9 files changed, 342 insertions, 58 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d4042c89d29b..938efe33be80 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3431,6 +3431,8 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root, u64 group_start,
                              struct extent_map *em);
 void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info);
+void btrfs_get_block_group_trimming(struct btrfs_block_group_cache *cache);
+void btrfs_put_block_group_trimming(struct btrfs_block_group_cache *cache);
 void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root);
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data);
@@ -4067,6 +4069,7 @@ __cold
 void __btrfs_std_error(struct btrfs_fs_info *fs_info, const char *function,
                      unsigned int line, int errno, const char *fmt, ...);
 
+const char *btrfs_decode_error(int errno);
 
 __cold
 void __btrfs_abort_transaction(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 230546b45474..cc15514b4a76 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3761,6 +3761,15 @@ void close_ctree(struct btrfs_root *root)
         cancel_work_sync(&fs_info->async_reclaim_work);
 
         if (!(fs_info->sb->s_flags & MS_RDONLY)) {
+                /*
+                 * If the cleaner thread is stopped and there are
+                 * block groups queued for removal, the deletion will be
+                 * skipped when we quit the cleaner thread.
+                 */
+                mutex_lock(&root->fs_info->cleaner_mutex);
+                btrfs_delete_unused_bgs(root->fs_info);
+                mutex_unlock(&root->fs_info->cleaner_mutex);
+
                 ret = btrfs_commit_super(root);
                 if (ret)
                         btrfs_err(fs_info, "commit super ret %d", ret);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 59d59d98bca1..5411f0ab5683 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1882,10 +1882,77 @@ static int remove_extent_backref(struct btrfs_trans_handle *trans,
         return ret;
 }
 
-static int btrfs_issue_discard(struct block_device *bdev,
-                                u64 start, u64 len)
+#define in_range(b, first, len)        ((b) >= (first) && (b) < (first) + (len))
+static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
+                               u64 *discarded_bytes)
 {
-        return blkdev_issue_discard(bdev, start >> 9, len >> 9, GFP_NOFS, 0);
+        int j, ret = 0;
+        u64 bytes_left, end;
+        u64 aligned_start = ALIGN(start, 1 << 9);
+
+        if (WARN_ON(start != aligned_start)) {
+                len -= aligned_start - start;
+                len = round_down(len, 1 << 9);
+                start = aligned_start;
+        }
+
+        *discarded_bytes = 0;
+
+        if (!len)
+                return 0;
+
+        end = start + len;
+        bytes_left = len;
+
+        /* Skip any superblocks on this device. */
+        for (j = 0; j < BTRFS_SUPER_MIRROR_MAX; j++) {
+                u64 sb_start = btrfs_sb_offset(j);
+                u64 sb_end = sb_start + BTRFS_SUPER_INFO_SIZE;
+                u64 size = sb_start - start;
+
+                if (!in_range(sb_start, start, bytes_left) &&
+                    !in_range(sb_end, start, bytes_left) &&
+                    !in_range(start, sb_start, BTRFS_SUPER_INFO_SIZE))
+                        continue;
+
+                /*
+                 * Superblock spans beginning of range.  Adjust start and
+                 * try again.
+                 */
+                if (sb_start <= start) {
+                        start += sb_end - start;
+                        if (start > end) {
+                                bytes_left = 0;
+                                break;
+                        }
+                        bytes_left = end - start;
+                        continue;
+                }
+
+                if (size) {
+                        ret = blkdev_issue_discard(bdev, start >> 9, size >> 9,
+                                                   GFP_NOFS, 0);
+                        if (!ret)
+                                *discarded_bytes += size;
+                        else if (ret != -EOPNOTSUPP)
+                                return ret;
+                }
+
+                start = sb_end;
+                if (start > end) {
+                        bytes_left = 0;
+                        break;
+                }
+                bytes_left = end - start;
+        }
+
+        if (bytes_left) {
+                ret = blkdev_issue_discard(bdev, start >> 9, bytes_left >> 9,
+                                           GFP_NOFS, 0);
+                if (!ret)
+                        *discarded_bytes += bytes_left;
+        }
+        return ret;
 }
 
 int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
@@ -1906,14 +1973,16 @@ int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
 
 
                 for (i = 0; i < bbio->num_stripes; i++, stripe++) {
+                        u64 bytes;
                         if (!stripe->dev->can_discard)
                                 continue;
 
