From nobody Thu Dec 26 15:36:56 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 48DB61D356E for ; Fri, 25 Oct 2024 09:32:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729848774; cv=none; b=iqjzRfQwPHGDI8ta7sB1IF37HJYLwkSpDTtLz6QezNJM11K1rtyoTJrV/mYkXYQW6WpogUf0/vmxjPdIB4zJrSPI7oY8Uh73NybfrFjmGPzNCP7mj2Sy9qR97iMkNKl4yY+QYEWVyM/8CFgXg4XcRdTxgNBISsJGFFqRByLrVDo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729848774; c=relaxed/simple; bh=pe0ozo/m4xULdH9orv2JKinsOrPLim+Ex/qUym0rLrs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=p7Ch4cRV09Z2AV/yvc1zFKA0YSu+RTmlRzwS/nD69jPHWLDK8zAfoudTqqUtiWx2jhJyWrMN/r21R1ALBxTSn4hT3Koip3cKk12oTXMeSGIEguymuNv8K8kfy0r2pRYX44/KHEhyXqeEeaU9a+SlzYL2T/X2fXdFUZirR9U9dWY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rI2nByDP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="rI2nByDP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D06BC4CEE7; Fri, 25 Oct 2024 09:32:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729848773; bh=pe0ozo/m4xULdH9orv2JKinsOrPLim+Ex/qUym0rLrs=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=rI2nByDPeYGZd8hz4KbZasbSOlldh0O9PQlCKcRQnUihkyPC5h2GiHrH7te10kkoS xZtt0rwwqqfRAtwjeMCyrhf69BbJjtF2Z4x9+aTO9VhsiyaTV5zlYZ70ojYZi1U+HH +eNQv9Smpi9/Lz19Ny8K9AhWsDaegNxiuBkmRkm4RWrm/KKPVrpjnJVNWpj6DPsKgG JzUuGO+Lp54vSlHD/mttQ+AUlsKeR7njp2q1CAaCZjrpipjRZqIXOMY58IVXBdVNK7 3qjPEOGeRk2CLTVbOyL2xJpxtgnUYoqb892Ij40UXPbecnFBWdluqpnjelHKgxUaTW kvxTpRg/0FO+A== From: "Matthieu Baerts (NGI0)" Date: Fri, 25 Oct 2024 11:32:30 +0200 Subject: [PATCH mptcp-net v2 2/3] mptcp: pm: lockless list traversal Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20241025-mptcp-pm-lookup_addr_rcu-v2-2-1478f6c4b205@kernel.org> References: <20241025-mptcp-pm-lookup_addr_rcu-v2-0-1478f6c4b205@kernel.org> In-Reply-To: <20241025-mptcp-pm-lookup_addr_rcu-v2-0-1478f6c4b205@kernel.org> To: mptcp@lists.linux.dev Cc: Paolo Abeni , "Matthieu Baerts (NGI0)" X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=4532; i=matttbe@kernel.org; h=from:subject:message-id; bh=pe0ozo/m4xULdH9orv2JKinsOrPLim+Ex/qUym0rLrs=; b=owEBbQKS/ZANAwAIAfa3gk9CaaBzAcsmYgBnG2XCE6q5DSbhHdp5/RJ3uYMBZYsNP19UFWnll KZH9yq5xdqJAjMEAAEIAB0WIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZxtlwgAKCRD2t4JPQmmg cxrtD/4pC8G1SWeVVX6GdIxSxAA0xUaRfb5mLG7HrU9b1tvKn0x+8K5nJVi1yuYw8MmT6X3aHxd X8vyC8GgxwJk3zXosPVn9fOyUtPtNNnuMwtKnAqzVs0W7WbxANROmtxrqcTeefMJxKiTnteWMnV Iu5X1jC/Vs74+84NO1hY0nHJb0V02ooONuAY4+99YpGKTCamyFAfeyCIndQmDlxzh0u1Bc7SL14 TmNis40CYuemAf2FpvPaZ3F9re/zYtQ/Zt5sO/H8pz08Yvz3vIs16VXetFbaEDLv/SeBkQ8IhJZ bK4hiRM+N2wdMMC5qUSWR0aJSEMK2X1OkanASZqadIoG2QvVF199ogCTfrTo0S+LsHVG+fbHd3P wLs5X2tj4ARgYtoOxbMozLHztgc3YbpmcCRE22CDwteMTwZ+JfuUqTf6CVMuFyt3B8CKT7Vya1k 1s59KTVzsbapF7iKDchcFjkH/mEZEaqumQS+Oo8i2xMRikIs/qFEU7UhOLbmdWkbH/elsKwsDc1 yzZR9SaR/kCk/NcuTex/9Wcc58B9WfYYE9cq7nhEkBfh1+IfgzWg/CuP1UoNEVGwMzCY+k5QIYI 53DiSy66FI0OYwunhpCqKdh7tF1bKXb8Af9zZy4adOc6MeN7tmo6k1V6HanLAqrolRX70CS2s/j 47JKRc1mO01bD0g== X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 In a few places -- to get an endpoint, dump all of them, and change their flags -- the list is iterated while holding the pernet->lock, but only to read the content of the list. In these cases, we can replace the spin locks, by RCU read ones, and use the _rcu variants to iterate over the entries list in a lockless way. To make it clear, the lookup helpers using the _rcu variant are renamed with a _rcu suffix. The previous __lookup_addr() helper can then be removed, but __lookup_addr_by_id() is still needed. While at it, the IDs bitmap is copied before iterating the list to dump the different addresses, to avoid any consistencies. Signed-off-by: