Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:34587 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751110Ab3CJU2o (ORCPT ); Sun, 10 Mar 2013 16:28:44 -0400 Date: Sun, 10 Mar 2013 16:28:38 -0400 From: "J. Bruce Fields" To: Tim Gardner Cc: linux-kernel@vger.kernel.org, Trond Myklebust , "David S. Miller" , Tom Tucker , Haggai Eran , Or Gerlitz , Shani Michaeli , linux-nfs@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH linux-next] SUNRPC: rpcrdma_register_default_external: Dynamically allocate ib_phys_buf Message-ID: <20130310202838.GL31448@fieldses.org> References: <1362929953-63785-1-git-send-email-tim.gardner@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1362929953-63785-1-git-send-email-tim.gardner@canonical.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 > Cc: "J. Bruce Fields" > Cc: "David S. Miller" > Cc: Tom Tucker > Cc: Haggai Eran > Cc: Or Gerlitz > Cc: Shani Michaeli > Cc: linux-nfs@vger.kernel.org > Cc: netdev@vger.kernel.org > Signed-off-by: Tim Gardner > --- > 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 >