ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 140 insertions, 0 deletions

diff --git a/fs/nfsd/stats.h b/fs/nfsd/stats.h
new file mode 100644
index 000000000..aabfbb1a9
--- /dev/null
+++ b/fs/nfsd/stats.h
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Statistics for NFS server.
+ *
+ * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
+ */
+#ifndef _NFSD_STATS_H
+#define _NFSD_STATS_H
+
+#include <uapi/linux/nfsd/stats.h>
+#include <linux/percpu_counter.h>
+
+#include "export.h"
+#include "netns.h"
+
+struct proc_dir_entry *nfsd_proc_stat_init(struct net *net);
+void nfsd_proc_stat_shutdown(struct net *net);
+
+/**
+ * nfsd_stats_rc_hits_inc - Count a duplicate reply cache hit
+ * @nn: target network namespace
+ *
+ * These reply cache counters are updated once per RPC. Readers use
+ * percpu_counter_sum_positive(), so local batching does not affect
+ * read accuracy.
+ */
+static inline void nfsd_stats_rc_hits_inc(struct nfsd_net *nn)
+{
+	percpu_counter_add_local(&nn->counter[NFSD_STATS_RC_HITS], 1);
+}
+
+/**
+ * nfsd_stats_rc_misses_inc - Count a duplicate reply cache miss
+ * @nn: target network namespace
+ *
+ * See nfsd_stats_rc_hits_inc() for batching rationale.
+ */
+static inline void nfsd_stats_rc_misses_inc(struct nfsd_net *nn)
+{
+	percpu_counter_add_local(&nn->counter[NFSD_STATS_RC_MISSES], 1);
+}
+
+/**
+ * nfsd_stats_rc_nocache_inc - Count a request not cached in the reply cache
+ * @nn: target network namespace
+ *
+ * See nfsd_stats_rc_hits_inc() for batching rationale.
+ */
+static inline void nfsd_stats_rc_nocache_inc(struct nfsd_net *nn)
+{
+	percpu_counter_add_local(&nn->counter[NFSD_STATS_RC_NOCACHE], 1);
+}
+
+static inline void nfsd_stats_fh_stale_inc(struct nfsd_net *nn,
+					   struct svc_export *exp)
+{
+	percpu_counter_inc(&nn->counter[NFSD_STATS_FH_STALE]);
+	if (exp && exp->ex_stats)
+		percpu_counter_inc(&exp->ex_stats->counter[EXP_STATS_FH_STALE]);
+}
+
+/**
+ * nfsd_stats_io_read_add - Count number of bytes for an NFS READ
+ * @nn: target network namespace
+ * @exp: target export
+ * @amount: byte count
+ *
+ * These counters are updated on every READ request. Readers use
+ * percpu_counter_sum_positive(), so local batching does not affect
+ * read accuracy.
+ */
+static inline void nfsd_stats_io_read_add(struct nfsd_net *nn,
+					  struct svc_export *exp, s64 amount)
+{
+	percpu_counter_add_local(&nn->counter[NFSD_STATS_IO_READ], amount);
+	if (exp && exp->ex_stats)
+		percpu_counter_add_local(&exp->ex_stats->counter[EXP_STATS_IO_READ],
+					 amount);
+}
+
+/**
+ * nfsd_stats_io_write_add - Count number of bytes for an NFS WRITE
+ * @nn: target network namespace
+ * @exp: target export
+ * @amount: byte count
+ *
+ * These counters are updated on every WRITE request. Readers use
+ * percpu_counter_sum_positive(), so local batching does not affect
+ * read accuracy.
+ */
+static inline void nfsd_stats_io_write_add(struct nfsd_net *nn,
+					   struct svc_export *exp, s64 amount)
+{
+	percpu_counter_add_local(&nn->counter[NFSD_STATS_IO_WRITE], amount);
+	if (exp && exp->ex_stats)
+		percpu_counter_add_local(&exp->ex_stats->counter[EXP_STATS_IO_WRITE],
+					 amount);
+}
+
+static inline void nfsd_stats_payload_misses_inc(struct nfsd_net *nn)
+{
+	percpu_counter_inc(&nn->counter[NFSD_STATS_PAYLOAD_MISSES]);
+}
+
+/**
+ * nfsd_stats_drc_mem_usage_add - Add memory used by a cache item
+ * @nn: target network namespace
+ * @amount: byte count
+ *
+ * percpu_counter_add_local() keeps updates on the per-CPU fast
+ * path. The sole reader, percpu_counter_sum_positive(), sums the
+ * per-CPU deltas, so batching locally does not lose accuracy.
+ */
+static inline void nfsd_stats_drc_mem_usage_add(struct nfsd_net *nn, s64 amount)
+{
+	percpu_counter_add_local(&nn->counter[NFSD_STATS_DRC_MEM_USAGE],
+				 amount);
+}
+
+/**
+ * nfsd_stats_drc_mem_usage_sub - Subtract memory used by a cache item
+ * @nn: target network namespace
+ * @amount: byte count
+ *
+ * See nfsd_stats_drc_mem_usage_add() for batching rationale.
+ */
+static inline void nfsd_stats_drc_mem_usage_sub(struct nfsd_net *nn, s64 amount)
+{
+	percpu_counter_sub_local(&nn->counter[NFSD_STATS_DRC_MEM_USAGE],
+				 amount);
+}
+
+#ifdef CONFIG_NFSD_V4
+static inline void nfsd_stats_cb_op_inc(struct nfsd_net *nn, u32 opcode)
+{
+	if (opcode >= OP_CB_GETATTR && opcode <= OP_CB_OFFLOAD)
+		percpu_counter_inc(&nn->cb_counter[opcode]);
+}
+#endif
+#endif /* _NFSD_STATS_H */