Re: large ufs2 partitions and 'df'

From: Kirk McKusick <mckusick_at_beastie.mckusick.com>
Date: Mon, 12 May 2003 12:33:17 -0700
	Date: Mon, 12 May 2003 07:53:49 -0700
	From: Terry Lambert <tlambert2_at_mindspring.com>
	To: Kirk McKusick <mckusick_at_mckusick.com>
	CC: Julian Elischer <julian_at_elischer.org>, freebsd-current_at_freebsd.org
	Subject: Re: large ufs2 partitions and 'df'
	X-ASK-Info: Whitelist match

	Kirk McKusick wrote:
	> Julian Elisher wrote:
	> > I think that swithing to a new syscall with a fixed structure
	> > and using the rules you mention above to populate the structure in
	> > an ostatfs call might be the best answer.
	> > Old binaries probably only need to know that there is > X blocks
	> > free and not necessarily the correct number.
	> > New binaries can use the new syscall.
	> 
	> So right you are. It would be possible to get the space by nibbling
	> a bit more space from MNAMELEN, but at some point we need to just bite
	> the bullet and define a new structure. I am leaning towards believing
	> that time is now. If we do define a new structure, I would like to
	> clean up the existing one a bit. I would propose this:

	If you're going to change the structure, please put a version
	number as the first field, so that it's never a problem again.

	Also, put a spare field on the end (64 bits) to allow for
	future expansion that maintains binary compatability (by way
	of choice about what to copy in).

	-- Terry

There are already ten spare 64-bit numbers in the middle of the 
proposed new structure. They are there where they are guaranteed
to be 64-bit aligned rather than at the end where there is danger
of them being aligned differently on different architectures since
they follow character arrays.

	Kirk McKusick
Received on Mon May 12 2003 - 10:33:20 UTC

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