Re: [next:akpm 147/308] net/sunrpc/clnt.c:720:36: sparse: dereference of noderef expression
From: Fengguang Wu <hidden>
Date: 2012-07-27 14:27:32
On Fri, Jul 27, 2012 at 03:10:36PM +0100, Mel Gorman wrote:
On Fri, Jul 27, 2012 at 09:02:25PM +0800, Fengguang Wu wrote:quoted
Hi Mel, There are new sparse warnings show up in tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm head: 247109fa112ac912f31efc28e130ed2a0cc1764c commit: 5bb176c86a868289d5d93d89919c3b5a339d6d20 [147/308] nfs: enable swap on NFSThanks (adding Andrew to cc for picking up in mm) How about the following?
Looks good to me. And it does fix the warning. I assume the fix will be folded into the original patch, otherwise the subject will look a bit strange ;) Thanks, Fengguang
quoted hunk ↗ jump to hunk
---8<--- sparsefix: nfs: enable swap on NFS Fengguang Wu reports the following sparse problem net/sunrpc/clnt.c:720:36: sparse: dereference of noderef expression task->tk_client->cl_xprt is RCU protected and must be dereferenced using rcu_dereference(). This patch checks if a socket is being used for swap and if so it takes the RCU read lock and dereferences properly. This is a fix for "nfs: enable swap on NFS" Signed-off-by: Mel Gorman <mgorman@suse.de> --- net/sunrpc/clnt.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index 2848e5b..df27890 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c@@ -717,8 +717,15 @@ void rpc_task_set_client(struct rpc_task *task, struct rpc_clnt *clnt) atomic_inc(&clnt->cl_count); if (clnt->cl_softrtry) task->tk_flags |= RPC_TASK_SOFT; - if (task->tk_client->cl_xprt->swapper) - task->tk_flags |= RPC_TASK_SWAPPER; + if (sk_memalloc_socks()) { + struct rpc_xprt *xprt; + + rcu_read_lock(); + xprt = rcu_dereference(clnt->cl_xprt); + if (xprt->swapper) + task->tk_flags |= RPC_TASK_SWAPPER; + rcu_read_unlock(); + } /* Add to the client's list of all tasks */ spin_lock(&clnt->cl_lock); list_add_tail(&task->tk_task, &clnt->cl_tasks);