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-rw-r--r--include/linux/relayfs_fs.h287
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diff --git a/include/linux/relayfs_fs.h b/include/linux/relayfs_fs.h
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1/*
2 * linux/include/linux/relayfs_fs.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 * RelayFS definitions and declarations
8 */
9
10#ifndef _LINUX_RELAYFS_FS_H
11#define _LINUX_RELAYFS_FS_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/*
23 * Tracks changes to rchan/rchan_buf structs
24 */
25#define RELAYFS_CHANNEL_VERSION 6
26
27/*
28 * Per-cpu relay channel buffer
29 */
30struct rchan_buf
31{
32 void *start; /* start of channel buffer */
33 void *data; /* start of current sub-buffer */
34 size_t offset; /* current offset into sub-buffer */
35 size_t subbufs_produced; /* count of sub-buffers produced */
36 size_t subbufs_consumed; /* count of sub-buffers consumed */
37 struct rchan *chan; /* associated channel */
38 wait_queue_head_t read_wait; /* reader wait queue */
39 struct work_struct wake_readers; /* reader wake-up work struct */
40 struct dentry *dentry; /* channel file dentry */
41 struct kref kref; /* channel buffer refcount */
42 struct page **page_array; /* array of current buffer pages */
43 unsigned int page_count; /* number of current buffer pages */
44 unsigned int finalized; /* buffer has been finalized */
45 size_t *padding; /* padding counts per sub-buffer */
46 size_t prev_padding; /* temporary variable */
47 size_t bytes_consumed; /* bytes consumed in cur read subbuf */
48 unsigned int cpu; /* this buf's cpu */
49} ____cacheline_aligned;
50
51/*
52 * Relay channel data structure
53 */
54struct rchan
55{
56 u32 version; /* the version of this struct */
57 size_t subbuf_size; /* sub-buffer size */
58 size_t n_subbufs; /* number of sub-buffers per buffer */
59 size_t alloc_size; /* total buffer size allocated */
60 struct rchan_callbacks *cb; /* client callbacks */
61 struct kref kref; /* channel refcount */
62 void *private_data; /* for user-defined data */
63 size_t last_toobig; /* tried to log event > subbuf size */
64 struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
65};
66
67/*
68 * Relay channel client callbacks
69 */
70struct rchan_callbacks
71{
72 /*
73 * subbuf_start - called on buffer-switch to a new sub-buffer
74 * @buf: the channel buffer containing the new sub-buffer
75 * @subbuf: the start of the new sub-buffer
76 * @prev_subbuf: the start of the previous sub-buffer
77 * @prev_padding: unused space at the end of previous sub-buffer
78 *
79 * The client should return 1 to continue logging, 0 to stop
80 * logging.
81 *
82 * NOTE: subbuf_start will also be invoked when the buffer is
83 * created, so that the first sub-buffer can be initialized
84 * if necessary. In this case, prev_subbuf will be NULL.
85 *
86 * NOTE: the client can reserve bytes at the beginning of the new
87 * sub-buffer by calling subbuf_start_reserve() in this callback.
88 */
89 int (*subbuf_start) (struct rchan_buf *buf,
90 void *subbuf,
91 void *prev_subbuf,
92 size_t prev_padding);
93
94 /*
95 * buf_mapped - relayfs buffer mmap notification
96 * @buf: the channel buffer
97 * @filp: relayfs file pointer
98 *
99 * Called when a relayfs file is successfully mmapped
100 */
101 void (*buf_mapped)(struct rchan_buf *buf,
102 struct file *filp);
103
104 /*
105 * buf_unmapped - relayfs buffer unmap notification
106 * @buf: the channel buffer
107 * @filp: relayfs file pointer
108 *
109 * Called when a relayfs file is successfully unmapped
110 */
111 void (*buf_unmapped)(struct rchan_buf *buf,
112 struct file *filp);
113 /*
114 * create_buf_file - create file to represent a relayfs channel buffer
115 * @filename: the name of the file to create
116 * @parent: the parent of the file to create
117 * @mode: the mode of the file to create
118 * @buf: the channel buffer
119 * @is_global: outparam - set non-zero if the buffer should be global
120 *
121 * Called during relay_open(), once for each per-cpu buffer,
122 * to allow the client to create a file to be used to
123 * represent the corresponding channel buffer. If the file is
124 * created outside of relayfs, the parent must also exist in
125 * that filesystem.
126 *
127 * The callback should return the dentry of the file created
128 * to represent the relay buffer.
129 *
130 * Setting the is_global outparam to a non-zero value will
131 * cause relay_open() to create a single global buffer rather
132 * than the default set of per-cpu buffers.
133 *
134 * See Documentation/filesystems/relayfs.txt for more info.
