1/* 2 * linux/include/linux/relay.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 * CONFIG_RELAY definitions and declarations 8 */ 9 10#ifndef _LINUX_RELAY_H 11#define _LINUX_RELAY_H 12 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/fs.h> 19#include <linux/poll.h> 20#include <linux/kref.h> 21 22/* Needs a _much_ better name... */ 23#define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE) 24 25/* 26 * Tracks changes to rchan/rchan_buf structs 27 */ 28#define RELAYFS_CHANNEL_VERSION 7 29 30/* 31 * Per-cpu relay channel buffer 32 */ 33struct rchan_buf 34{ 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 unsigned int cpu; /* this buf's cpu */ 52} ____cacheline_aligned; 53 54/* 55 * Relay channel data structure 56 */ 57struct rchan 58{ 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 *buf[NR_CPUS]; /* 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 char base_filename[NAME_MAX]; /* saved base filename */ 72}; 73 74/* 75 * Relay channel client callbacks 76 */ 77struct rchan_callbacks 78{ 79 /* 80 * subbuf_start - called on buffer-switch to a new sub-buffer 81 * @buf: the channel buffer containing the new sub-buffer 82 * @subbuf: the start of the new sub-buffer 83 * @prev_subbuf: the start of the previous sub-buffer 84 * @prev_padding: unused space at the end of previous sub-buffer 85 * 86 * The client should return 1 to continue logging, 0 to stop 87 * logging. 88 * 89 * NOTE: subbuf_start will also be invoked when the buffer is 90 * created, so that the first sub-buffer can be initialized 91 * if necessary. In this case, prev_subbuf will be NULL. 92 * 93 * NOTE: the client can reserve bytes at the beginning of the new 94 * sub-buffer by calling subbuf_start_reserve() in this callback. 95 */ 96 int (*subbuf_start) (struct rchan_buf *buf, 97 void *subbuf, 98 void *prev_subbuf, 99 size_t prev_padding); 100 101 /* 102 * buf_mapped - relay buffer mmap notification 103 * @buf: the channel buffer 104 * @filp: relay file pointer 105 * 106 * Called when a relay file is successfully mmapped 107 */ 108 void (*buf_mapped)(struct rchan_buf *buf, 109 struct file *filp); 110 111 /* 112 * buf_unmapped - relay buffer unmap notification 113 * @buf: the channel buffer 114 * @filp: relay file pointer 115 * 116 * Called when a relay file is successfully unmapped 117 */ 118 void (*buf_unmapped)(struct rchan_buf *buf, 119 struct file *filp); 120 /* 121 * create_buf_file - create file to represent a relay channel buffer 122 * @filename: the name of the file to create 123 * @parent: the parent of the file to create 124 * @mode: the mode of the file to create 125 * @buf: the channel buffer 126 * @is_global: outparam - set non-zero if the buffer should be global 127 * 128 * Called during relay_open(), once for each per-cpu buffer, 129 * to allow the client to create a file to be used to 130 * represent the corresponding channel buffer. If the file is 131 * created outside of relay, the parent must also exist in 132 * that filesystem. 133 * 134 * The callback should return the dentry of the file created 135 * to represent the relay buffer. 136 * 137 * Setting the is_global outparam to a non-zero value will 138 * cause relay_open() to create a single global buffer rather 139 * than the default set of per-cpu buffers. 140 * 141 * See Documentation/filesystems/relayfs.txt for more info. 142 */ 143 struct dentry *(*create_buf_file)(const char *filename, 144 struct dentry *parent, 145 int mode, 146 struct rchan_buf *buf, 147 int *is_global); 148 149 /* 150 * remove_buf_file - remove file representing a relay channel buffer 151 * @dentry: the dentry of the file to remove 152 * 153 * Called during relay_close(), once for each per-cpu buffer, 154 * to allow the client to remove a file used to represent a 155 * channel buffer. 