linux-kernel - Re: [RFC][PATCH] md: avoid fullsync if a faulty member missed a dirty transition

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Date:	Fri, 9 May 2008 01:26:58 -0400
From:	"Mike Snitzer" <snitzer@...il.com>
To:	"Neil Brown" <neilb@...e.de>
Cc:	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	paul.clements@...eleye.com
Subject: Re: [RFC][PATCH] md: avoid fullsync if a faulty member missed a dirty transition

On Fri, May 9, 2008 at 1:08 AM, Mike Snitzer <snitzer@...il.com> wrote:
> On Fri, May 9, 2008 at 12:42 AM, Mike Snitzer <snitzer@...il.com> wrote:
>
>  >  Was I supposed to use this latest patch in combination with your
>  >  previous patch (to validate_super)?  Because you'll note that with
>  >  your most recent patch nbd0's events (ev1) is still one less than
>  >  sdq's events_cleared.  As such the validate_super's "ev1 <
>  >  mddev->bitmap->events_cleared" check triggers a full rebuild.
>  >
>  >  The kernel log shows:
>  >  md: md0 stopped.
>  >  md: bind<nbd0>
>  >  md: bind<sdq>
>  >  md: kicking non-fresh nbd0 from array!
>  >  md: unbind<nbd0>
>  >  md: export_rdev(nbd0)
>  >  raid1: raid set md0 active with 1 out of 2 mirrors
>  >  md0: bitmap initialized from disk: read 13/13 pages, set 0 bits, status: 0
>
>  Also, no bits were set in the bitmap.. bitmap_create() must've thrown
>  away the dirty bits.  Given your latest patch, does bitmap_create()'s
>  "bitmap->events_cleared == mddev->events" check need to be adjusted?
>
>  Before I would always see something like:
>  md0: bitmap initialized from disk: read 13/13 pages, set 1 bits, status: 0

Actually, the mdadm -X output I provided shows that sdq's bitmap
doesn't have any bits set:
Bitmap : 409600 bits (chunks), 0 dirty (0.0%)

This can't be right, considering nbd0 was marked faulty and the array
became degraded, can it?
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