SUNRPC: serialize iostats updates
Occasionally mountstats reports a negative retransmission rate.
Ensure that two RPCs completing concurrently don't confuse the sums
in the transport's op_metrics array.
Since pNFS filelayout can invoke rpc_count_iostats() on another
transport from xprt_release(), we can't rely on simply holding the
transport_lock in xprt_release(). There's nothing for it but hard
serialization. One spin lock per RPC operation should make this as
painless as it can be.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/include/linux/sunrpc/metrics.h b/include/linux/sunrpc/metrics.h
index 1565bbe..eecb5a7 100644
--- a/include/linux/sunrpc/metrics.h
+++ b/include/linux/sunrpc/metrics.h
@@ -27,10 +27,13 @@
#include <linux/seq_file.h>
#include <linux/ktime.h>
+#include <linux/spinlock.h>
#define RPC_IOSTATS_VERS "1.0"
struct rpc_iostats {
+ spinlock_t om_lock;
+
/*
* These counters give an idea about how many request
* transmissions are required, on average, to complete that