[dm-devel] dm-multipath: Accept failed paths for multipath maps
hare at suse.de
Mon Jul 21 06:05:48 UTC 2014
On 07/18/2014 06:15 PM, Mike Snitzer wrote:
> On Fri, Jul 18 2014 at 12:04pm -0400,
> Mike Snitzer <snitzer at redhat.com> wrote:
>> On Fri, Jul 18 2014 at 2:00am -0400,
>> Hannes Reinecke <hare at suse.de> wrote:
>>> Will be sending some update once the testing is done.
>> OK. The stronger case that can be made for the stability of this change
>> (no missing checks for dev->bdev, etc) the better.
>> I did just do some basic testing, of both dm-mpath and dm-thinp, seems
>> fine. The DM core changes really are simple (just some extra negative
>> checks that won't ever apply for the normal case -- where "normal case"
>> is DM targets that use dm_get_device rather than __dm_get_device, and
>> had to add a dev_t to struct dm_dev).
> BTW, I noticed one thing that I didn't think of as logical fallout, but
> it makes sense: if configure multipthd to not use find_multipaths then
> multipathd will successfully push down an mpath table that covers the
> system disk (sda) -- but mpatha isn't able to dm_get_device:
> # lsblk /dev/sda /dev/mapper/mpatha
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
> sda 8:0 0 930.5G 0 disk
> ├─sda1 8:1 0 500M 0 part /boot
> └─sda2 8:2 0 930G 0 part
> ├─rhel_rhel--storage--02-swap 253:0 0 4G 0 lvm [SWAP]
> └─rhel_rhel--storage--02-root 253:1 0 350G 0 lvm /
> mpatha 253:6 0 930.5G 0 mpath
> # multipath -ll mpatha
> mpatha (36003005700ec189015d42b92237a76d1) dm-6 LSI ,RAID 5/6 SAS 6G
> size=930G features='0' hwhandler='0' wp=rw
> `-+- policy='service-time 0' prio=1 status=enabled
> `- 0:2:0:0 sda 8:0 failed ready running
> And multipathd keeps failing to reinstate_path:
> [ 1906.647322] device-mapper: multipath: message: error getting device 8:0
> [ 1912.652652] device-mapper: multipath: message: error getting device 8:0
> [ 1918.657949] device-mapper: multipath: message: error getting device 8:0
> [ 1924.664118] device-mapper: multipath: message: error getting device 8:0
> [ 1930.669635] device-mapper: multipath: message: error getting device 8:0
> Again, this all makes sense... but certainly shows that blacklisting the
> relevant devices is a must.
We have been taking the approach that starting multipath will
attempt to take over _any_ (eligible) device.
So this error would constitute a misconfiguration from our POV.
Either the device needs to be blacklisted or the process accessing
the device needs to be reconfigured to use multipathing.
Dr. Hannes Reinecke zSeries & Storage
hare at 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)
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