diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3d8c699e44eafc3c6ec09292c384c0f9b5a994f5..abe1e1242d7b063dce7d19b9fe272d9fbd63951c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2815,6 +2815,22 @@ u64 add_new_free_space(struct btrfs_block_group_cache *block_group,
 		       u64 start, u64 end);
 void btrfs_mark_bg_unused(struct btrfs_block_group_cache *bg);
 
+/*
+ * Get the size of a block reserve in a context where getting a stale value is
+ * acceptable, instead of accessing it directly and trigger data race warning
+ * from KCSAN.
+ */
+static inline u64 btrfs_block_rsv_size(struct btrfs_block_rsv *rsv)
+{
+	u64 ret;
+
+	spin_lock(&rsv->lock);
+	ret = rsv->size;
+	spin_unlock(&rsv->lock);
+
+	return ret;
+}
+
 /* ctree.c */
 int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
 		     int level, int *slot);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index dcbb76b62a0b07531595d1bee97426d55437628e..e579e19ebd4b804818d39381e8a75043ab523932 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8188,7 +8188,7 @@ use_block_rsv(struct btrfs_trans_handle *trans,
 
 	block_rsv = get_block_rsv(trans, root);
 
-	if (unlikely(block_rsv->size == 0))
+	if (unlikely(btrfs_block_rsv_size(block_rsv) == 0))
 		goto try_reserve;
 again:
 	ret = block_rsv_use_bytes(block_rsv, blocksize);