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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 746C7C433DF for ; Thu, 25 Jun 2020 13:48:23 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 528772081A for ; Thu, 25 Jun 2020 13:48:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 528772081A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1joSEV-0004wC-S4; Thu, 25 Jun 2020 13:48:03 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1joSEV-0004w7-22 for xen-devel@lists.xenproject.org; Thu, 25 Jun 2020 13:48:03 +0000 X-Inumbo-ID: 7c9ae872-b6ea-11ea-81c3-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 7c9ae872-b6ea-11ea-81c3-12813bfff9fa; Thu, 25 Jun 2020 13:48:02 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0E49EAEF7; Thu, 25 Jun 2020 13:48:01 +0000 (UTC) Subject: Re: [XEN RFC for-4.14] Re: use of "stat -" To: Ian Jackson References: <3bfd6384-fcaf-c74a-e560-a35aafa06a43@suse.com> <20200512141947.yqx4gmbvqs4grx5g@liuwe-devbox-debian-v2.j3c5onc20sse1dnehy4noqpfcg.zx.internal.cloudapp.net> <4b90b635-84bb-e827-d52e-dfe1ebdb4e4d@citrix.com> <814db557-4f6a-020d-9f71-4ee3724981e3@suse.com> <20200512195005.GA96154@mattapan.m5p.com> <049e0022-f9c1-6dc9-3360-d25d88eeb97f@citrix.com> <20200512225458.GA1530@mattapan.m5p.com> <24253.9543.974853.499775@mariner.uk.xensource.com> <0b449d5a-9629-8e41-5354-b985a063eba4@suse.com> <24307.32018.502303.817846@mariner.uk.xensource.com> <6cd9c568-84b9-8304-d56f-99d628d945a1@suse.com> <24308.42811.393047.88416@mariner.uk.xensource.com> From: Jan Beulich Message-ID: <810ea6c8-1ae4-3ecc-3559-fde819f366fe@suse.com> Date: Thu, 25 Jun 2020 15:48:02 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <24308.42811.393047.88416@mariner.uk.xensource.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Wei Liu , Paul Durrant , Andrew Cooper , Jason Andryuk , Elliott Mitchell , "xen-devel@lists.xenproject.org" Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 25.06.2020 15:31, Ian Jackson wrote: > Jan Beulich writes ("Re: [XEN RFC for-4.14] Re: use of "stat -""): >> Looking at vfs_statx() in the kernel, I can't see any provisions to >> get at the data without traversing the specified path. > > The question is what "traversing the path" means. > > How do you explain this ? > > $ >t > $ exec 3>t > $ stat -L -c '%F %i' /dev/stdin <&3 > regular empty file 421124 > $ ll /dev/stdin <&3 > lrwxrwxrwx 1 root root 15 Jun 7 02:01 /dev/stdin -> /proc/self/fd/0 > $ ll /proc/self/fd/0 <&3 > l-wx------ 1 ian ian 64 Jun 25 14:29 /proc/self/fd/0 -> /home/ian/t > $ mv t u > $ ll /proc/self/fd/0 <&3 > l-wx------ 1 ian ian 64 Jun 25 14:29 /proc/self/fd/0 -> /home/ian/u > $ rm u > $ ll /proc/self/fd/0 <&3 > l-wx------ 1 ian ian 64 Jun 25 14:29 /proc/self/fd/0 -> '/home/ian/u (deleted)' > $ stat -L -c '%F %i' /dev/stdin <&3 > regular empty file 421124 > $ ll -Li /dev/stdin <&3 > 421124 -rw-rw-r-- 0 ian ian 0 Jun 25 14:28 /dev/stdin > $ > > Clearly it isn't actually following this synthetic symlink to > "/home/ian/u (deleted)". Okay, so there's clearly some trickery then which don't know where to find. Jan