1 /* 2 * linux/include/linux/relay.h 3 * 4 * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi (at) us.ibm.com), IBM Corp 5 * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim (at) 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/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 6 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 work_struct 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 }; 68 69 /* 70 * Relay channel client callbacks 71 */ 72 struct rchan_callbacks 73 { 74 /* 75 * subbuf_start - called on buffer-switch to a new sub-buffer 76 * @buf: the channel buffer containing the new sub-buffer 77 * @subbuf: the start of the new sub-buffer 78 * @prev_subbuf: the start of the previous sub-buffer 79 * @prev_padding: unused space at the end of previous sub-buffer 80 * 81 * The client should return 1 to continue logging, 0 to stop 82 * logging. 83 * 84 * NOTE: subbuf_start will also be invoked when the buffer is 85 * created, so that the first sub-buffer can be initialized 86 * if necessary. In this case, prev_subbuf will be NULL. 87 * 88 * NOTE: the client can reserve bytes at the beginning of the new 89 * sub-buffer by calling subbuf_start_reserve() in this callback. 90 */ 91 int (*subbuf_start) (struct rchan_buf *buf, 92 void *subbuf, 93 void *prev_subbuf, 94 size_t prev_padding); 95 96 /* 97 * buf_mapped - relay buffer mmap notification 98 * @buf: the channel buffer 99 * @filp: relay file pointer 100 * 101 * Called when a relay file is successfully mmapped 102 */ 103 void (*buf_mapped)(struct rchan_buf *buf, 104 struct file *filp); 105 106 /* 107 * buf_unmapped - relay buffer unmap notification 108 * @buf: the channel buffer 109 * @filp: relay file pointer 110 * 111 * Called when a relay file is successfully unmapped 112 */ 113 void (*buf_unmapped)(struct rchan_buf *buf, 114 struct file *filp); 115 /* 116 * create_buf_file - create file to represent a relay channel buffer 117 * @filename: the name of the file to create 118 * @parent: the parent of the file to create 119 * @mode: the mode of the file to create 120 * @buf: the channel buffer 121 * @is_global: outparam - set non-zero if the buffer should be global 122 * 123 * Called during relay_open(), once for each per-cpu buffer, 124 * to allow the client to create a file to be used to 125 * represent the corresponding channel buffer. If the file is 126 * created outside of relay, the parent must also exist in 127 * that filesystem. 128 * 129 * The callback should return the dentry of the file created 130 * to represent the relay buffer. 131 * 132 * Setting the is_global outparam to a non-zero value will 133 * cause relay_open() to create a single global buffer rather 134 * than the default set of per-cpu buffers. 135 * 136 * See Documentation/filesystems/relayfs.txt for more info. 137 */ 138 struct dentry *(*create_buf_file)(const char *filename, 139 struct dentry *parent, 140 int mode, 141 struct rchan_buf *buf, 142 int *is_global); 143 144 /* 145 * remove_buf_file - remove file representing a relay channel buffer 146 * @dentry: the dentry of the file to remove 147 * 148 * Called during relay_close(), once for each per-cpu buffer, 149 * to allow the client to remove a file used to represent a 150 * channel buffer. 151 * 152 * The callback should return 0 if successful, negative if not. 153 */ 154 int (*remove_buf_file)(struct dentry *dentry); 155 }; 156 157 /* 158 * CONFIG_RELAY kernel API, kernel/relay.c 159 */ 160 161 struct rchan *relay_open(const char *base_filename, 162 struct dentry *parent, 163 size_t subbuf_size, 164 size_t n_subbufs, 165 struct rchan_callbacks *cb); 166 extern void relay_close(struct rchan *chan); 167 extern void relay_flush(struct rchan *chan); 168 extern void relay_subbufs_consumed(struct rchan *chan, 169 unsigned int cpu, 170 size_t consumed); 171 extern void relay_reset(struct rchan *chan); 172 extern int relay_buf_full(struct rchan_buf *buf); 173 174 extern size_t relay_switch_subbuf(struct rchan_buf *buf, 175 size_t length); 176 177 /** 178 * relay_write - write data into the channel 179 * @chan: relay channel 180 * @data: data to be written 181 * @length: number of bytes to write 182 * 183 * Writes data into the current cpu's channel buffer. 184 * 185 * Protects the buffer by disabling interrupts. Use this 186 * if you might be logging from interrupt context. Try 187 * __relay_write() if you know you won't be logging from 188 * interrupt context. 189 */ 190 static inline void relay_write(struct rchan *chan, 191 const void *data, 192 size_t length) 193 { 194 unsigned long flags; 195 struct rchan_buf *buf; 196 197 local_irq_save(flags); 198 buf = chan->buf[smp_processor_id()]; 199 if (unlikely(buf->offset + length > chan->subbuf_size)) 200 length = relay_switch_subbuf(buf, length); 201 memcpy(buf->data + buf->offset, data, length); 202 buf->offset += length; 203 local_irq_restore(flags); 204 } 205 206 /** 207 * __relay_write - write data into the channel 208 * @chan: relay channel 209 * @data: data to be written 210 * @length: number of bytes to write 211 * 212 * Writes data into the current cpu's channel buffer. 213 * 214 * Protects the buffer by disabling preemption. Use 215 * relay_write() if you might be logging from interrupt 216 * context. 217 */ 218 static inline void __relay_write(struct rchan *chan, 219 const void *data, 220 size_t length) 221 { 222 struct rchan_buf *buf; 223 224 buf = chan->buf[get_cpu()]; 225 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) 226 length = relay_switch_subbuf(buf, length); 227 memcpy(buf->data + buf->offset, data, length); 228 buf->offset += length; 229 put_cpu(); 230 } 231 232 /** 233 * relay_reserve - reserve slot in channel buffer 234 * @chan: relay channel 235 * @length: number of bytes to reserve 236 * 237 * Returns pointer to reserved slot, NULL if full. 238 * 239 * Reserves a slot in the current cpu's channel buffer. 240 * Does not protect the buffer at all - caller must provide 241 * appropriate synchronization. 242 */ 243 static inline void *relay_reserve(struct rchan *chan, size_t length) 244 { 245 void *reserved; 246 struct rchan_buf *buf = chan->buf[smp_processor_id()]; 247 248 if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { 249 length = relay_switch_subbuf(buf, length); 250 if (!length) 251 return NULL; 252 } 253 reserved = buf->data + buf->offset; 254 buf->offset += length; 255 256 return reserved; 257 } 258 259 /** 260 * subbuf_start_reserve - reserve bytes at the start of a sub-buffer 261 * @buf: relay channel buffer 262 * @length: number of bytes to reserve 263 * 264 * Helper function used to reserve bytes at the beginning of 265 * a sub-buffer in the subbuf_start() callback. 266 */ 267 static inline void subbuf_start_reserve(struct rchan_buf *buf, 268 size_t length) 269 { 270 BUG_ON(length >= buf->chan->subbuf_size - 1); 271 buf->offset = length; 272 } 273 274 /* 275 * exported relay file operations, kernel/relay.c 276 */ 277 extern struct file_operations relay_file_operations; 278 279 #endif /* _LINUX_RELAY_H */ 280 281
