On Jan 13, 2014, at 10:45, Paul Bolle <pebolle@xxxxxxxxxx> wrote:
> Building verbs.o on 32 bits x86, with CONFIG_FRAME_WARN set to 1024, its
> default value, triggers this GCC warning:
> net/sunrpc/xprtrdma/verbs.c: In function ‘rpcrdma_register_default_external’:
> net/sunrpc/xprtrdma/verbs.c:1774:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>
> Silence this warning by allocating "ipb" dynamically.
>
> Signed-off-by: Paul Bolle <pebolle@xxxxxxxxxx>
> ---
> 0) Compile tested only (on 32 bits x86). I don't have access to
> Infiniband hardware.
>
> 1) Please note that this is not a new warning. The oldest build log I
> have still available on this machine is for a v3.8 rc, and it already
> showed this warning.
>
> 2) I do hope my choice for the GFP_KERNEL flag is correct here.
>
> net/sunrpc/xprtrdma/verbs.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index 93726560..939ccc8 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -1736,11 +1736,14 @@ rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
> 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;
> int len, i, rc = 0;
>
> if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
> *nsegs = RPCRDMA_MAX_DATA_SEGS;
> + ipb = kmalloc(sizeof(*ipb) * *nsegs, GFP_KERNEL);
> + if (ipb == NULL)
> + return -ENOMEM;
> for (len = 0, i = 0; i < *nsegs;) {
> rpcrdma_map_one(ia, seg, writing);
> ipb[i].addr = seg->mr_dma;
> @@ -1770,6 +1773,7 @@ rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
> seg1->mr_len = len;
> }
> *nsegs = i;
> + kfree(ipb);
> return rc;
> }
Hi Paul,
Unfortunately, the above could be called from a file write back context, so we cannot use GFP_KERNEL allocations. In fact, I suspect we should only use GFP_ATOMIC, and then have the rpc_task delay and retry if the allocation fails.
The problem is that it looks to me as if xprt_rdma_send_request will currently fail, if we return an error from rpcrdma_register_default_external.
Chuck, will you be able to look into the above issue as part of your RDMA work?
Cheers
Trond
--
Trond Myklebust
Linux NFS client maintainer
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