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Date: Mon, 11 Mar 2013 18:02:09 -0500
From: Tom Tucker <tom@...ngridcomputing.com>
To: "J. Bruce Fields" <bfields@...ldses.org>
CC: Tim Gardner <tim.gardner@...onical.com>,
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 v3] SUNRPC: rpcrdma_register_default_external:
Dynamically allocate ib_phys_buf
On 3/11/13 4:25 PM, J. Bruce Fields wrote:
> On Mon, Mar 11, 2013 at 03:15:08PM -0600, Tim Gardner wrote:
>> rpcrdma_register_default_external() is several frames into the call stack which
>> goes deeper yet. You run the risk of stack corruption by declaring such a large
>> automatic variable, so move the array of 'struct ib_phys_buf' objects into the
>> transport structure 'struct rpcrdma_xprt' (which is dynamically allocated) in
>> order to silence the frame-larger-than warning. Access to each struct
>> rpcrdma_xprt is serialized by XPRT_LOCKED in xprt_reserve_xprt(), so there is
>> no danger of multiple accessors to the array of struct ib_phys_buf objects.
>>
>> net/sunrpc/xprtrdma/verbs.c: In function 'rpcrdma_register_default_external':
>> net/sunrpc/xprtrdma/verbs.c:1774:1: warning: the frame size of 1056 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>>
>> gcc version 4.6.3
>>
>> Cc: Trond Myklebust <Trond.Myklebust@...app.com>
>> Cc: "J. Bruce Fields" <bfields@...ldses.org>
>> Cc: "David S. Miller" <davem@...emloft.net>
>> Cc: Tom Tucker <tom@....us>
>> Cc: Haggai Eran <haggaie@...lanox.com>
>> Cc: Or Gerlitz <ogerlitz@...lanox.com>
>> Cc: Shani Michaeli <shanim@...lanox.com>
>> Cc: linux-nfs@...r.kernel.org
>> Cc: netdev@...r.kernel.org
>> Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
>> ---
>> v1 - Use kmalloc() to dynamically allocate and free the array of 'struct
>> ib_phys_buf' objects
>>
>> 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.
>>
>> v3 - Move the array of 'struct ib_phys_buf' objects into struct rpcrdma_xprt.
>> Pass a pointer to this transport structure into 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.
> Looks good to me; wish we could get it tested....
I will test it. Tim could you please send me a final version that you'd
like tested as a single message?
Would someone (like Tim maybe ... hint hint) look at tearing out all those
dead registration strategies? I don't think we need or will ever use
bounce-buffers, memory windows, or mlnx fmr. The only two that are used
and tested are all-phys and FRMR (the default).
Tom
> In future if we do decide to also increase the size of that array we may
> need to allocate it separately from struct rpcrdma_xprt itself, which
> looks already fairly large without it; on x86_64:
>
> $ gdb net/sunrpc/xprtrdma/xprtrdma.ko
> ...
> (gdb) p sizeof(struct rpcrdma_xprt)
> $1 = 2912
>
> But that shouldn't be a big deal to do.
>
> --b.
>
>> net/sunrpc/xprtrdma/verbs.c | 10 ++++++----
>> net/sunrpc/xprtrdma/xprt_rdma.h | 5 ++++-
>> 2 files changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
>> index 93726560..c7aa3da 100644
>> --- a/net/sunrpc/xprtrdma/verbs.c
>> +++ b/net/sunrpc/xprtrdma/verbs.c
>> @@ -1730,13 +1730,14 @@ rpcrdma_deregister_memwin_external(struct rpcrdma_mr_seg *seg,
>> }
>>
>> static int
>> -rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
>> - int *nsegs, int writing, struct rpcrdma_ia *ia)
>> +rpcrdma_register_default_external(struct rpcrdma_xprt *r_xprt,
>> + struct rpcrdma_mr_seg *seg, int *nsegs, int writing,
>> + struct rpcrdma_ia *ia)
>> {
>> int mem_priv = (writing ? IB_ACCESS_REMOTE_WRITE :
>> IB_ACCESS_REMOTE_READ);
>> struct rpcrdma_mr_seg *seg1 = seg;
>> - struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS];
>> + struct ib_phys_buf *ipb = r_xprt->ipb;
>> int len, i, rc = 0;
>>
>> if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
>> @@ -1827,7 +1828,8 @@ rpcrdma_register_external(struct rpcrdma_mr_seg *seg,
>>
>> /* Default registration each time */
>> default:
>> - rc = rpcrdma_register_default_external(seg, &nsegs, writing, ia);
>> + rc = rpcrdma_register_default_external(r_xprt, seg, &nsegs,
>> + writing, ia);
>> break;
>> }
>> if (rc)
>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>> index cc1445d..d7b440f 100644
>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>> @@ -269,7 +269,8 @@ struct rpcrdma_stats {
>> * for convenience. This structure need not be visible externally.
>> *
>> * It is allocated and initialized during mount, and released
>> - * during unmount.
>> + * during unmount. Access to this structure is serialized by XPRT_LOCKED
>> + * in xprt_reserve_xprt().
>> */
>> struct rpcrdma_xprt {
>> struct rpc_xprt xprt;
>> @@ -279,6 +280,8 @@ struct rpcrdma_xprt {
>> struct rpcrdma_create_data_internal rx_data;
>> struct delayed_work rdma_connect;
>> struct rpcrdma_stats rx_stats;
>> + /* temp work array */
>> + struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS];
>> };
>>
>> #define rpcx_to_rdmax(x) container_of(x, struct rpcrdma_xprt, xprt)
>> --
>> 1.7.9.5
>>
--
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