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Re: [PATCH 0/9] CRC support for superblock, ag headers, log and btree bl

To: Christoph Hellwig <hch@xxxxxx>
Subject: Re: [PATCH 0/9] CRC support for superblock, ag headers, log and btree blocks
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 26 Sep 2008 09:50:30 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20080925225613.GA9822@xxxxxx>
Mail-followup-to: Christoph Hellwig <hch@xxxxxx>, xfs@xxxxxxxxxxx
References: <20080925225613.GA9822@xxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Fri, Sep 26, 2008 at 12:56:13AM +0200, Christoph Hellwig wrote:
> Here's an updated crc series for various metadata structures.  We're still
> looking at the magic number in the log recovery case because getting down
> a buffer type for the other structures wasn't quite as easy as for the
> btree block.  I'll probably look into that again once we're done with all
> data structures.

FWIW, I note that you haven't done anything with the AGFL yet. I was
considering 2 different approaches. The first was to put the CRC for
the AGFL into the AGF so that the internals of the AGFL do not change.
However, that means we have interesting synchronisation problems
with the CRC, so I don't think that will fly.

The other option was to reduce the number of slots in the AGFL by
one and use the last slot to hold the CRC. I think that is OK to do;
the AGFL can change size with different secotr size support, so I
don't see this being a big problem. Nor do I think that we ever fill
the AGFL up to it's full 128 slots during any transaction, so
reducing the size by one should be safe.


Dave Chinner

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