                         ret = btrfs_issue_discard(stripe->dev->bdev,
                                                   stripe->physical,
-                                                  stripe->length);
+                                                  stripe->length,
+                                                  &bytes);
                         if (!ret)
-                                discarded_bytes += stripe->length;
+                                discarded_bytes += bytes;
                         else if (ret != -EOPNOTSUPP)
                                 break; /* Logic errors or -ENOMEM, or -EIO but I don't know how that could happen JDM */
 
@@ -6061,20 +6130,19 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root)
 {
         struct btrfs_fs_info *fs_info = root->fs_info;
+        struct btrfs_block_group_cache *block_group, *tmp;
+        struct list_head *deleted_bgs;
         struct extent_io_tree *unpin;
         u64 start;
         u64 end;
         int ret;
 
-        if (trans->aborted)
-                return 0;
-
         if (fs_info->pinned_extents == &fs_info->freed_extents[0])
                 unpin = &fs_info->freed_extents[1];
         else
                 unpin = &fs_info->freed_extents[0];
 
-        while (1) {
+        while (!trans->aborted) {
                 mutex_lock(&fs_info->unused_bg_unpin_mutex);
                 ret = find_first_extent_bit(unpin, 0, &start, &end,
                                             EXTENT_DIRTY, NULL);
@@ -6093,6 +6161,34 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                 cond_resched();
         }
 
+        /*
+         * Transaction is finished.  We don't need the lock anymore.  We
+         * do need to clean up the block groups in case of a transaction
+         * abort.
+         */
+        deleted_bgs = &trans->transaction->deleted_bgs;
+        list_for_each_entry_safe(block_group, tmp, deleted_bgs, bg_list) {
+                u64 trimmed = 0;
+
+                ret = -EROFS;
+                if (!trans->aborted)
+                        ret = btrfs_discard_extent(root,
+                                                   block_group->key.objectid,
+                                                   block_group->key.offset,
+                                                   &trimmed);
+
+                list_del_init(&block_group->bg_list);
+                btrfs_put_block_group_trimming(block_group);
+                btrfs_put_block_group(block_group);
+
+                if (ret) {
+                        const char *errstr = btrfs_decode_error(ret);
+                        btrfs_warn(fs_info,
+                                   "Discard failed while removing blockgroup: errno=%d %s\n",
+                                   ret, errstr);
+                }
+        }
+
         return 0;
 }
 
@@ -9830,6 +9926,11 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
          * currently running transaction might finish and a new one start,
          * allowing for new block groups to be created that can reuse the same
          * physical device locations unless we take this special care.
+         *
+         * There may also be an implicit trim operation if the file system
+         * is mounted with -odiscard. The same protections must remain
+         * in place until the extents have been discarded completely when
+         * the transaction commit has completed.
          */
         remove_em = (atomic_read(&block_group->trimming) == 0);
         /*
@@ -9904,6 +10005,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
         spin_lock(&fs_info->unused_bgs_lock);
         while (!list_empty(&fs_info->unused_bgs)) {
                 u64 start, end;
+                int trimming;
 
                 block_group = list_first_entry(&fs_info->unused_bgs,
                                                struct btrfs_block_group_cache,
@@ -10003,12 +10105,39 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
                 spin_unlock(&block_group->lock);
                 spin_unlock(&space_info->lock);
 
+                /* DISCARD can flip during remount */
+                trimming = btrfs_test_opt(root, DISCARD);
+
+                /* Implicit trim during transaction commit. */
+                if (trimming)
+                        btrfs_get_block_group_trimming(block_group);
+
                 /*
                  * Btrfs_remove_chunk will abort the transaction if things go
                  * horribly wrong.
                  */
                 ret = btrfs_remove_chunk(trans, root,
                                          block_group->key.objectid);
+
+                if (ret) {
+                        if (trimming)
+                                btrfs_put_block_group_trimming(block_group);
+                        goto end_trans;
+                }
+
+                /*
+                 * If we're not mounted with -odiscard, we can just forget
+                 * about this block group. Otherwise we'll need to wait
+                 * until transaction commit to do the actual discard.
+                 */
+                if (trimming) {
+                        WARN_ON(!list_empty(&block_group->bg_list));
+                        spin_lock(&trans->transaction->deleted_bgs_lock);
+                        list_move(&block_group->bg_list,
+                                  &trans->transaction->deleted_bgs);
+                        spin_unlock(&trans->transaction->deleted_bgs_lock);
+                        btrfs_get_block_group(block_group);
+                }
 end_trans:
                 btrfs_end_transaction(trans, root);
 next:
@@ -10062,10 +10191,99 @@ int btrfs_error_unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
         return unpin_extent_range(root, start, end, false);
 }
 
