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-rw-r--r--include/linux/relay.h281
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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/config.h>
14#include <linux/types.h>
15#include <linux/sched.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 6
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 work_struct wake_readers; /* reader wake-up work struct */
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};
69
70/*
71 * Relay channel client callbacks
72 */
73struct rchan_callbacks
74{
75 /*
76 * subbuf_start - called on buffer-switch to a new sub-buffer
77 * @buf: the channel buffer containing the new sub-buffer
78 * @subbuf: the start of the new sub-buffer
79 * @prev_subbuf: the start of the previous sub-buffer
80 * @prev_padding: unused space at the end of previous sub-buffer
81 *
82 * The client should return 1 to continue logging, 0 to stop
83 * logging.
84 *
85 * NOTE: subbuf_start will also be invoked when the buffer is
86 * created, so that the first sub-buffer can be initialized
87 * if necessary. In this case, prev_subbuf will be NULL.
88 *
89 * NOTE: the client can reserve bytes at the beginning of the new
90 * sub-buffer by calling subbuf_start_reserve() in this callback.
91 */
92 int (*subbuf_start) (struct rchan_buf *buf,
93 void *subbuf,
94 void *prev_subbuf,
95 size_t prev_padding);
96
97 /*
98 * buf_mapped - relay buffer mmap notification
99 * @buf: the channel buffer
100 * @filp: relay file pointer
101 *
102 * Called when a relay file is successfully mmapped
103 */
104 void (*buf_mapped)(struct rchan_buf *buf,
105 struct file *filp);
106
107 /*
108 * buf_unmapped - relay buffer unmap notification
109 * @buf: the channel buffer
110 * @filp: relay file pointer
111 *
112 * Called when a relay file is successfully unmapped
113 */
114 void (*buf_unmapped)(struct rchan_buf *buf,
115 struct file *filp);
116 /*
117 * create_buf_file - create file to represent a relay channel buffer
118 * @filename: the name of the file to create
119 * @parent: the parent of the file to create
120 * @mode: the mode of the file to create
121 * @buf: the channel buffer
122 * @is_global: outparam - set non-zero if the buffer should be global
123 *
124 * Called during relay_open(), once for each per-cpu buffer,
125 * to allow the client to create a file to be used to
126 * represent the corresponding channel buffer. If the file is
127 * created outside of relay, the parent must also exist in
128 * that filesystem.
129 *
130 * The callback should return the dentry of the file created
131 * to represent the relay buffer.
132 *
133 * Setting the is_global outparam to a non-zero value will
134 * cause relay_open() to create a single global buffer rather
135 * than the default set of per-cpu buffers.
136 *
137 * See Documentation/filesystems/relayfs.txt for more info.
138 */
139 struct dentry *(*create_buf_file)(const char *filename,
140 struct dentry *parent,
141 int mode,
142 struct rchan_buf *buf,
143 int *is_global);
144
145 /*
146 * remove_buf_file - remove file representing a relay channel buffer
147 * @dentry: the dentry of the file to remove
148 *
149 * Called during relay_close(), once for each per-cpu buffer,
150 * to allow the client to remove a file used to represent a
151 * channel buffer.
152 *
153 * The callback should return 0 if successful, negative if not.
154 */
155 int (*remove_buf_file)(struct dentry *dentry);
156};
157
158/*
159 * CONFIG_RELAY kernel API, kernel/relay.c
160 */
161
162struct rchan *relay_open(const char *base_filename,
163 struct dentry *parent,
164 size_t subbuf_size,
165 size_t n_subbufs,
166 struct rchan_callbacks *cb);
167extern void relay_close(struct rchan *chan);
168extern void relay_flush(struct rchan *chan);
169extern void relay_subbufs_consumed(struct rchan *chan,
170 unsigned int cpu,
171 size_t consumed);
172extern void relay_reset(struct rchan *chan);
173extern int relay_buf_full(struct rchan_buf *buf);
174
175extern size_t relay_switch_subbuf(struct rchan_buf *buf,
176 size_t length);
177
178/**
179 * relay_write - write data into the channel
180 * @chan: relay channel
181 * @data: data to be written
182 * @length: number of bytes to write
183 *
184 * Writes data into the current cpu's channel buffer.
185 *
186 * Protects the buffer by disabling interrupts. Use this
187 * if you might be logging from interrupt context. Try
188 * __relay_write() if you know you won't be logging from
189 * interrupt context.
190 */
191static inline void relay_write(struct rchan *chan,
192 const void *data,
193 size_t length)
194{
195 unsigned long flags;
196 struct rchan_buf *buf;
197
198 local_irq_save(flags);
199 buf = chan->buf[smp_processor_id()];
200 if (unlikely(buf->offset + length > chan->subbuf_size))
201 length = relay_switch_subbuf(buf, length);
202 memcpy(buf->data + buf->offset, data, length);
203 buf->offset += length;
204 local_irq_restore(flags);
205}
206
207/**
208 * __relay_write - write data into the channel
209 * @chan: relay channel
210 * @data: data to be written
211 * @length: number of bytes to write
212 *
213 * Writes data into the current cpu's channel buffer.
214 *
215 * Protects the buffer by disabling preemption. Use
216 * relay_write() if you might be logging from interrupt
217 * context.
218 */
219static inline void __relay_write(struct rchan *chan,
220 const void *data,
221 size_t length)
222{
223 struct rchan_buf *buf;
224
225 buf = chan->buf[get_cpu()];
226 if (unlikely(buf->offset + length > buf->chan->subbuf_size))
227 length = relay_switch_subbuf(buf, length);
228 memcpy(buf->data + buf->offset, data, length);
229 buf->offset += length;
230 put_cpu();
231}
232
233/**
234 * relay_reserve - reserve slot in channel buffer
235 * @chan: relay channel
236 * @length: number of bytes to reserve
237 *
238 * Returns pointer to reserved slot, NULL if full.
239 *
240 * Reserves a slot in the current cpu's channel buffer.
241 * Does not protect the buffer at all - caller must provide
242 * appropriate synchronization.
243 */
244static inline void *relay_reserve(struct rchan *chan, size_t length)
245{
246 void *reserved;
247 struct rchan_buf *buf = chan->buf[smp_processor_id()];
248
249 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
250 length = relay_switch_subbuf(buf, length);
251 if (!length)
252 return NULL;
253 }
254 reserved = buf->data + buf->offset;
255 buf->offset += length;
256
257 return reserved;
258}
259
260/**
261 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer
262 * @buf: relay channel buffer
263 * @length: number of bytes to reserve
264 *
265 * Helper function used to reserve bytes at the beginning of
266 * a sub-buffer in the subbuf_start() callback.
267 */
268static inline void subbuf_start_reserve(struct rchan_buf *buf,
269 size_t length)
270{
271 BUG_ON(length >= buf->chan->subbuf_size - 1);
272 buf->offset = length;
273}
274
275/*
276 * exported relay file operations, kernel/relay.c
277 */
278extern struct file_operations relay_file_operations;
279
280#endif /* _LINUX_RELAY_H */
281
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-02 14:07:13 -0500