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, 270 insertions, 0 deletions

diff --git a/drivers/md/dm-ps-io-affinity.c b/drivers/md/dm-ps-io-affinity.c
new file mode 100644
index 000000000..526d94d13
--- /dev/null
+++ b/drivers/md/dm-ps-io-affinity.c
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Oracle Corporation
+ *
+ * Module Author: Mike Christie
+ */
+#include "dm-path-selector.h"
+
+#include <linux/device-mapper.h>
+#include <linux/module.h>
+
+#define DM_MSG_PREFIX "multipath io-affinity"
+
+struct path_info {
+	struct dm_path *path;
+	cpumask_var_t cpumask;
+	refcount_t refcount;
+	bool failed;
+};
+
+struct selector {
+	struct path_info **path_map;
+	cpumask_var_t path_mask;
+	atomic_t map_misses;
+};
+
+static void ioa_free_path(struct selector *s, unsigned int cpu)
+{
+	struct path_info *pi = s->path_map[cpu];
+
+	if (!pi)
+		return;
+
+	if (refcount_dec_and_test(&pi->refcount)) {
+		cpumask_clear_cpu(cpu, s->path_mask);
+		free_cpumask_var(pi->cpumask);
+		kfree(pi);
+
+		s->path_map[cpu] = NULL;
+	}
+}
+
+static int ioa_add_path(struct path_selector *ps, struct dm_path *path,
+			int argc, char **argv, char **error)
+{
+	struct selector *s = ps->context;
+	struct path_info *pi = NULL;
+	unsigned int cpu;
+	int ret;
+
+	if (argc != 1) {
+		*error = "io-affinity ps: invalid number of arguments";
+		return -EINVAL;
+	}
+
+	pi = kzalloc_obj(*pi);
+	if (!pi) {
+		*error = "io-affinity ps: Error allocating path context";
+		return -ENOMEM;
+	}
+
+	pi->path = path;
+	path->pscontext = pi;
+	refcount_set(&pi->refcount, 1);
+
+	if (!zalloc_cpumask_var(&pi->cpumask, GFP_KERNEL)) {
+		*error = "io-affinity ps: Error allocating cpumask context";
+		ret = -ENOMEM;
+		goto free_pi;
+	}
+
+	ret = cpumask_parse(argv[0], pi->cpumask);
+	if (ret) {
+		*error = "io-affinity ps: invalid cpumask";
+		ret = -EINVAL;
+		goto free_mask;
+	}
+
+	for_each_cpu(cpu, pi->cpumask) {
+		if (cpu >= nr_cpu_ids) {
+			DMWARN_LIMIT("Ignoring mapping for CPU %u. Max CPU is %u",
+				     cpu, nr_cpu_ids);
+			break;
+		}
+
+		if (s->path_map[cpu]) {
+			DMWARN("CPU mapping for %u exists. Ignoring.", cpu);
+			continue;
+		}
+
+		cpumask_set_cpu(cpu, s->path_mask);
+		s->path_map[cpu] = pi;
+		refcount_inc(&pi->refcount);
+	}
+
+	if (refcount_dec_and_test(&pi->refcount)) {
+		*error = "io-affinity ps: No new/valid CPU mapping found";
+		ret = -EINVAL;
+		goto free_mask;
+	}
+
+	return 0;
+
+free_mask:
+	free_cpumask_var(pi->cpumask);
+free_pi:
+	kfree(pi);
+	return ret;
+}
+
+static int ioa_create(struct path_selector *ps, unsigned int argc, char **argv)
+{
+	struct selector *s;
+
+	s = kmalloc_obj(*s);
+	if (!s)
+		return -ENOMEM;
+
+	s->path_map = kzalloc_objs(struct path_info *, nr_cpu_ids);
+	if (!s->path_map)
+		goto free_selector;
+
+	if (!zalloc_cpumask_var(&s->path_mask, GFP_KERNEL))
+		goto free_map;
+
+	atomic_set(&s->map_misses, 0);
