linux-kernel - [PATCH 13/17] cls_u32: Reinstate cyclic allocation

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Message-Id: <20171128213312.28983-14-willy@infradead.org>
Date:   Tue, 28 Nov 2017 13:33:08 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Matthew Wilcox <mawilcox@...rosoft.com>,
        Chris Mi <chrism@...lanox.com>, Jiri Pirko <jiri@...lanox.com>,
        "David S . Miller" <davem@...emloft.net>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Biggers <ebiggers@...gle.com>,
        Lai Jiangshan <laijs@...fujitsu.com>,
        Tejun Heo <tj@...nel.org>, Rehas Sachdeva <aquannie@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 13/17] cls_u32: Reinstate cyclic allocation

From: Matthew Wilcox <mawilcox@...rosoft.com>

Commit e7614370d6f0 ("net_sched: use idr to allocate u32 filter handles)
converted htid allocation to use the IDR.  The ID allocated by this
scheme changes; it used to be cyclic, but now always allocates the
lowest available.  The IDR supports cyclic allocation, so just use
the right function.

Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
 net/sched/cls_u32.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 9d48674a70e0..e65b47483dc0 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -316,19 +316,13 @@ static void *u32_get(struct tcf_proto *tp, u32 handle)
 	return u32_lookup_key(ht, handle);
 }
 
+/* Protected by rtnl lock */
 static u32 gen_new_htid(struct tc_u_common *tp_c, struct tc_u_hnode *ptr)
 {
-	unsigned long idr_index;
-	int err;
-
-	/* This is only used inside rtnl lock it is safe to increment
-	 * without read _copy_ update semantics
-	 */
-	err = idr_alloc_ext(&tp_c->handle_idr, ptr, &idr_index,
-			    1, 0x7FF, GFP_KERNEL);
-	if (err)
+	int id = idr_alloc_cyclic(&tp_c->handle_idr, ptr, 1, 0x7FF, GFP_KERNEL);
+	if (id < 0)
 		return 0;
-	return (u32)(idr_index | 0x800) << 20;
+	return (id | 0x800U) << 20;
 }
 
 static struct hlist_head *tc_u_common_hash;
-- 
2.15.0