 +952,11 @@ struct reada_control *btrfs_reada_add(struct btrfs_root *root,
 int btrfs_reada_wait(void *handle)
 {
         struct reada_control *rc = handle;
+        struct btrfs_fs_info *fs_info = rc->root->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(rc->root->fs_info,
@@ -977,9 +973,13 @@ int btrfs_reada_wait(void *handle)
 int btrfs_reada_wait(void *handle)
 {
         struct reada_control *rc = handle;
+        struct btrfs_fs_info *fs_info = rc->root->fs_info;
 
         while (atomic_read(&rc->elems)) {
-                wait_event(rc->wait, atomic_read(&rc->elems) == 0);
+                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);