From: "Benjamin Marzinski" <bmarzins@redhat.com>
To: Hannes Reinecke <hare@suse.de>
Cc: dm-devel@redhat.com
Subject: Re: [PATCH 09/10] add disable_changed_wwids option
Date: Fri, 4 Nov 2016 10:32:40 -0500 [thread overview]
Message-ID: <20161104153240.GF1972@octiron.msp.redhat.com> (raw)
In-Reply-To: <55d8a18c-5c35-5d84-3b4a-557075aaa69d@suse.de>
On Sun, Oct 30, 2016 at 02:54:14PM +0100, Hannes Reinecke wrote:
> On 10/29/2016 04:55 AM, Benjamin Marzinski wrote:
> >If a LUN on a storage device gets remapped while in-use by multipath,
> >it's possible that the multipath device will continue writing to this
> >new LUN, causing corruption. This is not multipath's fault (users
> >should go remapping in-use LUNs), but it's possible for multipath to
> >detect this and disable IO to the device. If disable_changed_wwids
> >is set to "yes", multipathd will detect when a LUN changes wwids when it
> >receives the uevent for this, and will disable access to the device
> >until the LUN is mapped back.
> >
> >Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> >---
> > libmultipath/config.c | 1 +
> > libmultipath/config.h | 1 +
> > libmultipath/defaults.h | 1 +
> > libmultipath/dict.c | 4 ++++
> > libmultipath/discovery.c | 15 +++++++--------
> > libmultipath/discovery.h | 1 +
> > libmultipath/structs.h | 1 +
> > multipathd/main.c | 32 ++++++++++++++++++++++++++++++++
> > 8 files changed, 48 insertions(+), 8 deletions(-)
> >
> Hmm. Not sure if the really buys us anything. By the time we process the
> uevent it might already be too late, and I/O might already have been written
> to that device.
> I do agree on the warning, though.
I have taken some pains to try to explain this short-coming to the
customer who filed this bugzilla. The good news is that in practice, the
device ususally goes down when you are remapping the LUN, and you
disable the device before it ever comes back. In my testing, I wasn't
able to actually ever write to the wrong device with
disable_changed_wwids enabled, but I do agree that you have the
potential to race here.
-Ben
>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke zSeries & Storage
> hare@suse.de +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2016-11-04 15:32 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-29 2:55 [PATCH 00/10] misc. multipath patches Benjamin Marzinski
2016-10-29 2:55 ` [PATCH 01/10] libmultipath: add skip_kpartx option Benjamin Marzinski
2016-10-30 13:42 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 02/10] kpartx.rules: respect skip_kpartx flag Benjamin Marzinski
2016-10-30 13:42 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 03/10] do not allow in-use path to change wwid Benjamin Marzinski
2016-10-30 13:45 ` Hannes Reinecke
2016-10-31 14:30 ` Benjamin Marzinski
2016-10-29 2:55 ` [PATCH 04/10] multipathd: add "map failures" format wildcard Benjamin Marzinski
2016-10-30 13:45 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 05/10] mpath: don't wait for udev if all paths are down Benjamin Marzinski
2016-10-30 13:46 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 06/10] multipath: set cookie before using it Benjamin Marzinski
2016-10-30 13:46 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 07/10] recover from errors in multipathd startup Benjamin Marzinski
2016-10-30 13:47 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 08/10] fix INIT_REQUESTED_UDEV code Benjamin Marzinski
2016-10-30 13:48 ` Hannes Reinecke
2016-10-29 2:55 ` [PATCH 09/10] add disable_changed_wwids option Benjamin Marzinski
2016-10-30 13:54 ` Hannes Reinecke
2016-11-04 15:32 ` Benjamin Marzinski [this message]
2017-02-28 12:27 ` Zhangguanghui
2016-11-06 0:03 ` Xose Vazquez Perez
2016-11-07 14:47 ` Benjamin Marzinski
2016-10-29 2:55 ` [PATCH 10/10] set retrigger_tries to 0 for multipath Benjamin Marzinski
2016-10-30 13:54 ` Hannes Reinecke
2016-12-06 15:11 ` Xose Vazquez Perez
2016-12-06 15:22 ` Benjamin Marzinski
2017-04-25 14:07 ` Xose Vazquez Perez
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