On Fri, Jul 27, 2012 at 09:02:25PM +0800, Fengguang Wu wrote:
> 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 NFS
>
Thanks (adding Andrew to cc for picking up in mm)
How about the following?
---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@xxxxxxx>
---
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);
--
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