From patchwork Fri Jul 10 07:56:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rasmus Villemoes X-Patchwork-Id: 11655973 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 613B914E3 for ; Fri, 10 Jul 2020 07:56:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3AAFB207BC for ; Fri, 10 Jul 2020 07:56:46 +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 S1726942AbgGJH4m (ORCPT ); Fri, 10 Jul 2020 03:56:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726560AbgGJH4l (ORCPT ); Fri, 10 Jul 2020 03:56:41 -0400 Received: from mail-lf1-x144.google.com (mail-lf1-x144.google.com [IPv6:2a00:1450:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAB0EC08C5CE for ; Fri, 10 Jul 2020 00:56:40 -0700 (PDT) Received: by mail-lf1-x144.google.com with SMTP id k15so2681329lfc.4 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=k65+4hGf8nHvXCoXVAyV0KH1vWVfuejiflp3zU0cO7kh+qThaJ0j7XFzGtq/BI0x+7 3L7sgPkH6fJo2/5RsI1PZmEQccyvcD4CSafGSdIg5CBfJfqkNuljWQFkosOb5nVkaOIq DRSf1LkupT67L2JR+ROGbrjXDXKByg5/nNG9+dkV/mWsgaWM4ZsTgkke+E/uQ7UI4qqk Er9cB7FHEKuLu7mJkM4Sr4hMqjBO3MTRTE95YWQa59d/Do0oeTuBq34ApKRkKEiuSGdV dBFMkRt2Yh6152jNsDt4Yifd3ajXbzzZ0J9CXFXVSKPIMNTs+Xe3f8yiQoZOa7jtAf0P OCng== X-Gm-Message-State: AOAM532PGxDct3khiPiA3wpV5S9V6mXOU1uNXC7vlspmQNemeRA4TeWY Mp8izGsvTIDOIbyZ7MUGo7fsiw== 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 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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 Reviewed-by: Cyrill Gorcunov --- 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