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/fs.h>
19#include <linux/poll.h>
20#include <linux/kref.h>
21
22/* Needs a _much_ better name... */
23#define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
24
25/*
26 * Tracks changes to rchan/rchan_buf structs
27 */
28#define RELAYFS_CHANNEL_VERSION		7
29
30/*
31 * Per-cpu relay channel buffer
32 */
33struct rchan_buf
34{
35	void *start;			/* start of channel buffer */
36	void *data;			/* start of current sub-buffer */
37	size_t offset;			/* current offset into sub-buffer */
38	size_t subbufs_produced;	/* count of sub-buffers produced */
39	size_t subbufs_consumed;	/* count of sub-buffers consumed */
40	struct rchan *chan;		/* associated channel */
41	wait_queue_head_t read_wait;	/* reader wait queue */
42	struct timer_list timer; 	/* reader wake-up timer */
43	struct dentry *dentry;		/* channel file dentry */
44	struct kref kref;		/* channel buffer refcount */
45	struct page **page_array;	/* array of current buffer pages */
46	unsigned int page_count;	/* number of current buffer pages */
47	unsigned int finalized;		/* buffer has been finalized */
48	size_t *padding;		/* padding counts per sub-buffer */
49	size_t prev_padding;		/* temporary variable */
50	size_t bytes_consumed;		/* bytes consumed in cur read subbuf */
51	unsigned int cpu;		/* this buf's cpu */
52} ____cacheline_aligned;
53
54/*
55 * Relay channel data structure
56 */
57struct rchan
58{
59	u32 version;			/* the version of this struct */
60	size_t subbuf_size;		/* sub-buffer size */
61	size_t n_subbufs;		/* number of sub-buffers per buffer */
62	size_t alloc_size;		/* total buffer size allocated */
63	struct rchan_callbacks *cb;	/* client callbacks */
64	struct kref kref;		/* channel refcount */
65	void *private_data;		/* for user-defined data */
66	size_t last_toobig;		/* tried to log event > subbuf size */
67	struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
68	int is_global;			/* One global buffer ? */
69	struct list_head list;		/* for channel list */
70	struct dentry *parent;		/* parent dentry passed to open */
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/relayfs.txt for more info.
142	 */
143	struct dentry *(*create_buf_file)(const char *filename,
144					  struct dentry *parent,
145					  int 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 void relay_close(struct rchan *chan);
173extern void relay_flush(struct rchan *chan);
174extern void relay_subbufs_consumed(struct rchan *chan,
175				   unsigned int cpu,
176				   size_t consumed);
177extern void relay_reset(struct rchan *chan);
178extern int relay_buf_full(struct rchan_buf *buf);
179
180extern size_t relay_switch_subbuf(struct rchan_buf *buf,
181				  size_t length);
182
183/**
184 *	relay_write - write data into the channel
185 *	@chan: relay channel
186 *	@data: data to be written
187 *	@length: number of bytes to write
188 *
189 *	Writes data into the current cpu's channel buffer.
190 *
191 *	Protects the buffer by disabling interrupts.  Use this
192 *	if you might be logging from interrupt context.  Try
193 *	__relay_write() if you know you	won't be logging from
194 *	interrupt context.
195 */
196static inline void relay_write(struct rchan *chan,
197			       const void *data,
198			       size_t length)
199{
200	unsigned long flags;
201	struct rchan_buf *buf;
202
203	local_irq_save(flags);
204	buf = chan->buf[smp_processor_id()];
205	if (unlikely(buf->offset + length > chan->subbuf_size))
206		length = relay_switch_subbuf(buf, length);
207	memcpy(buf->data + buf->offset, data, length);
208	buf->offset += length;
209	local_irq_restore(flags);
210}
211
212/**
213 *	__relay_write - write data into the channel
214 *	@chan: relay channel
215 *	@data: data to be written
216 *	@length: number of bytes to write
217 *
218 *	Writes data into the current cpu's channel buffer.
219 *
220 *	Protects the buffer by disabling preemption.  Use
221 *	relay_write() if you might be logging from interrupt
222 *	context.
223 */
224static inline void __relay_write(struct rchan *chan,
225				 const void *data,
226				 size_t length)
227{
228	struct rchan_buf *buf;
229
230	buf = chan->buf[get_cpu()];
231	if (unlikely(buf->offset + length > buf->chan->subbuf_size))
232		length = relay_switch_subbuf(buf, length);
233	memcpy(buf->data + buf->offset, data, length);
234	buf->offset += length;
235	put_cpu();
236}
237
238/**
239 *	relay_reserve - reserve slot in channel buffer
240 *	@chan: relay channel
241 *	@length: number of bytes to reserve
242 *
243 *	Returns pointer to reserved slot, NULL if full.
244 *
245 *	Reserves a slot in the current cpu's channel buffer.
246 *	Does not protect the buffer at all - caller must provide
247 *	appropriate synchronization.
248 */
249static inline void *relay_reserve(struct rchan *chan, size_t length)
250{
251	void *reserved;
252	struct rchan_buf *buf = chan->buf[smp_processor_id()];
253
254	if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
255		length = relay_switch_subbuf(buf, length);
256		if (!length)
257			return NULL;
258	}
259	reserved = buf->data + buf->offset;
260	buf->offset += length;
261
262	return reserved;
263}
264
265/**
266 *	subbuf_start_reserve - reserve bytes at the start of a sub-buffer
267 *	@buf: relay channel buffer
268 *	@length: number of bytes to reserve
269 *
270 *	Helper function used to reserve bytes at the beginning of
271 *	a sub-buffer in the subbuf_start() callback.
272 */
273static inline void subbuf_start_reserve(struct rchan_buf *buf,
274					size_t length)
275{
276	BUG_ON(length >= buf->chan->subbuf_size - 1);
277	buf->offset = length;
278}
279
280/*
281 * exported relay file operations, kernel/relay.c
282 */
283extern const struct file_operations relay_file_operations;
284
285#endif /* _LINUX_RELAY_H */
286