Date: 12 May 2003 21:12:21 +0100 From: Paul Richards <paul@freebsd-services.com> To: Kirk McKusick <mckusick@beastie.mckusick.com> Cc: freebsd-current@freebsd.org Subject: Re: large ufs2 partitions and 'df' Message-ID: <1052770339.667.1.camel@cf.freebsd-services.com> In-Reply-To: <200305121933.h4CJXHTh037943@beastie.mckusick.com> References: <200305121933.h4CJXHTh037943@beastie.mckusick.com>
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On Mon, 2003-05-12 at 20:33, Kirk McKusick wrote: > Date: Mon, 12 May 2003 07:53:49 -0700 > From: Terry Lambert <tlambert2@mindspring.com> > To: Kirk McKusick <mckusick@mckusick.com> > CC: Julian Elischer <julian@elischer.org>, freebsd-current@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. A version number would be a good idea though so apps have some chance of knowing what fields are being used in the future. -- Paul Richards <paul@freebsd-services.com>
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