Tom Zanussi | e82894f | 2005-09-06 15:16:30 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Public API and common code for RelayFS. |
| 3 | * |
| 4 | * See Documentation/filesystems/relayfs.txt for an overview of relayfs. |
| 5 | * |
| 6 | * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp |
| 7 | * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com) |
| 8 | * |
| 9 | * This file is released under the GPL. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/errno.h> |
| 13 | #include <linux/stddef.h> |
| 14 | #include <linux/slab.h> |
| 15 | #include <linux/module.h> |
| 16 | #include <linux/string.h> |
| 17 | #include <linux/relayfs_fs.h> |
| 18 | #include "relay.h" |
| 19 | #include "buffers.h" |
| 20 | |
| 21 | /** |
| 22 | * relay_buf_empty - boolean, is the channel buffer empty? |
| 23 | * @buf: channel buffer |
| 24 | * |
| 25 | * Returns 1 if the buffer is empty, 0 otherwise. |
| 26 | */ |
| 27 | int relay_buf_empty(struct rchan_buf *buf) |
| 28 | { |
| 29 | return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1; |
| 30 | } |
| 31 | |
| 32 | /** |
| 33 | * relay_buf_full - boolean, is the channel buffer full? |
| 34 | * @buf: channel buffer |
| 35 | * |
| 36 | * Returns 1 if the buffer is full, 0 otherwise. |
| 37 | */ |
| 38 | int relay_buf_full(struct rchan_buf *buf) |
| 39 | { |
| 40 | size_t ready = buf->subbufs_produced - buf->subbufs_consumed; |
| 41 | return (ready >= buf->chan->n_subbufs) ? 1 : 0; |
| 42 | } |
| 43 | |
| 44 | /* |
| 45 | * High-level relayfs kernel API and associated functions. |
| 46 | */ |
| 47 | |
| 48 | /* |
| 49 | * rchan_callback implementations defining default channel behavior. Used |
| 50 | * in place of corresponding NULL values in client callback struct. |
| 51 | */ |
| 52 | |
| 53 | /* |
| 54 | * subbuf_start() default callback. Does nothing. |
| 55 | */ |
| 56 | static int subbuf_start_default_callback (struct rchan_buf *buf, |
| 57 | void *subbuf, |
| 58 | void *prev_subbuf, |
| 59 | size_t prev_padding) |
| 60 | { |
| 61 | if (relay_buf_full(buf)) |
| 62 | return 0; |
| 63 | |
| 64 | return 1; |
| 65 | } |
| 66 | |
| 67 | /* |
| 68 | * buf_mapped() default callback. Does nothing. |
| 69 | */ |
| 70 | static void buf_mapped_default_callback(struct rchan_buf *buf, |
| 71 | struct file *filp) |
| 72 | { |
| 73 | } |
| 74 | |
| 75 | /* |
| 76 | * buf_unmapped() default callback. Does nothing. |
| 77 | */ |
| 78 | static void buf_unmapped_default_callback(struct rchan_buf *buf, |
| 79 | struct file *filp) |
| 80 | { |
| 81 | } |
| 82 | |
| 83 | /* relay channel default callbacks */ |
| 84 | static struct rchan_callbacks default_channel_callbacks = { |
| 85 | .subbuf_start = subbuf_start_default_callback, |
| 86 | .buf_mapped = buf_mapped_default_callback, |
| 87 | .buf_unmapped = buf_unmapped_default_callback, |
| 88 | }; |
| 89 | |
| 90 | /** |
| 91 | * wakeup_readers - wake up readers waiting on a channel |
| 92 | * @private: the channel buffer |
| 93 | * |
| 94 | * This is the work function used to defer reader waking. The |
| 95 | * reason waking is deferred is that calling directly from write |
| 96 | * causes problems if you're writing from say the scheduler. |
| 97 | */ |
| 98 | static void wakeup_readers(void *private) |
| 99 | { |
| 100 | struct rchan_buf *buf = private; |
| 101 | wake_up_interruptible(&buf->read_wait); |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * __relay_reset - reset a channel buffer |
| 106 | * @buf: the channel buffer |
| 107 | * @init: 1 if this is a first-time initialization |
| 108 | * |
| 109 | * See relay_reset for description of effect. |
| 110 | */ |
