[mirror_ubuntu-bionic-kernel.git] / include / linux / relay.h

/*
 * 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/bug.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.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 timer_list timer; 	/* reader wake-up timer */
	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 */
	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 *buf[NR_CPUS]; /* 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.
	 *
	 * 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);

	/*
	 * buf_mapped - relay buffer mmap notification
	 * @buf: the channel buffer
	 * @filp: relay file pointer
	 *
	 * Called when a relay file is successfully mmapped
	 */
        void (*buf_mapped)(struct rchan_buf *buf,
			   struct file *filp);

	/*
	 * buf_unmapped - relay buffer unmap notification
	 * @buf: the channel buffer
	 * @filp: relay file pointer
	 *
	 * Called when a relay file is successfully unmapped
	 */
        void (*buf_unmapped)(struct rchan_buf *buf,
			     struct file *filp);
	/*
	 * 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
	 * that filesystem.
	 *
	 * The callback should return the dentry of the file created
	 * to represent the relay buffer.
	 *
	 * Setting the is_global outparam to a non-zero value will
	 * cause relay_open() to create a single global buffer rather
	 * than the default set of per-cpu buffers.
	 *
	 * See Documentation/filesystems/relay.txt for more info.
	 */
	struct dentry *(*create_buf_file)(const char *filename,
					  struct dentry *parent,
					  umode_t mode,
					  struct rchan_buf *buf,
					  int *is_global);

	/*
	 * remove_buf_file - remove file representing a relay channel buffer
	 * @dentry: the dentry of the file to remove
	 *
	 * Called during relay_close(), once for each per-cpu buffer,
	 * to allow the client to remove a file used to represent a
	 * channel buffer.
	 *
	 * The callback should return 0 if successful, negative if not.
	 */
	int (*remove_buf_file)(struct dentry *dentry);
};

/*
 * CONFIG_RELAY kernel API, kernel/relay.c
 */

struct rchan *relay_open(const char *base_filename,
			 struct dentry *parent,
			 size_t subbuf_size,
			 size_t n_subbufs,
			 struct rchan_callbacks *cb,
			 void *private_data);
extern int relay_late_setup_files(struct rchan *chan,
				  const char *base_filename,
				  struct dentry *parent);
extern void relay_close(struct rchan *chan);
extern void relay_flush(struct rchan *chan);
extern void relay_subbufs_consumed(struct rchan *chan,
				   unsigned int cpu,
				   size_t consumed);
extern void relay_reset(struct rchan *chan);
extern int relay_buf_full(struct rchan_buf *buf);

extern size_t relay_switch_subbuf(struct rchan_buf *buf,
				  size_t length);

/**
 *	relay_write - write data into the channel
 *	@chan: relay channel
 *	@data: data to be written
 *	@length: number of bytes to write
 *
 *	Writes data into the current cpu's channel buffer.
 *
 *	Protects the buffer by disabling interrupts.  Use this
 *	if you might be logging from interrupt context.  Try
 *	__relay_write() if you know you	won't be logging from
 *	interrupt context.
 */
static inline void relay_write(struct rchan *chan,
			       const void *data,
			       size_t length)
{
	unsigned long flags;
	struct rchan_buf *buf;

	local_irq_save(flags);
	buf = chan->buf[smp_processor_id()];
	if (unlikely(buf->offset + length > chan->subbuf_size))
		length = relay_switch_subbuf(buf, length);
	memcpy(buf->data + buf->offset, data, length);
	buf->offset += length;
	local_irq_restore(flags);
}

/**
 *	__relay_write - write data into the channel
 *	@chan: relay channel
 *	@data: data to be written
 *	@length: number of bytes to write
 *
 *	Writes data into the current cpu's channel buffer.
 *
 *	Protects the buffer by disabling preemption.  Use
 *	relay_write() if you might be logging from interrupt
 *	context.
 */
static inline void __relay_write(struct rchan *chan,
				 const void *data,
				 size_t length)
{
	struct rchan_buf *buf;

	buf = chan->buf[get_cpu()];
	if (unlikely(buf->offset + length > buf->chan->subbuf_size))
		length = relay_switch_subbuf(buf, length);
	memcpy(buf->data + buf->offset, data, length);
	buf->offset += length;
	put_cpu();
}

