[PATCH net-next v2 02/12] net: sched: flower: refactor fl_change

[Vlad Buslov <vladbu@mellanox.com>]

As a preparation for using classifier spinlock instead of relying on
external rtnl lock, rearrange code in fl_change. The goal is to group the
code which changes classifier state in single block in order to allow
following commits in this set to protect it from parallel modification with
tp->lock. Data structures that require tp->lock protection are mask
hashtable and filters list, and classifier handle_idr.

fl_hw_replace_filter() is a sleeping function and cannot be called while
holding a spinlock. In order to execute all sequence of changes to shared
classifier data structures atomically, call fl_hw_replace_filter() before
modifying them.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
---
Changes from V1 to V2:
  - Remove redundant check in fl_change error handling code.
  - Add empty line between error check and new handle assignment.

 net/sched/cls_flower.c | 87 ++++++++++++++++++++++++++------------------------
 1 file changed, 45 insertions(+), 42 deletions(-)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index 37bced9e2672..d36ceb5001f9 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1358,90 +1358,93 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	if (err < 0)
 		goto errout;
 
-	if (!handle) {
-		handle = 1;
-		err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
-				    INT_MAX, GFP_KERNEL);
-	} else if (!fold) {
-		/* user specifies a handle and it doesn't exist */
-		err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
-				    handle, GFP_KERNEL);
-	}
-	if (err)
-		goto errout;
-	fnew->handle = handle;
-
 	if (tb[TCA_FLOWER_FLAGS]) {
 		fnew->flags = nla_get_u32(tb[TCA_FLOWER_FLAGS]);
 
 		if (!tc_flags_valid(fnew->flags)) {
 			err = -EINVAL;
-			goto errout_idr;
+			goto errout;
 		}
 	}
 
 	err = fl_set_parms(net, tp, fnew, mask, base, tb, tca[TCA_RATE], ovr,
 			   tp->chain->tmplt_priv, extack);
 	if (err)
-		goto errout_idr;
+		goto errout;
 
 	err = fl_check_assign_mask(head, fnew, fold, mask);
 	if (err)
-		goto errout_idr;
-
-	if (!fold && __fl_lookup(fnew->mask, &fnew->mkey)) {
-		err = -EEXIST;
-		goto errout_mask;
-	}
-
-	err = rhashtable_insert_fast(&fnew->mask->ht, &fnew->ht_node,
-				     fnew->mask->filter_ht_params);
-	if (err)
-		goto errout_mask;
+		goto errout;
 
 	if (!tc_skip_hw(fnew->flags)) {
 		err = fl_hw_replace_filter(tp, fnew, extack);
 		if (err)
-			goto errout_mask_ht;
+			goto errout_mask;
 	}
 
 	if (!tc_in_hw(fnew->flags))
 		fnew->flags |= TCA_CLS_FLAGS_NOT_IN_HW;
 
 	if (fold) {
+		fnew->handle = handle;
+
+		err = rhashtable_insert_fast(&fnew->mask->ht, &fnew->ht_node,
+					     fnew->mask->filter_ht_params);
+		if (err)
+			goto errout_hw;
+
 		rhashtable_remove_fast(&fold->mask->ht,
 				       &fold->ht_node,
 				       fold->mask->filter_ht_params);
-		if (!tc_skip_hw(fold->flags))
-			fl_hw_destroy_filter(tp, fold, NULL);
-	}
-
-	*arg = fnew;
-
-	if (fold) {
 		idr_replace(&head->handle_idr, fnew, fnew->handle);
 		list_replace_rcu(&fold->list, &fnew->list);
+
+		if (!tc_skip_hw(fold->flags))
+			fl_hw_destroy_filter(tp, fold, NULL);
 		tcf_unbind_filter(tp, &fold->res);
 		tcf_exts_get_net(&fold->exts);
 		tcf_queue_work(&fold->rwork, fl_destroy_filter_work);
 	} else {
+		if (__fl_lookup(fnew->mask, &fnew->mkey)) {
+			err = -EEXIST;
+			goto errout_hw;
+		}
+
+		if (handle) {
+			/* user specifies a handle and it doesn't exist */
+			err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
+					    handle, GFP_ATOMIC);
+		} else {
+			handle = 1;
+			err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
+					    INT_MAX, GFP_ATOMIC);
+		}
+		if (err)
+			goto errout_hw;
+
+		fnew->handle = handle;
+
+		err = rhashtable_insert_fast(&fnew->mask->ht, &fnew->ht_node,
+					     fnew->mask->filter_ht_params);
+		if (err)
+			goto errout_idr;
+
 		list_add_tail_rcu(&fnew->list, &fnew->mask->filters);
 	}
 
+	*arg = fnew;
+
 	kfree(tb);
 	kfree(mask);
 	return 0;
 
-errout_mask_ht:
-	rhashtable_remove_fast(&fnew->mask->ht, &fnew->ht_node,
-			       fnew->mask->filter_ht_params);
-
+errout_idr:
+	idr_remove(&head->handle_idr, fnew->handle);
+errout_hw:
+	if (!tc_skip_hw(fnew->flags))
+		fl_hw_destroy_filter(tp, fnew, NULL);
 errout_mask:
 	fl_mask_put(head, fnew->mask, false);
-
-errout_idr:
-	if (!fold)
-		idr_remove(&head->handle_idr, fnew->handle);
 errout:
 	tcf_exts_destroy(&fnew->exts);
 	kfree(fnew);
-- 
2.13.6