| 111 | static inline void __relay_reset(struct rchan_buf *buf, unsigned int init) |
| 112 | { |
| 113 | size_t i; |
| 114 | |
| 115 | if (init) { |
| 116 | init_waitqueue_head(&buf->read_wait); |
| 117 | kref_init(&buf->kref); |
| 118 | INIT_WORK(&buf->wake_readers, NULL, NULL); |
| 119 | } else { |
| 120 | cancel_delayed_work(&buf->wake_readers); |
| 121 | flush_scheduled_work(); |
| 122 | } |
| 123 | |
| 124 | buf->subbufs_produced = 0; |
| 125 | buf->subbufs_consumed = 0; |
| 126 | buf->bytes_consumed = 0; |
| 127 | buf->finalized = 0; |
| 128 | buf->data = buf->start; |
| 129 | buf->offset = 0; |
| 130 | |
| 131 | for (i = 0; i < buf->chan->n_subbufs; i++) |
| 132 | buf->padding[i] = 0; |
| 133 | |
| 134 | buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0); |
| 135 | } |
| 136 | |
| 137 | /** |
| 138 | * relay_reset - reset the channel |
| 139 | * @chan: the channel |
| 140 | * |
| 141 | * This has the effect of erasing all data from all channel buffers |
| 142 | * and restarting the channel in its initial state. The buffers |
| 143 | * are not freed, so any mappings are still in effect. |
| 144 | * |
| 145 | * NOTE: Care should be taken that the channel isn't actually |
| 146 | * being used by anything when this call is made. |
| 147 | */ |
| 148 | void relay_reset(struct rchan *chan) |
| 149 | { |
| 150 | unsigned int i; |
| 151 | |
| 152 | if (!chan) |
| 153 | return; |
| 154 | |
| 155 | for (i = 0; i < NR_CPUS; i++) { |
| 156 | if (!chan->buf[i]) |
| 157 | continue; |
| 158 | __relay_reset(chan->buf[i], 0); |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | /** |
| 163 | * relay_open_buf - create a new channel buffer in relayfs |
| 164 | * |
| 165 | * Internal - used by relay_open(). |
| 166 | */ |
| 167 | static struct rchan_buf *relay_open_buf(struct rchan *chan, |
| 168 | const char *filename, |
| 169 | struct dentry *parent) |
| 170 | { |
| 171 | struct rchan_buf *buf; |
| 172 | struct dentry *dentry; |
| 173 | |
| 174 | /* Create file in fs */ |
| 175 | dentry = relayfs_create_file(filename, parent, S_IRUSR, chan); |
| 176 | if (!dentry) |
| 177 | return NULL; |
| 178 | |
| 179 | buf = RELAYFS_I(dentry->d_inode)->buf; |
| 180 | buf->dentry = dentry; |
| 181 | __relay_reset(buf, 1); |
| 182 | |
| 183 | return buf; |
| 184 | } |
| 185 | |
| 186 | /** |
| 187 | * relay_close_buf - close a channel buffer |
| 188 | * @buf: channel buffer |
| 189 | * |
| 190 | * Marks the buffer finalized and restores the default callbacks. |
| 191 | * The channel buffer and channel buffer data structure are then freed |
| 192 | * automatically when the last reference is given up. |
| 193 | */ |
| 194 | static inline void relay_close_buf(struct rchan_buf *buf) |
| 195 | { |
| 196 | buf->finalized = 1; |
| 197 | buf->chan->cb = &default_channel_callbacks; |
| 198 | cancel_delayed_work(&buf->wake_readers); |
| 199 | flush_scheduled_work(); |
| 200 | kref_put(&buf->kref, relay_remove_buf); |
| 201 | } |
| 202 | |
| 203 | static inline void setup_callbacks(struct rchan *chan, |
| 204 | struct rchan_callbacks *cb) |
| 205 | { |
| 206 | if (!cb) { |
| 207 | chan->cb = &default_channel_callbacks; |
| 208 | return; |
| 209 | } |
| 210 | |
| 211 | if (!cb->subbuf_start) |
| 212 | cb->subbuf_start = subbuf_start_default_callback; |
| 213 | if (!cb->buf_mapped) |
| 214 | cb->buf_mapped = buf_mapped_default_callback; |
| 215 | if (!cb->buf_unmapped) |
| 216 | cb->buf_unmapped = buf_unmapped_default_callback; |
| 217 | chan->cb = cb; |
| 218 | } |
| 219 | |
| 220 | /** |
| 221 | * relay_open - create a new relayfs channel |
| 222 | * @base_filename: base name of files to create |
