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Message-ID: <9a8748490510131310y2c31ac04w4ea34ee2333f7ff7@mail.gmail.com>
Date: Thu, 13 Oct 2005 22:10:25 +0200
From: Jesper Juhl <jesper.juhl@gmail.com>
To: "Miller, Mike (OS Dev)" <Mike.Miller@hp.com>
Subject: Re: [PATCH 09/14] Big kfree NULL check cleanup - misc remaining drivers
Cc: linux-kernel <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>,
       Len Brown <len.brown@intel.com>, ISS StorageDev <iss_storagedev@hp.com>,
       Jakub Jelinek <jj@ultra.linux.cz>, Frodo Looijaard <frodol@dds.nl>,
       Jean Delvare <khali@linux-fr.org>,
       Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       Jens Axboe <axboe@suse.de>, Roland Dreier <rolandd@cisco.com>,
       Sergio Rozanski Filho <aris@cathedrallabs.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Pierre Ossman <drzeus-wbsd@drzeus.cx>,
       Carsten Gross <carsten@sol.wh-hms.uni-ulm.de>,
       Greg Kroah-Hartman <greg@kroah.com>,
       David Hinds <dahinds@users.sourceforge.net>,
       Vinh Truong <vinh.truong@eng.sun.com>,
       Mark Douglas Corner <mcorner@umich.edu>,
       Michael Downey <downey@zymeta.com>, Antonino Daplas <adaplas@pol.net>,
       Ben Gardner <bgardner@wabtec.com>
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On 10/13/05, Miller, Mike (OS Dev) <Mike.Miller@hp.com> wrote:
> > From: Jesper Juhl [mailto:jesper.juhl@gmail.com]
> > This is the remaining misc drivers/ part of the big kfree
> > cleanup patch.
> >
> > Remove pointless checks for NULL prior to calling kfree() in
> > misc files in drivers/.
> >
> >
> > --- linux-2.6.14-rc4-orig/drivers/block/cciss.c
> > 2005-10-11 22:41:05.000000000 +0200
> > +++ linux-2.6.14-rc4/drivers/block/cciss.c    2005-10-12
> > 17:43:18.000000000 +0200
> > @@ -1096,14 +1096,11 @@ static int cciss_ioctl(struct inode *ino
> >  cleanup1:
> >               if (buff) {
> >                       for(i=0; i<sg_used; i++)
> > -                             if(buff[i] != NULL)
> > -                                     kfree(buff[i]);
>
> I'm not sure I agree that these are pointless checks. They're not in the
> main code path so nothing is lost by checking first. What if the pointer
> is NULL????
>

If the pointer is NULL then this bit of code in kfree takes care of things :

 void kfree(const void *objp)
 {
...

         if (unlikely(!objp))
                 return;
...

Runtime behaviour is exactely the same.
kfree checks if the pointer passed to it is NULL in any case and just
returns if it is.


--
Jesper Juhl <jesper.juhl@gmail.com>
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