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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT 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 7626AC072B5 for ; Fri, 24 May 2019 18:39:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BC60217D7 for ; Fri, 24 May 2019 18:39:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JR5MiP/3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391647AbfEXSjK (ORCPT ); Fri, 24 May 2019 14:39:10 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:53754 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391503AbfEXSjJ (ORCPT ); Fri, 24 May 2019 14:39:09 -0400 Received: by mail-wm1-f68.google.com with SMTP id 198so10335086wme.3; Fri, 24 May 2019 11:39:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=XPIocXIouKTkDsq9ddFn0FmCiChIBO5fjAM9DzsJTdI=; b=JR5MiP/3E9KQlEPkbf3bVjuNDWCTim/dDnUDdeHtj2t23smeutLwGwSM82p0foiJjC zd1+4hVWxyUapvHWgRprJF5R53gBjY1sgDNyHM/hX/4tJ+/qlYVANvxOc1cz7zj8vR0H iuJXjY4cP56w8cXy3zZ/DdHqqvu7MAtiov6k2uZNqAgoV1tjiBn1MjYwq4sxDNU+28Fp isNJ5YtPNkpf/RiavhKB/dnqbbXxALqkSyanZBYu8MrX5oaw284o9tttcvcslU8v/12U 4mm/zz69dt/Q/quPJBgQm+K1FKEi0pgn1qTmn6+1o7YSBkd64aJ8NCPgPFndCrrbVSGp uAEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=XPIocXIouKTkDsq9ddFn0FmCiChIBO5fjAM9DzsJTdI=; b=nt40z6z/hJOHQpb07nJJEL5NxsMh9t02uHVzaz8eXGfEZvMNjkTpQF7/75rBUqjDjJ 9G7TA1Jyv95lkKL1jPbVm4VKyHOIC72W44Qo2eB6KKmA6s5YyM1k/N8vV9BPqnlnlfG/ OIscNSehDP0flqohmqZqDXEo3Tmk16X6Vnvrx+qmjvGCBEduffjcor5VCj2e5FvodqeM qLemgx55R/pEYlHOLdqJO2wpduwvnoKiZioytTIBD6ZZy2/z5BlOZx/35grFSd4OJEld cjxtFz5h8Bw2Kbk3bbDxIiZ7UqCORhFpa/2eMXPGvRmJD2nX16TI0Hxw+Wjuf58esOUJ 46Cg== X-Gm-Message-State: APjAAAWXqn9iNSMgQOLmKc99KTpprfAncsmHl0uPOA/DzZcVPG8jNjHz GfWtGtyi/s91iK9bBf7CYfLB84I= X-Google-Smtp-Source: APXvYqzabLjPZ3fgjYT9Ndl6TZFvmbx3G+FBLsYHbNLV3ZwNQt2+22w9Cnb2H9ePWUaT5qnzR/Hf/Q== X-Received: by 2002:a1c:f606:: with SMTP id w6mr974343wmc.130.1558723147084; Fri, 24 May 2019 11:39:07 -0700 (PDT) Received: from avx2 ([46.53.250.220]) by smtp.gmail.com with ESMTPSA id u2sm7748190wra.82.2019.05.24.11.39.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 24 May 2019 11:39:06 -0700 (PDT) Date: Fri, 24 May 2019 21:39:03 +0300 From: Alexey Dobriyan To: Linus Torvalds Cc: Christian Brauner , Linux List Kernel Mailing , linux-fsdevel Subject: Re: [PATCH v2 0/2] close_range() Message-ID: <20190524183903.GB2658@avx2> References: <20190523182152.GA6875@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 23, 2019 at 02:34:31PM -0700, Linus Torvalds wrote: > On Thu, May 23, 2019 at 11:22 AM Alexey Dobriyan wrote: > > > > > This is v2 of this patchset. > > > > We've sent fdmap(2) back in the day: > > Well, if the main point of the exercise is performance, then fdmap() > is clearly inferior. This is not true because there are other usecases. Current equivalent is readdir() where getdents is essentially bulk fdmap() with pretty-printing. glibc does getdents into 32KB buffer. There was a bulk taskstats patch long before meltdown fiasco. Unfortunately closerange() only closes ranges. This is why I didn't even tried to send closefrom(2) from OpenBSD. > Sadly, with all the HW security mitigation, system calls are no longer cheap. > > Would there ever be any other reason to traverse unknown open files > than to close them? This is what lsof(1) does: 3140 openat(AT_FDCWD, "/proc/29499/fd", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 4 3140 fstat(4, {st_mode=S_IFDIR|0500, st_size=0, ...}) = 0 3140 getdents(4, /* 6 entries */, 32768) = 144 3140 readlink("/proc/29499/fd/0", "/dev/pts/4", 4096) = 10 3140 lstat("/proc/29499/fd/0", {st_mode=S_IFLNK|0700, st_size=64, ...}) = 0 3140 stat("/proc/29499/fd/0", {st_mode=S_IFCHR|0600, st_rdev=makedev(136, 4), ...}) = 0 3140 openat(AT_FDCWD, "/proc/29499/fdinfo/0", O_RDONLY) = 7 3140 fstat(7, {st_mode=S_IFREG|0400, st_size=0, ...}) = 0 3140 read(7, "pos:\t0\nflags:\t02002\nmnt_id:\t24\n", 1024) = 31 3140 read(7, "", 1024) = 0 3140 close(7) ... Once fdmap(2) or equivalent is in, more bulk system calls operating on descriptors can pop up. But closefrom() will remain closefrom().