+/*
+ * It used to be that old block groups would be left around forever.
+ * Iterating over them would be enough to trim unused space.  Since we
+ * now automatically remove them, we also need to iterate over unallocated
+ * space.
+ *
+ * We don't want a transaction for this since the discard may take a
+ * substantial amount of time.  We don't require that a transaction be
+ * running, but we do need to take a running transaction into account
+ * to ensure that we're not discarding chunks that were released in
+ * the current transaction.
+ *
+ * Holding the chunks lock will prevent other threads from allocating
+ * or releasing chunks, but it won't prevent a running transaction
+ * from committing and releasing the memory that the pending chunks
+ * list head uses.  For that, we need to take a reference to the
+ * transaction.
+ */
+static int btrfs_trim_free_extents(struct btrfs_device *device,
+                                   u64 minlen, u64 *trimmed)
+{
+        u64 start = 0, len = 0;
+        int ret;
+
+        *trimmed = 0;
+
+        /* Not writeable = nothing to do. */
+        if (!device->writeable)
+                return 0;
+
+        /* No free space = nothing to do. */
+        if (device->total_bytes <= device->bytes_used)
+                return 0;
+
+        ret = 0;
+
+        while (1) {
+                struct btrfs_fs_info *fs_info = device->dev_root->fs_info;
+                struct btrfs_transaction *trans;
+                u64 bytes;
+
+                ret = mutex_lock_interruptible(&fs_info->chunk_mutex);
+                if (ret)
+                        return ret;
+
+                down_read(&fs_info->commit_root_sem);
+
+                spin_lock(&fs_info->trans_lock);
+                trans = fs_info->running_transaction;
+                if (trans)
+                        atomic_inc(&trans->use_count);
+                spin_unlock(&fs_info->trans_lock);
+
+                ret = find_free_dev_extent_start(trans, device, minlen, start,
+                                                 &start, &len);
+                if (trans)
+                        btrfs_put_transaction(trans);
+
+                if (ret) {
+                        up_read(&fs_info->commit_root_sem);
+                        mutex_unlock(&fs_info->chunk_mutex);
+                        if (ret == -ENOSPC)
+                                ret = 0;
+                        break;
+                }
+
+                ret = btrfs_issue_discard(device->bdev, start, len, &bytes);
+                up_read(&fs_info->commit_root_sem);
+                mutex_unlock(&fs_info->chunk_mutex);
+
+                if (ret)
+                        break;
+
+                start += len;
+                *trimmed += bytes;
+
+                if (fatal_signal_pending(current)) {
+                        ret = -ERESTARTSYS;
+                        break;
+                }
+
+                cond_resched();
+        }
+
+        return ret;
+}
+
 int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
 {
         struct btrfs_fs_info *fs_info = root->fs_info;
         struct btrfs_block_group_cache *cache = NULL;
+        struct btrfs_device *device;
+        struct list_head *devices;
         u64 group_trimmed;
         u64 start;
         u64 end;
@@ -10120,6 +10338,18 @@ int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
                 cache = next_block_group(fs_info->tree_root, cache);
         }
 
+        mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
+        devices = &root->fs_info->fs_devices->alloc_list;
+        list_for_each_entry(device, devices, dev_alloc_list) {
+                ret = btrfs_trim_free_extents(device, range->minlen,
+                                              &group_trimmed);
+                if (ret)
+                        break;
+
+                trimmed += group_trimmed;
+        }
+        mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+
         range->len = trimmed;
         return ret;
 }
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index fb5a6b1c62a6..abe3a66bd3ba 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3272,35 +3272,23 @@ next:
         return ret;
 }
 
-int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
-                           u64 *trimmed, u64 start, u64 end, u64 minlen)
+void btrfs_get_block_group_trimming(struct btrfs_block_group_cache *cache)
 {
-        int ret;
+        atomic_inc(&cache->trimming);
+}
 
-        *trimmed = 0;
+void btrfs_put_block_group_trimming(struct btrfs_block_group_cache *block_group)
+{
+        struct extent_map_tree *em_tree;
+        struct extent_map *em;
+        bool cleanup;
 
         spin_lock(&block_group->lock);
-        if (block_group->removed) {
-                spin_unlock(&block_group->lock);
-                return 0;
-        }
-        atomic_inc(&block_group->trimming);
+        cleanup = (atomic_dec_and_test(&block_group->trimming) &&
+                   block_group->removed);
         spin_unlock(&block_group->lock);
 