Matthieu Baerts (NGI0) --- Notes: - This is not a fix, a small improvement for -next. --- net/mptcp/pm_netlink.c | 36 +++++++++++++++++++----------------- 1 file changed, 19 insertions(+), 17 deletions(-) diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index a93b9b7776b48781a883673fe5fd521a978487ff..f38e1ccd34e95cd88b179a8b50e= 6965731542871 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -520,12 +520,12 @@ __lookup_addr_by_id(struct pm_nl_pernet *pernet, unsi= gned int id) } =20 static struct mptcp_pm_addr_entry * -__lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *i= nfo) +__lookup_addr_by_id_rcu(struct pm_nl_pernet *pernet, unsigned int id) { struct mptcp_pm_addr_entry *entry; =20 - list_for_each_entry(entry, &pernet->local_addr_list, list) { - if (mptcp_addresses_equal(&entry->addr, info, entry->addr.port)) + list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) { + if (entry->addr.id =3D=3D id) return entry; } return NULL; @@ -1836,8 +1836,8 @@ int mptcp_pm_nl_get_addr(struct sk_buff *skb, struct = genl_info *info) goto fail; } =20 - spin_lock_bh(&pernet->lock); - entry =3D __lookup_addr_by_id(pernet, addr.addr.id); + rcu_read_lock(); + entry =3D __lookup_addr_by_id_rcu(pernet, addr.addr.id); if (!entry) { GENL_SET_ERR_MSG(info, "address not found"); ret =3D -EINVAL; @@ -1850,11 +1850,11 @@ int mptcp_pm_nl_get_addr(struct sk_buff *skb, struc= t genl_info *info) =20 genlmsg_end(msg, reply); ret =3D genlmsg_reply(msg, info); - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); return ret; =20 unlock_fail: - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); =20 fail: nlmsg_free(msg); @@ -1872,16 +1872,18 @@ int mptcp_pm_nl_dump_addr(struct sk_buff *msg, struct net *net =3D sock_net(msg->sk); struct mptcp_pm_addr_entry *entry; struct pm_nl_pernet *pernet; + unsigned long id_bitmap[4]; int id =3D cb->args[0]; void *hdr; int i; =20 pernet =3D pm_nl_get_pernet(net); + bitmap_copy(id_bitmap, pernet->id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1); =20 - spin_lock_bh(&pernet->lock); + rcu_read_lock(); for (i =3D id; i < MPTCP_PM_MAX_ADDR_ID + 1; i++) { - if (test_bit(i, pernet->id_bitmap)) { - entry =3D __lookup_addr_by_id(pernet, i); + if (test_bit(i, id_bitmap)) { + entry =3D __lookup_addr_by_id_rcu(pernet, i); if (!entry) break; =20 @@ -1903,7 +1905,7 @@ int mptcp_pm_nl_dump_addr(struct sk_buff *msg, genlmsg_end(msg, hdr); } } - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); =20 cb->args[0] =3D id; return msg->len; @@ -2060,17 +2062,17 @@ int mptcp_pm_nl_set_flags(struct sk_buff *skb, stru= ct genl_info *info) if (addr.flags & MPTCP_PM_ADDR_FLAG_BACKUP) bkup =3D 1; =20 - spin_lock_bh(&pernet->lock); - entry =3D lookup_by_id ? __lookup_addr_by_id(pernet, addr.addr.id) : - __lookup_addr(pernet, &addr.addr); + rcu_read_lock(); + entry =3D lookup_by_id ? __lookup_addr_by_id_rcu(pernet, addr.addr.id) : + __lookup_addr_rcu(pernet, &addr.addr); if (!entry) { - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); GENL_SET_ERR_MSG(info, "address not found"); return -EINVAL; } if ((addr.flags & MPTCP_PM_ADDR_FLAG_FULLMESH) && (entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) { - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); GENL_SET_ERR_MSG(info, "invalid addr flags"); return -EINVAL; } @@ -2078,7 +2080,7 @@ int mptcp_pm_nl_set_flags(struct sk_buff *skb, struct= genl_info *info) changed =3D (addr.flags ^ entry->flags) & mask; entry->flags =3D (entry->flags & ~mask) | (addr.flags & mask); addr =3D *entry; - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); =20 mptcp_nl_set_flags(net, &addr.addr, bkup, changed); return 0; --=20 2.45.2