1 files changed, 36 insertions, 0 deletions

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 1e9caa552235..12363081f53b 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -6593,6 +6593,38 @@ commit_trans:
 	return btrfs_commit_transaction(trans);
 }
 
+/*
+ * Make sure any existing dellaloc is flushed for any root used by a send
+ * operation so that we do not miss any data and we do not race with writeback
+ * finishing and changing a tree while send is using the tree. This could
+ * happen if a subvolume is in RW mode, has delalloc, is turned to RO mode and
+ * a send operation then uses the subvolume.
+ * After flushing delalloc ensure_commit_roots_uptodate() must be called.
+ */
+static int flush_delalloc_roots(struct send_ctx *sctx)
+{
+	struct btrfs_root *root = sctx->parent_root;
+	int ret;
+	int i;
+
+	if (root) {
+		ret = btrfs_start_delalloc_snapshot(root);
+		if (ret)
+			return ret;
+		btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX);
+	}
+
+	for (i = 0; i < sctx->clone_roots_cnt; i++) {
+		root = sctx->clone_roots[i].root;
+		ret = btrfs_start_delalloc_snapshot(root);
+		if (ret)
+			return ret;
+		btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX);
+	}
+
+	return 0;
+}
+
 static void btrfs_root_dec_send_in_progress(struct btrfs_root* root)
 {
 	spin_lock(&root->root_item_lock);
@@ -6817,6 +6849,10 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
 			NULL);
 	sort_clone_roots = 1;
 
+	ret = flush_delalloc_roots(sctx);
+	if (ret)
+		goto out;
+
 	ret = ensure_commit_roots_uptodate(sctx);
 	if (ret)
 		goto out;