3 files changed, 8 insertions, 5 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4b89680a1923..c4661db2b72a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10480,11 +10480,15 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
                  * 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);
+                        spin_lock(&fs_info->unused_bgs_lock);
+                        /*
+                         * A concurrent scrub might have added us to the list
+                         * fs_info->unused_bgs, so use a list_move operation
+                         * to add the block group to the deleted_bgs list.
+                         */
                         list_move(&block_group->bg_list,
                                   &trans->transaction->deleted_bgs);
-                        spin_unlock(&trans->transaction->deleted_bgs_lock);
+                        spin_unlock(&fs_info->unused_bgs_lock);
                         btrfs_get_block_group(block_group);
                 }
 end_trans:
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 3367a3c6f214..be8eae80ff65 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -274,7 +274,6 @@ loop:
         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);
         spin_lock_init(&cur_trans->dropped_roots_lock);
         list_add_tail(&cur_trans->list, &fs_info->trans_list);
         extent_io_tree_init(&cur_trans->dirty_pages,
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 0da21ca9b3fb..64c8221b6165 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -77,8 +77,8 @@ struct btrfs_transaction {
          */
         struct mutex cache_write_mutex;
         spinlock_t dirty_bgs_lock;
+        /* Protected by spin lock fs_info->unused_bgs_lock. */
         struct list_head deleted_bgs;
-        spinlock_t deleted_bgs_lock;
         spinlock_t dropped_roots_lock;
         struct btrfs_delayed_ref_root delayed_refs;
         int aborted;