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/config.h> 14 #include <linux/types.h> 15 #include <linux/sched.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 6 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 work_struct wake_readers; /* reader wake-up work struct */ 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 */ 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 *buf[NR_CPUS]; /* per-cpu channel buffers */ 68 }; 69 70 /* 71 * Relay channel client callbacks 72 */ 73 struct rchan_callbacks 74 { 75 /* 76 * subbuf_start - called on buffer-switch to a new sub-buffer 77 * @buf: the channel buffer containing the new sub-buffer 78 * @subbuf: the start of the new sub-buffer 79 * @prev_subbuf: the start of the previous sub-buffer 80 * @prev_padding: unused space at the end of previous sub-buffer 81 * 82 * The client should return 1 to continue logging, 0 to stop 83 * logging. 84 * 85 * NOTE: subbuf_start will also be invoked when the buffer is 86 * created, so that the first sub-buffer can be initialized 87 * if necessary. In this case, prev_subbuf will be NULL. 88 * 89 * NOTE: the client can reserve bytes at the beginning of the new 90 * sub-buffer by calling subbuf_start_reserve() in this callback. 91 */ 92 int (*subbuf_start) (struct rchan_buf *buf, 93 void *subbuf, 94 void *prev_subbuf, 95 size_t prev_padding); 96 97 /* 98 * buf_mapped - relay buffer mmap notification 99 * @buf: the channel buffer 100 * @filp: relay file pointer 101 * 102 * Called when a relay file is successfully mmapped 103 */ 104 void (*buf_mapped)(struct rchan_buf *buf, 105 struct file *filp); 106 107 /* 108 * buf_unmapped - relay buffer unmap notification 109 * @buf: the channel buffer 110 * @filp: relay file pointer 111 * 112 * Called when a relay file is successfully unmapped 113 */ 114 void (*buf_unmapped)(struct rchan_buf *buf, 115 struct file *filp); 116 /* 117 * create_buf_file - create file to represent a relay channel buffer 118 * @filename: the name of the file to create 119 * @parent: the parent of the file to create 120 * @mode: the mode of the file to create 121 * @buf: the channel buffer 122 * @is_global: outparam - set non-zero if the buffer should be global 123 * 124 * Called during relay_open(), once for each per-cpu buffer, 125 * to allow the client to create a file to be used to 126 * represent the corresponding channel buffer. If the file is 127 * created outside of relay, the parent must also exist in 128 * that filesystem. 129 * 130 * The callback should return the dentry of the file created 131 * to represent the relay buffer. 132 * 133 * Setting the is_global outparam to a non-zero value will 134 * cause relay_open() to create a single global buffer rather 135 * than the default set of per-cpu buffers. 136 * 137 * See Documentation/filesystems/relayfs.txt for more info. 138 */ 139 struct dentry *(*create_buf_file)(const char *filename, 140 struct dentry *parent, 141 int mode, 142 struct rchan_buf *buf, 143 int *is_global); 144 145 /* 146 * remove_buf_file - remove file representing a relay channel buffer 147 * @dentry: the dentry of the file to remove 148 * 149 * Called during relay_close(), once for each per-cpu buffer, 150 * to allow the client to remove a file used to represent a 151 * channel buffer. 152 * 153 * The callback should return 0 if successful, negative if not. 154 */ 155 int (*remove_buf_file)(struct dentry *dentry); 156 }; 157 158 /* 159 * CONFIG_RELAY kernel API, kernel/relay.c 160 */ 161 162 struct rchan *relay_open(const char *base_filename, 163 struct dentry *parent, 164 size_t subbuf_size, 165 size_t n_subbufs, 166 struct rchan_callbacks *cb); 167 extern void relay_close(struct rchan *chan); 168 extern void relay_flush(struct rchan *chan); 169 extern void relay_subbufs_consumed(struct rchan *chan, 170 unsigned int cpu, 171 size_t consumed); 172 extern void relay_reset(struct rchan *chan); 173 extern int relay_buf_full(struct rchan_buf *buf); 174 175 extern size_t relay_switch_subbuf(struct rchan_buf *buf, 176 size_t length); 177 178 /** 179 * relay_write - write data into the channel 180 * @chan: relay channel 181 * @data: data to be written 182 * @length: number of bytes to write 183 * 184 * Writes data into the current cpu's channel buffer. 185 * 186 * Protects the buffer by disabling interrupts. Use this 187 * if you might be logging from interrupt context. Try 188 * __relay_write() if you know you won't be logging from 189 * interrupt context. 190 */ 191 static inline void relay_write(struct rchan *chan, 192 const void *data, 193 size_t length) 194 { 195 unsigned long flags; 196 struct rchan_buf *buf; 197 198 local_irq_save(flags); 199 buf = chan->buf[smp_processor_id()]; 200 if (unlikely(buf->offset + length > chan->subbuf_size)) 201 length = relay_switch_subbuf(buf, length); 202 memcpy(buf->data + buf->offset, data, length); 203 buf->offset += length; 204 local_irq_restore(flags); 205 } 206 207 /** 208 * __relay_write - write data into the channel 209 * @chan: relay channel 210 * @data: data to be written 211 * @length: number of bytes to write 212 * 213 * Writes data into the current cpu's channel buffer. 214 * 215 * Protects the buffer by disabling preemption. Use 216 * relay_write() if you might be logging from interrupt 217 * context. 218 */ 219 static inline void __relay_write(struct rchan *chan, 220 const void *data, 221 size_t length) 222 { 223 struct rchan_buf *buf; 224 225 buf = chan->buf[get_cpu()]; 226 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) 227 length = relay_switch_subbuf(buf, length); 228 memcpy(buf->data + buf->offset, data, length); 229 buf->offset += length; 230 put_cpu(); 231 } 232 233 /** 234 * relay_reserve - reserve slot in channel buffer 235 * @chan: relay channel 236 * @length: number of bytes to reserve 237 * 238 * Returns pointer to reserved slot, NULL if full. 239 * 240 * Reserves a slot in the current cpu's channel buffer. 241 * Does not protect the buffer at all - caller must provide 242 * appropriate synchronization. 243 */ 244 static inline void *relay_reserve(struct rchan *chan, size_t length) 245 { 246 void *reserved; 247 struct rchan_buf *buf = chan->buf[smp_processor_id()]; 248 249 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 250 length = relay_switch_subbuf(buf, length); 251 if (!length) 252 return NULL; 253 } 254 reserved = buf->data + buf->offset; 255 buf->offset += length; 256 257 return reserved; 258 } 259 260 /** 261 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer 262 * @buf: relay channel buffer 263 * @length: number of bytes to reserve 264 * 265 * Helper function used to reserve bytes at the beginning of 266 * a sub-buffer in the subbuf_start() callback. 267 */ 268 static inline void subbuf_start_reserve(struct rchan_buf *buf, 269 size_t length) 270 { 271 BUG_ON(length >= buf->chan->subbuf_size - 1); 272 buf->offset = length; 273 } 274 275 /* 276 * exported relay file operations, kernel/relay.c 277 */ 278 extern struct file_operations relay_file_operations; 279 280 #endif /* _LINUX_RELAY_H */ 281 282