* Use is subject to license terms.
*/
/*
- * Copyright (c) 2012 Whamcloud, Inc.
+ * Copyright (c) 2011, 2012, Intel Corporation.
*/
/*
* This file is part of Lustre, http://www.lustre.org/
#endif /* __KERNEL__ */
#include <lustre_handles.h>
#include <libcfs/libcfs.h>
+#include <obd_class.h>
#include <lustre/lustre_idl.h>
#include <lustre_lib.h>
#include <lustre_dlm.h>
-#include <lustre_log.h>
#include <lustre_export.h>
struct ptlrpc_client;
struct ptlrpc_request;
struct obd_device;
+/**
+ * Serializes in-flight MDT-modifying RPC requests to preserve idempotency.
+ *
+ * This mutex is used to implement execute-once semantics on the MDT.
+ * The MDT stores the last transaction ID and result for every client in
+ * its last_rcvd file. If the client doesn't get a reply, it can safely
+ * resend the request and the MDT will reconstruct the reply being aware
+ * that the request has already been executed. Without this lock,
+ * execution status of concurrent in-flight requests would be
+ * overwritten.
+ *
+ * This design limits the extent to which we can keep a full pipeline of
+ * in-flight requests from a single client. This limitation could be
+ * overcome by allowing multiple slots per client in the last_rcvd file.
+ */
struct mdc_rpc_lock {
- cfs_mutex_t rpcl_mutex;
+ /** Lock protecting in-flight RPC concurrency. */
+ struct mutex rpcl_mutex;
+ /** Intent associated with currently executing request. */
struct lookup_intent *rpcl_it;
+ /** Used for MDS/RPC load testing purposes. */
int rpcl_fakes;
};
static inline void mdc_init_rpc_lock(struct mdc_rpc_lock *lck)
{
- cfs_mutex_init(&lck->rpcl_mutex);
+ mutex_init(&lck->rpcl_mutex);
lck->rpcl_it = NULL;
}
{
ENTRY;
- if (it != NULL && (it->it_op == IT_GETATTR || it->it_op == IT_LOOKUP))
+ if (it != NULL && (it->it_op == IT_GETATTR || it->it_op == IT_LOOKUP ||
+ it->it_op == IT_LAYOUT))
return;
/* This would normally block until the existing request finishes.
* Only when all fake requests are finished can normal requests
* be sent, to ensure they are recoverable again. */
again:
- cfs_mutex_lock(&lck->rpcl_mutex);
+ mutex_lock(&lck->rpcl_mutex);
if (CFS_FAIL_CHECK_QUIET(OBD_FAIL_MDC_RPCS_SEM)) {
lck->rpcl_it = MDC_FAKE_RPCL_IT;
lck->rpcl_fakes++;
- cfs_mutex_unlock(&lck->rpcl_mutex);
+ mutex_unlock(&lck->rpcl_mutex);
return;
}
* in this extremely rare case, just have low overhead in
* the common case when it isn't true. */
while (unlikely(lck->rpcl_it == MDC_FAKE_RPCL_IT)) {
- cfs_mutex_unlock(&lck->rpcl_mutex);
+ mutex_unlock(&lck->rpcl_mutex);
cfs_schedule_timeout(cfs_time_seconds(1) / 4);
goto again;
}
static inline void mdc_put_rpc_lock(struct mdc_rpc_lock *lck,
struct lookup_intent *it)
{
- if (it != NULL && (it->it_op == IT_GETATTR || it->it_op == IT_LOOKUP))
+ if (it != NULL && (it->it_op == IT_GETATTR || it->it_op == IT_LOOKUP ||
+ it->it_op == IT_LAYOUT))
goto out;
if (lck->rpcl_it == MDC_FAKE_RPCL_IT) { /* OBD_FAIL_MDC_RPCS_SEM */
- cfs_mutex_lock(&lck->rpcl_mutex);
+ mutex_lock(&lck->rpcl_mutex);
LASSERTF(lck->rpcl_fakes > 0, "%d\n", lck->rpcl_fakes);
lck->rpcl_fakes--;
lck->rpcl_it = NULL;
}
- cfs_mutex_unlock(&lck->rpcl_mutex);
+ mutex_unlock(&lck->rpcl_mutex);
out:
EXIT;
}