Re: 2.6.15-mm2

[Jens Axboe]

On Thu, Jan 12 2006, Neil Brown wrote:
> On Wednesday January 11, axboe@xxxxxxx wrote:
> > 
> > Then the barrier changes from git2 -> git3 should not have anything to
> > do with it. Strange... I guess you should try the git bisect method to
> > narrow it down.
> 
> Not true, though you seem to have already figured that out.
> 
> md uses barrier writes when writing the superblock.  This is partly
> because it seems like a good idea, but largely to test if barrier
> writes are going to work on the component devices.  If any device
> claims not to support barriers, then raid1 will claim not to support
> barriers.
> 
> And the strange hang happens while md is trying to update the
> superblock.

Yeah that's what I found out later on in the thread, indeed killing that
barrier write made the problem disappear.

-- 
Jens Axboe

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