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>
19 #include <linux/poll.h>
20 #include <linux/kref.h>
22 /* Needs a _much_ better name... */
23 #define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
26 * Tracks changes to rchan/rchan_buf structs
28 #define RELAYFS_CHANNEL_VERSION 7
31 * Per-cpu relay channel buffer
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 timer_list timer; /* reader wake-up timer */
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 size_t early_bytes; /* bytes consumed before VFS inited */
52 unsigned int cpu; /* this buf's cpu */
53 } ____cacheline_aligned;
56 * Relay channel data structure
60 u32 version; /* the version of this struct */
61 size_t subbuf_size; /* sub-buffer size */
62 size_t n_subbufs; /* number of sub-buffers per buffer */
63 size_t alloc_size; /* total buffer size allocated */
64 struct rchan_callbacks *cb; /* client callbacks */
65 struct kref kref; /* channel refcount */
66 void *private_data; /* for user-defined data */
67 size_t last_toobig; /* tried to log event > subbuf size */
68 struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
69 int is_global; /* One global buffer ? */
70 struct list_head list; /* for channel list */
71 struct dentry *parent; /* parent dentry passed to open */
72 int has_base_filename; /* has a filename associated? */
73 char base_filename[NAME_MAX]; /* saved base filename */
77 * Relay channel client callbacks
79 struct rchan_callbacks
82 * subbuf_start - called on buffer-switch to a new sub-buffer
83 * @buf: the channel buffer containing the new sub-buffer
84 * @subbuf: the start of the new sub-buffer
85 * @prev_subbuf: the start of the previous sub-buffer
86 * @prev_padding: unused space at the end of previous sub-buffer
88 * The client should return 1 to continue logging, 0 to stop
91 * NOTE: subbuf_start will also be invoked when the buffer is
92 * created, so that the first sub-buffer can be initialized
93 * if necessary. In this case, prev_subbuf will be NULL.
95 * NOTE: the client can reserve bytes at the beginning of the new
96 * sub-buffer by calling subbuf_start_reserve() in this callback.
98 int (*subbuf_start) (struct rchan_buf *buf,
101 size_t prev_padding);
104 * buf_mapped - relay buffer mmap notification
105 * @buf: the channel buffer
106 * @filp: relay file pointer
108 * Called when a relay file is successfully mmapped
110 void (*buf_mapped)(struct rchan_buf *buf,
114 * buf_unmapped - relay buffer unmap notification
115 * @buf: the channel buffer
116 * @filp: relay file pointer
118 * Called when a relay file is successfully unmapped
120 void (*buf_unmapped)(struct rchan_buf *buf,
123 * create_buf_file - create file to represent a relay channel buffer
124 * @filename: the name of the file to create
125 * @parent: the parent of the file to create
126 * @mode: the mode of the file to create
127 * @buf: the channel buffer
128 * @is_global: outparam - set non-zero if the buffer should be global
130 * Called during relay_open(), once for each per-cpu buffer,
131 * to allow the client to create a file to be used to
132 * represent the corresponding channel buffer. If the file is
133 * created outside of relay, the parent must also exist in
136 * The callback should return the dentry of the file created
137 * to represent the relay buffer.
139 * Setting the is_global outparam to a non-zero value will
140 * cause relay_open() to create a single global buffer rather
141 * than the default set of per-cpu buffers.
143 * See Documentation/filesystems/relay.txt for more info.
145 struct dentry *(*create_buf_file)(const char *filename,
146 struct dentry *parent,
148 struct rchan_buf *buf,
152 * remove_buf_file - remove file representing a relay channel buffer
153 * @dentry: the dentry of the file to remove
155 * Called during relay_close(), once for each per-cpu buffer,
156 * to allow the client to remove a file used to represent a
159 * The callback should return 0 if successful, negative if not.
161 int (*remove_buf_file)(struct dentry *dentry);
165 * CONFIG_RELAY kernel API, kernel/relay.c
168 struct rchan *relay_open(const char *base_filename,
169 struct dentry *parent,
172 struct rchan_callbacks *cb,
174 extern int relay_late_setup_files(struct rchan *chan,
175 const char *base_filename,
176 struct dentry *parent);
177 extern void relay_close(struct rchan *chan);
178 extern void relay_flush(struct rchan *chan);
179 extern void relay_subbufs_consumed(struct rchan *chan,
182 extern void relay_reset(struct rchan *chan);
183 extern int relay_buf_full(struct rchan_buf *buf);
185 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
189 * relay_write - write data into the channel
190 * @chan: relay channel
191 * @data: data to be written
192 * @length: number of bytes to write
194 * Writes data into the current cpu's channel buffer.
196 * Protects the buffer by disabling interrupts. Use this
197 * if you might be logging from interrupt context. Try
198 * __relay_write() if you know you won't be logging from
201 static inline void relay_write(struct rchan *chan,
206 struct rchan_buf *buf;
208 local_irq_save(flags);
209 buf = chan->buf[smp_processor_id()];
210 if (unlikely(buf->offset + length > chan->subbuf_size))
211 length = relay_switch_subbuf(buf, length);
212 memcpy(buf->data + buf->offset, data, length);
213 buf->offset += length;
214 local_irq_restore(flags);
218 * __relay_write - write data into the channel
219 * @chan: relay channel
220 * @data: data to be written
221 * @length: number of bytes to write
223 * Writes data into the current cpu's channel buffer.
225 * Protects the buffer by disabling preemption. Use
226 * relay_write() if you might be logging from interrupt
229 static inline void __relay_write(struct rchan *chan,
233 struct rchan_buf *buf;
235 buf = chan->buf[get_cpu()];
236 if (unlikely(buf->offset + length > buf->chan->subbuf_size))
237 length = relay_switch_subbuf(buf, length);
238 memcpy(buf->data + buf->offset, data, length);
239 buf->offset += length;
244 * relay_reserve - reserve slot in channel buffer
245 * @chan: relay channel
246 * @length: number of bytes to reserve
248 * Returns pointer to reserved slot, NULL if full.
250 * Reserves a slot in the current cpu's channel buffer.
251 * Does not protect the buffer at all - caller must provide
252 * appropriate synchronization.
254 static inline void *relay_reserve(struct rchan *chan, size_t length)
257 struct rchan_buf *buf = chan->buf[smp_processor_id()];
259 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
260 length = relay_switch_subbuf(buf, length);
264 reserved = buf->data + buf->offset;
265 buf->offset += length;
271 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer
272 * @buf: relay channel buffer
273 * @length: number of bytes to reserve
275 * Helper function used to reserve bytes at the beginning of
276 * a sub-buffer in the subbuf_start() callback.
278 static inline void subbuf_start_reserve(struct rchan_buf *buf,
281 BUG_ON(length >= buf->chan->subbuf_size - 1);
282 buf->offset = length;
286 * exported relay file operations, kernel/relay.c
288 extern const struct file_operations relay_file_operations;
290 #endif /* _LINUX_RELAY_H */