+	ps->context = s;
+	return 0;
+
+free_map:
+	kfree(s->path_map);
+free_selector:
+	kfree(s);
+	return -ENOMEM;
+}
+
+static void ioa_destroy(struct path_selector *ps)
+{
+	struct selector *s = ps->context;
+	unsigned int cpu;
+
+	for_each_cpu(cpu, s->path_mask)
+		ioa_free_path(s, cpu);
+
+	free_cpumask_var(s->path_mask);
+	kfree(s->path_map);
+	kfree(s);
+
+	ps->context = NULL;
+}
+
+static int ioa_status(struct path_selector *ps, struct dm_path *path,
+		      status_type_t type, char *result, unsigned int maxlen)
+{
+	struct selector *s = ps->context;
+	struct path_info *pi;
+	int sz = 0;
+
+	if (!path) {
+		DMEMIT("0 ");
+		return sz;
+	}
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		DMEMIT("%d ", atomic_read(&s->map_misses));
+		break;
+	case STATUSTYPE_TABLE:
+		pi = path->pscontext;
+		DMEMIT("%*pb ", cpumask_pr_args(pi->cpumask));
+		break;
+	case STATUSTYPE_IMA:
+		*result = '\0';
+		break;
+	}
+
+	return sz;
+}
+
+static void ioa_fail_path(struct path_selector *ps, struct dm_path *p)
+{
+	struct path_info *pi = p->pscontext;
+
+	pi->failed = true;
+}
+
+static int ioa_reinstate_path(struct path_selector *ps, struct dm_path *p)
+{
+	struct path_info *pi = p->pscontext;
+
+	pi->failed = false;
+	return 0;
+}
+
+static struct dm_path *ioa_select_path(struct path_selector *ps,
+				       size_t nr_bytes)
+{
+	unsigned int cpu, node;
+	struct selector *s = ps->context;
+	const struct cpumask *cpumask;
+	struct path_info *pi;
+	int i;
+
+	cpu = get_cpu();
+
+	pi = s->path_map[cpu];
+	if (pi && !pi->failed)
+		goto done;
+
+	/*
+	 * Perf is not optimal, but we at least try the local node then just
+	 * try not to fail.
+	 */
+	if (!pi)
+		atomic_inc(&s->map_misses);
+
+	node = cpu_to_node(cpu);
+	cpumask = cpumask_of_node(node);
+	for_each_cpu(i, cpumask) {
+		pi = s->path_map[i];
+		if (pi && !pi->failed)
+			goto done;
+	}
+
+	for_each_cpu(i, s->path_mask) {
+		pi = s->path_map[i];
+		if (pi && !pi->failed)
+			goto done;
+	}
+	pi = NULL;
+
+done:
+	put_cpu();
+	return pi ? pi->path : NULL;
+}
+
+static struct path_selector_type ioa_ps = {
+	.name		= "io-affinity",
+	.module		= THIS_MODULE,
+	.table_args	= 1,
+	.info_args	= 1,
+	.create		= ioa_create,
+	.destroy	= ioa_destroy,
+	.status		= ioa_status,
+	.add_path	= ioa_add_path,
+	.fail_path	= ioa_fail_path,
+	.reinstate_path	= ioa_reinstate_path,
+	.select_path	= ioa_select_path,
+};
+
+static int __init dm_ioa_init(void)
+{
+	int ret = dm_register_path_selector(&ioa_ps);
+
+	if (ret < 0)
+		DMERR("register failed %d", ret);
+	return ret;
+}
+
+static void __exit dm_ioa_exit(void)
+{
+	dm_unregister_path_selector(&ioa_ps);
+}
+
+module_init(dm_ioa_init);
+module_exit(dm_ioa_exit);
+
+MODULE_DESCRIPTION(DM_NAME " multipath path selector that selects paths based on the CPU IO is being executed on");
+MODULE_AUTHOR("Mike Christie <michael.christie@oracle.com>");
+MODULE_LICENSE("GPL");