tracing: Move snapshot code out of trace.c and into trace_snapshot.c

The trace.c file was a dumping ground for most tracing code. Start
organizing it better by moving various functions out into their own files.
Move all the snapshot code, including the max trace code into its own
trace_snapshot.c file.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20260324140145.36352d6a@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

include/linux/ftrace.h

@@ -31,7 +31,7 @@
 #define ARCH_SUPPORTS_FTRACE_OPS 0
 #endif
 
-#ifdef CONFIG_TRACING
+#ifdef CONFIG_TRACER_SNAPSHOT
 extern void ftrace_boot_snapshot(void);
 #else
 static inline void ftrace_boot_snapshot(void) { }

kernel/trace/Makefile

@@ -69,6 +69,7 @@ obj-$(CONFIG_TRACING) += trace_seq.o
 obj-$(CONFIG_TRACING) += trace_stat.o
 obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_TRACING) += trace_pid.o
+obj-$(CONFIG_TRACER_SNAPSHOT) += trace_snapshot.o
 obj-$(CONFIG_TRACING) += 	pid_list.o
 obj-$(CONFIG_TRACING_MAP) += tracing_map.o
 obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.o

kernel/trace/trace.h

@@ -264,6 +264,7 @@ static inline bool still_need_pid_events(int type, struct trace_pid_list *pid_li
 
 typedef bool (*cond_update_fn_t)(struct trace_array *tr, void *cond_data);
 
+#ifdef CONFIG_TRACER_SNAPSHOT
 /**
  * struct cond_snapshot - conditional snapshot data and callback
  *
@@ -306,6 +307,7 @@ struct cond_snapshot {
 	void				*cond_data;
 	cond_update_fn_t		update;
 };
+#endif /* CONFIG_TRACER_SNAPSHOT */
 
 /*
  * struct trace_func_repeats - used to keep track of the consecutive
@@ -675,6 +677,7 @@ void tracing_reset_all_online_cpus(void);
 void tracing_reset_all_online_cpus_unlocked(void);
 int tracing_open_generic(struct inode *inode, struct file *filp);
 int tracing_open_generic_tr(struct inode *inode, struct file *filp);
+int tracing_release(struct inode *inode, struct file *file);
 int tracing_release_generic_tr(struct inode *inode, struct file *file);
 int tracing_open_file_tr(struct inode *inode, struct file *filp);
 int tracing_release_file_tr(struct inode *inode, struct file *filp);
@@ -684,12 +687,48 @@ void tracer_tracing_on(struct trace_array *tr);
 void tracer_tracing_off(struct trace_array *tr);
 void tracer_tracing_disable(struct trace_array *tr);
 void tracer_tracing_enable(struct trace_array *tr);
+int allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, int size);
 struct dentry *trace_create_file(const char *name,
 				 umode_t mode,
 				 struct dentry *parent,
 				 void *data,
 				 const struct file_operations *fops);
 
+struct trace_iterator *__tracing_open(struct inode *inode, struct file *file,
+				      bool snapshot);
+int tracing_buffers_open(struct inode *inode, struct file *filp);
+ssize_t tracing_buffers_read(struct file *filp, char __user *ubuf,
+			     size_t count, loff_t *ppos);
+int tracing_buffers_release(struct inode *inode, struct file *file);
+ssize_t tracing_buffers_splice_read(struct file *file, loff_t *ppos,
+		   struct pipe_inode_info *pipe, size_t len, unsigned int flags);
+
+ssize_t tracing_nsecs_read(unsigned long *ptr, char __user *ubuf,
+			   size_t cnt, loff_t *ppos);
+ssize_t tracing_nsecs_write(unsigned long *ptr, const char __user *ubuf,
+			    size_t cnt, loff_t *ppos);
+
+void trace_set_buffer_entries(struct array_buffer *buf, unsigned long val);
+
+/*
+ * Should be used after trace_array_get(), trace_types_lock
+ * ensures that i_cdev was already initialized.
+ */
+static inline int tracing_get_cpu(struct inode *inode)
+{
+	if (inode->i_cdev) /* See trace_create_cpu_file() */
+		return (long)inode->i_cdev - 1;
+	return RING_BUFFER_ALL_CPUS;
+}
+void tracing_reset_cpu(struct array_buffer *buf, int cpu);
+
+struct ftrace_buffer_info {
+	struct trace_iterator	iter;
+	void			*spare;
+	unsigned int		spare_cpu;
+	unsigned int		spare_size;
+	unsigned int		read;
+};
 
