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/wait.h> 16 #include <linux/list.h> 17 #include <linux/fs.h> 18 #include <linux/poll.h> 19 #include <linux/kref.h> 20 21 /* Needs a _much_ better name... */ 22 #define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE) 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 delayed_work wake_readers; /* reader wake-up work struct */ 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 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 char base_filename[NAME_MAX]; /* saved base filename */ 71 }; 72 73 /* 74 * Relay channel client callbacks 75 */ 76 struct rchan_callbacks 77 { 78 /* 79 * subbuf_start - called on buffer-switch to a new sub-buffer 80 * @buf: the channel buffer containing the new sub-buffer 81 * @subbuf: the start of the new sub-buffer 82 * @prev_subbuf: the start of the previous sub-buffer 83 * @prev_padding: unused space at the end of previous sub-buffer 84 * 85 * The client should return 1 to continue logging, 0 to stop 86 * logging. 87 * 88 * NOTE: subbuf_start will also be invoked when the buffer is 89 * created, so that the first sub-buffer can be initialized 90 * if necessary. In this case, prev_subbuf will be NULL. 91 * 92 * NOTE: the client can reserve bytes at the beginning of the new 93 * sub-buffer by calling subbuf_start_reserve() in this callback. 94 */ 95 int (*subbuf_start) (struct rchan_buf *buf, 96 void *subbuf, 97 void *prev_subbuf, 98 size_t prev_padding); 99 100 /* 101 * buf_mapped - relay buffer mmap notification 102 * @buf: the channel buffer 103 * @filp: relay file pointer 104 * 105 * Called when a relay file is successfully mmapped 106 */ 107 void (*buf_mapped)(struct rchan_buf *buf, 108 struct file *filp); 109 110 /* 111 * buf_unmapped - relay buffer unmap notification 112 * @buf: the channel buffer 113 * @filp: relay file pointer 114 * 115 * Called when a relay file is successfully unmapped 116 */ 117 void (*buf_unmapped)(struct rchan_buf *buf, 118 struct file *filp); 119 /* 120 * create_buf_file - create file to represent a relay channel buffer 121 * @filename: the name of the file to create 122 * @parent: the parent of the file to create 123 * @mode: the mode of the file to create 124 * @buf: the channel buffer 125 * @is_global: outparam - set non-zero if the buffer should be global 126 * 127 * Called during relay_open(), once for each per-cpu buffer, 128 * to allow the client to create a file to be used to 129 * represent the corresponding channel buffer. If the file is 130 * created outside of relay, the parent must also exist in 131 * that filesystem. 132 * 133 * The callback should return the dentry of the file created 134 * to represent the relay buffer. 135 * 136 * Setting the is_global outparam to a non-zero value will 137 * cause relay_open() to create a single global buffer rather 138 * than the default set of per-cpu buffers. 139 * 140 * See Documentation/filesystems/relayfs.txt for more info. 141 */ 142 struct dentry *(*create_buf_file)(const char *filename, 143 struct dentry *parent, 144 int mode, 145 struct rchan_buf *buf, 146 int *is_global); 147 148 /* 149 * remove_buf_file - remove file representing a relay channel buffer 150 * @dentry: the dentry of the file to remove 151 * 152 * Called during relay_close(), once for each per-cpu buffer, 153 * to allow the client to remove a file used to represent a 154 * channel buffer. 155 * 156 * The callback should return 0 if successful, negative if not. 157 */ 158 int (*remove_buf_file)(struct dentry *dentry); 159 }; 160 161 /* 162 * CONFIG_RELAY kernel API, kernel/relay.c 163 */ 164 165 struct rchan *relay_open(const char *base_filename, 166 struct dentry *parent, 167 size_t subbuf_size, 168 size_t n_subbufs, 169 struct rchan_callbacks *cb, 170 void *private_data); 171 extern void relay_close(struct rchan *chan); 172 extern void relay_flush(struct rchan *chan); 173 extern void relay_subbufs_consumed(struct rchan *chan, 174 unsigned int cpu, 175 size_t consumed); 176 extern void relay_reset(struct rchan *chan); 177 extern int relay_buf_full(struct rchan_buf *buf); 178 179 extern size_t relay_switch_subbuf(struct rchan_buf *buf, 180 size_t length); 181 182 /** 183 * relay_write - write data into the channel 184 * @chan: relay channel 185 * @data: data to be written 186 * @length: number of bytes to write 187 * 188 * Writes data into the current cpu's channel buffer. 189 * 190 * Protects the buffer by disabling interrupts. Use this 191 * if you might be logging from interrupt context. Try 192 * __relay_write() if you know you won't be logging from 193 * interrupt context. 194 */ 195 static inline void relay_write(struct rchan *chan, 196 const void *data, 197 size_t length) 198 { 199 unsigned long flags; 200 struct rchan_buf *buf; 201 202 local_irq_save(flags); 203 buf = chan->buf[smp_processor_id()]; 204 if (unlikely(buf->offset + length > chan->subbuf_size)) 205 length = relay_switch_subbuf(buf, length); 206 memcpy(buf->data + buf->offset, data, length); 207 buf->offset += length; 208 local_irq_restore(flags); 209 } 210 211 /** 212 * __relay_write - write data into the channel 213 * @chan: relay channel 214 * @data: data to be written 215 * @length: number of bytes to write 216 * 217 * Writes data into the current cpu's channel buffer. 218 * 219 * Protects the buffer by disabling preemption. Use 220 * relay_write() if you might be logging from interrupt 221 * context. 222 */ 223 static inline void __relay_write(struct rchan *chan, 224 const void *data, 225 size_t length) 226 { 227 struct rchan_buf *buf; 228 229 buf = chan->buf[get_cpu()]; 230 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) 231 length = relay_switch_subbuf(buf, length); 232 memcpy(buf->data + buf->offset, data, length); 233 buf->offset += length; 234 put_cpu(); 235 } 236 237 /** 238 * relay_reserve - reserve slot in channel buffer 239 * @chan: relay channel 240 * @length: number of bytes to reserve 241 * 242 * Returns pointer to reserved slot, NULL if full. 243 * 244 * Reserves a slot in the current cpu's channel buffer. 245 * Does not protect the buffer at all - caller must provide 246 * appropriate synchronization. 247 */ 248 static inline void *relay_reserve(struct rchan *chan, size_t length) 249 { 250 void *reserved; 251 struct rchan_buf *buf = chan->buf[smp_processor_id()]; 252 253 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 254 length = relay_switch_subbuf(buf, length); 255 if (!length) 256 return NULL; 257 } 258 reserved = buf->data + buf->offset; 259 buf->offset += length; 260 261 return reserved; 262 } 263 264 /** 265 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer 266 * @buf: relay channel buffer 267 * @length: number of bytes to reserve 268 * 269 * Helper function used to reserve bytes at the beginning of 270 * a sub-buffer in the subbuf_start() callback. 271 */ 272 static inline void subbuf_start_reserve(struct rchan_buf *buf, 273 size_t length) 274 { 275 BUG_ON(length >= buf->chan->subbuf_size - 1); 276 buf->offset = length; 277 } 278 279 /* 280 * exported relay file operations, kernel/relay.c 281 */ 282 extern const struct file_operations relay_file_operations; 283 284 #endif /* _LINUX_RELAY_H */ 285 286