156 * 157 * The callback should return 0 if successful, negative if not. 158 */ 159 int (*remove_buf_file)(struct dentry *dentry); 160}; 161 162/* 163 * CONFIG_RELAY kernel API, kernel/relay.c 164 */ 165 166struct rchan *relay_open(const char *base_filename, 167 struct dentry *parent, 168 size_t subbuf_size, 169 size_t n_subbufs, 170 struct rchan_callbacks *cb, 171 void *private_data); 172extern void relay_close(struct rchan *chan); 173extern void relay_flush(struct rchan *chan); 174extern void relay_subbufs_consumed(struct rchan *chan, 175 unsigned int cpu, 176 size_t consumed); 177extern void relay_reset(struct rchan *chan); 178extern int relay_buf_full(struct rchan_buf *buf); 179 180extern size_t relay_switch_subbuf(struct rchan_buf *buf, 181 size_t length); 182 183/** 184 * relay_write - write data into the channel 185 * @chan: relay channel 186 * @data: data to be written 187 * @length: number of bytes to write 188 * 189 * Writes data into the current cpu's channel buffer. 190 * 191 * Protects the buffer by disabling interrupts. Use this 192 * if you might be logging from interrupt context. Try 193 * __relay_write() if you know you won't be logging from 194 * interrupt context. 195 */ 196static inline void relay_write(struct rchan *chan, 197 const void *data, 198 size_t length) 199{ 200 unsigned long flags; 201 struct rchan_buf *buf; 202 203 local_irq_save(flags); 204 buf = chan->buf[smp_processor_id()]; 205 if (unlikely(buf->offset + length > chan->subbuf_size)) 206 length = relay_switch_subbuf(buf, length); 207 memcpy(buf->data + buf->offset, data, length); 208 buf->offset += length; 209 local_irq_restore(flags); 210} 211 212/** 213 * __relay_write - write data into the channel 214 * @chan: relay channel 215 * @data: data to be written 216 * @length: number of bytes to write 217 * 218 * Writes data into the current cpu's channel buffer. 219 * 220 * Protects the buffer by disabling preemption. Use 221 * relay_write() if you might be logging from interrupt 222 * context. 223 */ 224static inline void __relay_write(struct rchan *chan, 225 const void *data, 226 size_t length) 227{ 228 struct rchan_buf *buf; 229 230 buf = chan->buf[get_cpu()]; 231 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) 232 length = relay_switch_subbuf(buf, length); 233 memcpy(buf->data + buf->offset, data, length); 234 buf->offset += length; 235 put_cpu(); 236} 237 238/** 239 * relay_reserve - reserve slot in channel buffer 240 * @chan: relay channel 241 * @length: number of bytes to reserve 242 * 243 * Returns pointer to reserved slot, NULL if full. 244 * 245 * Reserves a slot in the current cpu's channel buffer. 246 * Does not protect the buffer at all - caller must provide 247 * appropriate synchronization. 248 */ 249static inline void *relay_reserve(struct rchan *chan, size_t length) 250{ 251 void *reserved; 252 struct rchan_buf *buf = chan->buf[smp_processor_id()]; 253 254 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 255 length = relay_switch_subbuf(buf, length); 256 if (!length) 257 return NULL; 258 } 259 reserved = buf->data + buf->offset; 260 buf->offset += length; 261 262 return reserved; 263} 264 265/** 266 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer 267 * @buf: relay channel buffer 268 * @length: number of bytes to reserve 269 * 270 * Helper function used to reserve bytes at the beginning of 271 * a sub-buffer in the subbuf_start() callback. 272 */ 273static inline void subbuf_start_reserve(struct rchan_buf *buf, 274 size_t length) 275{ 276 BUG_ON(length >= buf->chan->subbuf_size - 1); 277 buf->offset = length; 278} 279 280/* 281 * exported relay file operations, kernel/relay.c 282 */ 283extern const struct file_operations relay_file_operations; 284 285#endif /* _LINUX_RELAY_H */ 286