Re: RAID-6: help wanted

On Saturday October 23, hpa@zytor.com wrote:

Okay, it's well overdue to do this...

There is currently a data-corruption bug in the RAID-6 md layer
(raid6main.c).  I have so far not been successful in locating it,
although it is easily reproducible, thanks to a set of scripts by Jim
Paris.  I suspect it is a race condition between raid6d and the rest
of the kernel.

Does this fix the problem?
It is definitely wrong as it is.

NeilBrown



 ----------- Diffstat output ------------
 ./drivers/md/raid6main.c |    1 -
 1 files changed, 1 deletion(-)

diff ./drivers/md/raid6main.c~current~ ./drivers/md/raid6main.c

--- ./drivers/md/raid6main.c~current~	2004-10-22 16:14:11.000000000 +1000
+++ ./drivers/md/raid6main.c	2004-10-25 15:39:36.000000000 +1000

@@ -734,7 +734,6 @@ static void compute_parity(struct stripe
 	case READ_MODIFY_WRITE:
 		BUG();		/* READ_MODIFY_WRITE N/A for RAID-6 */
 	case RECONSTRUCT_WRITE:
-	case UPDATE_PARITY:	/* Is this right? */
 		for (i= disks; i-- ;)
 			if ( i != pd_idx && i != qd_idx && sh->dev[i].towrite ) {
 				chosen = sh->dev[i].towrite;

Does this fix the problem?
It is definitely wrong as it is.

..

 	case RECONSTRUCT_WRITE:
-	case UPDATE_PARITY:	/* Is this right? */

No, it does not.  Same sort of corruption with that line removed.

-jim