From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753490AbeC1Orw (ORCPT ); Wed, 28 Mar 2018 10:47:52 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:33234 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752237AbeC1Orv (ORCPT ); Wed, 28 Mar 2018 10:47:51 -0400 Date: Wed, 28 Mar 2018 15:47:49 +0100 From: Al Viro To: Alexey Dobriyan Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] proc: register filesystem last Message-ID: <20180328144748.GU30522@ZenIV.linux.org.uk> References: <20180309222709.GA3843@avx2> <20180309144938.d308e0bf98fb6b5bbcb82189@linux-foundation.org> <20180310000634.GA12443@avx2> <20180328044823.GT30522@ZenIV.linux.org.uk> <20180328072657.GA2063@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180328072657.GA2063@avx2> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 28, 2018 at 10:26:57AM +0300, Alexey Dobriyan wrote: > On Wed, Mar 28, 2018 at 05:48:23AM +0100, Al Viro wrote: > > On Sat, Mar 10, 2018 at 03:06:34AM +0300, Alexey Dobriyan wrote: > > > On Fri, Mar 09, 2018 at 02:49:38PM -0800, Andrew Morton wrote: > > > > On Sat, 10 Mar 2018 01:27:09 +0300 Alexey Dobriyan wrote: > > > > > > > > > As soon as register_filesystem() exits, filesystem can be mounted. > > > > > It is better to present fully operational /proc. > > > > > > > > > > Of course it doesn't matter because /proc is not modular > > > > > but do it anyway. > > > > > > > > > > Drop error check, it should be handled by panicking. > > > > > > > > So... shouldn't we add a call to panic()? > > > > > > via FS_PANIC flag, yes. I have a patch somewhere. > > > There are 104 filesystems ATM, some internal, some not. > > > Some modular, some not. > > > > You do realize that the only case when register_filesystem() fails is > > "another driver has already registered filesystem type with the same > > name"? Is there *ever* a case when > > * you could expect that to happen and > > * panic would be a sane response? > > It is for standartizing all those error checks in init sequence by > removing them. Modules won't have FS_PANIC. Huh? Again, _when_ is that thing appropriate? To register_filesystem() failure in non-modular case you need several builtin fs drivers to try and register fs types with the same name. In this particular case, you need another in-kernel filesystem called "proc" registered first. It's not about extreme oom early in the boot or anything like that - plain and simple badly modified and misconfigured kernel.