linux-kernel - Re: [PATCH linux-next v2] SUNRPC: rpcrdma_register_default_external: Dynamically allocate ib_phys

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Date:	Mon, 11 Mar 2013 12:51:44 -0600
From:	Tim Gardner <tim.gardner@...onical.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
CC:	linux-kernel@...r.kernel.org,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	"David S. Miller" <davem@...emloft.net>, Tom Tucker <tom@....us>,
	Haggai Eran <haggaie@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Shani Michaeli <shanim@...lanox.com>,
	linux-nfs@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH linux-next v2] SUNRPC: rpcrdma_register_default_external:
 Dynamically allocate ib_phys_buf

On 03/11/2013 12:14 PM, J. Bruce Fields wrote:
<snip>
>>
>> v2 - Move the array of 'struct ib_phys_buf' objects into struct rpcrdma_req
>> and pass this request down through rpcrdma_register_external() and
>> rpcrdma_register_default_external(). This is less overhead then using
>> kmalloc() and requires no extra error checking as the allocation burden is
>> shifted to the transport client.
> 
> Oh good--so that works, and the req is the right place to put this?  How
> are you testing this?
> 
> (Just want to make it clear: I'm *not* an expert on the rdma code, so my
> suggestion to put this in the rpcrdma_req was a suggestion for something
> to look into, not a claim that it's correct.)
> 

Just compile tested so far. Incidentally, I've been through the call stack:

call_transmit
 xprt_transmit
  xprt->ops->send_request(task)
   xprt_rdma_send_request
    rpcrdma_marshal_req
     rpcrdma_create_chunks
      rpcrdma_register_external
       rpcrdma_register_default_external

It appears that the context for kmalloc() should be fine unless there is
a spinlock held around call_transmit() (which seems unlikely).

rtg
-- 
Tim Gardner tim.gardner@...onical.com
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