bcachefs: Check for dirents to overwritten inodes

This fixes various "dirent to missing inode" errors.

Signed-off-by: Kent Overstreet <[email protected]>

Author: Kent Overstreet

fs/bcachefs/fsck.c

@@ -832,11 +832,13 @@ struct inode_walker {
 	struct bpos			last_pos;
 
 	DARRAY(struct inode_walker_entry) inodes;
+	snapshot_id_list		deletes;
 };
 
 static void inode_walker_exit(struct inode_walker *w)
 {
 	darray_exit(&w->inodes);
+	darray_exit(&w->deletes);
 }
 
 static struct inode_walker inode_walker_init(void)
@@ -960,19 +962,23 @@ static int get_visible_inodes(struct btree_trans *trans,
 	int ret;
 
 	w->inodes.nr = 0;
+	w->deletes.nr = 0;
 
-	for_each_btree_key_norestart(trans, iter, BTREE_ID_inodes, POS(0, inum),
+	for_each_btree_key_reverse_norestart(trans, iter, BTREE_ID_inodes, SPOS(0, inum, s->pos.snapshot),
 			   BTREE_ITER_all_snapshots, k, ret) {
 		if (k.k->p.offset != inum)
 			break;
 
 		if (!ref_visible(c, s, s->pos.snapshot, k.k->p.snapshot))
 			continue;
 
-		if (bkey_is_inode(k.k))
-			add_inode(c, w, k);
+		if (snapshot_list_has_ancestor(c, &w->deletes, k.k->p.snapshot))
+			continue;
 
-		if (k.k->p.snapshot >= s->pos.snapshot)
+		ret = bkey_is_inode(k.k)
+			? add_inode(c, w, k)
+			: snapshot_list_add(c, &w->deletes, k.k->p.snapshot);
+		if (ret)
 			break;
 	}
 	bch2_trans_iter_exit(trans, &iter);
@@ -2380,6 +2386,30 @@ static int check_dirent(struct btree_trans *trans, struct btree_iter *iter,
 			if (ret)
 				goto err;
 		}
+
+		darray_for_each(target->deletes, i)
+			if (fsck_err_on(!snapshot_list_has_id(&s->ids, *i),
+					trans, dirent_to_overwritten_inode,
+					"dirent points to inode overwritten in snapshot %u:\n%s",
+					*i,
+					(printbuf_reset(&buf),
+					 bch2_bkey_val_to_text(&buf, c, k),
+					 buf.buf))) {
+				struct btree_iter delete_iter;
+				bch2_trans_iter_init(trans, &delete_iter,
+						     BTREE_ID_dirents,
+						     SPOS(k.k->p.inode, k.k->p.offset, *i),
+						     BTREE_ITER_intent);
+				ret =   bch2_btree_iter_traverse(&delete_iter) ?:
+					bch2_hash_delete_at(trans, bch2_dirent_hash_desc,
+							  hash_info,
+							  &delete_iter,
+							  BTREE_UPDATE_internal_snapshot_node);
+				bch2_trans_iter_exit(trans, &delete_iter);
+				if (ret)
+					goto err;
+
+			}
 	}
 
 	ret = bch2_trans_commit(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc);

fs/bcachefs/sb-errors_format.h

@@ -256,6 +256,7 @@ enum bch_fsck_flags {
 	x(dirent_in_missing_dir_inode,				227,	0)		\
 	x(dirent_in_non_dir_inode,				228,	0)		\
 	x(dirent_to_missing_inode,				229,	0)		\
+	x(dirent_to_overwritten_inode,				302,	0)		\
 	x(dirent_to_missing_subvol,				230,	0)		\
 	x(dirent_to_itself,					231,	0)		\
 	x(quota_type_invalid,					232,	0)		\
@@ -312,7 +313,7 @@ enum bch_fsck_flags {
 	x(logged_op_but_clean,					283,	FSCK_AUTOFIX)	\
 	x(compression_opt_not_marked_in_sb,			295,	FSCK_AUTOFIX)	\
 	x(compression_type_not_marked_in_sb,			296,	FSCK_AUTOFIX)	\
-	x(MAX,							302,	0)
+	x(MAX,							303,	0)
 
 enum bch_sb_error_id {
 #define x(t, n, ...) BCH_FSCK_ERR_##t = n,