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/wait.h>
16 #include <linux/list.h>
18 #include <linux/poll.h>
19 #include <linux/kref.h>
21 /* Needs a _much_ better name... */
22 #define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
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 delayed_work 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;
54 * Relay channel data structure
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 int is_global; /* One global buffer ? */
68 struct list_head list; /* for channel list */
69 struct dentry *parent; /* parent dentry passed to open */
70 char base_filename[NAME_MAX]; /* saved base filename */
74 * Relay channel client callbacks
76 struct rchan_callbacks
79 * subbuf_start - called on buffer-switch to a new sub-buffer
80 * @buf: the channel buffer containing the new sub-buffer
81 * @subbuf: the start of the new sub-buffer
82 * @prev_subbuf: the start of the previous sub-buffer
83 * @prev_padding: unused space at the end of previous sub-buffer
85 * The client should return 1 to continue logging, 0 to stop
88 * NOTE: subbuf_start will also be invoked when the buffer is
89 * created, so that the first sub-buffer can be initialized
90 * if necessary. In this case, prev_subbuf will be NULL.
92 * NOTE: the client can reserve bytes at the beginning of the new
93 * sub-buffer by calling subbuf_start_reserve() in this callback.
95 int (*subbuf_start) (struct rchan_buf *buf,
101 * buf_mapped - relay buffer mmap notification
102 * @buf: the channel buffer
103 * @filp: relay file pointer
105 * Called when a relay file is successfully mmapped
107 void (*buf_mapped)(struct rchan_buf *buf,
111 * buf_unmapped - relay buffer unmap notification
112 * @buf: the channel buffer
113 * @filp: relay file pointer
115 * Called when a relay file is successfully unmapped
117 void (*buf_unmapped)(struct rchan_buf *buf,
120 * create_buf_file - create file to represent a relay channel buffer
121 * @filename: the name of the file to create
122 * @parent: the parent of the file to create
123 * @mode: the mode of the file to create
124 * @buf: the channel buffer
125 * @is_global: outparam - set non-zero if the buffer should be global
127 * Called during relay_open(), once for each per-cpu buffer,
128 * to allow the client to create a file to be used to
129 * represent the corresponding channel buffer. If the file is
130 * created outside of relay, the parent must also exist in
133 * The callback should return the dentry of the file created
134 * to represent the relay buffer.
136 * Setting the is_global outparam to a non-zero value will
137 * cause relay_open() to create a single global buffer rather
138 * than the default set of per-cpu buffers.
140 * See Documentation/filesystems/relayfs.txt for more info.
142 struct dentry *(*create_buf_file)(const char *filename,
143 struct dentry *parent,
145 struct rchan_buf *buf,
149 * remove_buf_file - remove file representing a relay channel buffer
150 * @dentry: the dentry of the file to remove
152 * Called during relay_close(), once for each per-cpu buffer,
153 * to allow the client to remove a file used to represent a
156 * The callback should return 0 if successful, negative if not.
158 int (*remove_buf_file)(struct dentry *dentry);
162 * CONFIG_RELAY kernel API, kernel/relay.c
165 struct rchan *relay_open(const char *base_filename,
166 struct dentry *parent,
169 struct rchan_callbacks *cb,
171 extern void relay_close(struct rchan *chan);
172 extern void relay_flush(struct rchan *chan);
173 extern void relay_subbufs_consumed(struct rchan *chan,
176 extern void relay_reset(struct rchan *chan);
177 extern int relay_buf_full(struct rchan_buf *buf);
179 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
183 * relay_write - write data into the channel
184 * @chan: relay channel
185 * @data: data to be written
186 * @length: number of bytes to write
188 * Writes data into the current cpu's channel buffer.
190 * Protects the buffer by disabling interrupts. Use this
191 * if you might be logging from interrupt context. Try
192 * __relay_write() if you know you won't be logging from
195 static inline void relay_write(struct rchan *chan,
200 struct rchan_buf *buf;
202 local_irq_save(flags);
203 buf = chan->buf[smp_processor_id()];
204 if (unlikely(buf->offset + length > chan->subbuf_size))
205 length = relay_switch_subbuf(buf, length);
206 memcpy(buf->data + buf->offset, data, length);
207 buf->offset += length;
208 local_irq_restore(flags);
212 * __relay_write - write data into the channel
213 * @chan: relay channel
214 * @data: data to be written
215 * @length: number of bytes to write
217 * Writes data into the current cpu's channel buffer.
219 * Protects the buffer by disabling preemption. Use
220 * relay_write() if you might be logging from interrupt
223 static inline void __relay_write(struct rchan *chan,
227 struct rchan_buf *buf;
229 buf = chan->buf[get_cpu()];
230 if (unlikely(buf->offset + length > buf->chan->subbuf_size))
231 length = relay_switch_subbuf(buf, length);
232 memcpy(buf->data + buf->offset, data, length);
233 buf->offset += length;
238 * relay_reserve - reserve slot in channel buffer
239 * @chan: relay channel
240 * @length: number of bytes to reserve
242 * Returns pointer to reserved slot, NULL if full.
244 * Reserves a slot in the current cpu's channel buffer.
245 * Does not protect the buffer at all - caller must provide
246 * appropriate synchronization.
248 static inline void *relay_reserve(struct rchan *chan, size_t length)
251 struct rchan_buf *buf = chan->buf[smp_processor_id()];
253 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
254 length = relay_switch_subbuf(buf, length);
258 reserved = buf->data + buf->offset;
259 buf->offset += length;
265 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer
266 * @buf: relay channel buffer
267 * @length: number of bytes to reserve
269 * Helper function used to reserve bytes at the beginning of
270 * a sub-buffer in the subbuf_start() callback.
272 static inline void subbuf_start_reserve(struct rchan_buf *buf,
275 BUG_ON(length >= buf->chan->subbuf_size - 1);
276 buf->offset = length;
280 * exported relay file operations, kernel/relay.c
282 extern const struct file_operations relay_file_operations;
284 #endif /* _LINUX_RELAY_H */