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   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 /*
  84  * create_buf_file_create() default callback.  Creates file to represent buf.
  85  */
  86 static struct dentry *create_buf_file_default_callback(const char *filename,
  87                                                        struct dentry *parent,
  88                                                        int mode,
  89                                                        struct rchan_buf *buf,
  90                                                        int *is_global)
  91 {
  92         return relayfs_create_file(filename, parent, mode,
  93                                    &relay_file_operations, buf);
  94 }
  95
  96 /*
  97  * remove_buf_file() default callback.  Removes file representing relay buffer.
  98  */
  99 static int remove_buf_file_default_callback(struct dentry *dentry)
 100 {
 101         return relayfs_remove(dentry);
 102 }
 103
 104 /* relay channel default callbacks */
 105 static struct rchan_callbacks default_channel_callbacks = {
 106         .subbuf_start = subbuf_start_default_callback,
 107         .buf_mapped = buf_mapped_default_callback,
 108         .buf_unmapped = buf_unmapped_default_callback,
 109         .create_buf_file = create_buf_file_default_callback,
 110         .remove_buf_file = remove_buf_file_default_callback,
 111 };
 112
 113 /**
 114  *      wakeup_readers - wake up readers waiting on a channel
 115  *      @private: the channel buffer
 116  *
 117  *      This is the work function used to defer reader waking.  The
 118  *      reason waking is deferred is that calling directly from write
 119  *      causes problems if you're writing from say the scheduler.
 120  */
 121 static void wakeup_readers(void *private)
 122 {
 123         struct rchan_buf *buf = private;
 124         wake_up_interruptible(&buf->read_wait);
 125 }
 126
 127 /**
 128  *      __relay_reset - reset a channel buffer
 129  *      @buf: the channel buffer
 130  *      @init: 1 if this is a first-time initialization
 131  *
 132  *      See relay_reset for description of effect.
 133  */
 134 static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
 135 {
 136         size_t i;
 137
 138         if (init) {
 139                 init_waitqueue_head(&buf->read_wait);
 140                 kref_init(&buf->kref);
 141                 INIT_WORK(&buf->wake_readers, NULL, NULL);
 142         } else {
 143                 cancel_delayed_work(&buf->wake_readers);
 144                 flush_scheduled_work();
 145         }
 146
 147         buf->subbufs_produced = 0;
 148         buf->subbufs_consumed = 0;
 149         buf->bytes_consumed = 0;
 150         buf->finalized = 0;
 151         buf->data = buf->start;
 152         buf->offset = 0;
 153
 154         for (i = 0; i < buf->chan->n_subbufs; i++)
 155                 buf->padding[i] = 0;
 156
 157         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 158 }
 159
 160 /**
 161  *      relay_reset - reset the channel
 162  *      @chan: the channel
 163  *
 164  *      This has the effect of erasing all data from all channel buffers
 165  *      and restarting the channel in its initial state.  The buffers
 166  *      are not freed, so any mappings are still in effect.
 167  *
 168  *      NOTE: Care should be taken that the channel isn't actually
 169  *      being used by anything when this call is made.
 170  */
 171 void relay_reset(struct rchan *chan)
 172 {
 173         unsigned int i;
 174         struct rchan_buf *prev = NULL;
 175
 176         if (!chan)
 177                 return;
 178
 179         for (i = 0; i < NR_CPUS; i++) {
 180                 if (!chan->buf[i] || chan->buf[i] == prev)
 181                         break;
 182                 __relay_reset(chan->buf[i], 0);
 183                 prev = chan->buf[i];
 184         }
 185 }
 186
 187 /**
 188  *      relay_open_buf - create a new channel buffer in relayfs
 189  *
 190  *      Internal - used by relay_open().
 191  */
 192 static struct rchan_buf *relay_open_buf(struct rchan *chan,
 193                                         const char *filename,
 194                                         struct dentry *parent,
 195                                         int *is_global)
 196 {
 197         struct rchan_buf *buf;
 198         struct dentry *dentry;
 199
 200         if (*is_global)
 201                 return chan->buf[0];
 202
 203         buf = relay_create_buf(chan);
 204         if (!buf)
 205                 return NULL;
 206
 207         /* Create file in fs */
 208         dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
 209                                            buf, is_global);
 210         if (!dentry) {
 211                 relay_destroy_buf(buf);
 212                 return NULL;
 213         }
 214
 215         buf->dentry = dentry;
 216         __relay_reset(buf, 1);
 217
 218         return buf;
 219 }
 220
 221 /**
 222  *      relay_close_buf - close a channel buffer
 223  *      @buf: channel buffer
 224  *
 225  *      Marks the buffer finalized and restores the default callbacks.
