kernel/relay.c

   1 /*
   2  * Public API and common code for kernel->userspace relay file support.
   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  * Moved to kernel/relay.c by Paul Mundt, 2006.
  10  * November 2006 - CPU hotplug support by Mathieu Desnoyers
  11  *      (mathieu.desnoyers@polymtl.ca)
  12  *
  13  * This file is released under the GPL.
  14  */
  15 #include <linux/errno.h>
  16 #include <linux/stddef.h>
  17 #include <linux/slab.h>
  18 #include <linux/module.h>
  19 #include <linux/string.h>
  20 #include <linux/relay.h>
  21 #include <linux/vmalloc.h>
  22 #include <linux/mm.h>
  23 #include <linux/cpu.h>
  24
  25 /* list of open channels, for cpu hotplug */
  26 static DEFINE_MUTEX(relay_channels_mutex);
  27 static LIST_HEAD(relay_channels);
  28
  29 /*
  30  * close() vm_op implementation for relay file mapping.
  31  */
  32 static void relay_file_mmap_close(struct vm_area_struct *vma)
  33 {
  34         struct rchan_buf *buf = vma->vm_private_data;
  35         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  36 }
  37
  38 /*
  39  * nopage() vm_op implementation for relay file mapping.
  40  */
  41 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
  42                                      unsigned long address,
  43                                      int *type)
  44 {
  45         struct page *page;
  46         struct rchan_buf *buf = vma->vm_private_data;
  47         unsigned long offset = address - vma->vm_start;
  48
  49         if (address > vma->vm_end)
  50                 return NOPAGE_SIGBUS; /* Disallow mremap */
  51         if (!buf)
  52                 return NOPAGE_OOM;
  53
  54         page = vmalloc_to_page(buf->start + offset);
  55         if (!page)
  56                 return NOPAGE_OOM;
  57         get_page(page);
  58
  59         if (type)
  60                 *type = VM_FAULT_MINOR;
  61
  62         return page;
  63 }
  64
  65 /*
  66  * vm_ops for relay file mappings.
  67  */
  68 static struct vm_operations_struct relay_file_mmap_ops = {
  69         .nopage = relay_buf_nopage,
  70         .close = relay_file_mmap_close,
  71 };
  72
  73 /**
  74  *      relay_mmap_buf: - mmap channel buffer to process address space
  75  *      @buf: relay channel buffer
  76  *      @vma: vm_area_struct describing memory to be mapped
  77  *
  78  *      Returns 0 if ok, negative on error
  79  *
  80  *      Caller should already have grabbed mmap_sem.
  81  */
  82 int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
  83 {
  84         unsigned long length = vma->vm_end - vma->vm_start;
  85         struct file *filp = vma->vm_file;
  86
  87         if (!buf)
  88                 return -EBADF;
  89
  90         if (length != (unsigned long)buf->chan->alloc_size)
  91                 return -EINVAL;
  92
  93         vma->vm_ops = &relay_file_mmap_ops;
  94         vma->vm_private_data = buf;
  95         buf->chan->cb->buf_mapped(buf, filp);
  96
  97         return 0;
  98 }
  99
 100 /**
 101  *      relay_alloc_buf - allocate a channel buffer
 102  *      @buf: the buffer struct
 103  *      @size: total size of the buffer
 104  *
 105  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 106  *      passed in size will get page aligned, if it isn't already.
 107  */
 108 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 109 {
 110         void *mem;
 111         unsigned int i, j, n_pages;
 112
 113         *size = PAGE_ALIGN(*size);
 114         n_pages = *size >> PAGE_SHIFT;
 115
 116         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
 117         if (!buf->page_array)
 118                 return NULL;
 119
 120         for (i = 0; i < n_pages; i++) {
 121                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 122                 if (unlikely(!buf->page_array[i]))
 123                         goto depopulate;
 124         }
 125         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 126         if (!mem)
 127                 goto depopulate;
 128
 129         memset(mem, 0, *size);
 130         buf->page_count = n_pages;
 131         return mem;
 132
 133 depopulate:
 134         for (j = 0; j < i; j++)
 135                 __free_page(buf->page_array[j]);
 136         kfree(buf->page_array);
 137         return NULL;
 138 }
 139
 140 /**
 141  *      relay_create_buf - allocate and initialize a channel buffer
 142  *      @chan: the relay channel
 143  *
 144  *      Returns channel buffer if successful, %NULL otherwise.
