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

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Date:   Tue, 15 Jan 2019 15:53:48 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Chuck Lever <chuck.lever@...cle.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] svcrdma: Use struct_size() in kmalloc()



On 1/15/19 3:49 PM, 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>
> 

Thank you, Chuck.
--
Gustavo

> 
>> ---
>> 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
> 
> 
>