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
13#include <linux/types.h>
14#include <linux/sched.h>
15#include <linux/timer.h>
16#include <linux/wait.h>
17#include <linux/list.h>
18#include <linux/bug.h>
19#include <linux/fs.h>
20#include <linux/poll.h>
21#include <linux/kref.h>
22
23/*
24 * Tracks changes to rchan/rchan_buf structs
25 */
26#define RELAYFS_CHANNEL_VERSION		7
27
28/*
29 * Per-cpu relay channel buffer
30 */
31struct 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 */
40	struct timer_list timer; 	/* reader wake-up timer */
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 */
49	size_t early_bytes;		/* bytes consumed before VFS inited */
50	unsigned int cpu;		/* this buf's cpu */
51} ____cacheline_aligned;
52
53/*
54 * Relay channel data structure
55 */
56struct 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 */
67	int is_global;			/* One global buffer ? */
68	struct list_head list;		/* for channel list */
69	struct dentry *parent;		/* parent dentry passed to open */
70	int has_base_filename;		/* has a filename associated? */
71	char base_filename[NAME_MAX];	/* saved base filename */
72};
73
74/*
75 * Relay channel client callbacks
76 */
77struct 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	 *
141	 * See Documentation/filesystems/relay.txt for more info.
142	 */
143	struct dentry *(*create_buf_file)(const char *filename,
144					  struct dentry *parent,
145					  umode_t mode,
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
166struct rchan *relay_open(const char *base_filename,
167			 struct dentry *parent,
168			 size_t subbuf_size,
169			 size_t n_subbufs,
170			 struct rchan_callbacks *cb,
171			 void *private_data);
172extern int relay_late_setup_files(struct rchan *chan,
173				  const char *base_filename,
174				  struct dentry *parent);
175extern void relay_close(struct rchan *chan);
176extern void relay_flush(struct rchan *chan);
177extern void relay_subbufs_consumed(struct rchan *chan,
178				   unsigned int cpu,
179				   size_t consumed);
180extern void relay_reset(struct rchan *chan);
181extern int relay_buf_full(struct rchan_buf *buf);
182
183extern 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 */
199static 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 */
227static 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 */
252static 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 */
276static 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 */
286extern const struct file_operations relay_file_operations;
287
288#endif /* _LINUX_RELAY_H */
289
290