/**
 *	relay_reserve - reserve slot in channel buffer
 *	@chan: relay channel
 *	@length: number of bytes to reserve
 *
 *	Returns pointer to reserved slot, NULL if full.
 *
 *	Reserves a slot in the current cpu's channel buffer.
 *	Does not protect the buffer at all - caller must provide
 *	appropriate synchronization.
 */
static inline void *relay_reserve(struct rchan *chan, size_t length)
{
	void *reserved;
	struct rchan_buf *buf = chan->buf[smp_processor_id()];

	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
		length = relay_switch_subbuf(buf, length);
		if (!length)
			return NULL;
	}
	reserved = buf->data + buf->offset;
	buf->offset += length;

	return reserved;
}

/**
 *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer
 *	@buf: relay channel buffer
 *	@length: number of bytes to reserve
 *
 *	Helper function used to reserve bytes at the beginning of
 *	a sub-buffer in the subbuf_start() callback.
 */
static inline void subbuf_start_reserve(struct rchan_buf *buf,
					size_t length)
{
	BUG_ON(length >= buf->chan->subbuf_size - 1);
	buf->offset = length;
}

/*
 * exported relay file operations, kernel/relay.c
 */
extern const struct file_operations relay_file_operations;

#endif /* _LINUX_RELAY_H */
Commit	Line	Data
b86ff981 JA	1	/*
	2	* linux/include/linux/relay.h
	3	*
	4	* Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
	5	* Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
	6	*
	7	* CONFIG_RELAY definitions and declarations
	8	*/
	9
	10	#ifndef _LINUX_RELAY_H
	11	#define _LINUX_RELAY_H
	12
b86ff981 JA	13	#include <linux/types.h>
b86ff981 JA	14	#include <linux/sched.h>
7c9cb383	15	#include <linux/timer.h>
b86ff981 JA	16	#include <linux/wait.h>
b86ff981 JA	17	#include <linux/list.h>
187f1882	18	#include <linux/bug.h>
b86ff981 JA	19	#include <linux/fs.h>
	20	#include <linux/poll.h>
	21	#include <linux/kref.h>
	22
b86ff981 JA	23	/*
	24	* Tracks changes to rchan/rchan_buf structs
	25	*/
23c88752	26	#define RELAYFS_CHANNEL_VERSION 7
b86ff981 JA	27
	28	/*
	29	* Per-cpu relay channel buffer
	30	*/
	31	struct rchan_buf
	32	{
	33	void start; / start of channel buffer */
	34	void data; / start of current sub-buffer */
	35	size_t offset; /* current offset into sub-buffer */
	36	size_t subbufs_produced; /* count of sub-buffers produced */
	37	size_t subbufs_consumed; /* count of sub-buffers consumed */
	38	struct rchan chan; / associated channel */
	39	wait_queue_head_t read_wait; /* reader wait queue */
7c9cb383	40	struct timer_list timer; /* reader wake-up timer */
b86ff981 JA	41	struct dentry dentry; / channel file dentry */
	42	struct kref kref; /* channel buffer refcount */
	43	struct page *page_array; / array of current buffer pages */
	44	unsigned int page_count; /* number of current buffer pages */
	45	unsigned int finalized; /* buffer has been finalized */
	46	size_t padding; / padding counts per sub-buffer */
	47	size_t prev_padding; /* temporary variable */
	48	size_t bytes_consumed; /* bytes consumed in cur read subbuf */
20d8b67c	49	size_t early_bytes; /* bytes consumed before VFS inited */
b86ff981 JA	50	unsigned int cpu; /* this buf's cpu */
	51	} ____cacheline_aligned;
	52
	53	/*
	54	* Relay channel data structure
	55	*/
	56	struct rchan
	57	{
	58	u32 version; /* the version of this struct */
	59	size_t subbuf_size; /* sub-buffer size */
	60	size_t n_subbufs; /* number of sub-buffers per buffer */
	61	size_t alloc_size; /* total buffer size allocated */
	62	struct rchan_callbacks cb; / client callbacks */
	63	struct kref kref; /* channel refcount */
	64	void private_data; / for user-defined data */
	65	size_t last_toobig; /* tried to log event > subbuf size */
