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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 EF662C2BB84 for ; Thu, 10 Sep 2020 07:09:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C4BEF207EA for ; Thu, 10 Sep 2020 07:09:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730335AbgIJHJi (ORCPT ); Thu, 10 Sep 2020 03:09:38 -0400 Received: from mx2.suse.de ([195.135.220.15]:45186 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730393AbgIJHHM (ORCPT ); Thu, 10 Sep 2020 03:07:12 -0400 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 41023AF9C; Thu, 10 Sep 2020 07:07:25 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 4DB811E12EB; Thu, 10 Sep 2020 09:07:09 +0200 (CEST) Date: Thu, 10 Sep 2020 09:07:09 +0200 From: Jan Kara To: "Darrick J. Wong" Cc: Jan Kara , Matthew Wilcox , linux-fsdevel , xfs , hch@lst.de Subject: Re: [PATCH v3] quota: widen timestamps for the fs_disk_quota structure Message-ID: <20200910070709.GA17540@quack2.suse.cz> References: <20200909013251.GG7955@magnolia> <20200909014933.GC6583@casper.infradead.org> <20200909022909.GI7955@magnolia> <20200909105133.GC24207@quack2.suse.cz> <20200909124252.GE6583@casper.infradead.org> <20200909135645.GB29150@quack2.suse.cz> <20200909172701.GK7955@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200909172701.GK7955@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed 09-09-20 10:27:01, Darrick J. Wong wrote: > On Wed, Sep 09, 2020 at 03:56:45PM +0200, Jan Kara wrote: > > On Wed 09-09-20 13:42:52, Matthew Wilcox wrote: > > > On Wed, Sep 09, 2020 at 12:51:33PM +0200, Jan Kara wrote: > > > > On Tue 08-09-20 19:29:09, Darrick J. Wong wrote: > > > > > On Wed, Sep 09, 2020 at 02:49:33AM +0100, Matthew Wilcox wrote: > > > > > > On Tue, Sep 08, 2020 at 06:32:51PM -0700, Darrick J. Wong wrote: > > > > > > > +static inline void copy_to_xfs_dqblk_ts(const struct fs_disk_quota *d, > > > > > > > + __s32 *timer_lo, __s8 *timer_hi, s64 timer) > > > > > > > +{ > > > > > > > + *timer_lo = timer; > > > > > > > + if (d->d_fieldmask & FS_DQ_BIGTIME) > > > > > > > + *timer_hi = timer >> 32; > > > > > > > + else > > > > > > > + *timer_hi = 0; > > > > > > > +} > > > > > > > > > > > > I'm still confused by this. What breaks if you just do: > > > > > > > > > > > > *timer_lo = timer; > > > > > > *timer_hi = timer >> 32; > > > > > > > > > > "I don't know." > > > > > > > > > > The manpage for quotactl doesn't actually specify the behavior of the > > > > > padding fields. The /implementation/ is careful enough to zero > > > > > everything, but the interface specification doesn't explicitly require > > > > > software to do so. > > > > > > > > > > Because the contents of the padding fields aren't defined by the > > > > > documentation, the kernel cannot simply start using the d_padding2 field > > > > > because there could be an old kernel that doesn't zero the padding, > > > > > which would lead to confusion if the new userspace were mated to such a > > > > > kernel. > > > > > > > > > > Therefore, we have to add a flag that states explicitly that we are > > > > > using the timer_hi fields. This is also the only way that an old > > > > > program can detect that it's being fed a structure that it might not > > > > > recognise. > > > > > > > > Well, this is in the direction from kernel to userspace and what Matthew > > > > suggests would just make kernel posssibly store non-zero value in *timer_hi > > > > without setting FS_DQ_BIGTIME flag (for negative values of timer). I don't > > > > think it would break anything but I agree the complication isn't big so > > > > let's be careful and only set *timer_hi to non-zero if FS_DQ_BIGTIME is > > > > set. > > > > > > OK, thanks. I must admit, I'd completely forgotten about the negative > > > values ... and the manpage (quotactl(2)) could be clearer: > > > > > > int32_t d_itimer; /* Zero if within inode limits */ > > > /* If not, we refuse service */ > > > int32_t d_btimer; /* Similar to above; for > > > disk blocks */ > > > > > > I can't tell if this is a relative time or seconds since 1970 since we > > > exceeded the quota. > > > > In fact, it is time (in seconds since epoch) when softlimit becomes > > enforced (i.e. when you cannot write any more blocks/inodes if you are > > still over softlimit). I agree the comment incomplete at best. Something > > like attached patch? > > > > Honza > > -- > > Jan Kara > > SUSE Labs, CR > > > From 3e3260a337ff444e3a1396834b20da63d7b87ccb Mon Sep 17 00:00:00 2001 > > From: Jan Kara > > Date: Wed, 9 Sep 2020 15:54:46 +0200 > > Subject: [PATCH] quota: Expand comment describing d_itimer > > > > Expand comment describing d_itimer in struct fs_disk_quota. > > > > Reported-by: Matthew Wilcox > > Signed-off-by: Jan Kara > > --- > > include/uapi/linux/dqblk_xfs.h | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/include/uapi/linux/dqblk_xfs.h b/include/uapi/linux/dqblk_xfs.h > > index 16d73f54376d..e4b3fd7f0a50 100644 > > --- a/include/uapi/linux/dqblk_xfs.h > > +++ b/include/uapi/linux/dqblk_xfs.h > > @@ -62,7 +62,8 @@ typedef struct fs_disk_quota { > > __u64 d_bcount; /* # disk blocks owned by the user */ > > __u64 d_icount; /* # inodes owned by the user */ > > __s32 d_itimer; /* zero if within inode limits */ > > - /* if not, we refuse service */ > > + /* if not, we refuse service at this > > + * time (in seconds since epoch) */ > > "since Unix epoch"? > > Otherwise looks fine to me... Thanks for having a look. Patch updated and added to my tree. Honza -- Jan Kara SUSE Labs, CR