From patchwork Fri Aug 25 05:32:24 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 9921241 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 4CB58600C5 for ; Fri, 25 Aug 2017 05:32:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3F41923B3C for ; Fri, 25 Aug 2017 05:32:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 33F9224151; Fri, 25 Aug 2017 05:32:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BE53D23B3C for ; Fri, 25 Aug 2017 05:32:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751829AbdHYFci (ORCPT ); Fri, 25 Aug 2017 01:32:38 -0400 Received: from mx2.suse.de ([195.135.220.15]:37279 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751453AbdHYFch (ORCPT ); Fri, 25 Aug 2017 01:32:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 49410AC93; Fri, 25 Aug 2017 05:32:35 +0000 (UTC) From: NeilBrown To: mtk.manpages@gmail.com Date: Fri, 25 Aug 2017 15:32:24 +1000 Cc: Ian Kent , Jeff Layton , Trond Myklebust , "viro\@zeniv.linux.org.uk" , "linux-kernel\@vger.kernel.org" , "mkoutny\@suse.com" , "linux-nfs\@vger.kernel.org" , "linux-fsdevel\@vger.kernel.org" , David Howells , "H. Peter Anvin" Subject: [PATCH manpages] stat.2: correct AT_NO_AUTOMOUNT text and general revisions. In-Reply-To: References: <87bmnmrai9.fsf@notabene.neil.brown.name> <1502430944.3822.1.camel@primarydata.com> <1502449309.4950.2.camel@redhat.com> <87zib3niqn.fsf@notabene.neil.brown.name> <1502705432.4978.1.camel@redhat.com> <877ey4nsep.fsf@notabene.neil.brown.name> <1502883253.4847.6.camel@redhat.com> <1e4665a6-30d6-c16a-760a-2892fb147760@redhat.com> <878tihmora.fsf@notabene.neil.brown.name> <2e289bba-677b-cc50-5fa3-2d24d1f6b858@redhat.com> <87h8x1l9qp.fsf@notabene.neil.brown.name> <733c15c2-ffbb-9a89-90ec-3ba1d574590e@redhat.com> <87r2w3jdn5.fsf@notabene.neil.brown.name> <42ba2fa5-d756-d70f-370c-c2fe1a61c5bf@redhat.com> <87inhdk3rq.fsf@notabene.neil.brown.name> Message-ID: <87valci55j.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Expand on the relationship between fstatat() and the other three functions, and improve the description of AT_NO_AUTOMOUNT. Specifically, both stat() and lstat() act the same way with respect to automounts, and that behavior matches fstatat with the AT_NO_AUTOMOUNT flag. The text in the NOTES is removed and places with the text for AT_NO_AUTOMOUNT to improve cohesion. New text for a difference to be introduced in 4.14. Cc: Ian Kent Signed-off-by: NeilBrown --- Thanks Ian and Michael. I considered your input and read through the whole again, and came up with this which is quite different to what I suggested before. If this patch is applied, the result probably shouldn't be released until the relevant patch actually lands in Linus's tree. NeilBrown man2/stat.2 | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-) diff --git a/man2/stat.2 b/man2/stat.2 index d8a9e76b3d9f..c6dddfe0d3a7 100644 --- a/man2/stat.2 +++ b/man2/stat.2 @@ -260,9 +260,12 @@ For further information on the above fields, see .SS fstatat() The .BR fstatat () -system call operates in exactly the same way as +system call is a more general interface for accessing file information +which can still provide exactly the behavior of each of .BR stat (), -except for the differences described here. +.BR lstat (), +and +.BR fstat (). .PP If the pathname given in .I pathname @@ -272,6 +275,8 @@ referred to by the file descriptor (rather than relative to the current working directory of the calling process, as is done by .BR stat () +and +.BR lstat () for a relative pathname). .PP If @@ -284,7 +289,9 @@ then .I pathname is interpreted relative to the current working directory of the calling process (like -.BR stat ()). +.BR stat () +and +.BR lstat ()). .PP If .I pathname @@ -307,7 +314,11 @@ is an empty string, operate on the file referred to by flag). In this case, .I dirfd -can refer to any type of file, not just a directory. +can refer to any type of file, not just a directory, and +the behavior of +.BR fstatat () +is similar to that of +.BR fstat (). If .I dirfd is @@ -324,6 +335,8 @@ Don't automount the terminal ("basename") component of if it is a directory that is an automount point. This allows the caller to gather attributes of an automount point (rather than the location it would mount). +Since Linux 4.14, also don't instantiate a non-existent name in an +on-demand directory such as used for automounter indirect maps. This flag can be used in tools that scan directories to prevent mass-automounting of a directory of automount points. The @@ -333,6 +346,13 @@ This flag is Linux-specific; define .B _GNU_SOURCE .\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed to obtain its definition. +Both +.BR stat () +and +.BR lstat () +act as though +.B AT_NO_AUTOMOUNT +was set. .TP .B AT_SYMLINK_NOFOLLOW If @@ -474,15 +494,6 @@ fields may be less portable. The interpretation differs between systems, and possibly on a single system when NFS mounts are involved.) .SH NOTES -On Linux, -.BR lstat () -will generally not trigger automounter action, whereas -.BR stat () -will (but see the description of the -.BR fstatat () -.B AT_NO_AUTOMOUNT -fag, above). -.\" .SS Timestamp fields Older kernels and older standards did not support nanosecond timestamp fields.