 226  *      The channel buffer and channel buffer data structure are then freed
 227  *      automatically when the last reference is given up.
 228  */
 229 static inline void relay_close_buf(struct rchan_buf *buf)
 230 {
 231         buf->finalized = 1;
 232         buf->chan->cb = &default_channel_callbacks;
 233         cancel_delayed_work(&buf->wake_readers);
 234         flush_scheduled_work();
 235         kref_put(&buf->kref, relay_remove_buf);
 236 }
 237
 238 static inline void setup_callbacks(struct rchan *chan,
 239                                    struct rchan_callbacks *cb)
 240 {
 241         if (!cb) {
 242                 chan->cb = &default_channel_callbacks;
 243                 return;
 244         }
 245
 246         if (!cb->subbuf_start)
 247                 cb->subbuf_start = subbuf_start_default_callback;
 248         if (!cb->buf_mapped)
 249                 cb->buf_mapped = buf_mapped_default_callback;
 250         if (!cb->buf_unmapped)
 251                 cb->buf_unmapped = buf_unmapped_default_callback;
 252         if (!cb->create_buf_file)
 253                 cb->create_buf_file = create_buf_file_default_callback;
 254         if (!cb->remove_buf_file)
 255                 cb->remove_buf_file = remove_buf_file_default_callback;
 256         chan->cb = cb;
 257 }
 258
 259 /**
 260  *      relay_open - create a new relayfs channel
 261  *      @base_filename: base name of files to create
 262  *      @parent: dentry of parent directory, NULL for root directory
 263  *      @subbuf_size: size of sub-buffers
 264  *      @n_subbufs: number of sub-buffers
 265  *      @cb: client callback functions
 266  *
 267  *      Returns channel pointer if successful, NULL otherwise.
 268  *
 269  *      Creates a channel buffer for each cpu using the sizes and
 270  *      attributes specified.  The created channel buffer files
 271  *      will be named base_filename0...base_filenameN-1.  File
 272  *      permissions will be S_IRUSR.
 273  */
 274 struct rchan *relay_open(const char *base_filename,
 275                          struct dentry *parent,
 276                          size_t subbuf_size,
 277                          size_t n_subbufs,
 278                          struct rchan_callbacks *cb)
 279 {
 280         unsigned int i;
 281         struct rchan *chan;
 282         char *tmpname;
 283         int is_global = 0;
 284
 285         if (!base_filename)
 286                 return NULL;
 287
 288         if (!(subbuf_size && n_subbufs))
 289                 return NULL;
 290
 291         chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
 292         if (!chan)
 293                 return NULL;
 294
 295         chan->version = RELAYFS_CHANNEL_VERSION;
 296         chan->n_subbufs = n_subbufs;
 297         chan->subbuf_size = subbuf_size;
 298         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 299         setup_callbacks(chan, cb);
 300         kref_init(&chan->kref);
 301
 302         tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 303         if (!tmpname)
 304                 goto free_chan;
 305
 306         for_each_online_cpu(i) {
 307                 sprintf(tmpname, "%s%d", base_filename, i);
 308                 chan->buf[i] = relay_open_buf(chan, tmpname, parent,
 309                                               &is_global);
 310                 chan->buf[i]->cpu = i;
 311                 if (!chan->buf[i])
 312                         goto free_bufs;
 313         }
 314
 315         kfree(tmpname);
 316         return chan;
 317
 318 free_bufs:
 319         for (i = 0; i < NR_CPUS; i++) {
 320                 if (!chan->buf[i])
 321                         break;
 322                 relay_close_buf(chan->buf[i]);
 323                 if (is_global)
 324                         break;
 325         }
 326         kfree(tmpname);
 327
 328 free_chan:
 329         kref_put(&chan->kref, relay_destroy_channel);
 330         return NULL;
 331 }
 332
 333 /**
 334  *      relay_switch_subbuf - switch to a new sub-buffer
 335  *      @buf: channel buffer
 336  *      @length: size of current event
 337  *
 338  *      Returns either the length passed in or 0 if full.
 339
 340  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 341  *      updating padding counts, waking up readers, etc.
