From: NeilBrown <neilb@suse.de>
To: "Kwolek, Adam" <adam.kwolek@intel.com>
Cc: "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"Ciechanowski, Ed" <ed.ciechanowski@intel.com>,
"Labun, Marcin" <Marcin.Labun@intel.com>
Subject: Re: [PATCH 13/14] Check if md allows to control reshape
Date: Wed, 21 Sep 2011 17:51:14 +1000 [thread overview]
Message-ID: <20110921175114.0dc9042b@notabene.brown> (raw)
In-Reply-To: <79556383A0E1384DB3A3903742AAC04A0324E2@IRSMSX101.ger.corp.intel.com>
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On Wed, 21 Sep 2011 07:31:48 +0000 "Kwolek, Adam" <adam.kwolek@intel.com>
wrote:
>
>
> > -----Original Message-----
> > From: NeilBrown [mailto:neilb@suse.de]
> > Sent: Wednesday, September 21, 2011 4:34 AM
> > To: Kwolek, Adam
> > Cc: linux-raid@vger.kernel.org; Ciechanowski, Ed; Labun, Marcin
> > Subject: Re: [PATCH 13/14] Check if md allows to control reshape
> >
> > On Fri, 16 Sep 2011 13:55:25 +0200 Adam Kwolek <adam.kwolek@intel.com>
> > wrote:
> >
> > > It can happen that there is no mdadm in memory and 'max' was already
> > > set to sync_max. Such array cannot be put under check pointing control
> > > again.
> >
> > Again I don't understand what you are trying to guard against.
> > If resync_max is 'max', then the kernel is allowed to fun reshape to
> > completion without any help from mdadm. If mdadm needs to monitor
> > things it always sets resync_max to a smaller value.
> >
> > Confused.
>
> In my opinion running reshape continuation on array that is allowed to freely reshape to the end
> is race condition (another mdadm or user via sysfs manage this array already).
> We can tell nothing about restart point (read from metadata) when md runs with reshape already.
> I think we should not allow to attach mdadm to such reshape process.
>
> I think this guard is required.
>
I see what your point is now. I was just a bit confused by the message that
is printed which seems to say something different.
If we need to guard something here, we need to guard against a lot more than
just sync_max == "max". We need to guard against another mdadm process
monitoring the array (the extra .pid file I mentioned) and also if sync_max
has any value larger than what we would expect from the metadata.
So a test that rejects an attempt to continue reshape on an array where
sync_max is not the correct value makes sense. Just testing for "max"
doesn't.
Thanks,
NeilBrown
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next prev parent reply other threads:[~2011-09-21 7:51 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-16 11:53 [PATCH 00/14] Series short description Adam Kwolek
2011-09-16 11:53 ` [PATCH 01/14] Stop array reshape when mounted initramfs is detected Adam Kwolek
2011-09-19 10:42 ` NeilBrown
2011-09-19 11:14 ` Kwolek, Adam
2011-09-16 11:54 ` [PATCH 02/14] Stop container reshape while using initramfs Adam Kwolek
2011-09-16 11:54 ` [PATCH 03/14] FIX: Do not unblock array accidentally Adam Kwolek
2011-09-21 2:19 ` NeilBrown
2011-09-16 11:54 ` [PATCH 04/14] Add continue option to grow command Adam Kwolek
2011-09-21 2:22 ` NeilBrown
2011-09-21 7:47 ` Kwolek, Adam
2011-09-16 11:54 ` [PATCH 05/14] Add Grow_continue_command Adam Kwolek
2011-09-16 11:54 ` [PATCH 06/14] Check and run mdmon Adam Kwolek
2011-09-16 11:54 ` [PATCH 07/14] FIX: Memory leak during Assembly Adam Kwolek
2011-09-21 2:23 ` NeilBrown
2011-09-16 11:54 ` [PATCH 08/14] Check if reshape can be restarted Adam Kwolek
2011-09-21 2:27 ` NeilBrown
2011-09-21 7:45 ` Kwolek, Adam
2011-09-16 11:54 ` [PATCH 09/14] Move restore backup code to function Adam Kwolek
2011-09-21 2:28 ` NeilBrown
2011-09-16 11:55 ` [PATCH 10/14] Perform restore backup for reshape continuation Adam Kwolek
2011-09-21 2:29 ` NeilBrown
2011-09-21 7:35 ` Kwolek, Adam
2011-09-16 11:55 ` [PATCH 11/14] Add possibility to restart reshape for native metadata Adam Kwolek
2011-09-16 11:55 ` [PATCH 12/14] Early reshape backup verification Adam Kwolek
2011-09-21 2:31 ` NeilBrown
2011-09-21 7:33 ` Kwolek, Adam
2011-09-16 11:55 ` [PATCH 13/14] Check if md allows to control reshape Adam Kwolek
2011-09-21 2:33 ` NeilBrown
2011-09-21 7:31 ` Kwolek, Adam
2011-09-21 7:51 ` NeilBrown [this message]
2011-09-16 11:55 ` [PATCH 14/14] Manual update for --continue option Adam Kwolek
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