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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 3F49AC3A5A1 for ; Wed, 28 Aug 2019 13:28:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D5A220828 for ; Wed, 28 Aug 2019 13:28:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726415AbfH1N2K (ORCPT ); Wed, 28 Aug 2019 09:28:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40526 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726394AbfH1N2K (ORCPT ); Wed, 28 Aug 2019 09:28:10 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CF9E62A09A7; Wed, 28 Aug 2019 13:28:09 +0000 (UTC) Received: from bfoster (dhcp-41-2.bos.redhat.com [10.18.41.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 51A5960C5D; Wed, 28 Aug 2019 13:28:05 +0000 (UTC) Date: Wed, 28 Aug 2019 09:28:03 -0400 From: Brian Foster To: Ian Kent Cc: linux-xfs , Dave Chinner , David Howells , Al Viro , Eric Sandeen Subject: Re: [PATCH v2 11/15] xfs: mount api - add xfs_reconfigure() Message-ID: <20190828132803.GD16389@bfoster> References: <156652158924.2607.14608448087216437699.stgit@fedora-28> <156652201687.2607.7837619342391140067.stgit@fedora-28> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156652201687.2607.7837619342391140067.stgit@fedora-28> User-Agent: Mutt/1.12.0 (2019-05-25) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 28 Aug 2019 13:28:09 +0000 (UTC) Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Fri, Aug 23, 2019 at 09:00:16AM +0800, Ian Kent wrote: > Add the fs_context_operations method .reconfigure that performs > remount validation as previously done by the super_operations > .remount_fs method. > > An attempt has also been made to update the comment about options > handling problems with mount(8) to reflect the current situation. > > Signed-off-by: Ian Kent > --- > fs/xfs/xfs_super.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 84 insertions(+) > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > index 76374d602257..aae0098fecab 100644 > --- a/fs/xfs/xfs_super.c > +++ b/fs/xfs/xfs_super.c > @@ -1522,6 +1522,89 @@ xfs_fs_remount( > return 0; > } > > +/* > + * There have been problems in the past with options passed from mount(8). > + * > + * The problem being that options passed by mount(8) in the case where only > + * the the mount point path is given would consist of the existing fstab > + * options with the options from mtab for the current mount merged in and > + * the options given on the command line last. But the result couldn't be > + * relied upon to accurately reflect the current mount options so that > + * rejecting options that can't be changed on reconfigure could erronously > + * cause mount failure. > + * > + * The mount-api uses a legacy mount options handler in the VFS to handle > + * mount(8) so these options will continue to be passed. Even if mount(8) > + * is updated to use fsopen()/fsconfig()/fsmount() it's likely to continue > + * to set the existing options so options problems with reconfigure could > + * continue. > + * > + * For the longest time mtab locking was a problem and this could have been > + * one possible cause. It's also possible there could have been options > + * order problems. > + * > + * That has changed now as mtab is a link to the proc file system mount > + * table so mtab options should be always accurate. > + * > + * Consulting the util-linux maintainer (Karel Zak) he is confident that, > + * in this case, the options passed by mount(8) will be those of the current > + * mount and the options order should be a correct merge of fstab and mtab > + * options, and new options given on the command line. > + * > + * So, in theory, it should be possible to compare incoming options and > + * return an error for options that differ from the current mount and can't > + * be changed on reconfigure to prevent users from believing they might have > + * changed mount options using remount which can't be changed. > + * > + * But for now continue to return success for every reconfigure request, and > + * silently ignore all options that can't actually be changed. > + */ This seems like all good information for a commit log description or perhaps to land in a common header where some of these fs context bits are declared, but overly broad for a function header comment for an XFS callback. I'd more expect some information around the fundamental difference between 'mp' and 'new_mp,' where those come from, what they mean, etc. From the code, it seems like new_mp is transient and reflects changes that we need to incorporate in the original mp..? Brian > +STATIC int > +xfs_reconfigure( > + struct fs_context *fc) > +{ > + struct xfs_fs_context *ctx = fc->fs_private; > + struct xfs_mount *mp = XFS_M(fc->root->d_sb); > + struct xfs_mount *new_mp = fc->s_fs_info; > + xfs_sb_t *sbp = &mp->m_sb; > + int flags = fc->sb_flags; > + int error; > + > + error = xfs_validate_params(new_mp, ctx, false); > + if (error) > + return error; > + > + /* inode32 -> inode64 */ > + if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) && > + !(new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) { > + mp->m_flags &= ~XFS_MOUNT_SMALL_INUMS; > + mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount); > + } > + > + /* inode64 -> inode32 */ > + if (!(mp->m_flags & XFS_MOUNT_SMALL_INUMS) && > + (new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) { > + mp->m_flags |= XFS_MOUNT_SMALL_INUMS; > + mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount); > + } > + > + /* ro -> rw */ > + if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(flags & SB_RDONLY)) { > + error = xfs_remount_rw(mp); > + if (error) > + return error; > + } > + > + /* rw -> ro */ > + if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (flags & SB_RDONLY)) { > + error = xfs_remount_ro(mp); > + if (error) > + return error; > + } > + > + return 0; > +} > + > /* > * Second stage of a freeze. The data is already frozen so we only > * need to take care of the metadata. Once that's done sync the superblock > @@ -2049,6 +2132,7 @@ static const struct super_operations xfs_super_operations = { > static const struct fs_context_operations xfs_context_ops = { > .parse_param = xfs_parse_param, > .get_tree = xfs_get_tree, > + .reconfigure = xfs_reconfigure, > }; > > static struct file_system_type xfs_fs_type = { >