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Date: Sun, 1 May 2011 16:47:02 -0400 (EDT)
From: Rick Macklem <rmacklem@uoguelph.ca>
To: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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Cc: rmacklem@freebsd.org, fs@freebsd.org
Subject: Re: newnfs client and statfs
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> On Sun, 1 May 2011, Rick Macklem wrote:
> >
> > Or should I try and do the division to see if the large
> > value in sf_abytes will fit in INT64_MAX after the division?
> > Something
> > like:
> >  int64_t tmp;
> >
> >  tmp = sfp->sf_abytes;
> >  tmp /= NFS_FABLKSIZE;
> >  if (tmp < 0)
> >     sbp->f_bavail = INT64_MAX;
> >  else
> >     sbp->f_bavail = tmp;
> 
> That one seems better because it preserves more of the value, but
> perhaps this is better because it does not depend on
> undocumented/undefined behavior (also untested):
> 
> uint64_t tmp;
> tmp = sfp->sf_abytes / NFS_FABLKSIZE;
> if (tmp > (uint64_t) INT64_MAX)
> sbp->f_bavail = INT64_MAX;
> else
> sbp->f_bavail = tmp;
> 
That's basically what I went with for the updated patch, except I
didn't put in the "if (tmp > (uint64_t) INT64_MAX)" since once
you divide sf_abytes by 2 or more it is guaranteed to be less than
or equal INT64_MAX.

rick