linux-kernel - [PATCH 4.9 037/138] NFS: Avoid RCU usage in tracepoints

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Date:   Tue, 28 Nov 2017 11:22:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Jones <davej@...emonkey.org.uk>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Subject: [PATCH 4.9 037/138] NFS: Avoid RCU usage in tracepoints

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Anna Schumaker <Anna.Schumaker@...app.com>

commit 3944369db701f075092357b511fd9f5755771585 upstream.

There isn't an obvious way to acquire and release the RCU lock during a
tracepoint, so we can't use the rpc_peeraddr2str() function here.
Instead, rely on the client's cl_hostname, which should have similar
enough information without needing an rcu_dereference().

Reported-by: Dave Jones <davej@...emonkey.org.uk>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/nfs4trace.h |   24 ++++++------------------
 1 file changed, 6 insertions(+), 18 deletions(-)

--- a/fs/nfs/nfs4trace.h
+++ b/fs/nfs/nfs4trace.h
@@ -201,17 +201,13 @@ DECLARE_EVENT_CLASS(nfs4_clientid_event,
 		TP_ARGS(clp, error),
 
 		TP_STRUCT__entry(
-			__string(dstaddr,
-				rpc_peeraddr2str(clp->cl_rpcclient,
-					RPC_DISPLAY_ADDR))
+			__string(dstaddr, clp->cl_hostname)
 			__field(int, error)
 		),
 
 		TP_fast_assign(
 			__entry->error = error;
-			__assign_str(dstaddr,
-				rpc_peeraddr2str(clp->cl_rpcclient,
-						RPC_DISPLAY_ADDR));
+			__assign_str(dstaddr, clp->cl_hostname);
 		),
 
 		TP_printk(
@@ -1103,9 +1099,7 @@ DECLARE_EVENT_CLASS(nfs4_inode_callback_
 			__field(dev_t, dev)
 			__field(u32, fhandle)
 			__field(u64, fileid)
-			__string(dstaddr, clp ?
-				rpc_peeraddr2str(clp->cl_rpcclient,
-					RPC_DISPLAY_ADDR) : "unknown")
+			__string(dstaddr, clp ? clp->cl_hostname : "unknown")
 		),
 
 		TP_fast_assign(
@@ -1118,9 +1112,7 @@ DECLARE_EVENT_CLASS(nfs4_inode_callback_
 				__entry->fileid = 0;
 				__entry->dev = 0;
 			}
-			__assign_str(dstaddr, clp ?
-				rpc_peeraddr2str(clp->cl_rpcclient,
-					RPC_DISPLAY_ADDR) : "unknown")
+			__assign_str(dstaddr, clp ? clp->cl_hostname : "unknown")
 		),
 
 		TP_printk(
@@ -1162,9 +1154,7 @@ DECLARE_EVENT_CLASS(nfs4_inode_stateid_c
 			__field(dev_t, dev)
 			__field(u32, fhandle)
 			__field(u64, fileid)
-			__string(dstaddr, clp ?
-				rpc_peeraddr2str(clp->cl_rpcclient,
-					RPC_DISPLAY_ADDR) : "unknown")
+			__string(dstaddr, clp ? clp->cl_hostname : "unknown")
 			__field(int, stateid_seq)
 			__field(u32, stateid_hash)
 		),
@@ -1179,9 +1169,7 @@ DECLARE_EVENT_CLASS(nfs4_inode_stateid_c
 				__entry->fileid = 0;
 				__entry->dev = 0;
 			}
-			__assign_str(dstaddr, clp ?
-				rpc_peeraddr2str(clp->cl_rpcclient,
-					RPC_DISPLAY_ADDR) : "unknown")
+			__assign_str(dstaddr, clp ? clp->cl_hostname : "unknown")
 			__entry->stateid_seq =
 				be32_to_cpu(stateid->seqid);
 			__entry->stateid_hash =