-        ret = trim_no_bitmap(block_group, trimmed, start, end, minlen);
-        if (ret)
-                goto out;
-
-        ret = trim_bitmaps(block_group, trimmed, start, end, minlen);
-out:
-        spin_lock(&block_group->lock);
-        if (atomic_dec_and_test(&block_group->trimming) &&
-            block_group->removed) {
-                struct extent_map_tree *em_tree;
-                struct extent_map *em;
-
-                spin_unlock(&block_group->lock);
-
+        if (cleanup) {
                 lock_chunks(block_group->fs_info->chunk_root);
                 em_tree = &block_group->fs_info->mapping_tree.map_tree;
                 write_lock(&em_tree->lock);
@@ -3324,10 +3312,31 @@ out:
                  * this block group have left 1 entry each one. Free them.
                  */
                 __btrfs_remove_free_space_cache(block_group->free_space_ctl);
-        } else {
+        }
+}
+
+int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
+                           u64 *trimmed, u64 start, u64 end, u64 minlen)
+{
+        int ret;
+
+        *trimmed = 0;
+
+        spin_lock(&block_group->lock);
+        if (block_group->removed) {
                 spin_unlock(&block_group->lock);
+                return 0;
         }
+        btrfs_get_block_group_trimming(block_group);
+        spin_unlock(&block_group->lock);
+
+        ret = trim_no_bitmap(block_group, trimmed, start, end, minlen);
+        if (ret)
+                goto out;
 
+        ret = trim_bitmaps(block_group, trimmed, start, end, minlen);
+out:
+        btrfs_put_block_group_trimming(block_group);
         return ret;
 }
 
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d366dd4664d0..c389c13f0f38 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -69,7 +69,7 @@ static struct file_system_type btrfs_fs_type;
 
 static int btrfs_remount(struct super_block *sb, int *flags, char *data);
 
-static const char *btrfs_decode_error(int errno)
+const char *btrfs_decode_error(int errno)
 {
         char *errstr = "unknown";
 
@@ -1651,6 +1651,17 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 
                 sb->s_flags |= MS_RDONLY;
 
+                /*
+                 * Setting MS_RDONLY will put the cleaner thread to
+                 * sleep at the next loop if it's already active.
+                 * If it's already asleep, we'll leave unused block
+                 * groups on disk until we're mounted read-write again
+                 * unless we clean them up here.
+                 */
+                mutex_lock(&root->fs_info->cleaner_mutex);
+                btrfs_delete_unused_bgs(fs_info);
+                mutex_unlock(&root->fs_info->cleaner_mutex);
+
                 btrfs_dev_replace_suspend_for_unmount(fs_info);
                 btrfs_scrub_cancel(fs_info);
                 btrfs_pause_balance(fs_info);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 91f44c9f7ebc..20267d47dbcd 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -258,6 +258,8 @@ loop:
         mutex_init(&cur_trans->cache_write_mutex);
         cur_trans->num_dirty_bgs = 0;
         spin_lock_init(&cur_trans->dirty_bgs_lock);
+        INIT_LIST_HEAD(&cur_trans->deleted_bgs);
+        spin_lock_init(&cur_trans->deleted_bgs_lock);
         list_add_tail(&cur_trans->list, &fs_info->trans_list);
         extent_io_tree_init(&cur_trans->dirty_pages,
                              fs_info->btree_inode->i_mapping);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index eb09c2067fa8..edc2fbc262d7 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -74,6 +74,8 @@ struct btrfs_transaction {
          */
         struct mutex cache_write_mutex;
         spinlock_t dirty_bgs_lock;
+        struct list_head deleted_bgs;
+        spinlock_t deleted_bgs_lock;
         struct btrfs_delayed_ref_root delayed_refs;
         int aborted;
         int dirty_bg_run;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 88e2fe931bde..7c84a8122c37 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1116,15 +1116,18 @@ out:
         return ret;
 }
 
-static int contains_pending_extent(struct btrfs_trans_handle *trans,
+static int contains_pending_extent(struct btrfs_transaction *transaction,
                                    struct btrfs_device *device,
                                    u64 *start, u64 len)
 {
+        struct btrfs_fs_info *fs_info = device->dev_root->fs_info;
         struct extent_map *em;
-        struct list_head *search_list = &trans->transaction->pending_chunks;
+        struct list_head *search_list = &fs_info->pinned_chunks;
         int ret = 0;
         u64 physical_start = *start;
 
+        if (transaction)
+                search_list = &transaction->pending_chunks;
 again:
         list_for_each_entry(em, search_list, list) {
                 struct map_lookup *map;
@@ -1159,8 +1162,8 @@ again:
                         }
                 }
         }
-        if (search_list == &trans->transaction->pending_chunks) {
-                search_list = &trans->root->fs_info->pinned_chunks;
+        if (search_list != &fs_info->pinned_chunks) {
+                search_list = &fs_info->pinned_chunks;
                 goto again;
         }
 
