From: Mike Snitzer <snitzer@redhat.com>
To: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com, lvm-devel@redhat.com
Subject: Re: dm snapshot: allow live exception store handover between tables
Date: Fri, 6 Nov 2009 15:37:43 -0500 [thread overview]
Message-ID: <20091106203742.GF13427@redhat.com> (raw)
In-Reply-To: <20091106200739.GU13375@agk-dp.fab.redhat.com>
On Fri, Nov 06 2009 at 3:07pm -0500,
Alasdair G Kergon <agk@redhat.com> wrote:
> On Fri, Nov 06, 2009 at 02:54:30PM -0500, Mike Snitzer wrote:
> > Alasdair G Kergon <agk@redhat.com> wrote:
> > > On Fri, Nov 06, 2009 at 02:26:21PM -0500, Mike Snitzer wrote:
> > > > OK, actually in practice 'lvchange --refresh' is:
> > > > old->suspend
> > > > new->ctr
> > > Those two need to be swapped.
> > Why do they _need_ to be swapped?
>
> old->suspend stops I/O to the device.
> new->ctr allocates memory and in a bad case might lead to waiting for I/O to
> the device we've just suspended.
Ouch, yes good point.
So I'll put the following on my lvm2 TODO:
- establish a REFRESH flag (set on lvchange --refresh)
- if REFRESH is set then _lv_suspend() will treat the live metadata as
if it is precommitted metadata
Mike
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WARNING: multiple messages have this Message-ID (diff)
From: Mike Snitzer <snitzer@redhat.com>
To: lvm-devel@redhat.com
Subject: Re: dm snapshot: allow live exception store handover between tables
Date: Fri, 6 Nov 2009 15:37:43 -0500 [thread overview]
Message-ID: <20091106203742.GF13427@redhat.com> (raw)
In-Reply-To: <20091106200739.GU13375@agk-dp.fab.redhat.com>
On Fri, Nov 06 2009 at 3:07pm -0500,
Alasdair G Kergon <agk@redhat.com> wrote:
> On Fri, Nov 06, 2009 at 02:54:30PM -0500, Mike Snitzer wrote:
> > Alasdair G Kergon <agk@redhat.com> wrote:
> > > On Fri, Nov 06, 2009 at 02:26:21PM -0500, Mike Snitzer wrote:
> > > > OK, actually in practice 'lvchange --refresh' is:
> > > > old->suspend
> > > > new->ctr
> > > Those two need to be swapped.
> > Why do they _need_ to be swapped?
>
> old->suspend stops I/O to the device.
> new->ctr allocates memory and in a bad case might lead to waiting for I/O to
> the device we've just suspended.
Ouch, yes good point.
So I'll put the following on my lvm2 TODO:
- establish a REFRESH flag (set on lvchange --refresh)
- if REFRESH is set then _lv_suspend() will treat the live metadata as
if it is precommitted metadata
Mike
next prev parent reply other threads:[~2009-11-06 20:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-06 18:40 [PATCH] dm snapshot: allow live exception store handover between tables Mike Snitzer
2009-11-06 18:46 ` Mike Snitzer
2009-11-06 19:26 ` Mike Snitzer
2009-11-06 19:41 ` Alasdair G Kergon
2009-11-06 19:54 ` Mike Snitzer
2009-11-06 20:07 ` Alasdair G Kergon
2009-11-06 20:37 ` Mike Snitzer [this message]
2009-11-06 20:37 ` Mike Snitzer
2009-11-11 3:26 ` [PATCH] " Mikulas Patocka
2009-11-11 12:41 ` Mike Snitzer
2009-11-11 20:46 ` Mikulas Patocka
2009-11-11 23:35 ` Mike Snitzer
2009-11-11 23:47 ` Mikulas Patocka
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