2 * linux/include/linux/relay.h
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)
7 * CONFIG_RELAY definitions and declarations
10 #ifndef _LINUX_RELAY_H
11 #define _LINUX_RELAY_H
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/bug.h>
20 #include <linux/poll.h>
21 #include <linux/kref.h>
22 #include <linux/percpu.h>
25 * Tracks changes to rchan/rchan_buf structs
27 #define RELAYFS_CHANNEL_VERSION 7
30 * Per-cpu relay channel buffer
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 timer_list timer; /* reader wake-up timer */
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 size_t early_bytes; /* bytes consumed before VFS inited */
51 unsigned int cpu; /* this buf's cpu */
52 } ____cacheline_aligned;
55 * Relay channel data structure
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 ** __percpu buf; /* 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 int has_base_filename; /* has a filename associated? */
72 char base_filename[NAME_MAX]; /* saved base filename */
76 * Relay channel client callbacks
78 struct rchan_callbacks
81 * subbuf_start - called on buffer-switch to a new sub-buffer
82 * @buf: the channel buffer containing the new sub-buffer
83 * @subbuf: the start of the new sub-buffer
84 * @prev_subbuf: the start of the previous sub-buffer
85 * @prev_padding: unused space at the end of previous sub-buffer
87 * The client should return 1 to continue logging, 0 to stop
90 * NOTE: subbuf_start will also be invoked when the buffer is
91 * created, so that the first sub-buffer can be initialized
92 * if necessary. In this case, prev_subbuf will be NULL.
94 * NOTE: the client can reserve bytes at the beginning of the new
95 * sub-buffer by calling subbuf_start_reserve() in this callback.
97 int (*subbuf_start) (struct rchan_buf *buf,
100 size_t prev_padding);
103 * buf_mapped - relay buffer mmap notification
104 * @buf: the channel buffer
105 * @filp: relay file pointer
107 * Called when a relay file is successfully mmapped
109 void (*buf_mapped)(struct rchan_buf *buf,
113 * buf_unmapped - relay buffer unmap notification
114 * @buf: the channel buffer
115 * @filp: relay file pointer
117 * Called when a relay file is successfully unmapped
119 void (*buf_unmapped)(struct rchan_buf *buf,
122 * create_buf_file - create file to represent a relay channel buffer
123 * @filename: the name of the file to create
124 * @parent: the parent of the file to create
125 * @mode: the mode of the file to create
126 * @buf: the channel buffer
127 * @is_global: outparam - set non-zero if the buffer should be global
129 * Called during relay_open(), once for each per-cpu buffer,
130 * to allow the client to create a file to be used to
131 * represent the corresponding channel buffer. If the file is
132 * created outside of relay, the parent must also exist in
135 * The callback should return the dentry of the file created
136 * to represent the relay buffer.
138 * Setting the is_global outparam to a non-zero value will
139 * cause relay_open() to create a single global buffer rather
140 * than the default set of per-cpu buffers.
142 * See Documentation/filesystems/relay.txt for more info.
144 struct dentry *(*create_buf_file)(const char *filename,
145 struct dentry *parent,
147 struct rchan_buf *buf,
151 * remove_buf_file - remove file representing a relay channel buffer
152 * @dentry: the dentry of the file to remove
154 * Called during relay_close(), once for each per-cpu buffer,
155 * to allow the client to remove a file used to represent a
158 * The callback should return 0 if successful, negative if not.
160 int (*remove_buf_file)(struct dentry *dentry);
164 * CONFIG_RELAY kernel API, kernel/relay.c
167 struct rchan *relay_open(const char *base_filename,
168 struct dentry *parent,
171 struct rchan_callbacks *cb,
173 extern int relay_late_setup_files(struct rchan *chan,
174 const char *base_filename,
175 struct dentry *parent);
176 extern void relay_close(struct rchan *chan);
177 extern void relay_flush(struct rchan *chan);
178 extern void relay_subbufs_consumed(struct rchan *chan,
181 extern void relay_reset(struct rchan *chan);
182 extern int relay_buf_full(struct rchan_buf *buf);
184 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
188 * relay_write - write data into the channel
189 * @chan: relay channel
190 * @data: data to be written
191 * @length: number of bytes to write
193 * Writes data into the current cpu's channel buffer.
195 * Protects the buffer by disabling interrupts. Use this
196 * if you might be logging from interrupt context. Try
197 * __relay_write() if you know you won't be logging from
200 static inline void relay_write(struct rchan *chan,
205 struct rchan_buf *buf;
207 local_irq_save(flags);
208 buf = *this_cpu_ptr(chan->buf);
209 if (unlikely(buf->offset + length > chan->subbuf_size))
210 length = relay_switch_subbuf(buf, length);
211 memcpy(buf->data + buf->offset, data, length);
212 buf->offset += length;
213 local_irq_restore(flags);
217 * __relay_write - write data into the channel
218 * @chan: relay channel
219 * @data: data to be written
220 * @length: number of bytes to write
222 * Writes data into the current cpu's channel buffer.
224 * Protects the buffer by disabling preemption. Use
225 * relay_write() if you might be logging from interrupt
228 static inline void __relay_write(struct rchan *chan,
232 struct rchan_buf *buf;
234 buf = *get_cpu_ptr(chan->buf);
235 if (unlikely(buf->offset + length > buf->chan->subbuf_size))
236 length = relay_switch_subbuf(buf, length);
237 memcpy(buf->data + buf->offset, data, length);
238 buf->offset += length;
239 put_cpu_ptr(chan->buf);
243 * relay_reserve - reserve slot in channel buffer
244 * @chan: relay channel
245 * @length: number of bytes to reserve
247 * Returns pointer to reserved slot, NULL if full.
249 * Reserves a slot in the current cpu's channel buffer.
250 * Does not protect the buffer at all - caller must provide
251 * appropriate synchronization.
253 static inline void *relay_reserve(struct rchan *chan, size_t length)
255 void *reserved = NULL;
256 struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
258 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
259 length = relay_switch_subbuf(buf, length);
263 reserved = buf->data + buf->offset;
264 buf->offset += length;
267 put_cpu_ptr(chan->buf);
272 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer
273 * @buf: relay channel buffer
274 * @length: number of bytes to reserve
276 * Helper function used to reserve bytes at the beginning of
277 * a sub-buffer in the subbuf_start() callback.
279 static inline void subbuf_start_reserve(struct rchan_buf *buf,
282 BUG_ON(length >= buf->chan->subbuf_size - 1);
283 buf->offset = length;
287 * exported relay file operations, kernel/relay.c
289 extern const struct file_operations relay_file_operations;
292 int relay_prepare_cpu(unsigned int cpu);
294 #define relay_prepare_cpu NULL
297 #endif /* _LINUX_RELAY_H */