1 /* 2 * linux/include/linux/relay.h 3 * 4 * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp 5 * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected]) 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/bug.h> 19 #include <linux/fs.h> 20 #include <linux/poll.h> 21 #include <linux/kref.h> 22 #include <linux/percpu.h> 23 24 /* 25 * Tracks changes to rchan/rchan_buf structs 26 */ 27 #define RELAYFS_CHANNEL_VERSION 7 28 29 /* 30 * Per-cpu relay channel buffer 31 */ 32 struct rchan_buf 33 { 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; 53 54 /* 55 * Relay channel data structure 56 */ 57 struct 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 ** __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 */ 73 }; 74 75 /* 76 * Relay channel client callbacks 77 */ 78 struct rchan_callbacks 79 { 80 /* 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 86 * 87 * The client should return 1 to continue logging, 0 to stop 88 * logging. 89 * 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. 93 * 94 * NOTE: the client can reserve bytes at the beginning of the new 95 * sub-buffer by calling subbuf_start_reserve() in this callback. 96 */ 97 int (*subbuf_start) (struct rchan_buf *buf, 98 void *subbuf, 99 void *prev_subbuf, 100 size_t prev_padding); 101 102 /* 103 * buf_mapped - relay buffer mmap notification 104 * @buf: the channel buffer 105 * @filp: relay file pointer 106 * 107 * Called when a relay file is successfully mmapped 108 */ 109 void (*buf_mapped)(struct rchan_buf *buf, 110 struct file *filp); 111 112 /* 113 * buf_unmapped - relay buffer unmap notification 114 * @buf: the channel buffer 115 * @filp: relay file pointer 116 * 117 * Called when a relay file is successfully unmapped 118 */ 119 void (*buf_unmapped)(struct rchan_buf *buf, 120 struct file *filp); 121 /* 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 128 * 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 133 * that filesystem. 134 * 135 * The callback should return the dentry of the file created 136 * to represent the relay buffer. 137 * 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. 141 * 142 * See Documentation/filesystems/relay.txt for more info. 143 */ 144 struct dentry *(*create_buf_file)(const char *filename, 145 struct dentry *parent, 146 umode_t mode, 147 struct rchan_buf *buf, 148 int *is_global); 149 150 /* 151 * remove_buf_file - remove file representing a relay channel buffer 152 * @dentry: the dentry of the file to remove 153 * 154 * Called during relay_close(), once for each per-cpu buffer, 155 * to allow the client to remove a file used to represent a 156 * channel buffer. 157 * 158 * The callback should return 0 if successful, negative if not. 159 */ 160 int (*remove_buf_file)(struct dentry *dentry); 161 }; 162 163 /* 164 * CONFIG_RELAY kernel API, kernel/relay.c 165 */ 166 167 struct rchan *relay_open(const char *base_filename, 168 struct dentry *parent, 169 size_t subbuf_size, 170 size_t n_subbufs, 171 struct rchan_callbacks *cb, 172 void *private_data); 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, 179 unsigned int cpu, 180 size_t consumed); 181 extern void relay_reset(struct rchan *chan); 182 extern int relay_buf_full(struct rchan_buf *buf); 183 184 extern size_t relay_switch_subbuf(struct rchan_buf *buf, 185 size_t length); 186 187 /** 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 192 * 193 * Writes data into the current cpu's channel buffer. 194 * 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 198 * interrupt context. 199 */ 200 static inline void relay_write(struct rchan *chan, 201 const void *data, 202 size_t length) 203 { 204 unsigned long flags; 205 struct rchan_buf *buf; 206 207 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); 214 } 215 216 /** 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 221 * 222 * Writes data into the current cpu's channel buffer. 223 * 224 * Protects the buffer by disabling preemption. Use 225 * relay_write() if you might be logging from interrupt 226 * context. 227 */ 228 static inline void __relay_write(struct rchan *chan, 229 const void *data, 230 size_t length) 231 { 232 struct rchan_buf *buf; 233 234 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); 240 } 241 242 /** 243 * relay_reserve - reserve slot in channel buffer 244 * @chan: relay channel 245 * @length: number of bytes to reserve 246 * 247 * Returns pointer to reserved slot, NULL if full. 248 * 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. 252 */ 253 static inline void *relay_reserve(struct rchan *chan, size_t length) 254 { 255 void *reserved = NULL; 256 struct rchan_buf *buf = *get_cpu_ptr(chan->buf); 257 258 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 259 length = relay_switch_subbuf(buf, length); 260 if (!length) 261 goto end; 262 } 263 reserved = buf->data + buf->offset; 264 buf->offset += length; 265 266 end: 267 put_cpu_ptr(chan->buf); 268 return reserved; 269 } 270 271 /** 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 275 * 276 * Helper function used to reserve bytes at the beginning of 277 * a sub-buffer in the subbuf_start() callback. 278 */ 279 static inline void subbuf_start_reserve(struct rchan_buf *buf, 280 size_t length) 281 { 282 BUG_ON(length >= buf->chan->subbuf_size - 1); 283 buf->offset = length; 284 } 285 286 /* 287 * exported relay file operations, kernel/relay.c 288 */ 289 extern const struct file_operations relay_file_operations; 290 291 #ifdef CONFIG_RELAY 292 int relay_prepare_cpu(unsigned int cpu); 293 #else 294 #define relay_prepare_cpu NULL 295 #endif 296 297 #endif /* _LINUX_RELAY_H */ 298 299