2 * linux/include/linux/relayfs_fs.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 * RelayFS definitions and declarations
10 #ifndef _LINUX_RELAYFS_FS_H
11 #define _LINUX_RELAYFS_FS_H
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>
19 #include <linux/poll.h>
20 #include <linux/kref.h>
23 * Tracks changes to rchan/rchan_buf structs
25 #define RELAYFS_CHANNEL_VERSION 6
28 * Per-cpu relay channel buffer
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
;
52 * Relay channel data structure
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 */
68 * Relay channel client callbacks
70 struct rchan_callbacks
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
79 * The client should return 1 to continue logging, 0 to stop
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.
86 * NOTE: the client can reserve bytes at the beginning of the new
87 * sub-buffer by calling subbuf_start_reserve() in this callback.
89 int (*subbuf_start
) (struct rchan_buf
*buf
,
95 * buf_mapped - relayfs buffer mmap notification
96 * @buf: the channel buffer
97 * @filp: relayfs file pointer
99 * Called when a relayfs file is successfully mmapped
101 void (*buf_mapped
)(struct rchan_buf
*buf
,
105 * buf_unmapped - relayfs buffer unmap notification
106 * @buf: the channel buffer
107 * @filp: relayfs file pointer
109 * Called when a relayfs file is successfully unmapped
111 void (*buf_unmapped
)(struct rchan_buf
*buf
,
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
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
127 * The callback should return the dentry of the file created
128 * to represent the relay buffer.
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.
134 * See Documentation/filesystems/relayfs.txt for more info.
136 struct dentry
*(*create_buf_file
)(const char *filename
,
137 struct dentry
*parent
,
139 struct rchan_buf
*buf
,
143 * remove_buf_file - remove file representing a relayfs channel buffer
144 * @dentry: the dentry of the file to remove
146 * Called during relay_close(), once for each per-cpu buffer,
147 * to allow the client to remove a file used to represent a
150 * The callback should return 0 if successful, negative if not.
152 int (*remove_buf_file
)(struct dentry
*dentry
);
156 * relayfs kernel API, fs/relayfs/relay.c
159 struct rchan
*relay_open(const char *base_filename
,
160 struct dentry
*parent
,
163 struct rchan_callbacks
*cb
);
164 extern void relay_close(struct rchan
*chan
);
165 extern void relay_flush(struct rchan
*chan
);
166 extern void relay_subbufs_consumed(struct rchan
*chan
,
169 extern void relay_reset(struct rchan
*chan
);
170 extern int relay_buf_full(struct rchan_buf
*buf
);
172 extern size_t relay_switch_subbuf(struct rchan_buf
*buf
,
174 extern struct dentry
*relayfs_create_dir(const char *name
,
175 struct dentry
*parent
);
176 extern int relayfs_remove_dir(struct dentry
*dentry
);
177 extern struct dentry
*relayfs_create_file(const char *name
,
178 struct dentry
*parent
,
180 struct file_operations
*fops
,
182 extern int relayfs_remove_file(struct dentry
*dentry
);
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
190 * Writes data into the current cpu's channel buffer.
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
197 static inline void relay_write(struct rchan
*chan
,
202 struct rchan_buf
*buf
;
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
);
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
219 * Writes data into the current cpu's channel buffer.
221 * Protects the buffer by disabling preemption. Use
222 * relay_write() if you might be logging from interrupt
225 static inline void __relay_write(struct rchan
*chan
,
229 struct rchan_buf
*buf
;
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
;
240 * relay_reserve - reserve slot in channel buffer
241 * @chan: relay channel
242 * @length: number of bytes to reserve
244 * Returns pointer to reserved slot, NULL if full.
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.
250 static inline void *relay_reserve(struct rchan
*chan
, size_t length
)
253 struct rchan_buf
*buf
= chan
->buf
[smp_processor_id()];
255 if (unlikely(buf
->offset
+ length
> buf
->chan
->subbuf_size
)) {
256 length
= relay_switch_subbuf(buf
, length
);
260 reserved
= buf
->data
+ buf
->offset
;
261 buf
->offset
+= length
;
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
271 * Helper function used to reserve bytes at the beginning of
272 * a sub-buffer in the subbuf_start() callback.
274 static inline void subbuf_start_reserve(struct rchan_buf
*buf
,
277 BUG_ON(length
>= buf
->chan
->subbuf_size
- 1);
278 buf
->offset
= length
;
282 * exported relay file operations, fs/relayfs/inode.c
284 extern struct file_operations relay_file_operations
;
286 #endif /* _LINUX_RELAYFS_FS_H */