netdev - Re: [PATCH] SCTP: Reduce log spamming for sctp setsockopt

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Date:	Mon, 16 Dec 2013 12:02:54 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Daniel Borkmann <dborkman@...hat.com>, linux-sctp@...r.kernel.org,
	Vlad Yasevich <vyasevich@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] SCTP: Reduce log spamming for sctp setsockopt

On Mon, Dec 16, 2013 at 08:50:35AM -0800, Joe Perches wrote:
> On Mon, 2013-12-16 at 11:04 -0500, Neil Horman wrote:
> > On Mon, Dec 16, 2013 at 04:45:05PM +0100, Daniel Borkmann wrote:
> > > On 12/16/2013 04:21 PM, Joe Perches wrote:
> > > >On Mon, 2013-12-16 at 16:13 +0100, Daniel Borkmann wrote:
> > > >>On 12/16/2013 04:03 PM, Joe Perches wrote:
> > > >>>On Mon, 2013-12-16 at 09:44 -0500, Neil Horman wrote:
> > > >>>>During a recent discussion regarding some sctp socket options, it was noted that
> > > >>>>we have several points at which we issue log warnings that can be flooded at an
> > > >>>>unbounded rate by any user.  Fix this by converting all the pr_warns in the
> > > >>>>sctp_setsockopt path to be pr_warn_ratelimited.
> > > >>>
> > > >>>trivial note:
> > > >>[...]
> > > >>>>@@ -5311,8 +5311,8 @@ static int sctp_getsockopt_maxburst(struct sock *sk, int len,
> > > >>>[]
> > > >>>>+		pr_warn_ratelimited("Use of int in max_burst socket option deprecated\n");
> > > >>>>+		pr_warn_ratelimited("Use struct sctp_assoc_value instead\n");
> > > >>>
> > > >>>Perhaps a dedicated "deprecated" warning function
> > > >>>to centralize these?
> > > >>>
> > > >>>void _sctp_warn_deprecated(const char *func, const char *from, const char *to);
> > > >>>{
> > > >>>	etc.
> > > >>>}
> > > >>>#define sctp_warn_deprecated(from, to)		\
> > > >>>	_sctp_warn_deprecated(__func__, from, to)
> > > >>
> > > >>If so, then this should better get even more "centralized" ... as e.g.
> > > >>pr_warn_deprecated() [which internally is ratelimited]. I don't see the
> > > >>point why only SCTP should have this special-cased.
> > > >
> > > >Sure, if it's useful outside of sctp, but I didn't
> > > >notice any other uses like it.
> > > 
> > > If we have a generic API for that, they might come, sure.
> > I agree with Daniel.  If we're going to make this common, theres no reason to
> > not make it common for all uses.  Searching the kernel for uses of printk/pr_*
> > and the string "deprecated" shows lots of potential use sites.
> 
> Does adding a couple of functions like:
> 
> void pr_warn_deprecated(const char *old, const char *new)
> {
> 	static DEFINE_RATELIMIT_STATE(_rs,
> 				      DEFAULT_RATELIMIT_INTERVAL,
> 				      DEFAULT_RATELIMIT_BURST);
> 
> 	if (!__ratelimit(&_rs))
> 		return;
> 
> 	if (new)
> 		printk(KERN_WARNING "%pf: Use of \"%s\" is deprecated - use \"%s\" instead\n",
> 				    __builtin_return_address(1), old, new); 
> 	else
> 		printk(KERN_WARNING "%pf: Use of \"%s\" is deprecated\n",
> 				    __builtin_return_address(1), old); 
> }
> 
> suit?  Other suggestions?
> 

i'm just doing this:
#define pr_warn_deprecated(fmt, ...) \
pr_warn_ratelimited("Deprecated: " fmt, ##__VA_ARGS__)

That will work for every form, giving consistency to the location of a single
word for ease of searching.  I don't really see the need to institutionalize
"use <blank> instead", since there may be no drop in replacement for something
that is deprecated.

Neil

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