From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12E6FC4161B for ; Fri, 9 Nov 2018 20:11:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1A6520855 for ; Fri, 9 Nov 2018 20:11:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1A6520855 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728491AbeKJFyB (ORCPT ); Sat, 10 Nov 2018 00:54:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37832 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725872AbeKJFyB (ORCPT ); Sat, 10 Nov 2018 00:54:01 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8712489AD5; Fri, 9 Nov 2018 20:11:53 +0000 (UTC) Received: from llong.com (dhcp-17-55.bos.redhat.com [10.18.17.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1BFED608C1; Fri, 9 Nov 2018 20:11:52 +0000 (UTC) From: Waiman Long To: "Luis R. Rodriguez" , Kees Cook , Andrew Morton , Jonathan Corbet Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Al Viro , Matthew Wilcox , "Eric W. Biederman" , Takashi Iwai , Davidlohr Bueso , Manfred Spraul , Waiman Long Subject: [PATCH v11 3/3] ipc: Do cyclic id allocation with ipcmni_extend mode Date: Fri, 9 Nov 2018 15:11:32 -0500 Message-Id: <1541794292-19425-4-git-send-email-longman@redhat.com> In-Reply-To: <1541794292-19425-1-git-send-email-longman@redhat.com> References: <1541794292-19425-1-git-send-email-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 09 Nov 2018 20:11:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For ipcmni_extend mode, the sequence number space is only 7 bits. So the chance of id reuse is relatively high compared with the non-extended mode. To alleviate this id reuse problem, the id allocation will be done cyclically to cycle through all the 24-bit id space before wrapping around when in ipcmni_extend mode. This may cause the use of more memory in term of the number of xa_nodes allocated as well as potentially more cachelines used as the xa_nodes may be spread more sparsely in this case. There is probably a slight memory and performance cost in doing cyclic id allocation. For applications that really need more than 32k unique IPC identifiers, this is a small price to pay to avoid the id reuse problem. As a result, the chance of id reuse should be even smaller in the ipcmni_extend mode. For users who worry about id reuse, they can turn on ipcmni_extend mode, even if they don't need more than 32k IPC identifiers. Signed-off-by: Waiman Long --- Documentation/admin-guide/kernel-parameters.txt | 5 ++++- ipc/ipc_sysctl.c | 2 ++ ipc/util.c | 6 +++++- ipc/util.h | 2 ++ 4 files changed, 13 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 93d1454..49620b9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1800,7 +1800,10 @@ See Documentation/filesystems/nfs/nfsroot.txt. ipcmni_extend [KNL] Extend the maximum number of unique System V - IPC identifiers from 32,768 to 16,777,216. + IPC identifiers from 32,768 to 16,777,216. Also do + cyclical identifier allocation through the entire + 24-bit identifier space to reduce the chance of + identifier reuse. irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index 73b7782..d9ac6ca 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -122,6 +122,7 @@ static int proc_ipc_sem_dointvec(struct ctl_table *table, int write, static int int_max = INT_MAX; int ipc_mni = IPCMNI; int ipc_mni_shift = IPCMNI_SHIFT; +bool ipc_mni_extended; static struct ctl_table ipc_kern_table[] = { { @@ -252,6 +253,7 @@ static int __init ipc_mni_extend(char *str) { ipc_mni = IPCMNI_EXTEND; ipc_mni_shift = IPCMNI_EXTEND_SHIFT; + ipc_mni_extended = true; pr_info("IPCMNI extended to %d.\n", ipc_mni); return 0; } diff --git a/ipc/util.c b/ipc/util.c index 00000a1..634b190 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -228,7 +228,11 @@ static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new) ids->deleted = false; } new->seq = ids->seq; - idx = idr_alloc(&ids->ipcs_idr, new, 0, 0, GFP_NOWAIT); + if (ipc_mni_extended) + idx = idr_alloc_cyclic(&ids->ipcs_idr, new, 0, ipc_mni, + GFP_NOWAIT); + else + idx = idr_alloc(&ids->ipcs_idr, new, 0, 0, GFP_NOWAIT); } else { new->seq = ipcid_to_seqx(next_id); idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id), diff --git a/ipc/util.h b/ipc/util.h index 6a88d51..9f0dd79 100644 --- a/ipc/util.h +++ b/ipc/util.h @@ -33,6 +33,7 @@ #ifdef CONFIG_SYSVIPC_SYSCTL extern int ipc_mni; extern int ipc_mni_shift; +extern bool ipc_mni_extended; #define IPCMNI_SEQ_SHIFT ipc_mni_shift #define IPCMNI_IDX_MASK ((1 << ipc_mni_shift) - 1) @@ -40,6 +41,7 @@ #else /* CONFIG_SYSVIPC_SYSCTL */ #define ipc_mni IPCMNI +#define ipc_mni_extended false #define IPCMNI_SEQ_SHIFT IPCMNI_SHIFT #define IPCMNI_IDX_MASK ((1 << IPCMNI_SHIFT) - 1) #endif /* CONFIG_SYSVIPC_SYSCTL */ -- 1.8.3.1