Re: [GIT PULL REQUEST] late md/raid1 bug fixes for 3.17

[NeilBrown <neilb@suse.de>]

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On Fri, 26 Sep 2014 14:08:08 -0500 BillStuff <billstuff2001@sbcglobal.net>
wrote:

> On 09/23/2014 09:18 PM, NeilBrown wrote:
> [snip]
> >        md/raid1: intialise start_next_window for READ case to avoid hang
> >
> 
> Neil, I've been testing these patches for the past week or two to see if 
> they help a raid1 "check" hang I had.
> 
> They seem to help, but I noticed the above patch is different from what 
> you originally sent on the list.
> 
> The original patch has an extra chunk:
> 
> @@ -1444,6 +1445,7 @@ read_again:
> 		r1_bio->state = 0;
> 		r1_bio->mddev = mddev;
> 		r1_bio->sector = bio->bi_iter.bi_sector + sectors_handled;
> +		start_next_window = wait_barrier(conf, bio);
> 		goto retry_write;
> 	}
> 
> Is the correct patch with or without this chunk?
> 
> Thanks,
> Bill

That hunk was wrong.
This new r1_bio is attached to the previous one and they all complete (and
particularly all "allow_barrier") as a unit.  So only one wait_barrier is
needed.

That chunk only has any affect if you have a bad-blocks list with bad blocks
in it, and try to write a range of the device which includes the bad block.

Thanks,
NeilBrown

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