	66	struct rchan_buf buf[NR_CPUS]; / per-cpu channel buffers */
23c88752 MD	67	int is_global; /* One global buffer ? */
	68	struct list_head list; /* for channel list */
	69	struct dentry parent; / parent dentry passed to open */
20d8b67c	70	int has_base_filename; /* has a filename associated? */
23c88752	71	char base_filename[NAME_MAX]; /* saved base filename */
b86ff981 JA	72	};
	73
	74	/*
	75	* Relay channel client callbacks
	76	*/
	77	struct rchan_callbacks
	78	{
	79	/*
	80	* subbuf_start - called on buffer-switch to a new sub-buffer
	81	* @buf: the channel buffer containing the new sub-buffer
	82	* @subbuf: the start of the new sub-buffer
	83	* @prev_subbuf: the start of the previous sub-buffer
	84	* @prev_padding: unused space at the end of previous sub-buffer
	85	*
	86	* The client should return 1 to continue logging, 0 to stop
	87	* logging.
	88	*
	89	* NOTE: subbuf_start will also be invoked when the buffer is
	90	* created, so that the first sub-buffer can be initialized
	91	* if necessary. In this case, prev_subbuf will be NULL.
	92	*
	93	* NOTE: the client can reserve bytes at the beginning of the new
	94	* sub-buffer by calling subbuf_start_reserve() in this callback.
	95	*/
	96	int (subbuf_start) (struct rchan_buf buf,
	97	void *subbuf,
	98	void *prev_subbuf,
	99	size_t prev_padding);
	100
	101	/*
	102	* buf_mapped - relay buffer mmap notification
	103	* @buf: the channel buffer
	104	* @filp: relay file pointer
	105	*
	106	* Called when a relay file is successfully mmapped
	107	*/
	108	void (buf_mapped)(struct rchan_buf buf,
	109	struct file *filp);
	110
	111	/*
	112	* buf_unmapped - relay buffer unmap notification
	113	* @buf: the channel buffer
	114	* @filp: relay file pointer
	115	*
	116	* Called when a relay file is successfully unmapped
	117	*/
	118	void (buf_unmapped)(struct rchan_buf buf,
	119	struct file *filp);
	120	/*
	121	* create_buf_file - create file to represent a relay channel buffer
	122	* @filename: the name of the file to create
	123	* @parent: the parent of the file to create
	124	* @mode: the mode of the file to create
	125	* @buf: the channel buffer
	126	* @is_global: outparam - set non-zero if the buffer should be global
	127	*
	128	* Called during relay_open(), once for each per-cpu buffer,
	129	* to allow the client to create a file to be used to
	130	* represent the corresponding channel buffer. If the file is
	131	* created outside of relay, the parent must also exist in
	132	* that filesystem.
	133	*
	134	* The callback should return the dentry of the file created
	135	* to represent the relay buffer.
136	*
137	* Setting the is_global outparam to a non-zero value will
138	* cause relay_open() to create a single global buffer rather
139	* than the default set of per-cpu buffers.
140	*
55dff495	141	* See Documentation/filesystems/relay.txt for more info.
b86ff981 JA	142	*/
	143	struct dentry (create_buf_file)(const char *filename,
	144	struct dentry *parent,
f4ae40a6	145	umode_t mode,
b86ff981 JA	146	struct rchan_buf *buf,
	147	int *is_global);
	148
	149	/*
	150	* remove_buf_file - remove file representing a relay channel buffer
	151	* @dentry: the dentry of the file to remove
	152	*
	153	* Called during relay_close(), once for each per-cpu buffer,
	154	* to allow the client to remove a file used to represent a
	155	* channel buffer.
	156	*
	157	* The callback should return 0 if successful, negative if not.
	158	*/
	159	int (remove_buf_file)(struct dentry dentry);
	160	};
	161
	162	/*
	163	* CONFIG_RELAY kernel API, kernel/relay.c
	164	*/
	165
	166	struct rchan relay_open(const char base_filename,
	167	struct dentry *parent,
	168	size_t subbuf_size,
	169	size_t n_subbufs,
23c88752 MD	170	struct rchan_callbacks *cb,
