To: Amit Choudhary <amit2030@yahoo.com>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>,
       Pekka Enberg <penberg@cs.helsinki.fi>, linux-kernel@vger.kernel.org
Subject: Re: Hopefully, kmalloc() will always succeed, but if it doesn't then....
References: <20061022230957.78480.qmail@web55615.mail.re4.yahoo.com>
From: Roland Dreier <rdreier@cisco.com>
Date: Sun, 22 Oct 2006 17:25:30 -0700
In-Reply-To: <20061022230957.78480.qmail@web55615.mail.re4.yahoo.com> (Amit Choudhary's message of "Sun, 22 Oct 2006 16:09:56 -0700 (PDT)")
Message-ID: <adalkn7j2th.fsf@cisco.com>
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 >         struct mixart_enum_connector_resp *connector;
 >         struct mixart_audio_info_req  *audio_info_req;
 >         struct mixart_audio_info_resp *audio_info;
 > 
 >         connector = kmalloc(sizeof(*connector), GFP_KERNEL);
 >         audio_info_req = kmalloc(sizeof(*audio_info_req), GFP_KERNEL);
 >         audio_info = kmalloc(sizeof(*audio_info), GFP_KERNEL);
 >         if (! connector || ! audio_info_req || ! audio_info) {
 >                 err = -ENOMEM;
 >                 goto __error;
 >         }

This is not a bug.  All of the pointers are initialized, and if
kmalloc() fails, then one of them will be set to NULL.  However,
kfree(NULL) is a perfectly fine thing to do (kfree just returns
immediately in this case).

So this is just a way of saving some tests and optimizing for the
common case when all allocations succeed.  In other words, this is
good code -- although the spacing is slightly bogus: it should be

        if (!connector || !audio_info_req || !audio_info) {

and also using __error as a label is slightly silly -- why not just
make it "error"?

 - R.
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