netdev - Re: [PATCH net-next] svcrdma: Use struct

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Date:   Wed, 16 Jan 2019 18:07:49 -0500
From:   Bruce Fields <bfields@...ldses.org>
To:     Chuck Lever <chuck.lever@...cle.com>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Jeff Layton <jlayton@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] svcrdma: Use struct_size() in kmalloc()

On Tue, Jan 15, 2019 at 04:49:16PM -0500, Chuck Lever wrote:
> 
> 
> On Jan 15, 2019, at 4:11 PM, Gustavo A. R. Silva <gustavo@...eddedor.com> wrote:
> 
> > One of the more common cases of allocation size calculations is finding
> > the size of a structure that has a zero-sized array at the end, along
> > with memory for some number of elements for that array. For example:
> > 
> > struct foo {
> >    int stuff;
> >    struct boo entry[];
> > };
> > 
> > instance = kmalloc(sizeof(struct foo) + count * sizeof(struct boo), GFP_KERNEL);
> > 
> > Instead of leaving these open-coded and prone to type mistakes, we can
> > now use the new struct_size() helper:
> > 
> > instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
> > 
> > This code was detected with the help of Coccinelle.
> > 
> > Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> 
> Reviewed-by: Chuck Lever <chuck.lever@...cle.com>

Thanks, applying for 5.1.--b.

> 
> 
> > ---
> > net/sunrpc/xprtrdma/svc_rdma_rw.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> > index dc1951759a8e..cad37c2122ab 100644
> > --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
> > +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
> > @@ -64,8 +64,7 @@ svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
> > 		spin_unlock(&rdma->sc_rw_ctxt_lock);
> > 	} else {
> > 		spin_unlock(&rdma->sc_rw_ctxt_lock);
> > -		ctxt = kmalloc(sizeof(*ctxt) +
> > -			       SG_CHUNK_SIZE * sizeof(struct scatterlist),
> > +		ctxt = kmalloc(struct_size(ctxt, rw_first_sgl, SG_CHUNK_SIZE),
> > 			       GFP_KERNEL);
> > 		if (!ctxt)
> > 			goto out;
> > -- 
> > 2.20.1
> 
> --
> Chuck Lever
> 
>