 145  */
 146 struct rchan_buf *relay_create_buf(struct rchan *chan)
 147 {
 148         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 149         if (!buf)
 150                 return NULL;
 151
 152         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 153         if (!buf->padding)
 154                 goto free_buf;
 155
 156         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 157         if (!buf->start)
 158                 goto free_buf;
 159
 160         buf->chan = chan;
 161         kref_get(&buf->chan->kref);
 162         return buf;
 163
 164 free_buf:
 165         kfree(buf->padding);
 166         kfree(buf);
 167         return NULL;
 168 }
 169
 170 /**
 171  *      relay_destroy_channel - free the channel struct
 172  *      @kref: target kernel reference that contains the relay channel
 173  *
 174  *      Should only be called from kref_put().
 175  */
 176 void relay_destroy_channel(struct kref *kref)
 177 {
 178         struct rchan *chan = container_of(kref, struct rchan, kref);
 179         kfree(chan);
 180 }
 181
 182 /**
 183  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 184  *      @buf: the buffer struct
 185  */
 186 void relay_destroy_buf(struct rchan_buf *buf)
 187 {
 188         struct rchan *chan = buf->chan;
 189         unsigned int i;
 190
 191         if (likely(buf->start)) {
 192                 vunmap(buf->start);
 193                 for (i = 0; i < buf->page_count; i++)
 194                         __free_page(buf->page_array[i]);
 195                 kfree(buf->page_array);
 196         }
 197         chan->buf[buf->cpu] = NULL;
 198         kfree(buf->padding);
 199         kfree(buf);
 200         kref_put(&chan->kref, relay_destroy_channel);
 201 }
 202
 203 /**
 204  *      relay_remove_buf - remove a channel buffer
 205  *      @kref: target kernel reference that contains the relay buffer
 206  *
 207  *      Removes the file from the fileystem, which also frees the
 208  *      rchan_buf_struct and the channel buffer.  Should only be called from
 209  *      kref_put().
 210  */
 211 void relay_remove_buf(struct kref *kref)
 212 {
 213         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 214         buf->chan->cb->remove_buf_file(buf->dentry);
 215         relay_destroy_buf(buf);
 216 }
 217
 218 /**
 219  *      relay_buf_empty - boolean, is the channel buffer empty?
 220  *      @buf: channel buffer
 221  *
 222  *      Returns 1 if the buffer is empty, 0 otherwise.
 223  */
 224 int relay_buf_empty(struct rchan_buf *buf)
 225 {
 226         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 227 }
 228 EXPORT_SYMBOL_GPL(relay_buf_empty);
 229
 230 /**
 231  *      relay_buf_full - boolean, is the channel buffer full?
 232  *      @buf: channel buffer
 233  *
 234  *      Returns 1 if the buffer is full, 0 otherwise.
 235  */
 236 int relay_buf_full(struct rchan_buf *buf)
 237 {
 238         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 239         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 240 }
 241 EXPORT_SYMBOL_GPL(relay_buf_full);
 242
 243 /*
 244  * High-level relay kernel API and associated functions.
 245  */
 246
 247 /*
 248  * rchan_callback implementations defining default channel behavior.  Used
 249  * in place of corresponding NULL values in client callback struct.
 250  */
 251
 252 /*
 253  * subbuf_start() default callback.  Does nothing.
 254  */
 255 static int subbuf_start_default_callback (struct rchan_buf *buf,
 256                                           void *subbuf,
 257                                           void *prev_subbuf,
 258                                           size_t prev_padding)
 259 {
 260         if (relay_buf_full(buf))
 261                 return 0;
 262
 263         return 1;
 264 }
 265
 266 /*
 267  * buf_mapped() default callback.  Does nothing.
