Re: Accounting changes


On Thu, 19 Apr 2007, Robert Watson wrote:

If we're willing to assume architectures can only read their own accounting files (the status quo), the above argument doesn't really make sense. You end up with a series of versions of "struct acct", and that code is architecture-neutral. Thinking about it more, I'm not sure a per file header is even required or desired (as I had previously suggested), simply a per-record versioning scheme, allowing a reboot onto a new kernel to continue to write to the existing accounting data. Read the first 16 bytes, if the first byte is non-0 then it's the original "struct acct" layout, and otherwise the second byte is the version number to use. Or in the interests of forward compatibility, include a length parameter in another 16 bytes so you can skip over records if necessary in order to allow the kernel to move back and forward across file versions if there's a problem after the upgrade.

s/16 bytes/16 bits/ was intended in the above. :-)

Robert N M Watson
Computer Laboratory
University of Cambridge
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