 342  */
 343 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 344 {
 345         void *old, *new;
 346         size_t old_subbuf, new_subbuf;
 347
 348         if (unlikely(length > buf->chan->subbuf_size))
 349                 goto toobig;
 350
 351         if (buf->offset != buf->chan->subbuf_size + 1) {
 352                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 353                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 354                 buf->padding[old_subbuf] = buf->prev_padding;
 355                 buf->subbufs_produced++;
 356                 if (waitqueue_active(&buf->read_wait)) {
 357                         PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
 358                         schedule_delayed_work(&buf->wake_readers, 1);
 359                 }
 360         }
 361
 362         old = buf->data;
 363         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 364         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 365         buf->offset = 0;
 366         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 367                 buf->offset = buf->chan->subbuf_size + 1;
 368                 return 0;
 369         }
 370         buf->data = new;
 371         buf->padding[new_subbuf] = 0;
 372
 373         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 374                 goto toobig;
 375
 376         return length;
 377
 378 toobig:
 379         buf->chan->last_toobig = length;
 380         return 0;
 381 }
 382
 383 /**
 384  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 385  *      @chan: the channel
 386  *      @cpu: the cpu associated with the channel buffer to update
 387  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 388  *
 389  *      Adds to the channel buffer's consumed sub-buffer count.
 390  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 391  *      not the total consumed.
 392  *
 393  *      NOTE: kernel clients don't need to call this function if the channel
 394  *      mode is 'overwrite'.
 395  */
 396 void relay_subbufs_consumed(struct rchan *chan,
 397                             unsigned int cpu,
 398                             size_t subbufs_consumed)
 399 {
 400         struct rchan_buf *buf;
 401
 402         if (!chan)
 403                 return;
 404
 405         if (cpu >= NR_CPUS || !chan->buf[cpu])
 406                 return;
 407
 408         buf = chan->buf[cpu];
 409         buf->subbufs_consumed += subbufs_consumed;
 410         if (buf->subbufs_consumed > buf->subbufs_produced)
 411                 buf->subbufs_consumed = buf->subbufs_produced;
 412 }
 413
 414 /**
 415  *      relay_destroy_channel - free the channel struct
 416  *
 417  *      Should only be called from kref_put().
 418  */
 419 void relay_destroy_channel(struct kref *kref)
 420 {
 421         struct rchan *chan = container_of(kref, struct rchan, kref);
 422         kfree(chan);
 423 }
 424
 425 /**
 426  *      relay_close - close the channel
 427  *      @chan: the channel
 428  *
 429  *      Closes all channel buffers and frees the channel.
 430  */
 431 void relay_close(struct rchan *chan)
 432 {
 433         unsigned int i;
 434         struct rchan_buf *prev = NULL;
 435
 436         if (!chan)
 437                 return;
 438
 439         for (i = 0; i < NR_CPUS; i++) {
 440                 if (!chan->buf[i] || chan->buf[i] == prev)
 441                         break;
 442                 relay_close_buf(chan->buf[i]);
 443                 prev = chan->buf[i];
 444         }
 445
 446         if (chan->last_toobig)
 447                 printk(KERN_WARNING "relayfs: one or more items not logged "
 448                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 449                        chan->last_toobig, chan->subbuf_size);
 450
 451         kref_put(&chan->kref, relay_destroy_channel);
 452 }
 453
 454 /**
 455  *      relay_flush - close the channel
 456  *      @chan: the channel
 457  *
 458  *      Flushes all channel buffers i.e. forces buffer switch.
 459  */
 460 void relay_flush(struct rchan *chan)
 461 {
 462         unsigned int i;
 463         struct rchan_buf *prev = NULL;
 464
 465         if (!chan)
 466                 return;
 467
 468         for (i = 0; i < NR_CPUS; i++) {
 469                 if (!chan->buf[i] || chan->buf[i] == prev)
 470                         break;
 471                 relay_switch_subbuf(chan->buf[i], 0);
 472                 prev = chan->buf[i];
 473         }
 474 }
 475
 476 EXPORT_SYMBOL_GPL(relay_open);
 477 EXPORT_SYMBOL_GPL(relay_close);
 478 EXPORT_SYMBOL_GPL(relay_flush);
 479 EXPORT_SYMBOL_GPL(relay_reset);
 480 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 481 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 482 EXPORT_SYMBOL_GPL(relay_buf_full);