linux-kernel - Re: [PATCH 3/3] proc: use kzalloc instead of kmalloc and memset

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Message-ID: <CAH+=+MEuVqZhXMELQ=Faewg=4MU2VQr1X1Qq8QCyAu=E-qSeLQ@mail.gmail.com>
Date:	Tue, 4 Sep 2012 17:10:40 +0800
From:	yan yan <clouds.yan@...il.com>
To:	Ryan Mallon <rmallon@...il.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] proc: use kzalloc instead of kmalloc and memset

2012/9/4 Ryan Mallon <rmallon@...il.com>
>
> On 04/09/12 00:14, yan wrote:
> > Signed-off-by: yan <clouds.yan@...il.com>
> > ---
> >  fs/proc/generic.c |    3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> > index 9e8f631..38de015 100644
> > --- a/fs/proc/generic.c
> > +++ b/fs/proc/generic.c
> > @@ -616,10 +616,9 @@ static struct proc_dir_entry *__proc_create(struct
> > proc_dir_entry **parent,
> >
> >       len = strlen(fn);
> >
> > -     ent = kmalloc(sizeof(struct proc_dir_entry) + len + 1,
> > GFP_KERNEL);
> > +     ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1,
> > GFP_KERNEL);
> >       if (!ent) goto out;
> >
> > -     memset(ent, 0, sizeof(struct proc_dir_entry));
> >       memcpy(ent->name, fn, len + 1);
> >       ent->namelen = len;
> >       ent->mode = mode;
>
> Note that this change results in slightly different behaviour. Before
> your change only sizeof(struct proc_dir_entry) is zero'ed by memset, and
> then the name is filled in (the len + 1 part). After your change the
> structure and the name field are both zeroed, so the name field is being
> written to twice. The cost is probably negligible though.

Oh, I didn't notice that actually. Thank you.
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