Subject: [PATCH net-next 1/9] devlink: bump the instance index directly when iterating

From: Jakub Kicinski <[email-masked]>
Date: Thu, 5 Jan 2023 22:33:54 -0800

xa_find_after() is designed to handle multi-index entries correctly.
If a xarray has two entries one which spans indexes 0-3 and one at
index 4 xa_find_after(0) will return the entry at index 4.

Having to juggle the two callbacks, however, is unnecessary in case
of the devlink xarray, as there is 1:1 relationship with indexes.

Always use xa_find() and increment the index manually.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 net/devlink/core.c          | 31 +++++++++----------------------
 net/devlink/devl_internal.h | 17 ++++-------------
 2 files changed, 13 insertions(+), 35 deletions(-)

diff --git a/net/devlink/core.c b/net/devlink/core.c
index 371d6821315d..88c88b8053e2 100644
--- a/net/devlink/core.c
+++ b/net/devlink/core.c
@@ -91,16 +91,13 @@ void devlink_put(struct devlink *devlink)
 		call_rcu(&devlink->rcu, __devlink_put_rcu);
 }
 
-struct devlink *
-devlinks_xa_find_get(struct net *net, unsigned long *indexp,
-		     void * (*xa_find_fn)(struct xarray *, unsigned long *,
-					  unsigned long, xa_mark_t))
+struct devlink *devlinks_xa_find_get(struct net *net, unsigned long *indexp)
 {
-	struct devlink *devlink;
+	struct devlink *devlink = NULL;
 
 	rcu_read_lock();
 retry:
-	devlink = xa_find_fn(&devlinks, indexp, ULONG_MAX, DEVLINK_REGISTERED);
+	devlink = xa_find(&devlinks, indexp, ULONG_MAX, DEVLINK_REGISTERED);
 	if (!devlink)
 		goto unlock;
 
@@ -109,31 +106,21 @@ devlinks_xa_find_get(struct net *net, unsigned long *indexp,
 	 * This prevents live-lock of devlink_unregister() wait for completion.
 	 */
 	if (xa_get_mark(&devlinks, *indexp, DEVLINK_UNREGISTERING))
-		goto retry;
+		goto next;
 
-	/* For a possible retry, the xa_find_after() should be always used */
-	xa_find_fn = xa_find_after;
 	if (!devlink_try_get(devlink))
-		goto retry;
+		goto next;
 	if (!net_eq(devlink_net(devlink), net)) {
 		devlink_put(devlink);
-		goto retry;
+		goto next;
 	}
 unlock:
 	rcu_read_unlock();
 	return devlink;
-}
-
-struct devlink *
-devlinks_xa_find_get_first(struct net *net, unsigned long *indexp)
-{
-	return devlinks_xa_find_get(net, indexp, xa_find);
-}
 
-struct devlink *
-devlinks_xa_find_get_next(struct net *net, unsigned long *indexp)
-{
-	return devlinks_xa_find_get(net, indexp, xa_find_after);
+next:
+	(*indexp)++;
+	goto retry;
 }
 
 /**
diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
index adf9f6c177db..14767e809178 100644
--- a/net/devlink/devl_internal.h
+++ b/net/devlink/devl_internal.h
@@ -82,18 +82,9 @@ extern struct genl_family devlink_nl_family;
  * in loop body in order to release the reference.
  */
 #define devlinks_xa_for_each_registered_get(net, index, devlink)	\
-	for (index = 0,							\
-	     devlink = devlinks_xa_find_get_first(net, &index);	\
-	     devlink; devlink = devlinks_xa_find_get_next(net, &index))
-
-struct devlink *
-devlinks_xa_find_get(struct net *net, unsigned long *indexp,
-		     void * (*xa_find_fn)(struct xarray *, unsigned long *,
-					  unsigned long, xa_mark_t));
-struct devlink *
-devlinks_xa_find_get_first(struct net *net, unsigned long *indexp);
-struct devlink *
-devlinks_xa_find_get_next(struct net *net, unsigned long *indexp);
+	for (index = 0; (devlink = devlinks_xa_find_get(net, &index)); index++)
+
+struct devlink *devlinks_xa_find_get(struct net *net, unsigned long *indexp);
 
 /* Netlink */
 #define DEVLINK_NL_FLAG_NEED_PORT		BIT(0)
@@ -135,7 +126,7 @@ struct devlink_gen_cmd {
  */
 #define devlink_dump_for_each_instance_get(msg, state, devlink)		\
 	for (; (devlink = devlinks_xa_find_get(sock_net(msg->sk),	\
-					       &state->instance, xa_find)); \
+					       &state->instance));	\
 	     state->instance++, state->idx = 0)
 
 extern const struct genl_small_ops devlink_nl_ops[56];
-- 
2.38.1