Re: Raid1 doesn't balance under high load [patch]

On Monday June 14, miquels@cistron.nl wrote:

On 2004.06.11 03:26, Neil Brown wrote:

quoted

On Thursday June 10, miquels@cistron.nl wrote:

quoted

The problem is in raid1.c:read_balance().

Now if you write to the array, the array is marked not in sync by
md.c:md_write_start(). conf->next_resync is initialized to zero, so
that means read balancing doesn't work anymore.

Yes, you are right.  Thanks.
Your patch is close, but not quite right (though it would be hard to
cause it to actually fail).
I think it patch is more correct.  I would appreciate it if you could
confirm that it works for you.

It doesn't because of a small typo:

quoted

diff ./drivers/md/raid1.c~current~ ./drivers/md/raid1.c

--- ./drivers/md/raid1.c~current~	2004-06-11 11:20:34.000000000 +1000
+++ ./drivers/md/raid1.c	2004-06-11 11:21:57.000000000 +1000

@@ -375,7 +375,8 @@ static int read_balance(conf_t *conf, st
 	 * device if no resync is going on, or below the resync window.
 	 * We take the first readable disk when above the resync window.
 	 */
-	if (!conf->mddev->in_sync && (this_sector + sectors >= conf->next_resync)) {
+	if (!conf->mddev->recovery_cp < MaxSector &&
+	    (this_sector + sectors >= conf->next_resync)) {
 		/* make sure that disk is operational */
 		new_disk = 0;

I think that should read:


-	if (!conf->mddev->in_sync && (this_sector + sectors >= conf->next_resync)) {
+	if (conf->mddev->recovery_cp < MaxSector &&
+	    this_sector + sectors >= conf->next_resync) {

and then it works.

Yes.... thanks for the fix and thanks for testing it.  I appreciate
it.
I'll send the correct patch off to Andrew Morton.

NeilBrown