 268  */
 269 static void buf_mapped_default_callback(struct rchan_buf *buf,
 270                                         struct file *filp)
 271 {
 272 }
 273
 274 /*
 275  * buf_unmapped() default callback.  Does nothing.
 276  */
 277 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 278                                           struct file *filp)
 279 {
 280 }
 281
 282 /*
 283  * create_buf_file_create() default callback.  Does nothing.
 284  */
 285 static struct dentry *create_buf_file_default_callback(const char *filename,
 286                                                        struct dentry *parent,
 287                                                        int mode,
 288                                                        struct rchan_buf *buf,
 289                                                        int *is_global)
 290 {
 291         return NULL;
 292 }
 293
 294 /*
 295  * remove_buf_file() default callback.  Does nothing.
 296  */
 297 static int remove_buf_file_default_callback(struct dentry *dentry)
 298 {
 299         return -EINVAL;
 300 }
 301
 302 /* relay channel default callbacks */
 303 static struct rchan_callbacks default_channel_callbacks = {
 304         .subbuf_start = subbuf_start_default_callback,
 305         .buf_mapped = buf_mapped_default_callback,
 306         .buf_unmapped = buf_unmapped_default_callback,
 307         .create_buf_file = create_buf_file_default_callback,
 308         .remove_buf_file = remove_buf_file_default_callback,
 309 };
 310
 311 /**
 312  *      wakeup_readers - wake up readers waiting on a channel
 313  *      @work: work struct that contains the the channel buffer
 314  *
 315  *      This is the work function used to defer reader waking.  The
 316  *      reason waking is deferred is that calling directly from write
 317  *      causes problems if you're writing from say the scheduler.
 318  */
 319 static void wakeup_readers(struct work_struct *work)
 320 {
 321         struct rchan_buf *buf =
 322                 container_of(work, struct rchan_buf, wake_readers.work);
 323         wake_up_interruptible(&buf->read_wait);
 324 }
 325
 326 /**
 327  *      __relay_reset - reset a channel buffer
 328  *      @buf: the channel buffer
 329  *      @init: 1 if this is a first-time initialization
 330  *
 331  *      See relay_reset() for description of effect.
 332  */
 333 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 334 {
 335         size_t i;
 336
 337         if (init) {
 338                 init_waitqueue_head(&buf->read_wait);
 339                 kref_init(&buf->kref);
 340                 INIT_DELAYED_WORK(&buf->wake_readers, NULL);
 341         } else {
 342                 cancel_delayed_work(&buf->wake_readers);
 343                 flush_scheduled_work();
 344         }
 345
 346         buf->subbufs_produced = 0;
 347         buf->subbufs_consumed = 0;
 348         buf->bytes_consumed = 0;
 349         buf->finalized = 0;
 350         buf->data = buf->start;
 351         buf->offset = 0;
 352
 353         for (i = 0; i < buf->chan->n_subbufs; i++)
 354                 buf->padding[i] = 0;
 355
 356         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 357 }
 358
 359 /**
 360  *      relay_reset - reset the channel
 361  *      @chan: the channel
 362  *
 363  *      This has the effect of erasing all data from all channel buffers
 364  *      and restarting the channel in its initial state.  The buffers
 365  *      are not freed, so any mappings are still in effect.
 366  *
 367  *      NOTE. Care should be taken that the channel isn't actually
 368  *      being used by anything when this call is made.
 369  */
 370 void relay_reset(struct rchan *chan)
 371 {
 372         unsigned int i;
 373
 374         if (!chan)
 375                 return;
 376
 377         if (chan->is_global && chan->buf[0]) {
 378                 __relay_reset(chan->buf[0], 0);
 379                 return;
 380         }
 381
 382         mutex_lock(&relay_channels_mutex);
 383         for_each_online_cpu(i)
 384                 if (chan->buf[i])
 385                         __relay_reset(chan->buf[i], 0);
 386         mutex_unlock(&relay_channels_mutex);
 387 }
 388 EXPORT_SYMBOL_GPL(relay_reset);
 389
 390 /*
 391  *      relay_open_buf - create a new relay channel buffer
 392  *
 393  *      used by relay_open() and CPU hotplug.
