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, 88 insertions, 0 deletions

diff --git a/fs/nfsd/stats.c b/fs/nfsd/stats.c
new file mode 100644
index 000000000..f16559813
--- /dev/null
+++ b/fs/nfsd/stats.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * procfs-based user access to knfsd statistics
+ *
+ * /proc/net/rpc/nfsd
+ *
+ * Format:
+ *	rc <hits> <misses> <nocache>
+ *			Statistsics for the reply cache
+ *	fh <stale> <deprecated filehandle cache stats>
+ *			statistics for filehandle lookup
+ *	io <bytes-read> <bytes-written>
+ *			statistics for IO throughput
+ *	th <threads> <deprecated thread usage histogram stats>
+ *			number of threads
+ *	ra <deprecated ra-cache stats>
+ *
+ *	plus generic RPC stats (see net/sunrpc/stats.c)
+ *
+ * Copyright (C) 1995, 1996, 1997 Olaf Kirch <okir@monad.swb.de>
+ */
+
+#include <linux/seq_file.h>
+#include <linux/module.h>
+#include <linux/sunrpc/stats.h>
+#include <net/net_namespace.h>
+
+#include "nfsd.h"
+#include "netns.h"
+#include "stats.h"
+
+static int nfsd_show(struct seq_file *seq, void *v)
+{
+	struct net *net = pde_data(file_inode(seq->file));
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	int i;
+
+	seq_printf(seq, "rc %lld %lld %lld\nfh %lld 0 0 0 0\nio %lld %lld\n",
+		   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_HITS]),
+		   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_MISSES]),
+		   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_NOCACHE]),
+		   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_FH_STALE]),
+		   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_IO_READ]),
+		   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_IO_WRITE]));
+
+	/* thread usage: */
+	seq_printf(seq, "th %u 0", atomic_read(&nfsd_th_cnt));
+
+	/* deprecated thread usage histogram stats */
+	for (i = 0; i < 10; i++)
+		seq_puts(seq, " 0.000");
+
+	/* deprecated ra-cache stats */
+	seq_puts(seq, "\nra 0 0 0 0 0 0 0 0 0 0 0 0\n");
+
+	/* show my rpc info */
+	svc_seq_show(seq, &nn->nfsd_svcstats);
+
+#ifdef CONFIG_NFSD_V4
+	/* Show count for individual nfsv4 operations */
+	/* Writing operation numbers 0 1 2 also for maintaining uniformity */
+	seq_printf(seq, "proc4ops %u", LAST_NFS4_OP + 1);
+	for (i = 0; i <= LAST_NFS4_OP; i++) {
+		seq_printf(seq, " %lld",
+			   percpu_counter_sum_positive(&nn->counter[NFSD_STATS_NFS4_OP(i)]));
+	}
+	seq_printf(seq, "\nwdeleg_getattr %lld",
+		percpu_counter_sum_positive(&nn->cb_counter[OP_CB_GETATTR]));
+
+	seq_putc(seq, '\n');
+#endif
+
+	return 0;
+}
+
+DEFINE_PROC_SHOW_ATTRIBUTE(nfsd);
+
+struct proc_dir_entry *nfsd_proc_stat_init(struct net *net)
+{
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+	return svc_proc_register(net, &nn->nfsd_svcstats, &nfsd_proc_ops);
+}
+
+void nfsd_proc_stat_shutdown(struct net *net)
+{
+	svc_proc_unregister(net, "nfsd");
+}