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Date: Mon, 11 Mar 2013 14:14:50 -0400
From: "J. Bruce Fields" <bfields@...ldses.org>
To: Tim Gardner <tim.gardner@...onical.com>
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 Mon, Mar 11, 2013 at 11:37:27AM -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
> requestor structure 'struct rpcrdma_req' (which is dynamically allocated) in
> order to silence the frame-larger-than warning.
>
> 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.
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.)
--b.
>
> net/sunrpc/xprtrdma/rpc_rdma.c | 2 +-
> net/sunrpc/xprtrdma/verbs.c | 11 ++++++-----
> net/sunrpc/xprtrdma/xprt_rdma.h | 3 ++-
> 3 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index e03725b..c89448b 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -203,7 +203,7 @@ rpcrdma_create_chunks(struct rpc_rqst *rqst, struct xdr_buf *target,
>
> do {
> /* bind/register the memory, then build chunk from result. */
> - int n = rpcrdma_register_external(seg, nsegs,
> + int n = rpcrdma_register_external(req, seg, nsegs,
> cur_wchunk != NULL, r_xprt);
> if (n <= 0)
> goto out;
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index 93726560..5b439ed 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_req *req,
> + 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 = req->rl_ipb;
> int len, i, rc = 0;
>
> if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
> @@ -1791,7 +1792,7 @@ rpcrdma_deregister_default_external(struct rpcrdma_mr_seg *seg,
> }
>
> int
> -rpcrdma_register_external(struct rpcrdma_mr_seg *seg,
> +rpcrdma_register_external(struct rpcrdma_req *req, struct rpcrdma_mr_seg *seg,
> int nsegs, int writing, struct rpcrdma_xprt *r_xprt)
> {
> struct rpcrdma_ia *ia = &r_xprt->rx_ia;
> @@ -1827,7 +1828,7 @@ 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(req, 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..b10ed34 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -192,6 +192,7 @@ struct rpcrdma_req {
> struct ib_sge rl_send_iov[4]; /* for active requests */
> struct ib_sge rl_iov; /* for posting */
> struct ib_mr *rl_handle; /* handle for mem in rl_iov */
> + struct ib_phys_buf rl_ipb[RPCRDMA_MAX_DATA_SEGS]; /* temp work array */
> char rl_base[MAX_RPCRDMAHDR]; /* start of actual buffer */
> __u32 rl_xdr_buf[0]; /* start of returned rpc rq_buffer */
> };
> @@ -327,7 +328,7 @@ int rpcrdma_register_internal(struct rpcrdma_ia *, void *, int,
> int rpcrdma_deregister_internal(struct rpcrdma_ia *,
> struct ib_mr *, struct ib_sge *);
>
> -int rpcrdma_register_external(struct rpcrdma_mr_seg *,
> +int rpcrdma_register_external(struct rpcrdma_req *, struct rpcrdma_mr_seg *,
> int, int, struct rpcrdma_xprt *);
> int rpcrdma_deregister_external(struct rpcrdma_mr_seg *,
> struct rpcrdma_xprt *, void *);
> --
> 1.7.9.5
>
> --
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