 394  */
 395 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 396 {
 397         struct rchan_buf *buf = NULL;
 398         struct dentry *dentry;
 399         char *tmpname;
 400
 401         if (chan->is_global)
 402                 return chan->buf[0];
 403
 404         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 405         if (!tmpname)
 406                 goto end;
 407         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 408
 409         buf = relay_create_buf(chan);
 410         if (!buf)
 411                 goto free_name;
 412
 413         buf->cpu = cpu;
 414         __relay_reset(buf, 1);
 415
 416         /* Create file in fs */
 417         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
 418                                            buf, &chan->is_global);
 419         if (!dentry)
 420                 goto free_buf;
 421
 422         buf->dentry = dentry;
 423
 424         if(chan->is_global) {
 425                 chan->buf[0] = buf;
 426                 buf->cpu = 0;
 427         }
 428
 429         goto free_name;
 430
 431 free_buf:
 432         relay_destroy_buf(buf);
 433 free_name:
 434         kfree(tmpname);
 435 end:
 436         return buf;
 437 }
 438
 439 /**
 440  *      relay_close_buf - close a channel buffer
 441  *      @buf: channel buffer
 442  *
 443  *      Marks the buffer finalized and restores the default callbacks.
 444  *      The channel buffer and channel buffer data structure are then freed
 445  *      automatically when the last reference is given up.
 446  */
 447 static void relay_close_buf(struct rchan_buf *buf)
 448 {
 449         buf->finalized = 1;
 450         cancel_delayed_work(&buf->wake_readers);
 451         flush_scheduled_work();
 452         kref_put(&buf->kref, relay_remove_buf);
 453 }
 454
 455 static void setup_callbacks(struct rchan *chan,
 456                                    struct rchan_callbacks *cb)
 457 {
 458         if (!cb) {
 459                 chan->cb = &default_channel_callbacks;
 460                 return;
 461         }
 462
 463         if (!cb->subbuf_start)
 464                 cb->subbuf_start = subbuf_start_default_callback;
 465         if (!cb->buf_mapped)
 466                 cb->buf_mapped = buf_mapped_default_callback;
 467         if (!cb->buf_unmapped)
 468                 cb->buf_unmapped = buf_unmapped_default_callback;
 469         if (!cb->create_buf_file)
 470                 cb->create_buf_file = create_buf_file_default_callback;
 471         if (!cb->remove_buf_file)
 472                 cb->remove_buf_file = remove_buf_file_default_callback;
 473         chan->cb = cb;
 474 }
 475
 476 /**
 477  *      relay_hotcpu_callback - CPU hotplug callback
 478  *      @nb: notifier block
 479  *      @action: hotplug action to take
 480  *      @hcpu: CPU number
 481  *
 482  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 483  */
 484 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 485                                 unsigned long action,
 486                                 void *hcpu)
 487 {
 488         unsigned int hotcpu = (unsigned long)hcpu;
 489         struct rchan *chan;
 490
 491         switch(action) {
 492         case CPU_UP_PREPARE:
 493                 mutex_lock(&relay_channels_mutex);
 494                 list_for_each_entry(chan, &relay_channels, list) {
 495                         if (chan->buf[hotcpu])
 496                                 continue;
 497                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 498                         if(!chan->buf[hotcpu]) {
 499                                 printk(KERN_ERR
 500                                         "relay_hotcpu_callback: cpu %d buffer "
 501                                         "creation failed\n", hotcpu);
 502                                 mutex_unlock(&relay_channels_mutex);
 503                                 return NOTIFY_BAD;
 504                         }
 505                 }
 506                 mutex_unlock(&relay_channels_mutex);
 507                 break;
 508         case CPU_DEAD:
 509                 /* No need to flush the cpu : will be flushed upon
 510                  * final relay_flush() call. */
 511                 break;
 512         }
 513         return NOTIFY_OK;
 514 }
 515
 516 /**
 517  *      relay_open - create a new relay channel
 518  *      @base_filename: base name of files to create
 519  *      @parent: dentry of parent directory, %NULL for root directory
 520  *      @subbuf_size: size of sub-buffers
 521  *      @n_subbufs: number of sub-buffers
 522  *      @cb: client callback functions
 523  *      @private_data: user-defined data
 524  *
 525  *      Returns channel pointer if successful, %NULL otherwise.
