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From: "Michal Piotrowski" <michal.k.k.piotrowski@gmail.com>
To: tglx@linutronix.de
Cc: "Ingo Molnar" <mingo@elte.hu>, "Andrew Morton" <akpm@osdl.org>,
	"Neil Brown" <neilb@cse.unsw.edu.au>,
	LKML <linux-kernel@vger.kernel.org>,
	"Jens Axboe" <jens.axboe@oracle.com>
Subject: Re: [patch-mm] Workaround for RAID breakage
Date: Mon, 15 Jan 2007 21:17:30 +0100	[thread overview]
Message-ID: <6bffcb0e0701151217w3b20d24q9df0a54f0a65b99@mail.gmail.com> (raw)
In-Reply-To: <1168884220.2941.144.camel@localhost.localdomain>

On 15/01/07, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Mon, 2007-01-15 at 09:08 +0100, Thomas Gleixner wrote:
> > > Thomas saw something similar yesterday and he the partial results that
> > > git.block (between rc2-mm1 and rc4-mm1) breaks certain disk drivers or
> > > filesystems drivers. For me it worked fine, so it must be only on some
> > > combinations. The changes to ll_rw_block.c look quite extensive.
> >
> > Yes. Jens Axboe confirmed yesterday that the plug changes broke RAID.
>
> I tracked this down and found two problems:
>
> - The new plug/unplug code does not check for underruns. That allows the
> plug count (ioc->plugged) to become negative. This gets triggered from
> various places.
>
> AFAICS this is intentional to avoid checks all over the place, but the
> underflow check is missing. All we need to do is make sure, that in case
> of ioc->plugged == 0 we return early and bug, if there is either a queue
> plugged in or the plugged_list is not empty.
>
> Jens ?
>
> - The raid1 code has no bitmap set in remount r/w. So the
> pending_bio_list gets not processed for quite a time. The workaround is
> to kick mddev->thread, so the list is processed. Not sure about that.
>
> Neil ?
>
> At least it boots and behaves normal.

Yes, it works fine now. Thanks!

>         tglx

Regards,
Michal

-- 
Michal K. K. Piotrowski
LTG - Linux Testers Group
(http://www.stardust.webpages.pl/ltg/)

  reply	other threads:[~2007-01-15 20:17 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-12 13:33 2.6.20-rc4-mm1 md problem Michal Piotrowski
2007-01-12 15:52 ` Rafael J. Wysocki
2007-01-12 17:40   ` Michal Piotrowski
2007-01-12 17:58     ` Michal Piotrowski
2007-01-14 21:59       ` Jens Axboe
2007-01-15  7:17 ` Ingo Molnar
2007-01-15  8:08   ` Thomas Gleixner
2007-01-15 18:03     ` [patch-mm] Workaround for RAID breakage Thomas Gleixner
2007-01-15 20:17       ` Michal Piotrowski [this message]
2007-01-16  0:41       ` Jens Axboe
2007-01-16  8:27         ` Thomas Gleixner
2007-01-16 10:07           ` Jens Axboe

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