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=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=unavailable 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 0290DC04AAF for ; Tue, 21 May 2019 16:41:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBD57217F4 for ; Tue, 21 May 2019 16:41:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=brauner.io header.i=@brauner.io header.b="DrUfMEDj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728510AbfEUQlr (ORCPT ); Tue, 21 May 2019 12:41:47 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:37479 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728099AbfEUQlr (ORCPT ); Tue, 21 May 2019 12:41:47 -0400 Received: by mail-wm1-f65.google.com with SMTP id 7so3585142wmo.2 for ; Tue, 21 May 2019 09:41:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brauner.io; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=QRw4dWFrlFKNeC2Hv6jFCNR7pmJ9ZVloUzzaJsWHe3k=; b=DrUfMEDjMCX/F/kpAns9Xje6tAglSh3UhG5Ut0HpXQH/i/WF067F5FUZoHtyFcz92J B9zO7Q3xmWBLCoBBlKTKoCtUiQsaTMx3Npeppmj4pHHAb15DBLIi9tECGzeTa0qz68HY 5SJCekbjPP909njq82OecOWv07W5VLYr5VkHE6sbSe+2o5Mw73nXEvvOijdE8vUJH9BM uSenbJ2wN1Uv1xiE6qAy9CpI8LAAlCfwF/dLDfgYTm5Xge0CjqlWt1lxcYk7Ou9/XL7L lIMEXS/i0lcGD5hbzAqtPxjiA1/NY2p62maSbnW0JtvlH3GgYQ9nmlSCeM60N0klvzp1 geRQ== 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=QRw4dWFrlFKNeC2Hv6jFCNR7pmJ9ZVloUzzaJsWHe3k=; b=G2fjd0CrOX0cBupWT5LfI+JKphI3nBI5g4qvLq4ZT8iEH+oMsfCq1mcAQH2ZoRvcoL +sljo4rfvHiBQvyjeNmtMV8+xLaLkgz62vfMP0BDSokra8uf2l/PPyWSk8oBHPpB+Gei Pqp/s3mr5RV9MdnAm+cf4AxtFZerisbNO6a337kl61xtdCy5TnmJqXh+wOywwnjLxPuG Y3WXWx7rh5o88AoSWKk6REtTKjO+eHUxticJJd1LEw7BqZDMXDgZtfUUgpT1gaK047/J gvk18AYSC37SVrJ3o8CQCUFxdcslTLtB7p0E1NuLee8QjxpmP/J3VNEFpCJwoCGRkDAa LFzw== X-Gm-Message-State: APjAAAWGAQ8IG2q9w7sDTSUBTr2DJkcMtpLoodu0OUDrkMaIuX84xykt NIhQIMyUUI96tAjWvAlTFM78pQ== X-Google-Smtp-Source: APXvYqy9lGE6AuIM688BrnvZ7pn7z99PmptY1DxlEejau1I+HdIPSmSJeaZzuDaCQae7Ot/VplE6/A== X-Received: by 2002:a7b:c40e:: with SMTP id k14mr3957899wmi.114.1558456904711; Tue, 21 May 2019 09:41:44 -0700 (PDT) Received: from brauner.io ([212.91.227.56]) by smtp.gmail.com with ESMTPSA id q14sm7089531wrx.86.2019.05.21.09.41.43 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 21 May 2019 09:41:44 -0700 (PDT) Date: Tue, 21 May 2019 18:41:42 +0200 From: Christian Brauner To: David Howells Cc: Al Viro , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, jannh@google.com, fweimer@redhat.com, oleg@redhat.com, tglx@linutronix.de, torvalds@linux-foundation.org, arnd@arndb.de, shuah@kernel.org, tkjos@android.com, ldv@altlinux.org, miklos@szeredi.hu, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH 1/2] open: add close_range() Message-ID: <20190521164141.rbehqnghiej3gfua@brauner.io> References: <20190521150006.GJ17978@ZenIV.linux.org.uk> <20190521113448.20654-1-christian@brauner.io> <28114.1558456227@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <28114.1558456227@warthog.procyon.org.uk> User-Agent: NeoMutt/20180716 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, May 21, 2019 at 05:30:27PM +0100, David Howells wrote: > Al Viro wrote: > > > Umm... That's going to be very painful if you dup2() something to MAX_INT and > > then run that; roughly 2G iterations of bouncing ->file_lock up and down, > > without anything that would yield CPU in process. > > > > If anything, I would suggest something like > > > > fd = *start_fd; > > grab the lock > > fdt = files_fdtable(files); > > more: > > look for the next eviction candidate in ->open_fds, starting at fd > > if there's none up to max_fd > > drop the lock > > return NULL > > *start_fd = fd + 1; > > if the fscker is really opened and not just reserved > > rcu_assign_pointer(fdt->fd[fd], NULL); > > __put_unused_fd(files, fd); > > drop the lock > > return the file we'd got > > if (unlikely(need_resched())) > > drop lock > > cond_resched(); > > grab lock > > fdt = files_fdtable(files); > > goto more; > > > > with the main loop being basically > > while ((file = pick_next(files, &start_fd, max_fd)) != NULL) > > filp_close(file, files); > > If we can live with close_from(int first) rather than close_range(), then this > can perhaps be done a lot more efficiently by: Yeah, you mentioned this before. I do like being able to specify an upper bound to have the ability to place fds strategically after said upper bound. I have used this quite a few times where I know that given task may have inherited up to m fds and I want to inherit a specific pipe who's fd I know. Then I'd dup2(pipe_fd, ) and then close all other fds. Is that too much of a corner case? Christian