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Commit e474619a authored by Vlad Buslov's avatar Vlad Buslov Committed by David S. Miller
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net: sched: flower: don't check for rtnl on head dereference 



Flower classifier only changes root pointer during init and destroy. Cls
API implements reference counting for tcf_proto, so there is no danger of
concurrent access to tp when it is being destroyed, even without protection
provided by rtnl lock.

Implement new function fl_head_dereference() to dereference tp->root
without checking for rtnl lock. Use it in all flower function that obtain
head pointer instead of rtnl_dereference().

Signed-off-by: default avatarVlad Buslov <vladbu@mellanox.com>
Reviewed-by: default avatarStefano Brivio <sbrivio@redhat.com>
Acked-by: default avatarJiri Pirko <jiri@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 31f1a0e3

net/sched/cls_flower.c

+17 −7
Original line number Diff line number Diff line
@@ -437,10 +437,20 @@ static void fl_hw_update_stats(struct tcf_proto *tp, struct cls_fl_filter *f) 
			      cls_flower.stats.lastused);

}



static struct cls_fl_head *fl_head_dereference(struct tcf_proto *tp)

{

	/* Flower classifier only changes root pointer during init and destroy.

	 * Users must obtain reference to tcf_proto instance before calling its

	 * API, so tp->root pointer is protected from concurrent call to

	 * fl_destroy() by reference counting.

	 */

	return rcu_dereference_raw(tp->root);

}



static bool __fl_delete(struct tcf_proto *tp, struct cls_fl_filter *f,

			struct netlink_ext_ack *extack)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);

	bool async = tcf_exts_get_net(&f->exts);

	bool last;
@@ -472,7 +482,7 @@ static void fl_destroy_sleepable(struct work_struct *work) 
static void fl_destroy(struct tcf_proto *tp, bool rtnl_held,

		       struct netlink_ext_ack *extack)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);

	struct fl_flow_mask *mask, *next_mask;

	struct cls_fl_filter *f, *next;
@@ -490,7 +500,7 @@ static void fl_destroy(struct tcf_proto *tp, bool rtnl_held, 


static void *fl_get(struct tcf_proto *tp, u32 handle)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);



	return idr_find(&head->handle_idr, handle);

}
@@ -1308,7 +1318,7 @@ static int fl_change(struct net *net, struct sk_buff *in_skb, 
		     void **arg, bool ovr, bool rtnl_held,

		     struct netlink_ext_ack *extack)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);

	struct cls_fl_filter *fold = *arg;

	struct cls_fl_filter *fnew;

	struct fl_flow_mask *mask;
@@ -1446,7 +1456,7 @@ static int fl_change(struct net *net, struct sk_buff *in_skb, 
static int fl_delete(struct tcf_proto *tp, void *arg, bool *last,

		     bool rtnl_held, struct netlink_ext_ack *extack)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);

	struct cls_fl_filter *f = arg;



	rhashtable_remove_fast(&f->mask->ht, &f->ht_node,
@@ -1459,7 +1469,7 @@ static int fl_delete(struct tcf_proto *tp, void *arg, bool *last, 
static void fl_walk(struct tcf_proto *tp, struct tcf_walker *arg,

		    bool rtnl_held)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);

	struct cls_fl_filter *f;



	arg->count = arg->skip;
@@ -1478,7 +1488,7 @@ static void fl_walk(struct tcf_proto *tp, struct tcf_walker *arg, 
static int fl_reoffload(struct tcf_proto *tp, bool add, tc_setup_cb_t *cb,

			void *cb_priv, struct netlink_ext_ack *extack)

{

	struct cls_fl_head *head = rtnl_dereference(tp->root);

	struct cls_fl_head *head = fl_head_dereference(tp);

	struct tc_cls_flower_offload cls_flower = {};

	struct tcf_block *block = tp->chain->block;

	struct fl_flow_mask *mask;