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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 0F15DC433E0 for ; Fri, 10 Jul 2020 07:56:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5DB72078D for ; Fri, 10 Jul 2020 07:56:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=rasmusvillemoes.dk header.i=@rasmusvillemoes.dk header.b="M4g7tke+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727005AbgGJH4n (ORCPT ); Fri, 10 Jul 2020 03:56:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726921AbgGJH4l (ORCPT ); Fri, 10 Jul 2020 03:56:41 -0400 Received: from mail-lf1-x141.google.com (mail-lf1-x141.google.com [IPv6:2a00:1450:4864:20::141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E352CC08C5DC for ; Fri, 10 Jul 2020 00:56:40 -0700 (PDT) Received: by mail-lf1-x141.google.com with SMTP id d21so2684080lfb.6 for ; Fri, 10 Jul 2020 00:56:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rasmusvillemoes.dk; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=ZXcbxwgnNdN6AgFOPfHDAbPj/lmoR2tjjqmqpya8o/k=; b=M4g7tke+QMNS6x69qNRAFRRs2OoINGT4rqJVDko7GDKiHHusV9GiXnYqVIxiQp51x2 M/fXV8G16zmHM57h6KEORDkR8Iis4QYoObo7XjmhehmLjOI+InV7Eig/X/axf2d6m/DN BgAyP9luxsKIJPW9ZEa9RkDRgeqdwe2IeW0yE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=ZXcbxwgnNdN6AgFOPfHDAbPj/lmoR2tjjqmqpya8o/k=; b=LDZw/UsH3+5TLVZY9ItstKqNt2wmV/euMhBSnbSOm53Z7zvbbYNCIICiyNuhf0yWZX Pv1gLJ61Biel/lXGw2wjVirVevoXLlmkvj96yNxZG6LcNkHOk6AhYMtvDzzphjDZ+8Hm YNWV9KOG90ZfThx6sFHawTDJHBRRYbex7eT6NFWBEVGImvITDCRlnxlt0SyyANweIb9M CD8ByR3vLj6fveYR/tTi4Nt3G0uNTmQIJdQFJNyu/WdnusdHuHR5d78mxNeKvNKfS/qU IjdjCGB8EnPQ8Hie/11z603l+SPTpMfL2XqS2Qe4bbrSFy8miZf1rUgoMf5y+h4dzyQH dpMg== X-Gm-Message-State: AOAM532zZWlUpNVtLe+r6tHbukeDKeJUBM0N6XXt/CLrOXOeXPh0/VlH 7HfGLNKwr7Adcg0RSgmkeZ4VUA== X-Google-Smtp-Source: ABdhPJwLXd9N89jj8OkZWkL9WrDn9m+IDjaPdKXVOLaUH/xRC7rpgvaiSvc5ePtH3hMM3iAG0b0UgQ== X-Received: by 2002:a19:8307:: with SMTP id f7mr42333880lfd.174.1594367799309; Fri, 10 Jul 2020 00:56:39 -0700 (PDT) Received: from prevas-ravi.prevas.se ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id f18sm1634609ljn.73.2020.07.10.00.56.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2020 00:56:38 -0700 (PDT) From: Rasmus Villemoes To: Cyrill Gorcunov Cc: Andrew Morton , Rasmus Villemoes , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] kcmp: add separate Kconfig symbol for kcmp syscall Date: Fri, 10 Jul 2020 09:56:31 +0200 Message-Id: <20200710075632.14661-1-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ability to check open file descriptions for equality (without resorting to unreliable fstat() and fcntl(F_GETFL) comparisons) can be useful outside of the checkpoint/restore use case - for example, systemd uses kcmp() to deduplicate the per-service file descriptor store. Make it possible to have the kcmp() syscall without the full CONFIG_CHECKPOINT_RESTORE. Signed-off-by: Rasmus Villemoes --- I deliberately drop the ifdef in the eventpoll.h header rather than replace with KCMP_SYSCALL; it's harmless to declare a function that isn't defined anywhere. fs/eventpoll.c | 4 ++-- include/linux/eventpoll.h | 2 -- init/Kconfig | 11 +++++++++++ kernel/Makefile | 2 +- 4 files changed, 14 insertions(+), 5 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 12eebcdea9c8..b0313ce2df73 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1064,7 +1064,7 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) return epir; } -#ifdef CONFIG_CHECKPOINT_RESTORE +#ifdef CONFIG_KCMP_SYSCALL static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff) { struct rb_node *rbp; @@ -1106,7 +1106,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, return file_raw; } -#endif /* CONFIG_CHECKPOINT_RESTORE */ +#endif /* CONFIG_KCMP_SYSCALL */ /** * Adds a new entry to the tail of the list in a lockless way, i.e. diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h index 8f000fada5a4..aa799295e373 100644 --- a/include/linux/eventpoll.h +++ b/include/linux/eventpoll.h @@ -18,9 +18,7 @@ struct file; #ifdef CONFIG_EPOLL -#ifdef CONFIG_CHECKPOINT_RESTORE struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff); -#endif /* Used to initialize the epoll bits inside the "struct file" */ static inline void eventpoll_init_file(struct file *file) diff --git a/init/Kconfig b/init/Kconfig index 0498af567f70..95e9486d4217 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1158,9 +1158,20 @@ config NET_NS endif # NAMESPACES +config KCMP_SYSCALL + bool "kcmp system call" + help + Enable the kcmp system call, which allows one to determine + whether to tasks share various kernel resources, for example + whether they share address space, or if two file descriptors + refer to the same open file description. + + If unsure, say N. + config CHECKPOINT_RESTORE bool "Checkpoint/restore support" select PROC_CHILDREN + select KCMP_SYSCALL default n help Enables additional kernel features in a sake of checkpoint/restore. diff --git a/kernel/Makefile b/kernel/Makefile index f3218bc5ec69..3daedba2146a 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -49,7 +49,7 @@ obj-y += rcu/ obj-y += livepatch/ obj-y += dma/ -obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o +obj-$(CONFIG_KCMP_SYSCALL) += kcmp.o obj-$(CONFIG_FREEZER) += freezer.o obj-$(CONFIG_PROFILING) += profile.o obj-$(CONFIG_STACKTRACE) += stacktrace.o -- 2.23.0