drbd: remove DRBD_GENLA_F_MANDATORY flag handling

DRBD used a custom mechanism to mark netlink attributes as "mandatory":
bit 14 of nla_type was repurposed as DRBD_GENLA_F_MANDATORY. Attributes
sent from userspace that had this bit present and that were unknown
to the kernel would lead to an error.

Since commit ef6243a ("genetlink: optionally validate strictly/dumps"),
the generic netlink layer rejects unknown top-level attributes when
strict validation is enabled. DRBD never opted out of strict
validation, so unknown top-level attributes are already rejected by
the netlink core.

The mandatory flag mechanism was required for nested attributes, because
these are parsed liberally, silently dropping attributes unknown to the
kernel.

This prepares for the move to a new YNL-based family, which will use the
now-default strict parsing.
The current family is not expected to gain any new attributes, which
makes this change safe.

Old userspace that still sets bit 14 is unaffected: nla_type()
strips it before __nla_validate_parse() performs attribute validation,
so the bit never reaches DRBD.

Remove all references to the mandatory flag in DRBD.

Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Link: https://patch.msgid.link/20260403132953.2248751-1-christoph.boehmwalder@linbit.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: chrboe

drivers/block/drbd/Makefile

@@ -3,7 +3,6 @@ drbd-y := drbd_buildtag.o drbd_bitmap.o drbd_proc.o
 drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
 drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
 drbd-y += drbd_interval.o drbd_state.o
-drbd-y += drbd_nla.o
 drbd-$(CONFIG_DEBUG_FS) += drbd_debugfs.o
 
 obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o

drivers/block/drbd/drbd_nl.c

@@ -74,7 +74,6 @@ int drbd_adm_dump_peer_devices_done(struct netlink_callback *cb);
 int drbd_adm_get_initial_state(struct sk_buff *skb, struct netlink_callback *cb);
 
 #include <linux/drbd_genl_api.h>
-#include "drbd_nla.h"
 
 static int drbd_pre_doit(const struct genl_split_ops *ops,
 			 struct sk_buff *skb, struct genl_info *info);
@@ -239,14 +238,14 @@ static int drbd_adm_prepare(struct drbd_config_context *adm_ctx,
 			goto fail;
 
 		/* and assign stuff to the adm_ctx */
-		nla = nested_attr_tb[__nla_type(T_ctx_volume)];
+		nla = nested_attr_tb[T_ctx_volume];
 		if (nla)
 			adm_ctx->volume = nla_get_u32(nla);
-		nla = nested_attr_tb[__nla_type(T_ctx_resource_name)];
+		nla = nested_attr_tb[T_ctx_resource_name];
 		if (nla)
 			adm_ctx->resource_name = nla_data(nla);
-		adm_ctx->my_addr = nested_attr_tb[__nla_type(T_ctx_my_addr)];
-		adm_ctx->peer_addr = nested_attr_tb[__nla_type(T_ctx_peer_addr)];
+		adm_ctx->my_addr = nested_attr_tb[T_ctx_my_addr];
+		adm_ctx->peer_addr = nested_attr_tb[T_ctx_peer_addr];
 		if ((adm_ctx->my_addr &&
 		     nla_len(adm_ctx->my_addr) > sizeof(adm_ctx->connection->my_addr)) ||
 		    (adm_ctx->peer_addr &&
@@ -825,7 +824,6 @@ drbd_set_role(struct drbd_device *const device, enum drbd_role new_role, int for
 static const char *from_attrs_err_to_txt(int err)
 {
 	return	err == -ENOMSG ? "required attribute missing" :
-		err == -EOPNOTSUPP ? "unknown mandatory attribute" :
 		err == -EEXIST ? "can not change invariant setting" :
 		"invalid attribute value";
 }
@@ -3303,14 +3301,13 @@ static int nla_put_drbd_cfg_context(struct sk_buff *skb,
 static struct nlattr *find_cfg_context_attr(const struct nlmsghdr *nlh, int attr)
 {
 	const unsigned hdrlen = GENL_HDRLEN + GENL_MAGIC_FAMILY_HDRSZ;
-	const int maxtype = ARRAY_SIZE(drbd_cfg_context_nl_policy) - 1;
 	struct nlattr *nla;
 
 	nla = nla_find(nlmsg_attrdata(nlh, hdrlen), nlmsg_attrlen(nlh, hdrlen),
 		       DRBD_NLA_CFG_CONTEXT);
 	if (!nla)
 		return NULL;
-	return drbd_nla_find_nested(maxtype, nla, __nla_type(attr));
+	return nla_find_nested(nla, attr);
 }
 
 static void resource_to_info(struct resource_info *, struct drbd_resource *);
@@ -4068,7 +4065,6 @@ int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
 	struct nlattr *nla;
 	const char *resource_name;
 	struct drbd_resource *resource;
-	int maxtype;
 
 	/* Is this a followup call? */
 	if (cb->args[0]) {
@@ -4088,10 +4084,7 @@ int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
 	/* No explicit context given.  Dump all. */
 	if (!nla)
 		goto dump;
-	maxtype = ARRAY_SIZE(drbd_cfg_context_nl_policy) - 1;
-	nla = drbd_nla_find_nested(maxtype, nla, __nla_type(T_ctx_resource_name));
-	if (IS_ERR(nla))
-		return PTR_ERR(nla);
+	nla = nla_find_nested(nla, T_ctx_resource_name);
 	/* context given, but no name present? */
 	if (!nla)
 		return -EINVAL;