| 223 | * @parent: dentry of parent directory, NULL for root directory |
| 224 | * @subbuf_size: size of sub-buffers |
| 225 | * @n_subbufs: number of sub-buffers |
| 226 | * @cb: client callback functions |
| 227 | * |
| 228 | * Returns channel pointer if successful, NULL otherwise. |
| 229 | * |
| 230 | * Creates a channel buffer for each cpu using the sizes and |
| 231 | * attributes specified. The created channel buffer files |
| 232 | * will be named base_filename0...base_filenameN-1. File |
| 233 | * permissions will be S_IRUSR. |
| 234 | */ |
| 235 | struct rchan *relay_open(const char *base_filename, |
| 236 | struct dentry *parent, |
| 237 | size_t subbuf_size, |
| 238 | size_t n_subbufs, |
| 239 | struct rchan_callbacks *cb) |
| 240 | { |
| 241 | unsigned int i; |
| 242 | struct rchan *chan; |
| 243 | char *tmpname; |
| 244 | |
| 245 | if (!base_filename) |
| 246 | return NULL; |
| 247 | |
| 248 | if (!(subbuf_size && n_subbufs)) |
| 249 | return NULL; |
| 250 | |
| 251 | chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL); |
| 252 | if (!chan) |
| 253 | return NULL; |
| 254 | |
| 255 | chan->version = RELAYFS_CHANNEL_VERSION; |
| 256 | chan->n_subbufs = n_subbufs; |
| 257 | chan->subbuf_size = subbuf_size; |
| 258 | chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs); |
| 259 | setup_callbacks(chan, cb); |
| 260 | kref_init(&chan->kref); |
| 261 | |
| 262 | tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL); |
| 263 | if (!tmpname) |
| 264 | goto free_chan; |
| 265 | |
| 266 | for_each_online_cpu(i) { |
| 267 | sprintf(tmpname, "%s%d", base_filename, i); |
| 268 | chan->buf[i] = relay_open_buf(chan, tmpname, parent); |
| 269 | chan->buf[i]->cpu = i; |
| 270 | if (!chan->buf[i]) |
| 271 | goto free_bufs; |
| 272 | } |
| 273 | |
| 274 | kfree(tmpname); |
| 275 | return chan; |
| 276 | |
| 277 | free_bufs: |
| 278 | for (i = 0; i < NR_CPUS; i++) { |
| 279 | if (!chan->buf[i]) |
| 280 | break; |
| 281 | relay_close_buf(chan->buf[i]); |
| 282 | } |
| 283 | kfree(tmpname); |
| 284 | |
| 285 | free_chan: |
| 286 | kref_put(&chan->kref, relay_destroy_channel); |
| 287 | return NULL; |
| 288 | } |
| 289 | |
| 290 | /** |
| 291 | * relay_switch_subbuf - switch to a new sub-buffer |
| 292 | * @buf: channel buffer |
| 293 | * @length: size of current event |
| 294 | * |
| 295 | * Returns either the length passed in or 0 if full. |
| 296 | |
| 297 | * Performs sub-buffer-switch tasks such as invoking callbacks, |
| 298 | * updating padding counts, waking up readers, etc. |
| 299 | */ |
| 300 | size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) |
| 301 | { |
| 302 | void *old, *new; |
| 303 | size_t old_subbuf, new_subbuf; |
| 304 | |
| 305 | if (unlikely(length > buf->chan->subbuf_size)) |
| 306 | goto toobig; |
| 307 | |
| 308 | if (buf->offset != buf->chan->subbuf_size + 1) { |
| 309 | buf->prev_padding = buf->chan->subbuf_size - buf->offset; |
| 310 | old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; |
| 311 | buf->padding[old_subbuf] = buf->prev_padding; |
| 312 | buf->subbufs_produced++; |
| 313 | if (waitqueue_active(&buf->read_wait)) { |
| 314 | PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf); |
| 315 | schedule_delayed_work(&buf->wake_readers, 1); |
| 316 | } |
| 317 | } |
| 318 | |
| 319 | old = buf->data; |
| 320 | new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; |
| 321 | new = buf->start + new_subbuf * buf->chan->subbuf_size; |
| 322 | buf->offset = 0; |
| 323 | if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) { |
| 324 | buf->offset = buf->chan->subbuf_size + 1; |
| 325 | return 0; |
| 326 | } |