 /**
  * tracer_tracing_is_on_cpu - show real state of ring buffer enabled on for a cpu
@@ -828,11 +867,15 @@ static inline bool tracer_uses_snapshot(struct tracer *tracer)
 {
 	return tracer->use_max_tr;
 }
+void trace_create_maxlat_file(struct trace_array *tr,
+			      struct dentry *d_tracer);
 #else
 static inline bool tracer_uses_snapshot(struct tracer *tracer)
 {
 	return false;
 }
+static inline void trace_create_maxlat_file(struct trace_array *tr,
+					    struct dentry *d_tracer) { }
 #endif
 
 void trace_last_func_repeats(struct trace_array *tr,
@@ -2140,12 +2183,6 @@ static inline bool event_command_needs_rec(struct event_command *cmd_ops)
 
 extern int trace_event_enable_disable(struct trace_event_file *file,
 				      int enable, int soft_disable);
-extern int tracing_alloc_snapshot(void);
-extern void tracing_snapshot_cond(struct trace_array *tr, void *cond_data);
-extern int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data, cond_update_fn_t update);
-
-extern int tracing_snapshot_cond_disable(struct trace_array *tr);
-extern void *tracing_cond_snapshot_data(struct trace_array *tr);
 
 extern const char *__start___trace_bprintk_fmt[];
 extern const char *__stop___trace_bprintk_fmt[];
@@ -2233,19 +2270,71 @@ static inline void trace_event_update_all(struct trace_eval_map **map, int len)
 #endif
 
 #ifdef CONFIG_TRACER_SNAPSHOT
+extern const struct file_operations snapshot_fops;
+extern const struct file_operations snapshot_raw_fops;
+
+/* Used when creating instances */
+int trace_allocate_snapshot(struct trace_array *tr, int size);
+
+int tracing_alloc_snapshot(void);
+void tracing_snapshot_cond(struct trace_array *tr, void *cond_data);
+int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data, cond_update_fn_t update);
+int tracing_snapshot_cond_disable(struct trace_array *tr);
+void *tracing_cond_snapshot_data(struct trace_array *tr);
 void tracing_snapshot_instance(struct trace_array *tr);
 int tracing_alloc_snapshot_instance(struct trace_array *tr);
+int tracing_arm_snapshot_locked(struct trace_array *tr);
 int tracing_arm_snapshot(struct trace_array *tr);
 void tracing_disarm_snapshot(struct trace_array *tr);
-#else
+void free_snapshot(struct trace_array *tr);
+void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter);
+int get_snapshot_map(struct trace_array *tr);
+void put_snapshot_map(struct trace_array *tr);
+int resize_buffer_duplicate_size(struct array_buffer *trace_buf,
+				 struct array_buffer *size_buf, int cpu_id);
+__init void do_allocate_snapshot(const char *name);
+# ifdef CONFIG_DYNAMIC_FTRACE
+__init int register_snapshot_cmd(void);
+# else
+static inline int register_snapshot_cmd(void) { return 0; }
+# endif
+#else /* !CONFIG_TRACER_SNAPSHOT */
+static inline int trace_allocate_snapshot(struct trace_array *tr, int size) { return 0; }
 static inline void tracing_snapshot_instance(struct trace_array *tr) { }
 static inline int tracing_alloc_snapshot_instance(struct trace_array *tr)
 {
 	return 0;
 }
+static inline int tracing_arm_snapshot_locked(struct trace_array *tr) { return -EBUSY; }
 static inline int tracing_arm_snapshot(struct trace_array *tr) { return 0; }
 static inline void tracing_disarm_snapshot(struct trace_array *tr) { }
-#endif
+static inline void free_snapshot(struct trace_array *tr) {}
+static inline void tracing_snapshot_cond(struct trace_array *tr, void *cond_data)
+{
+	WARN_ONCE(1, "Snapshot feature not enabled, but internal conditional snapshot used");
+}
+static inline void *tracing_cond_snapshot_data(struct trace_array *tr)
+{
+	return NULL;
+}
+static inline int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data, cond_update_fn_t update)
+{
+	return -ENODEV;
+}
+static inline int tracing_snapshot_cond_disable(struct trace_array *tr)
+{
+	return false;
+}
+static inline void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter)
+{
+	/* Should never be called */
+	WARN_ONCE(1, "Snapshot print function called without snapshot configured");
+}
+static inline int get_snapshot_map(struct trace_array *tr) { return 0; }
+static inline void put_snapshot_map(struct trace_array *tr) { }
+static inline void do_allocate_snapshot(const char *name) { }
+static inline int register_snapshot_cmd(void) { return 0; }
+#endif /* CONFIG_TRACER_SNAPSHOT */
 
 #ifdef CONFIG_PREEMPT_TRACER
 void tracer_preempt_on(unsigned long a0, unsigned long a1);