0x0008
     ¡ˆÚÙƒyÇØÁÖ !İ    ¡/* SPDX-License-Identifier: GPL-2.0 */
/*
 * linux/include/linux/relay.h
 *
 * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
 * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
 *
 * CONFIG_RELAY definitions and declarations
 */

#ifndef _LINUX_RELAY_H
#define _LINUX_RELAY_H

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/wait.h>
#include <linux/list.h>
#include <linux/irq_work.h>
#include <linux/bug.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.h>
#include <linux/percpu.h>

/*
 * Tracks changes to rchan/rchan_buf structs
 */
#define RELAYFS_CHANNEL_VERSION		7

/*
 * Per-cpu relay channel buffer
 */
struct rchan_buf
{
	void *start;			/* start of channel buffer */
	void *data;			/* start of current sub-buffer */
	size_t offset;			/* current offset into sub-buffer */
	size_t subbufs_produced;	/* count of sub-buffers produced */
	size_t subbufs_consumed;	/* count of sub-buffers consumed */
	struct rchan *chan;		/* associated channel */
	wait_queue_head_t read_wait;	/* reader wait queue */
	struct irq_work wakeup_work;	/* reader wakeup */
	struct dentry *dentry;		/* channel file dentry */
	struct kref kref;		/* channel buffer refcount */
	struct page **page_array;	/* array of current buffer pages */
	unsigned int page_count;	/* number of current buffer pages */
	unsigned int finalized;		/* buffer has been finalized */
	size_t *padding;		/* padding counts per sub-buffer */
	size_t prev_padding;		/* temporary variable */
	size_t bytes_consumed;		/* bytes consumed in cur read subbuf */
	size_t early_bytes;		/* bytes consumed before VFS inited */
	unsigned int cpu;		/* this buf's cpu */
} ____cacheline_aligned;

/*
 * Relay channel data structure
 */
struct rchan
{
	u32 version;			/* the version of this struct */
	size_t subbuf_size;		/* sub-buffer size */
	size_t n_subbufs;		/* number of sub-buffers per buffer */
	size_t alloc_size;		/* total buffer size allocated */
	const struct rchan_callbacks *cb; /* client callbacks */
	struct kref kref;		/* channel refcount */
	void *private_data;		/* for user-defined data */
	size_t last_toobig;		/* tried to log event > subbuf size */
	struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
	int is_global;			/* One global buffer ? */
	struct list_head list;		/* for channel list */
	struct dentry *parent;		/* parent dentry passed to open */
	int has_base_filename;		/* has a filename associated? */
	char base_filename[NAME_MAX];	/* saved base filename */
};

/*
 * Relay channel client callbacks
 */
struct rchan_callbacks
{
	/*
	 * subbuf_start - called on buffer-switch to a new sub-buffer
	 * @buf: the channel buffer containing the new sub-buffer
	 * @subbuf: the start of the new sub-buffer
	 * @prev_subbuf: the start of the previous sub-buffer
	 * @prev_padding: unused space at the end of previous sub-buffer
	 *
	 * The client should return 1 to continue logging, 0 to stop
	 * logging.
	 *
	 * This callback is optional.
	 *
	 * NOTE: subbuf_start will also be invoked when the buffer is
	 *       created, so that the first sub-buffer can be initialized
	 *       if necessary.  In this case, prev_subbuf will be NULL.
	 *
	 * NOTE: the client can reserve bytes at the beginning of the new
	 *       sub-buffer by calling subbuf_start_reserve() in this callback.
	 */
	int (*subbuf_start) (struct rchan_buf *buf,
			     void *subbuf,
			     void *prev_subbuf,
			     size_t prev_padding);

	/*
	 * create_buf_file - create file to represent a relay channel buffer
	 * @filename: the name of the file to create
	 * @parent: the parent of the file to create
	 * @mode: the mode of the file to create
	 * @buf: the channel buffer
	 * @is_global: outparam - set non-zero if the buffer should be global
	 *
	 * Called during relay_open(), once for each per-cpu buffer,
	 * to allow the client to create a file to be used to
	 * represent the corresponding channel buffer.  If the file is
	 * created outside of relay, the parent must also exist in
	 *