Re: possible bug - bitmap dirty pages status

[NeilBrown <neilb@suse.de>]

On Thu, 1 Sep 2011 00:16:36 +0400 CoolCold <coolthecold@gmail.com> wrote:

> On Wed, Aug 31, 2011 at 6:08 PM, Paul Clements
> <paul.clements@us.sios.com> wrote:
> > On Wed, Aug 31, 2011 at 9:16 AM, CoolCold <coolthecold@gmail.com> wrote:
> >
> >>          Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
> >>
> >> And 16/22 lasts for 4 days.
> >
> > So if you force another resync, does it change/clear up?
> >
> > If you unmount/stop all activity does it change?
> Well, this server is in production now, may be i'll be able to do
> array stop/start later..right now i've set "cat /proc/mdstat" every
> minute, and bitmap examine every minute, will see later is it changing
> or not.
> 

I spent altogether too long staring at the code and I can see various things
that could be usefully tidied but but nothing that really explains what you
have.

If there was no write activity to the array at all I can just see how that
last bits to be set might not get cleared, but as soon as another write
happened all those old bits would get cleared pretty quickly.  And it seems
unlikely that there have been no writes for over 4 days (???).

I don't think having these bits here is harmful and it would be easy to get
rid of them by using "mdadm --grow" to remove and then re-add the bitmap,
but I wish I knew what caused it...

I clean up the little issues I found in mainline and hope there isn't a
larger problem luking behind all this..

NeilBrown
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