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, 183 insertions, 0 deletions

diff --git a/fs/netfs/main.c b/fs/netfs/main.c
new file mode 100644
index 000000000..927badf39
--- /dev/null
+++ b/fs/netfs/main.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Miscellaneous bits for the netfs support library.
+ *
+ * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/module.h>
+#include <linux/export.h>
+#include <linux/mempool.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+#define CREATE_TRACE_POINTS
+#include <trace/events/netfs.h>
+
+MODULE_DESCRIPTION("Network fs support");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+EXPORT_TRACEPOINT_SYMBOL(netfs_sreq);
+
+unsigned netfs_debug;
+module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
+
+static struct kmem_cache *netfs_request_slab;
+static struct kmem_cache *netfs_subrequest_slab;
+mempool_t netfs_request_pool;
+mempool_t netfs_subrequest_pool;
+mempool_t netfs_folioq_pool;
+
+#ifdef CONFIG_PROC_FS
+LIST_HEAD(netfs_io_requests);
+DEFINE_SPINLOCK(netfs_proc_lock);
+
+static const char *netfs_origins[nr__netfs_io_origin] = {
+	[NETFS_READAHEAD]		= "RA",
+	[NETFS_READPAGE]		= "RP",
+	[NETFS_READ_GAPS]		= "RG",
+	[NETFS_READ_SINGLE]		= "R1",
+	[NETFS_READ_FOR_WRITE]		= "RW",
+	[NETFS_UNBUFFERED_READ]		= "UR",
+	[NETFS_DIO_READ]		= "DR",
+	[NETFS_WRITEBACK]		= "WB",
+	[NETFS_WRITEBACK_SINGLE]	= "W1",
+	[NETFS_WRITETHROUGH]		= "WT",
+	[NETFS_UNBUFFERED_WRITE]	= "UW",
+	[NETFS_DIO_WRITE]		= "DW",
+	[NETFS_PGPRIV2_COPY_TO_CACHE]	= "2C",
+};
+
+/*
+ * Generate a list of I/O requests in /proc/fs/netfs/requests
+ */
+static int netfs_requests_seq_show(struct seq_file *m, void *v)
+{
+	struct netfs_io_request *rreq;
+
+	if (v == &netfs_io_requests) {
+		seq_puts(m,
+			 "REQUEST  OR REF FLAG ERR  OPS COVERAGE\n"
+			 "======== == === ==== ==== === =========\n"
+			 );
+		return 0;
+	}
+
+	rreq = list_entry(v, struct netfs_io_request, proc_link);
+	seq_printf(m,
+		   "%08x %s %3d %4lx %4ld %3d @%04llx %llx/%llx",
+		   rreq->debug_id,
+		   netfs_origins[rreq->origin],
+		   refcount_read(&rreq->ref),
+		   rreq->flags,
+		   rreq->error,
+		   0,
+		   rreq->start, rreq->submitted, rreq->len);
+	seq_putc(m, '\n');
+	return 0;
+}
+
+static void *netfs_requests_seq_start(struct seq_file *m, loff_t *_pos)
+	__acquires(rcu)
+{
+	rcu_read_lock();
+	return seq_list_start_head(&netfs_io_requests, *_pos);
+}
+
+static void *netfs_requests_seq_next(struct seq_file *m, void *v, loff_t *_pos)
+{
+	return seq_list_next(v, &netfs_io_requests, _pos);
+}
+
+static void netfs_requests_seq_stop(struct seq_file *m, void *v)
+	__releases(rcu)
+{
+	rcu_read_unlock();
+}
+
+static const struct seq_operations netfs_requests_seq_ops = {
+	.start  = netfs_requests_seq_start,
+	.next   = netfs_requests_seq_next,
+	.stop   = netfs_requests_seq_stop,
+	.show   = netfs_requests_seq_show,
+};
+#endif /* CONFIG_PROC_FS */
+
+static int __init netfs_init(void)
+{
+	int ret = -ENOMEM;
+
+	if (mempool_init_kmalloc_pool(&netfs_folioq_pool, 100, sizeof(struct folio_queue)) < 0)
+		goto error_folioq_pool;
+
+	netfs_request_slab = kmem_cache_create("netfs_request",
+					       sizeof(struct netfs_io_request), 0,
+					       SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT,
+					       NULL);
+	if (!netfs_request_slab)
+		goto error_req;
+
+	if (mempool_init_slab_pool(&netfs_request_pool, 100, netfs_request_slab) < 0)
+		goto error_reqpool;
+
+	netfs_subrequest_slab = kmem_cache_create("netfs_subrequest",
+						  sizeof(struct netfs_io_subrequest) + 16, 0,
+						  SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT,
+						  NULL);
+	if (!netfs_subrequest_slab)
+		goto error_subreq;
+
+	if (mempool_init_slab_pool(&netfs_subrequest_pool, 100, netfs_subrequest_slab) < 0)
+		goto error_subreqpool;
+
+#ifdef CONFIG_PROC_FS
+	if (!proc_mkdir("fs/netfs", NULL))
+		goto error_proc;
+	if (!proc_create_seq("fs/netfs/requests", S_IFREG | 0444, NULL,
+			     &netfs_requests_seq_ops))
+		goto error_procfile;
+#endif
+#ifdef CONFIG_FSCACHE_STATS
+	if (!proc_create_single("fs/netfs/stats", S_IFREG | 0444, NULL,
+				netfs_stats_show))
+		goto error_procfile;
+#endif
+
+	ret = fscache_init();
+	if (ret < 0)
+		goto error_fscache;
+	return 0;
+
+error_fscache:
+#ifdef CONFIG_PROC_FS
+error_procfile:
+	remove_proc_subtree("fs/netfs", NULL);
+error_proc:
+#endif
+	mempool_exit(&netfs_subrequest_pool);
+error_subreqpool:
+	kmem_cache_destroy(netfs_subrequest_slab);
+error_subreq:
+	mempool_exit(&netfs_request_pool);
+error_reqpool:
+	kmem_cache_destroy(netfs_request_slab);
+error_req:
+	mempool_exit(&netfs_folioq_pool);
+error_folioq_pool:
+	return ret;
+}
+fs_initcall(netfs_init);
+
+static void __exit netfs_exit(void)
+{
+	fscache_exit();
+	remove_proc_subtree("fs/netfs", NULL);
+	mempool_exit(&netfs_subrequest_pool);
+	kmem_cache_destroy(netfs_subrequest_slab);
+	mempool_exit(&netfs_request_pool);
+	kmem_cache_destroy(netfs_request_slab);
+	mempool_exit(&netfs_folioq_pool);
+}
+module_exit(netfs_exit);