Re: [PATCH] md: fix raid5 'repair' operations

[Michael Tokarev <mjt@tls.msk.ru>]

Neil Brown wrote:
> On Thursday May 1, dan.j.williams@intel.com wrote:
>> commit bd2ab67030e9116f1e4aae1289220255412b37fd "md: close a livelock
>> window in handle_parity_checks5" introduced a bug in handling 'repair'
>> operations.  After a repair operation completes we clear the state bits
>> tracking this operation.  However, they are cleared too early and this
>> results in the code deciding to re-run the parity check operation.  Since
>> we have done the repair in memory the second check does not find a mismatch
>> and thus does not do a writeback.
> 
> yes....
> I must admit that I find that code fairly hard to make sense of, but I
> can see how it was failing before and how this fixes it, and testing
> confirms that, so I suspect it is right.
> 
> I cannot help feeling that there must be some way to simplify all
> those .pending and .complete bits and make it somewhat clearer, but I
> haven't been able to figure out how :-(
> 
> So: Acked-by: NeilBrown <neilb@suse.de>
> 
> I'm heading for a weekend, but feel free to send this to akpm.

Hmm.  Should this be sent to stable- as well?  I were just biten by
this very bug here, and after applying the patch and rebooting the
problem went away...  2.6.25.0 here.

/mjt