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/bug.h> 19 #include <linux/fs.h> 20 #include <linux/poll.h> 21 #include <linux/kref.h> 22 23 /* 24 * Tracks changes to rchan/rchan_buf structs 25 */ 26 #define RELAYFS_CHANNEL_VERSION 7 27 28 /* 29 * Per-cpu relay channel buffer 30 */ 31 struct rchan_buf 32 { 33 void *start; /* start of channel buffer */ 34 void *data; /* start of current sub-buffer */ 35 size_t offset; /* current offset into sub-buffer */ 36 size_t subbufs_produced; /* count of sub-buffers produced */ 37 size_t subbufs_consumed; /* count of sub-buffers consumed */ 38 struct rchan *chan; /* associated channel */ 39 wait_queue_head_t read_wait; /* reader wait queue */ 40 struct timer_list timer; /* reader wake-up timer */ 41 struct dentry *dentry; /* channel file dentry */ 42 struct kref kref; /* channel buffer refcount */ 43 struct page **page_array; /* array of current buffer pages */ 44 unsigned int page_count; /* number of current buffer pages */ 45 unsigned int finalized; /* buffer has been finalized */ 46 size_t *padding; /* padding counts per sub-buffer */ 47 size_t prev_padding; /* temporary variable */ 48 size_t bytes_consumed; /* bytes consumed in cur read subbuf */ 49 size_t early_bytes; /* bytes consumed before VFS inited */ 50 unsigned int cpu; /* this buf's cpu */ 51 } ____cacheline_aligned; 52 53 /* 54 * Relay channel data structure 55 */ 56 struct rchan 57 { 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 int has_base_filename; /* has a filename associated? */ 71 char base_filename[NAME_MAX]; /* saved base filename */ 72 }; 73 74 /* 75 * Relay channel client callbacks 76 */ 77 struct 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/relay.txt for more info. 142 */ 143 struct dentry *(*create_buf_file)(const char *filename, 144 struct dentry *parent, 145 umode_t 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 */ 165 166 struct 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); 172 extern int relay_late_setup_files(struct rchan *chan, 173 const char *base_filename, 174 struct dentry *parent); 175 extern void relay_close(struct rchan *chan); 176 extern void relay_flush(struct rchan *chan); 177 extern void relay_subbufs_consumed(struct rchan *chan, 178 unsigned int cpu, 179 size_t consumed); 180 extern void relay_reset(struct rchan *chan); 181 extern int relay_buf_full(struct rchan_buf *buf); 182 183 extern size_t relay_switch_subbuf(struct rchan_buf *buf, 184 size_t length); 185 186 /** 187 * relay_write - write data into the channel 188 * @chan: relay channel 189 * @data: data to be written 190 * @length: number of bytes to write 191 * 192 * Writes data into the current cpu's channel buffer. 193 * 194 * Protects the buffer by disabling interrupts. Use this 195 * if you might be logging from interrupt context. Try 196 * __relay_write() if you know you won't be logging from 197 * interrupt context. 198 */ 199 static inline void relay_write(struct rchan *chan, 200 const void *data, 201 size_t length) 202 { 203 unsigned long flags; 204 struct rchan_buf *buf; 205 206 local_irq_save(flags); 207 buf = chan->buf[smp_processor_id()]; 208 if (unlikely(buf->offset + length > chan->subbuf_size)) 209 length = relay_switch_subbuf(buf, length); 210 memcpy(buf->data + buf->offset, data, length); 211 buf->offset += length; 212 local_irq_restore(flags); 213 } 214 215 /** 216 * __relay_write - write data into the channel 217 * @chan: relay channel 218 * @data: data to be written 219 * @length: number of bytes to write 220 * 221 * Writes data into the current cpu's channel buffer. 222 * 223 * Protects the buffer by disabling preemption. Use 224 * relay_write() if you might be logging from interrupt 225 * context. 226 */ 227 static inline void __relay_write(struct rchan *chan, 228 const void *data, 229 size_t length) 230 { 231 struct rchan_buf *buf; 232 233 buf = chan->buf[get_cpu()]; 234 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) 235 length = relay_switch_subbuf(buf, length); 236 memcpy(buf->data + buf->offset, data, length); 237 buf->offset += length; 238 put_cpu(); 239 } 240 241 /** 242 * relay_reserve - reserve slot in channel buffer 243 * @chan: relay channel 244 * @length: number of bytes to reserve 245 * 246 * Returns pointer to reserved slot, NULL if full. 247 * 248 * Reserves a slot in the current cpu's channel buffer. 249 * Does not protect the buffer at all - caller must provide 250 * appropriate synchronization. 251 */ 252 static inline void *relay_reserve(struct rchan *chan, size_t length) 253 { 254 void *reserved; 255 struct rchan_buf *buf = chan->buf[smp_processor_id()]; 256 257 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 258 length = relay_switch_subbuf(buf, length); 259 if (!length) 260 return NULL; 261 } 262 reserved = buf->data + buf->offset; 263 buf->offset += length; 264 265 return reserved; 266 } 267 268 /** 269 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer 270 * @buf: relay channel buffer 271 * @length: number of bytes to reserve 272 * 273 * Helper function used to reserve bytes at the beginning of 274 * a sub-buffer in the subbuf_start() callback. 275 */ 276 static inline void subbuf_start_reserve(struct rchan_buf *buf, 277 size_t length) 278 { 279 BUG_ON(length >= buf->chan->subbuf_size - 1); 280 buf->offset = length; 281 } 282 283 /* 284 * exported relay file operations, kernel/relay.c 285 */ 286 extern const struct file_operations relay_file_operations; 287 288 #endif /* _LINUX_RELAY_H */ 289 290