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=-2.3 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 7CDACC32753 for ; Wed, 14 Aug 2019 23:39:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 55732206C1 for ; Wed, 14 Aug 2019 23:39:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727937AbfHNXjr (ORCPT ); Wed, 14 Aug 2019 19:39:47 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:50356 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727217AbfHNXjr (ORCPT ); Wed, 14 Aug 2019 19:39:47 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hy2rq-0001jN-5Z; Wed, 14 Aug 2019 23:39:46 +0000 Date: Thu, 15 Aug 2019 00:39:46 +0100 From: Al Viro To: Sascha Hauer Cc: linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org, Jan Kara , Richard Weinberger , kernel@pengutronix.de Subject: Re: [PATCH 05/11] quota: Allow to pass quotactl a mountpoint Message-ID: <20190814233946.GX1131@ZenIV.linux.org.uk> References: <20190814121834.13983-1-s.hauer@pengutronix.de> <20190814121834.13983-6-s.hauer@pengutronix.de> <20190814233632.GW1131@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190814233632.GW1131@ZenIV.linux.org.uk> User-Agent: Mutt/1.12.0 (2019-05-25) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Aug 15, 2019 at 12:36:32AM +0100, Al Viro wrote: > On Wed, Aug 14, 2019 at 02:18:28PM +0200, Sascha Hauer wrote: > > +/** > > + * reference_super - get a reference to a given superblock > > + * @sb: superblock to get the reference from > > + * > > + * Takes a reference to a superblock. Can be used as when the superblock > > + * is known and leaves it in a state as if get_super had been called. > > + */ > > +void reference_super(struct super_block *sb) > > +{ > > + spin_lock(&sb_lock); > > + sb->s_count++; > > + spin_unlock(&sb_lock); > > + > > + down_read(&sb->s_umount); > > +} > > +EXPORT_SYMBOL_GPL(reference_super); > > NAK, for a plenty of reasons > > 1) introduction of EXPORT_SYMBOL_GPL garbage > 2) aforementioned garbage on something that doesn't need to be exported > 3) *way* too easily abused - get_super() is, at least, not tempting to > play with in random code. This one is, and it's too low-level to > allow. ... and this is a crap userland API. *IF* you want mountpoint-based variants of quotactl() commands, by all means, add those. Do not overload the old ones. And for path-based you don't need to mess with superblock references - just keep the struct path until the end. That will keep the superblock alive and active just fine.