135 */
136 struct dentry *(*create_buf_file)(const char *filename,
137 struct dentry *parent,
138 int mode,
139 struct rchan_buf *buf,
140 int *is_global);
141
142 /*
143 * remove_buf_file - remove file representing a relayfs channel buffer
144 * @dentry: the dentry of the file to remove
145 *
146 * Called during relay_close(), once for each per-cpu buffer,
147 * to allow the client to remove a file used to represent a
148 * channel buffer.
149 *
150 * The callback should return 0 if successful, negative if not.
151 */
152 int (*remove_buf_file)(struct dentry *dentry);
153};
154
155/*
156 * relayfs kernel API, fs/relayfs/relay.c
157 */
158
159struct rchan *relay_open(const char *base_filename,
160 struct dentry *parent,
161 size_t subbuf_size,
162 size_t n_subbufs,
163 struct rchan_callbacks *cb);
164extern void relay_close(struct rchan *chan);
165extern void relay_flush(struct rchan *chan);
166extern void relay_subbufs_consumed(struct rchan *chan,
167 unsigned int cpu,
168 size_t consumed);
169extern void relay_reset(struct rchan *chan);
170extern int relay_buf_full(struct rchan_buf *buf);
171
172extern size_t relay_switch_subbuf(struct rchan_buf *buf,
173 size_t length);
174extern struct dentry *relayfs_create_dir(const char *name,
175 struct dentry *parent);
176extern int relayfs_remove_dir(struct dentry *dentry);
177extern struct dentry *relayfs_create_file(const char *name,
178 struct dentry *parent,
179 int mode,
180 struct file_operations *fops,
181 void *data);
182extern int relayfs_remove_file(struct dentry *dentry);
183
184/**
185 * relay_write - write data into the channel
186 * @chan: relay channel
187 * @data: data to be written
188 * @length: number of bytes to write
189 *
190 * Writes data into the current cpu's channel buffer.
191 *
192 * Protects the buffer by disabling interrupts. Use this
193 * if you might be logging from interrupt context. Try
194 * __relay_write() if you know you won't be logging from
195 * interrupt context.
196 */
197static inline void relay_write(struct rchan *chan,
198 const void *data,
199 size_t length)
200{
201 unsigned long flags;
202 struct rchan_buf *buf;
203
204 local_irq_save(flags);
205 buf = chan->buf[smp_processor_id()];
206 if (unlikely(buf->offset + length > chan->subbuf_size))
207 length = relay_switch_subbuf(buf, length);
208 memcpy(buf->data + buf->offset, data, length);
209 buf->offset += length;
210 local_irq_restore(flags);
211}
212
213/**
214 * __relay_write - write data into the channel
215 * @chan: relay channel
216 * @data: data to be written
217 * @length: number of bytes to write
218 *
219 * Writes data into the current cpu's channel buffer.
220 *
221 * Protects the buffer by disabling preemption. Use
222 * relay_write() if you might be logging from interrupt
223 * context.
224 */
225static inline void __relay_write(struct rchan *chan,
226 const void *data,
227 size_t length)
228{
229 struct rchan_buf *buf;
230
231 buf = chan->buf[get_cpu()];
232 if (unlikely(buf->offset + length > buf->chan->subbuf_size))
233 length = relay_switch_subbuf(buf, length);
234 memcpy(buf->data + buf->offset, data, length);
235 buf->offset += length;
236 put_cpu();
237}
238
239/**
240 * relay_reserve - reserve slot in channel buffer
241 * @chan: relay channel
242 * @length: number of bytes to reserve
243 *
244 * Returns pointer to reserved slot, NULL if full.
245 *
246 * Reserves a slot in the current cpu's channel buffer.
247 * Does not protect the buffer at all - caller must provide
248 * appropriate synchronization.
249 */
250static inline void *relay_reserve(struct rchan *chan, size_t length)
251{
252 void *reserved;
253 struct rchan_buf *buf = chan->buf[smp_processor_id()];
254
255 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
256 length = relay_switch_subbuf(buf, length);
257 if (!length)
258 return NULL;
259 }
260 reserved = buf->data + buf->offset;
261 buf->offset += length;
262
263 return reserved;
264}
265
266/**
267 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer
268 * @buf: relay channel buffer
269 * @length: number of bytes to reserve
270 *
271 * Helper function used to reserve bytes at the beginning of
272 * a sub-buffer in the subbuf_start() callback.
273 */
274static inline void subbuf_start_reserve(struct rchan_buf *buf,
275 size_t length)
276{
277 BUG_ON(length >= buf->chan->subbuf_size - 1);
278 buf->offset = length;
279}
280
281/*
282 * exported relay file operations, fs/relayfs/inode.c
283 */
284extern struct file_operations relay_file_operations;
285
286#endif /* _LINUX_RELAYFS_FS_H */
287
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