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Jens Axboeb86ff9812006-03-23 19:56:55 +01001/*
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
Jens Axboeb86ff9812006-03-23 19:56:55 +010013#include <linux/types.h>
14#include <linux/sched.h>
Tom Zanussi7c9cb382007-05-09 02:34:01 -070015#include <linux/timer.h>
Jens Axboeb86ff9812006-03-23 19:56:55 +010016#include <linux/wait.h>
17#include <linux/list.h>
Paul Gortmaker187f1882011-11-23 20:12:59 -050018#include <linux/bug.h>
Jens Axboeb86ff9812006-03-23 19:56:55 +010019#include <linux/fs.h>
20#include <linux/poll.h>
21#include <linux/kref.h>
22
Jens Axboeb86ff9812006-03-23 19:56:55 +010023/*
24 * Tracks changes to rchan/rchan_buf structs
25 */
Mathieu Desnoyers23c88752007-02-10 01:45:05 -080026#define RELAYFS_CHANNEL_VERSION 7
Jens Axboeb86ff9812006-03-23 19:56:55 +010027
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 */
Tom Zanussi7c9cb382007-05-09 02:34:01 -070040 struct timer_list timer; /* reader wake-up timer */
Jens Axboeb86ff9812006-03-23 19:56:55 +010041 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 */
Eduard - Gabriel Munteanu20d8b672008-07-25 19:45:12 -070049 size_t early_bytes; /* bytes consumed before VFS inited */
Jens Axboeb86ff9812006-03-23 19:56:55 +010050 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 */
Mathieu Desnoyers23c88752007-02-10 01:45:05 -080067 int is_global; /* One global buffer ? */
68 struct list_head list; /* for channel list */
69 struct dentry *parent; /* parent dentry passed to open */
Eduard - Gabriel Munteanu20d8b672008-07-25 19:45:12 -070070 int has_base_filename; /* has a filename associated? */
Mathieu Desnoyers23c88752007-02-10 01:45:05 -080071 char base_filename[NAME_MAX]; /* saved base filename */
Jens Axboeb86ff9812006-03-23 19:56:55 +010072};
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 *
Randy Dunlap55dff492009-09-23 15:56:17 -0700141 * See Documentation/filesystems/relay.txt for more info.
Jens Axboeb86ff9812006-03-23 19:56:55 +0100142 */
143 struct dentry *(*create_buf_file)(const char *filename,
144 struct dentry *parent,
Al Virof4ae40a2011-07-24 04:33:43 -0400145 umode_t mode,
Jens Axboeb86ff9812006-03-23 19:56:55 +0100146 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,
Mathieu Desnoyers23c88752007-02-10 01:45:05 -0800170 struct rchan_callbacks *cb,
171 void *private_data);
Eduard - Gabriel Munteanu20d8b672008-07-25 19:45:12 -0700172extern int relay_late_setup_files(struct rchan *chan,
173 const char *base_filename,
174 struct dentry *parent);
Jens Axboeb86ff9812006-03-23 19:56:55 +0100175extern 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 */
Helge Deller15ad7cd2006-12-06 20:40:36 -0800286extern const struct file_operations relay_file_operations;
Jens Axboeb86ff9812006-03-23 19:56:55 +0100287
288#endif /* _LINUX_RELAY_H */
289