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/irq_work.h> 19 #include <linux/bug.h> 20 #include <linux/fs.h> 21 #include <linux/poll.h> 22 #include <linux/kref.h> 23 #include <linux/percpu.h> 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 */ 33 struct 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 irq_work wakeup_work; /* reader wakeup */ 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; 54 55 /* 56 * Relay channel data structure 57 */ 58 struct rchan 59 { 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 ** __percpu buf; /* 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 */ 74 }; 75 76 /* 77 * Relay channel client callbacks 78 */ 79 struct rchan_callbacks 80 { 81 /* 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 87 * 88 * The client should return 1 to continue logging, 0 to stop 89 * logging. 90 * 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. 94 * 95 * NOTE: the client can reserve bytes at the beginning of the new 96 * sub-buffer by calling subbuf_start_reserve() in this callback. 97 */ 98 int (*subbuf_start) (struct rchan_buf *buf, 99 void *subbuf, 100 void *prev_subbuf, 101 size_t prev_padding); 102 103 /* 104 * buf_mapped - relay buffer mmap notification 105 * @buf: the channel buffer 106 * @filp: relay file pointer 107 * 108 * Called when a relay file is successfully mmapped 109 */ 110 void (*buf_mapped)(struct rchan_buf *buf, 111 struct file *filp); 112 113 /* 114 * buf_unmapped - relay buffer unmap notification 115 * @buf: the channel buffer 116 * @filp: relay file pointer 117 * 118 * Called when a relay file is successfully unmapped 119 */ 120 void (*buf_unmapped)(struct rchan_buf *buf, 121 struct file *filp); 122 /* 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 129 * 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 134 * that filesystem. 135 * 136 * The callback should return the dentry of the file created 137 * to represent the relay buffer. 138 * 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. 142 * 143 * See Documentation/filesystems/relay.txt for more info. 144 */ 145 struct dentry *(*create_buf_file)(const char *filename, 146 struct dentry *parent, 147 umode_t mode, 148 struct rchan_buf *buf, 149 int *is_global); 150 151 /* 152 * remove_buf_file - remove file representing a relay channel buffer 153 * @dentry: the dentry of the file to remove 154 * 155 * Called during relay_close(), once for each per-cpu buffer, 156 * to allow the client to remove a file used to represent a 157 * channel buffer. 158 * 159 * The callback should return 0 if successful, negative if not. 160 */ 161 int (*remove_buf_file)(struct dentry *dentry); 162 }; 163 164 /* 165 * CONFIG_RELAY kernel API, kernel/relay.c 166 */ 167 168 struct rchan *relay_open(const char *base_filename, 169 struct dentry *parent, 170 size_t subbuf_size, 171 size_t n_subbufs, 172 struct rchan_callbacks *cb, 173 void *private_data); 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, 180 unsigned int cpu, 181 size_t consumed); 182 extern void relay_reset(struct rchan *chan); 183 extern int relay_buf_full(struct rchan_buf *buf); 184 185 extern size_t relay_switch_subbuf(struct rchan_buf *buf, 186 size_t length); 187 188 /** 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 193 * 194 * Writes data into the current cpu's channel buffer. 195 * 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 199 * interrupt context. 200 */ 201 static inline void relay_write(struct rchan *chan, 202 const void *data, 203 size_t length) 204 { 205 unsigned long flags; 206 struct rchan_buf *buf; 207 208 local_irq_save(flags); 209 buf = *this_cpu_ptr(chan->buf); 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); 215 } 216 217 /** 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 222 * 223 * Writes data into the current cpu's channel buffer. 224 * 225 * Protects the buffer by disabling preemption. Use 226 * relay_write() if you might be logging from interrupt 227 * context. 228 */ 229 static inline void __relay_write(struct rchan *chan, 230 const void *data, 231 size_t length) 232 { 233 struct rchan_buf *buf; 234 235 buf = *get_cpu_ptr(chan->buf); 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; 240 put_cpu_ptr(chan->buf); 241 } 242 243 /** 244 * relay_reserve - reserve slot in channel buffer 245 * @chan: relay channel 246 * @length: number of bytes to reserve 247 * 248 * Returns pointer to reserved slot, NULL if full. 249 * 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. 253 */ 254 static inline void *relay_reserve(struct rchan *chan, size_t length) 255 { 256 void *reserved = NULL; 257 struct rchan_buf *buf = *get_cpu_ptr(chan->buf); 258 259 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 260 length = relay_switch_subbuf(buf, length); 261 if (!length) 262 goto end; 263 } 264 reserved = buf->data + buf->offset; 265 buf->offset += length; 266 267 end: 268 put_cpu_ptr(chan->buf); 269 return reserved; 270 } 271 272 /** 273 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer 274 * @buf: relay channel buffer 275 * @length: number of bytes to reserve 276 * 277 * Helper function used to reserve bytes at the beginning of 278 * a sub-buffer in the subbuf_start() callback. 279 */ 280 static inline void subbuf_start_reserve(struct rchan_buf *buf, 281 size_t length) 282 { 283 BUG_ON(length >= buf->chan->subbuf_size - 1); 284 buf->offset = length; 285 } 286 287 /* 288 * exported relay file operations, kernel/relay.c 289 */ 290 extern const struct file_operations relay_file_operations; 291 292 #ifdef CONFIG_RELAY 293 int relay_prepare_cpu(unsigned int cpu); 294 #else 295 #define relay_prepare_cpu NULL 296 #endif 297 298 #endif /* _LINUX_RELAY_H */ 299 300