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    SubjectRe: [PATCH linux-next] SUNRPC: rpcrdma_register_default_external: Dynamically allocate ib_phys_buf

    This is the result of 2773395b34883fe54418de188733a63bb38e0ad6. Steve
    might want to weigh in on this since it was done for performance reasons.

    Tom

    On 3/10/13 10:39 AM, 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@netapp.com>
    > Cc: "J. Bruce Fields" <bfields@fieldses.org>
    > Cc: "David S. Miller" <davem@davemloft.net>
    > Cc: Tom Tucker <tom@ogc.us>
    > Cc: Haggai Eran <haggaie@mellanox.com>
    > Cc: Or Gerlitz <ogerlitz@mellanox.com>
    > Cc: Shani Michaeli <shanim@mellanox.com>
    > Cc: linux-nfs@vger.kernel.org
    > Cc: netdev@vger.kernel.org
    > Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
    > ---
    > 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);
    > + 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;
    > }
    >



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