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