23c88752 MD	171	void *private_data);
20d8b67c EGM	172	extern int relay_late_setup_files(struct rchan *chan,
	173	const char *base_filename,
	174	struct dentry *parent);
b86ff981 JA	175	extern void relay_close(struct rchan *chan);
	176	extern void relay_flush(struct rchan *chan);
	177	extern void relay_subbufs_consumed(struct rchan *chan,
	178	unsigned int cpu,
	179	size_t consumed);
	180	extern void relay_reset(struct rchan *chan);
	181	extern int relay_buf_full(struct rchan_buf *buf);
	182
	183	extern size_t relay_switch_subbuf(struct rchan_buf *buf,
	184	size_t length);
	185
	186	/**
	187	* relay_write - write data into the channel
	188	* @chan: relay channel
	189	* @data: data to be written
	190	* @length: number of bytes to write
	191	*
	192	* Writes data into the current cpu's channel buffer.
	193	*
	194	* Protects the buffer by disabling interrupts. Use this
	195	* if you might be logging from interrupt context. Try
	196	* __relay_write() if you know you won't be logging from
	197	* interrupt context.
	198	*/
	199	static inline void relay_write(struct rchan *chan,
	200	const void *data,
	201	size_t length)
	202	{
	203	unsigned long flags;
	204	struct rchan_buf *buf;
	205
	206	local_irq_save(flags);
	207	buf = chan->buf[smp_processor_id()];
	208	if (unlikely(buf->offset + length > chan->subbuf_size))
	209	length = relay_switch_subbuf(buf, length);
	210	memcpy(buf->data + buf->offset, data, length);
	211	buf->offset += length;
	212	local_irq_restore(flags);
	213	}
	214
	215	/**
	216	* __relay_write - write data into the channel
	217	* @chan: relay channel
	218	* @data: data to be written
	219	* @length: number of bytes to write
	220	*
	221	* Writes data into the current cpu's channel buffer.
	222	*
	223	* Protects the buffer by disabling preemption. Use
	224	* relay_write() if you might be logging from interrupt
	225	* context.
	226	*/
	227	static inline void __relay_write(struct rchan *chan,
	228	const void *data,
	229	size_t length)
	230	{
	231	struct rchan_buf *buf;
	232
	233	buf = chan->buf[get_cpu()];
	234	if (unlikely(buf->offset + length > buf->chan->subbuf_size))
	235	length = relay_switch_subbuf(buf, length);
	236	memcpy(buf->data + buf->offset, data, length);
	237	buf->offset += length;
	238	put_cpu();
239	}
240
241	/**
242	* relay_reserve - reserve slot in channel buffer
243	* @chan: relay channel
244	* @length: number of bytes to reserve
245	*
246	* Returns pointer to reserved slot, NULL if full.
247	*
248	* Reserves a slot in the current cpu's channel buffer.
249	* Does not protect the buffer at all - caller must provide
250	* appropriate synchronization.
251	*/
252	static inline void relay_reserve(struct rchan chan, size_t length)
253	{
254	void *reserved;
255	struct rchan_buf *buf = chan->buf[smp_processor_id()];
256
257	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
258	length = relay_switch_subbuf(buf, length);
259	if (!length)
260	return NULL;
261	}
262	reserved = buf->data + buf->offset;
263	buf->offset += length;
264
265	return reserved;
266	}
267
268	/**
269	* subbuf_start_reserve - reserve bytes at the start of a sub-buffer
270	* @buf: relay channel buffer
271	* @length: number of bytes to reserve
272	*
273	* Helper function used to reserve bytes at the beginning of
274	* a sub-buffer in the subbuf_start() callback.
275	*/
276	static inline void subbuf_start_reserve(struct rchan_buf *buf,
277	size_t length)
278	{
279	BUG_ON(length >= buf->chan->subbuf_size - 1);
280	buf->offset = length;
281	}
282
283	/*
284	* exported relay file operations, kernel/relay.c
285	*/
15ad7cdc	286	extern const struct file_operations relay_file_operations;
b86ff981 JA	287
	288	#endif /* _LINUX_RELAY_H */
	289