From owner-freebsd-net@FreeBSD.ORG  Wed Jan 24 13:10:51 2007
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Date: Wed, 24 Jan 2007 05:10:50 -0800
From: Luigi Rizzo <rizzo@icir.org>
To: Randall Stewart <rrs@cisco.com>
Message-ID: <20070124051050.A56064@xorpc.icir.org>
References: <45B679F3.3080407@cisco.com>
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	from rrs@cisco.com on Tue, Jan 23, 2007 at 04:11:15PM -0500
Cc: freebsd-net <freebsd-net@freebsd.org>
Subject: Re: mbuf patch with sysctl suggestions too
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On Tue, Jan 23, 2007 at 04:11:15PM -0500, Randall Stewart wrote:
> Hi all:
> 
> Here is iteration 2 of the mbuf patch with limits I
> proposed.
> 
> Also note the changes for sysctl stuff that Lugi suggested.
> Please let me know what you think :-)

...
> +	newnmbjclusters = nmbjumbop;
> +	error = sysctl_int_checked(oidp, &newnmbjclusters, nmbjumbop, 
> +           SYSCTL_NO_LIMIT, req);

A few things here:
- i don't see much of a point in defining SYSCTL_NO_LIMIT;
  UINT32_MAX would do perfectly there, and i think it is easier
  to understand than SYSCTL_NO_LIMIT (which looks like a flag).

- here and in other places you do not allow decresaing the value
  (by putting min = nmbjumbop etc.), and i am not sure why.
  I understand a reasonable lower bound, but i guess the worst
  that can happen, when you reduce the limit to something above
  the current allocation, is that nothing is allocated until
  you go again below the limit, right ?
  
- given that you don't use the new value if error != 0, perhaps
  you can save the assignment newnmbjclusters = nmbjumbop;

And below:

> +/*
> + * Handle an int, unsigned, but limited
> + * between min and max (unsigned)
> + * Two cases:
> + *     a variable:  point arg1 at it.
> + *     a constant:  pass it in arg2.
> + * 
> + */
> +
> +extern int nmbjumbo9;
> +
> +int
> +sysctl_int_checked(struct sysctl_oid *oidp, void *val, uint32_t min, uint32_t max, struct sysctl_req *req)
> +{

the comment refers to something else and should be fixed e.g.

	Handle an unsigned int variable with bound checking.
	Returns 0 (and updates *val) if min <= v <= max;
	returns EINVAL otherwhise (in which case *val is unchanged)

cheers
luigi