On Tue, Jan 29, 2013 at 09:22:44AM +1100, NeilBrown wrote:
>
> From: Jonathan Brassow <jbras...@redhat.com>
> Subject: [PATCH] DM-RAID: Fix RAID10's check for sufficient redundancy
>
> commit 55ebbb59c1c6eb1b040f62b8c4ae0b724de6e55a upstream.
>
> Before attempting to activate a RAID array, it is checked for sufficient
> redundancy. That is, we make sure that there are not too many failed
> devices - or devices specified for rebuild - to undermine our ability to
> activate the array. The current code performs this check twice - once to
> ensure there were not too many devices specified for rebuild by the user
> ('validate_rebuild_devices') and again after possibly experiencing a failure
> to read the superblock ('analyse_superblocks'). Neither of these checks are
> sufficient. The first check is done properly but with insufficient
> information about the possible failure state of the devices to make a good
> determination if the array can be activated. The second check is simply
> done wrong in the case of RAID10 because it doesn't account for the
> independence of the stripes (i.e. mirror sets). The solution is to use the
> properly written check ('validate_rebuild_devices'), but perform the check
> after the superblocks have been read and we know which devices have failed.
> This gives us one check instead of two and performs it in a location where
> it can be done right.
>
> Only RAID10 was affected and it was affected in the following ways:
> - the code did not properly catch the condition where a user specified
> a device for rebuild that already had a failed device in the same mirror
> set. (This condition would, however, be caught at a deeper level in MD.)
> - the code triggers a false positive and denies activation when devices in
> independent mirror sets have failed - counting the failures as though they
> were all in the same set.
>
> The most likely place this error was introduced (or this patch should have
> been included) is in commit 4ec1e369 - first introduced in v3.7-rc1.
> Consequently this fix should also go in v3.7.y, however there is a
> small conflict on the .version in raid_target, so this is a separate patch
> for -stable.
>
> Signed-off-by: Jonathan Brassow <jbras...@redhat.com>
> Signed-off-by: NeilBrown <ne...@suse.de>
I've applied this, but I now get the following build warning. Are you
sure it's ok?
drivers/md/dm-raid.c: In function ‘raid_ctr’:
drivers/md/dm-raid.c:397:53: warning: ‘rebuilds_per_group’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
drivers/md/dm-raid.c:352:11: note: ‘rebuilds_per_group’ was declared here
thanks,
greg k-h
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