bcachefs: Update data move path for snapshots

The data move path operates on existing extents, and not within a
subvolume as the regular IO paths do. It needs to change because it may
cause existing extents to be split, and when splitting an existing
extent in an ancestor snapshot we need to make sure the new split has
the same visibility in child snapshots as the existing extent.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 80 insertions, 1 deletions

diff --git a/fs/bcachefs/move.c b/fs/bcachefs/move.c
index 9dc6684139de..2e7d8e2fe331 100644
--- a/fs/bcachefs/move.c
+++ b/fs/bcachefs/move.c
@@ -14,6 +14,7 @@
 #include "keylist.h"
 #include "move.h"
 #include "replicas.h"
+#include "subvolume.h"
 #include "super-io.h"
 #include "trace.h"
 
@@ -52,6 +53,81 @@ struct moving_context {
 	wait_queue_head_t	wait;
 };
 
+static int insert_snapshot_whiteouts(struct btree_trans *trans,
+				     enum btree_id id,
+				     struct bpos old_pos,
+				     struct bpos new_pos)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_iter iter, update_iter;
+	struct bkey_s_c k;
+	struct snapshots_seen s;
+	int ret;
+
+	if (!btree_type_has_snapshots(id))
+		return 0;
+
+	snapshots_seen_init(&s);
+
+	if (!bkey_cmp(old_pos, new_pos))
+		return 0;
+
+	if (!snapshot_t(c, old_pos.snapshot)->children[0])
+		return 0;
+
+	bch2_trans_iter_init(trans, &iter, id, old_pos,
+			     BTREE_ITER_NOT_EXTENTS|
+			     BTREE_ITER_ALL_SNAPSHOTS);
+	while (1) {
+next:
+		k = bch2_btree_iter_prev(&iter);
+		ret = bkey_err(k);
+		if (ret)
+			break;
+
+		if (bkey_cmp(old_pos, k.k->p))
+			break;
+
+		if (bch2_snapshot_is_ancestor(c, k.k->p.snapshot, old_pos.snapshot)) {
+			struct bkey_i *update;
+			size_t i;
+
+			for (i = 0; i < s.nr; i++)
+				if (bch2_snapshot_is_ancestor(c, k.k->p.snapshot, s.d[i]))
+					goto next;
+
+			update = bch2_trans_kmalloc(trans, sizeof(struct bkey_i));
+
+			ret = PTR_ERR_OR_ZERO(update);
+			if (ret)
+				break;
+
+			bkey_init(&update->k);
+			update->k.p = new_pos;
+			update->k.p.snapshot = k.k->p.snapshot;
+
+			bch2_trans_iter_init(trans, &update_iter, id, update->k.p,
+					     BTREE_ITER_NOT_EXTENTS|
+					     BTREE_ITER_ALL_SNAPSHOTS|
+					     BTREE_ITER_INTENT);
+			ret   = bch2_btree_iter_traverse(&update_iter) ?:
+				bch2_trans_update(trans, &update_iter, update,
+					  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+			bch2_trans_iter_exit(trans, &update_iter);
+			if (ret)
+				break;
+
+			ret = snapshots_seen_add(c, &s, k.k->p.snapshot);
+			if (ret)
+				break;
+		}
+	}
+	bch2_trans_iter_exit(trans, &iter);
+	kfree(s.d);
+
+	return ret;
+}
+
 int bch2_migrate_index_update(struct bch_write_op *op)
 {
 	struct bch_fs *c = op->c;
@@ -165,7 +241,10 @@ int bch2_migrate_index_update(struct bch_write_op *op)
 
 		next_pos = insert->k.p;
 
-		ret   = bch2_trans_update(&trans, &iter, insert, 0) ?:
+		ret   = insert_snapshot_whiteouts(&trans, m->btree_id,
+						  k.k->p, insert->k.p) ?:
+			bch2_trans_update(&trans, &iter, insert,
+				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE) ?:
 			bch2_trans_commit(&trans, &op->res,
 				op_journal_seq(op),
 				BTREE_INSERT_NOFAIL|