netdev - Re: [PATCH v2] sctp: loading sctp when load sctp

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Message-ID: <20131216134814.GA19809@hmsreliant.think-freely.org>
Date:	Mon, 16 Dec 2013 08:48:14 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Wang Weidong <wangweidong1@...wei.com>
Cc:	Vlad Yasevich <vyasevich@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-sctp@...r.kernel.org
Subject: Re: [PATCH v2] sctp: loading sctp when load sctp_probe

On Mon, Dec 16, 2013 at 10:47:00AM +0800, Wang Weidong wrote:
> On 2013/12/13 20:26, Neil Horman wrote:
> > On Fri, Dec 13, 2013 at 11:00:10AM +0800, Wang Weidong wrote:
> >> when I modprobe sctp_probe, it failed with "FATAL: ". I found that
> >> sctp should load before sctp_probe register jprobe. So I add a
> >> sctp_setup_jprobe for loading 'sctp' when first failed to register
> >> jprobe, just do this similar to dccp_probe.
> >>
> >> v2: add MODULE_SOFTDEP and check of request_module, as suggested by Neil
> >>
> >> Signed-off-by: Wang Weidong <wangweidong1@...wei.com>
> >> ---
> >>  net/sctp/probe.c | 17 ++++++++++++++++-
> >>  1 file changed, 16 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/net/sctp/probe.c b/net/sctp/probe.c
> >> index 53c452e..5e68b94 100644
> >> --- a/net/sctp/probe.c
> >> +++ b/net/sctp/probe.c
> >> @@ -38,6 +38,7 @@
> >>  #include <net/sctp/sctp.h>
> >>  #include <net/sctp/sm.h>
> >>  
> >> +MODULE_SOFTDEP("pre: sctp");
> >>  MODULE_AUTHOR("Wei Yongjun <yjwei@...fujitsu.com>");
> >>  MODULE_DESCRIPTION("SCTP snooper");
> >>  MODULE_LICENSE("GPL");
> >> @@ -182,6 +183,20 @@ static struct jprobe sctp_recv_probe = {
> >>  	.entry	= jsctp_sf_eat_sack,
> >>  };
> >>  
> >> +static __init int sctp_setup_jprobe(void)
> >> +{
> >> +	int ret = register_jprobe(&sctp_recv_probe);
> >> +
> >> +	if (ret) {
> >> +		if (request_module("sctp"))
> >> +			goto out;
> >> +		ret = register_jprobe(&sctp_recv_probe);
> >> +	}
> >> +
> >> +out:
> >> +	return ret;
> >> +}
> >> +
> >>  static __init int sctpprobe_init(void)
> >>  {
> >>  	int ret = -ENOMEM;
> >> @@ -202,7 +217,7 @@ static __init int sctpprobe_init(void)
> >>  			 &sctpprobe_fops))
> >>  		goto free_kfifo;
> >>  
> >> -	ret = register_jprobe(&sctp_recv_probe);
> >> +	ret = sctp_setup_jprobe();
> > You don't need to create your own function for this, you can collapse it down to
> > a call to try_then_request_module(regitser_jprobe(...), "sctp");
> > Neil
> > 
> Hi Neil,
> 
> I try to use try_then_request_module(!regitser_jprobe(...), "sctp"); I found that if
> I used this, I couldn't get the ture value which returned by register_jprobe(). Is the
> returned value not important? The problem("if sctp.ko doesn't exist") you had pointed out
> is exist as well.
> 
> Regards.
> Wang

Not sure I follow.  There appear to be lots of examples in the kernel where
exactly what you are trying to do is done.  try_then_request_module calls your
requested method, and if it returns non-zero, calls request_module, then calls
your requested method again, returning the final result.  What problem are you
running into?
Neil

> > 
> >>  	if (ret)
> >>  		goto remove_proc;
> >>  
> > 
> > .
> > 
> 
> 
> 
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