From: Alasdair G Kergon <agk@redhat.com>
To: Petr Rockai <prockai@redhat.com>
Cc: lvm-devel@redhat.com,
LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [PATCH] Re: [linux-lvm] Clarifications wanted about locking process
Date: Fri, 14 Aug 2009 18:12:34 +0100 [thread overview]
Message-ID: <20090814171234.GA7033@agk-dp.fab.redhat.com> (raw)
In-Reply-To: <87my62sjie.fsf_-_@twilight.int.mornfall.net.>
On Fri, Aug 14, 2009 at 01:49:13PM +0200, Peter Rockai wrote:
> The attached patch should fix the issue. I believe that taking a global write
> lock while scanning is a mistake (I consulted with Milan, he says it only
> serves to enable metadata caching).
Well only one instance of pvscan and/or vgscan is allowed to run at once,
and IIRC VG_GLOBAL with LCK_VG_WRITE is what enforces that.
IOW The write lock is correct.
See the comment in toollib:
/*
* If the lock_type is LCK_VG_READ (used only in reporting commands),
* we lock VG_GLOBAL to enable use of metadata cache.
* This can pause alongide pvscan or vgscan process for a while.
*/
I don't want to touch the VG_GLOBAL logic here at this stage.
Are there any problems with just excluding an already-held VG_GLOBAL from the
test that generates this error message?
Alasdair
prev parent reply other threads:[~2009-08-14 17:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-14 0:13 [linux-lvm] Clarifications wanted about locking process Eric Bélanger
2009-08-14 8:24 ` Alasdair G Kergon
2009-08-14 11:49 ` [PATCH] " Petr Rockai
2009-08-14 17:12 ` Alasdair G Kergon [this message]
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