bcachefs: Check that keys are in the correct btrees

We've started seeing bug reports of pointers to btree nodes being
detected in leaf nodes. This should catch that before it's happened, and
it's something we should've been checking anyways.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bkey_methods.c

@@ -98,12 +98,51 @@ const char *bch2_bkey_val_invalid(struct bch_fs *c, struct bkey_s_c k)
 	return bch2_bkey_ops[k.k->type].key_invalid(c, k);
 }
 
+static unsigned bch2_key_types_allowed[] = {
+	[BKEY_TYPE_extents] =
+		(1U << KEY_TYPE_error)|
+		(1U << KEY_TYPE_cookie)|
+		(1U << KEY_TYPE_extent)|
+		(1U << KEY_TYPE_reservation)|
+		(1U << KEY_TYPE_reflink_p)|
+		(1U << KEY_TYPE_inline_data),
+	[BKEY_TYPE_inodes] =
+		(1U << KEY_TYPE_inode)|
+		(1U << KEY_TYPE_inode_generation),
+	[BKEY_TYPE_dirents] =
+		(1U << KEY_TYPE_hash_whiteout)|
+		(1U << KEY_TYPE_dirent),
+	[BKEY_TYPE_xattrs] =
+		(1U << KEY_TYPE_cookie)|
+		(1U << KEY_TYPE_hash_whiteout)|
+		(1U << KEY_TYPE_xattr),
+	[BKEY_TYPE_alloc] =
+		(1U << KEY_TYPE_alloc)|
+		(1U << KEY_TYPE_alloc_v2),
+	[BKEY_TYPE_quotas] =
+		(1U << KEY_TYPE_quota),
+	[BKEY_TYPE_stripes] =
+		(1U << KEY_TYPE_stripe),
+	[BKEY_TYPE_reflink] =
+		(1U << KEY_TYPE_reflink_v)|
+		(1U << KEY_TYPE_indirect_inline_data),
+	[BKEY_TYPE_btree] =
+		(1U << KEY_TYPE_btree_ptr)|
+		(1U << KEY_TYPE_btree_ptr_v2),
+};
+
 const char *__bch2_bkey_invalid(struct bch_fs *c, struct bkey_s_c k,
 				enum btree_node_type type)
 {
+	unsigned key_types_allowed = (1U << KEY_TYPE_deleted)|
+		bch2_key_types_allowed[type] ;
+
 	if (k.k->u64s < BKEY_U64s)
 		return "u64s too small";
 
+	if (!(key_types_allowed & (1U << k.k->type)))
+		return "invalid key type for this btree";
+
 	if (type == BKEY_TYPE_btree &&
 	    bkey_val_u64s(k.k) > BKEY_BTREE_PTR_VAL_U64s_MAX)
 		return "value too big";