On Sun, Mar 10, 2013 at 09:39:13AM -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 dynamically allocate the array of 'struct ib_phys_buf' objects 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@xxxxxxxxxx>
> Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Tom Tucker <tom@xxxxxx>
> Cc: Haggai Eran <haggaie@xxxxxxxxxxxx>
> Cc: Or Gerlitz <ogerlitz@xxxxxxxxxxxx>
> Cc: Shani Michaeli <shanim@xxxxxxxxxxxx>
> Cc: linux-nfs@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
> ---
> net/sunrpc/xprtrdma/verbs.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index 93726560..0916467 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -1736,9 +1736,13 @@ 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;
>
> + ipb = kmalloc(sizeof(*ipb) * RPCRDMA_MAX_DATA_SEGS, GFP_KERNEL);
Have you checked that this occurs in a context where allocations are OK?
Checking very quickly through the callers I can't see any spinlocks or
anything, but I also don't see any other allocations.
Assuming this is just in rpciod context.... Trond's the authority, but
I think we generally try to avoid allocations here, or make them
GFP_NOFS if we must.
Would it be possible to allocate this array as part of the rpcrdma_req?
--b.
> + if (!ipb)
> + return -ENOMEM;
> +
> if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
> *nsegs = RPCRDMA_MAX_DATA_SEGS;
> for (len = 0, i = 0; i < *nsegs;) {
> @@ -1770,6 +1774,7 @@ rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
> seg1->mr_len = len;
> }
> *nsegs = i;
> + kfree(ipb);
> return rc;
> }
>
> --
> 1.7.9.5
>
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