@@ -1169,12 +1172,13 @@ again:
 
 
 /*
- * find_free_dev_extent - find free space in the specified device
- * @device:     the device which we search the free space in
- * @num_bytes:  the size of the free space that we need
- * @start:      store the start of the free space.
- * @len:        the size of the free space. that we find, or the size of the max
- *              free space if we don't find suitable free space
+ * find_free_dev_extent_start - find free space in the specified device
+ * @device:       the device which we search the free space in
+ * @num_bytes:    the size of the free space that we need
+ * @search_start: the position from which to begin the search
+ * @start:        store the start of the free space.
+ * @len:          the size of the free space. that we find, or the size
+ *                of the max free space if we don't find suitable free space
  *
  * this uses a pretty simple search, the expectation is that it is
  * called very infrequently and that a given device has a small number
@@ -1188,9 +1192,9 @@ again:
  * But if we don't find suitable free space, it is used to store the size of
  * the max free space.
  */
-int find_free_dev_extent(struct btrfs_trans_handle *trans,
-                         struct btrfs_device *device, u64 num_bytes,
-                         u64 *start, u64 *len)
+int find_free_dev_extent_start(struct btrfs_transaction *transaction,
+                               struct btrfs_device *device, u64 num_bytes,
+                               u64 search_start, u64 *start, u64 *len)
 {
         struct btrfs_key key;
         struct btrfs_root *root = device->dev_root;
@@ -1200,19 +1204,11 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans,
         u64 max_hole_start;
         u64 max_hole_size;
         u64 extent_end;
-        u64 search_start;
         u64 search_end = device->total_bytes;
         int ret;
         int slot;
         struct extent_buffer *l;
 
-        /* FIXME use last free of some kind */
-
-        /* we don't want to overwrite the superblock on the drive,
-         * so we make sure to start at an offset of at least 1MB
-         */
-        search_start = max(root->fs_info->alloc_start, 1024ull * 1024);
-
         path = btrfs_alloc_path();
         if (!path)
                 return -ENOMEM;
@@ -1273,7 +1269,7 @@ again:
                          * Have to check before we set max_hole_start, otherwise
                          * we could end up sending back this offset anyway.
                          */
-                        if (contains_pending_extent(trans, device,
+                        if (contains_pending_extent(transaction, device,
                                                     &search_start,
                                                     hole_size)) {
                                 if (key.offset >= search_start) {
@@ -1322,7 +1318,7 @@ next:
         if (search_end > search_start) {
                 hole_size = search_end - search_start;
 
-                if (contains_pending_extent(trans, device, &search_start,
+                if (contains_pending_extent(transaction, device, &search_start,
                                             hole_size)) {
                         btrfs_release_path(path);
                         goto again;
@@ -1348,6 +1344,24 @@ out:
         return ret;
 }
 
+int find_free_dev_extent(struct btrfs_trans_handle *trans,
+                         struct btrfs_device *device, u64 num_bytes,
+                         u64 *start, u64 *len)
+{
+        struct btrfs_root *root = device->dev_root;
+        u64 search_start;
+
+        /* FIXME use last free of some kind */
+
+        /*
+         * we don't want to overwrite the superblock on the drive,
+         * so we make sure to start at an offset of at least 1MB
+         */
+        search_start = max(root->fs_info->alloc_start, 1024ull * 1024);
+        return find_free_dev_extent_start(trans->transaction, device,
+                                          num_bytes, search_start, start, len);
+}
+
 static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
                           struct btrfs_device *device,
                           u64 start, u64 *dev_extent_len)
@@ -4196,7 +4210,8 @@ again:
                 u64 start = new_size;
                 u64 len = old_size - new_size;
 
-                if (contains_pending_extent(trans, device, &start, len)) {
+                if (contains_pending_extent(trans->transaction, device,
+                                            &start, len)) {
                         unlock_chunks(root);
                         checked_pending_chunks = true;
                         failed = 0;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 95842a909e7f..2ca784a14e84 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -453,6 +453,9 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info);
 int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info);
 int btrfs_check_uuid_tree(struct btrfs_fs_info *fs_info);
 int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset);
+int find_free_dev_extent_start(struct btrfs_transaction *transaction,
+                         struct btrfs_device *device, u64 num_bytes,
+                         u64 search_start, u64 *start, u64 *max_avail);
 int find_free_dev_extent(struct btrfs_trans_handle *trans,
                          struct btrfs_device *device, u64 num_bytes,
                          u64 *start, u64 *max_avail);