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

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Date:   Thu, 31 Jan 2019 09:11:24 -0500
From:   Chuck Lever <chuck.lever@...cle.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Bruce Fields <bfields@...ldses.org>,
        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] xprtrdma: Use struct_size() in kzalloc()



> On Jan 30, 2019, at 7:46 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 = kzalloc(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 = kzalloc(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>


> ---
> net/sunrpc/xprtrdma/verbs.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index 4994e75945b8..9e8cf7456840 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -811,8 +811,7 @@ static struct rpcrdma_sendctx *rpcrdma_sendctx_create(struct rpcrdma_ia *ia)
> {
> 	struct rpcrdma_sendctx *sc;
> 
> -	sc = kzalloc(sizeof(*sc) +
> -		     ia->ri_max_send_sges * sizeof(struct ib_sge),
> +	sc = kzalloc(struct_size(sc, sc_sges, ia->ri_max_send_sges),
> 		     GFP_KERNEL);
> 	if (!sc)
> 		return NULL;
> -- 
> 2.20.1
> 

--
Chuck Lever