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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 3AFEFC433DB for ; Thu, 28 Jan 2021 04:05:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED1C364DD7 for ; Thu, 28 Jan 2021 04:05:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231307AbhA1EFf (ORCPT ); Wed, 27 Jan 2021 23:05:35 -0500 Received: from mx2.suse.de ([195.135.220.15]:53908 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231259AbhA1EEX (ORCPT ); Wed, 27 Jan 2021 23:04:23 -0500 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 A82D6AF82; Thu, 28 Jan 2021 03:50:36 +0000 (UTC) From: NeilBrown To: Fox Chen , corbet@lwn.net, vegard.nossum@oracle.com, viro@zeniv.linux.org.uk, rdunlap@infradead.org, grandmaster@al2klimov.de Date: Thu, 28 Jan 2021 14:50:30 +1100 Cc: Fox Chen , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/12] docs: path-lookup: update do_last() part In-Reply-To: <20210126072443.33066-5-foxhlchen@gmail.com> References: <20210126072443.33066-1-foxhlchen@gmail.com> <20210126072443.33066-5-foxhlchen@gmail.com> Message-ID: <875z3hhg8p.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Tue, Jan 26 2021, Fox Chen wrote: > traling_symlink() was merged into lookup_last, do_last(). > > do_last() has later been split into open_last_lookups() > and do_open(). > > see related commit: c5971b8c6354a95c9ee7eb722928af5000bac247 > > Signed-off-by: Fox Chen > --- > Documentation/filesystems/path-lookup.rst | 34 +++++++++++------------ > 1 file changed, 17 insertions(+), 17 deletions(-) > > diff --git a/Documentation/filesystems/path-lookup.rst b/Documentation/fi= lesystems/path-lookup.rst > index 4e77c8520fa9..1f05b1417a55 100644 > --- a/Documentation/filesystems/path-lookup.rst > +++ b/Documentation/filesystems/path-lookup.rst > @@ -496,11 +496,11 @@ one provided by a dead NFS server. In the current = kernel, path_mountpoint > has been merged into ``path_lookup_at()`` with a new flag LOOKUP_MOUNTPO= INT. >=20=20 > Finally ``path_openat()`` is used for the ``open()`` system call; it > -contains, in support functions starting with "``do_last()``", all the > +contains, in support functions starting with "``open_last_lookups()``", = all the > complexity needed to handle the different subtleties of O_CREAT (with > or without O_EXCL), final "``/``" characters, and trailing symbolic > links. We will revisit this in the final part of this series, which > -focuses on those symbolic links. "``do_last()``" will sometimes, but > +focuses on those symbolic links. "``open_last_lookups()``" will sometim= es, but > not always, take ``i_rwsem``, depending on what it finds. >=20=20 > Each of these, or the functions which call them, need to be alert to > @@ -1201,26 +1201,26 @@ symlink. > This case is handled by the relevant caller of ``link_path_walk()``, suc= h as > ``path_lookupat()`` using a loop that calls ``link_path_walk()``, and th= en > handles the final component. If the final component is a symlink > -that needs to be followed, then ``trailing_symlink()`` is called to set > -things up properly and the loop repeats, calling ``link_path_walk()`` > -again. This could loop as many as 40 times if the last component of > -each symlink is another symlink. > +that needs to be followed, then ``open_last_lookups()`` and ``do_open()`= ` is > +called to set things up properly and the loop repeats, calling This implies that do_open() is inside the loop (in path_openat()). But it isn't, it comes after the loop. (I haven't closely examined this rest of this patch). NeilBrown > +``link_path_walk()`` again. This could loop as many as 40 times if the = last > +component of each symlink is another symlink. >=20=20 > The various functions that examine the final component and possibly > -report that it is a symlink are ``lookup_last()``, ``mountpoint_last()`` > -and ``do_last()``, each of which use the same convention as > -``walk_component()`` of returning ``1`` if a symlink was found that needs > -to be followed. > +report that it is a symlink are ``lookup_last()``, ``open_last_lookups()= `` > +, each of which use the same convention as > +``walk_component()`` of returning ``char *name`` if a symlink was found = that > +needs to be followed. >=20=20 > -Of these, ``do_last()`` is the most interesting as it is used for > -opening a file. Part of ``do_last()`` runs with ``i_rwsem`` held and th= is > -part is in a separate function: ``lookup_open()``. > +Of these, ``open_last_lookups()``, ``do_open()`` is the most interesting= as it is > +used for opening a file. Part of ``open_last_lookups()`` runs with ``i_= rwsem`` > +held and this part is in a separate function: ``lookup_open()``. >=20=20 > -Explaining ``do_last()`` completely is beyond the scope of this article, > -but a few highlights should help those interested in exploring the > -code. > +Explaining ``open_last_lookups()``, ``do_open()`` completely is beyond t= he scope > +of this article, but a few highlights should help those interested in ex= ploring > +the code. >=20=20 > -1. Rather than just finding the target file, ``do_last()`` needs to open > +1. Rather than just finding the target file, ``do_open()`` needs to open > it. If the file was found in the dcache, then ``vfs_open()`` is used= for > this. If not, then ``lookup_open()`` will either call ``atomic_open(= )`` (if > the filesystem provides it) to combine the final lookup with the open= , or > --=20 > 2.30.0 --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQJCBAEBCAAsFiEEG8Yp69OQ2HB7X0l6Oeye3VZigbkFAmASNIYOHG5laWxiQHN1 c2UuZGUACgkQOeye3VZigbmddRAAw28JyGI4YjJoVUS0B5R4frhT+rE/efN8zDgU Yi2pcckfdt/uTZDSNPkXiOnhTZwfvHgAUblhBkAvxnkdhdE7NeaQmFtwBu7mMU2I l60+UR/mH/5KKoxUiYLcEf6mOi8DyGD5tibGst8Xm322iJbg1+yPMzW6KwRekLfv WXLIr4xoIAMwNdTzynzXnJjhrc4yLE9LL8lwj0wr8JturTvvOKcNk44mDZS6vIr0 aXU+J9xLDLOX5S8Fh/Oc8IYr1z99MDCOpZ1Bc06g+6iW0izLIL+DxhIV21Oje0ts +pS1pxchzIB4gQa8CilEQ+Rzach/8YXOnfSJUmXLTHz/m8SxTPIBprgd2fp/3nEK /rwuElDSPFuziySkVMqJ4cnrCe8fiZNSU8qMdwk2RyiI4BkaD0BCU3wibv0vOF9f k2uHHqyH+c1fXTjwCCBuKdjAIOL+6v25uShoVze5gk7Amr0XXXZTHUnZXVq1x0Ve C7wBekOWzYq5E8LE0Vo2FIz9phKlkFGhe5owcNPe8ZAYQVIkIJiOWGotaGw7tNR/ QV/Jmni+FzLuI+ZWjShTwiFwGFBhCSYrfKpMPSYBDB6vONQtAIhFUSlmdYFApVbS eYUWaIEhQMBrwWJYkGuaWjdyti6XrhkJvkIldmEQ1xXejrfNNabZ+Mif3VMj7oL0 5FQX7zo= =CAWi -----END PGP SIGNATURE----- --=-=-=--