| 327 | buf->data = new; |
| 328 | buf->padding[new_subbuf] = 0; |
| 329 | |
| 330 | if (unlikely(length + buf->offset > buf->chan->subbuf_size)) |
| 331 | goto toobig; |
| 332 | |
| 333 | return length; |
| 334 | |
| 335 | toobig: |
Tom Zanussi | fd30fc3 | 2005-12-20 13:10:22 -0600 | [diff] [blame] | 336 | buf->chan->last_toobig = length; |
Tom Zanussi | e82894f | 2005-09-06 15:16:30 -0700 | [diff] [blame] | 337 | return 0; |
| 338 | } |
| 339 | |
| 340 | /** |
| 341 | * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count |
| 342 | * @chan: the channel |
| 343 | * @cpu: the cpu associated with the channel buffer to update |
| 344 | * @subbufs_consumed: number of sub-buffers to add to current buf's count |
| 345 | * |
| 346 | * Adds to the channel buffer's consumed sub-buffer count. |
| 347 | * subbufs_consumed should be the number of sub-buffers newly consumed, |
| 348 | * not the total consumed. |
| 349 | * |
| 350 | * NOTE: kernel clients don't need to call this function if the channel |
| 351 | * mode is 'overwrite'. |
| 352 | */ |
| 353 | void relay_subbufs_consumed(struct rchan *chan, |
| 354 | unsigned int cpu, |
| 355 | size_t subbufs_consumed) |
| 356 | { |
| 357 | struct rchan_buf *buf; |
| 358 | |
| 359 | if (!chan) |
| 360 | return; |
| 361 | |
| 362 | if (cpu >= NR_CPUS || !chan->buf[cpu]) |
| 363 | return; |
| 364 | |
| 365 | buf = chan->buf[cpu]; |
| 366 | buf->subbufs_consumed += subbufs_consumed; |
| 367 | if (buf->subbufs_consumed > buf->subbufs_produced) |
| 368 | buf->subbufs_consumed = buf->subbufs_produced; |
| 369 | } |
| 370 | |
| 371 | /** |
| 372 | * relay_destroy_channel - free the channel struct |
| 373 | * |
| 374 | * Should only be called from kref_put(). |
| 375 | */ |
| 376 | void relay_destroy_channel(struct kref *kref) |
| 377 | { |
| 378 | struct rchan *chan = container_of(kref, struct rchan, kref); |
| 379 | kfree(chan); |
| 380 | } |
| 381 | |
| 382 | /** |
| 383 | * relay_close - close the channel |
| 384 | * @chan: the channel |
| 385 | * |
| 386 | * Closes all channel buffers and frees the channel. |
| 387 | */ |
| 388 | void relay_close(struct rchan *chan) |
| 389 | { |
| 390 | unsigned int i; |
| 391 | |
| 392 | if (!chan) |
| 393 | return; |
| 394 | |
| 395 | for (i = 0; i < NR_CPUS; i++) { |
| 396 | if (!chan->buf[i]) |
| 397 | continue; |
| 398 | relay_close_buf(chan->buf[i]); |
| 399 | } |
| 400 | |
Tom Zanussi | fd30fc3 | 2005-12-20 13:10:22 -0600 | [diff] [blame] | 401 | if (chan->last_toobig) |
| 402 | printk(KERN_WARNING "relayfs: one or more items not logged " |
| 403 | "[item size (%Zd) > sub-buffer size (%Zd)]\n", |
| 404 | chan->last_toobig, chan->subbuf_size); |
| 405 | |
Tom Zanussi | e82894f | 2005-09-06 15:16:30 -0700 | [diff] [blame] | 406 | kref_put(&chan->kref, relay_destroy_channel); |
| 407 | } |
| 408 | |
| 409 | /** |
| 410 | * relay_flush - close the channel |
| 411 | * @chan: the channel |
| 412 | * |
| 413 | * Flushes all channel buffers i.e. forces buffer switch. |
| 414 | */ |
| 415 | void relay_flush(struct rchan *chan) |
| 416 | { |
| 417 | unsigned int i; |
| 418 | |
| 419 | if (!chan) |
| 420 | return; |
| 421 | |
| 422 | for (i = 0; i < NR_CPUS; i++) { |
| 423 | if (!chan->buf[i]) |
| 424 | continue; |
| 425 | relay_switch_subbuf(chan->buf[i], 0); |
| 426 | } |
| 427 | } |
| 428 | |
| 429 | EXPORT_SYMBOL_GPL(relay_open); |
| 430 | EXPORT_SYMBOL_GPL(relay_close); |
| 431 | EXPORT_SYMBOL_GPL(relay_flush); |
| 432 | EXPORT_SYMBOL_GPL(relay_reset); |
| 433 | EXPORT_SYMBOL_GPL(relay_subbufs_consumed); |
| 434 | EXPORT_SYMBOL_GPL(relay_switch_subbuf); |
| 435 | EXPORT_SYMBOL_GPL(relay_buf_full); |