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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 CF27AC2BB1D for ; Tue, 17 Mar 2020 08:54:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A287C20674 for ; Tue, 17 Mar 2020 08:54:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="J4eDu3Cs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726019AbgCQIyH (ORCPT ); Tue, 17 Mar 2020 04:54:07 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:36243 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725957AbgCQIyH (ORCPT ); Tue, 17 Mar 2020 04:54:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584435246; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TNEcRgJYG2FHvRPL0to6kfT0Q5dHg4uObpbCvKN7dtE=; b=J4eDu3Csp29Qu1QFjFOMuXBXMkOyXPHi6N0fs3dQqXikG9dqImYk9AFDQZS1wwC2zAbxM2 rQcqdeAG1Lz0gFm0ylpLkVG4eDQphqI2DPdPwoWbKE1aOl0EwIF3ZXxEiqxeLQ9hiHGhlB QYHbyudv2UwHHZzwHV2t2Po4YjEYZbE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-130-K6SU7qjLP4-cYPg-Wrh8ng-1; Tue, 17 Mar 2020 04:54:02 -0400 X-MC-Unique: K6SU7qjLP4-cYPg-Wrh8ng-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A194566F; Tue, 17 Mar 2020 08:54:00 +0000 (UTC) Received: from localhost (ovpn-113-80.rdu2.redhat.com [10.10.113.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id F077E90811; Tue, 17 Mar 2020 08:53:59 +0000 (UTC) Date: Tue, 17 Mar 2020 05:53:58 -0300 From: Bruno Meneguele To: Sergey Senozhatsky Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org Subject: Re: [PATCH] kernel/printk: add kmsg SEEK_CUR handling Message-ID: <20200317085358.GE11152@glitch> References: <20200313003533.2203429-1-bmeneg@redhat.com> <20200313073425.GA219881@google.com> <20200313110229.GI13406@glitch> <20200317020326.GC219881@google.com> MIME-Version: 1.0 In-Reply-To: <20200317020326.GC219881@google.com> X-PGP-Key: http://keys.gnupg.net/pks/lookup?op=get&search=0x3823031E4660608D X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KlAEzMkarCnErv5Q" Content-Disposition: inline Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org --KlAEzMkarCnErv5Q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 17, 2020 at 11:03:26AM +0900, Sergey Senozhatsky wrote: > On (20/03/13 08:02), Bruno Meneguele wrote: > > Ok, I poorly expressed the notion of "documentantion". The userspace > > doesn't tell about returning -ESPIPE, but to the functions work properl= y > > they watch for -ESPIPE returning from the syscall. For instance, gblic > > dprintf() implementation: > >=20 > > dprintf: > > __vdprintf_internal: > > _IO_new_file_attach: > >=20 > > if (_IO_SEEKOFF (fp, (off64_t)0, _IO_seek_cur, _IOS_INPUT|_IOS_OUTPUT= ) > > =3D=3D _IO_pos_BAD && errno !=3D ESPIPE) > > return NULL; > >=20 > > With that, if the seek fails, but return anything other than ESPIPE the > > dprintf() will also fail returning -EINVAL to dprintf() caller. While i= f > > ESPIPE is returned, it's "ignored" and the call still works. The way we > > have today make kmsg an exception case among the rest of the system > > files where you can open with dprintf. > >=20 > > One of the things I could agree with is removing the SEEK call from > > dprintf, since fprintf basically follows the same steps, but doesn't > > seek anything. But at the same time, IMO it makes sense to make kmsg > > interface complaint with the errno return values. >=20 > The code in questions is very old. So let's add the missing bit to the > kernel. At the same time, we probably can have a slightly more detailed > documentation / code comment. >=20 > =09-ss >=20 Sure thing. I'm going to send a v2 of this patch with more details still today or tomorrow. Thanks! --=20 bmeneg=20 PGP Key: http://bmeneg.com/pubkey.txt --KlAEzMkarCnErv5Q Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEdWo6nTbnZdbDmXutYdRkFR+RokMFAl5wkCYACgkQYdRkFR+R okOt6wgAs3dyaz7bUjahq+okFkTiDc6plFTMf+OgYLwsF7b1FCDcFwuzdUptfAXR muOlZ4t0hcTfTOYb6uCWITVdOwKR76RVMieoEfaSYY+g8RpT5e+xfHmxB268Ud3b /9Tz1J86cnN8jjoj/B6exMg3ZzwrQXgmPhF+B8NAoPnEkscmr5sDWXVoSchXy8mZ 7iezmGVaaLthlqIrsQU9CUXpDYMhXlaUiLi/U/euzxLTl8Es14UdEAw3xKP5Accs 2KTctmiyTr2VGaZ6B04DIU0SFGAEstgk4IUvn2bkrjnkyoLhz5mQBVk4vRC3Lu3Z pd7KCXg8F8GOdiZ7dwYQ5CtQNEkxlg== =MnH8 -----END PGP SIGNATURE----- --KlAEzMkarCnErv5Q--