LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jens Axboe <jens.axboe@oracle.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>,
	Michal Piotrowski <michal.k.k.piotrowski@gmail.com>,
	Andrew Morton <akpm@osdl.org>, Neil Brown <neilb@cse.unsw.edu.au>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [patch-mm] Workaround for RAID breakage
Date: Tue, 16 Jan 2007 11:41:36 +1100	[thread overview]
Message-ID: <20070116004136.GF4067@kernel.dk> (raw)
In-Reply-To: <1168884220.2941.144.camel@localhost.localdomain>

On Mon, Jan 15 2007, Thomas Gleixner 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 ?

It should not go negative, that would be a bug elsewhere. So it's
interesting if it does, we should definitely put a WARN_ON() check in
there for that.

> - 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 ?

Super, thanks for that Thomas! I'll merge it in the plug branch.

-- 
Jens Axboe


  parent reply	other threads:[~2007-01-16  0:41 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
2007-01-16  0:41       ` Jens Axboe [this message]
2007-01-16  8:27         ` Thomas Gleixner
2007-01-16 10:07           ` Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20070116004136.GF4067@kernel.dk \
    --to=jens.axboe@oracle.com \
    --cc=akpm@osdl.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=michal.k.k.piotrowski@gmail.com \
    --cc=mingo@elte.hu \
    --cc=neilb@cse.unsw.edu.au \
    --cc=tglx@linutronix.de \
    --subject='Re: [patch-mm] Workaround for RAID breakage' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).