 526  *
 527  *      Creates a channel buffer for each cpu using the sizes and
 528  *      attributes specified.  The created channel buffer files
 529  *      will be named base_filename0...base_filenameN-1.  File
 530  *      permissions will be %S_IRUSR.
 531  */
 532 struct rchan *relay_open(const char *base_filename,
 533                          struct dentry *parent,
 534                          size_t subbuf_size,
 535                          size_t n_subbufs,
 536                          struct rchan_callbacks *cb,
 537                          void *private_data)
 538 {
 539         unsigned int i;
 540         struct rchan *chan;
 541         if (!base_filename)
 542                 return NULL;
 543
 544         if (!(subbuf_size && n_subbufs))
 545                 return NULL;
 546
 547         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 548         if (!chan)
 549                 return NULL;
 550
 551         chan->version = RELAYFS_CHANNEL_VERSION;
 552         chan->n_subbufs = n_subbufs;
 553         chan->subbuf_size = subbuf_size;
 554         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 555         chan->parent = parent;
 556         chan->private_data = private_data;
 557         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 558         setup_callbacks(chan, cb);
 559         kref_init(&chan->kref);
 560
 561         mutex_lock(&relay_channels_mutex);
 562         for_each_online_cpu(i) {
 563                 chan->buf[i] = relay_open_buf(chan, i);
 564                 if (!chan->buf[i])
 565                         goto free_bufs;
 566         }
 567         list_add(&chan->list, &relay_channels);
 568         mutex_unlock(&relay_channels_mutex);
 569
 570         return chan;
 571
 572 free_bufs:
 573         for_each_online_cpu(i) {
 574                 if (!chan->buf[i])
 575                         break;
 576                 relay_close_buf(chan->buf[i]);
 577         }
 578
 579         kref_put(&chan->kref, relay_destroy_channel);
 580         mutex_unlock(&relay_channels_mutex);
 581         return NULL;
 582 }
 583 EXPORT_SYMBOL_GPL(relay_open);
 584
 585 /**
 586  *      relay_switch_subbuf - switch to a new sub-buffer
 587  *      @buf: channel buffer
 588  *      @length: size of current event
 589  *
 590  *      Returns either the length passed in or 0 if full.
 591  *
 592  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 593  *      updating padding counts, waking up readers, etc.
 594  */
 595 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 596 {
 597         void *old, *new;
 598         size_t old_subbuf, new_subbuf;
 599
 600         if (unlikely(length > buf->chan->subbuf_size))
 601                 goto toobig;
 602
 603         if (buf->offset != buf->chan->subbuf_size + 1) {
 604                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 605                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 606                 buf->padding[old_subbuf] = buf->prev_padding;
 607                 buf->subbufs_produced++;
 608                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
 609                         buf->padding[old_subbuf];
 610                 smp_mb();
 611                 if (waitqueue_active(&buf->read_wait)) {
 612                         PREPARE_DELAYED_WORK(&buf->wake_readers,
 613                                              wakeup_readers);
 614                         schedule_delayed_work(&buf->wake_readers, 1);
 615                 }
 616         }
 617
 618         old = buf->data;
 619         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 620         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 621         buf->offset = 0;
 622         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 623                 buf->offset = buf->chan->subbuf_size + 1;
 624                 return 0;
 625         }
 626         buf->data = new;
 627         buf->padding[new_subbuf] = 0;
 628
 629         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 630                 goto toobig;
 631
 632         return length;
 633
 634 toobig:
 635         buf->chan->last_toobig = length;
 636         return 0;
 637 }
 638 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 639
 640 /**
 641  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 642  *      @chan: the channel
 643  *      @cpu: the cpu associated with the channel buffer to update
 644  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 645  *
 646  *      Adds to the channel buffer's consumed sub-buffer count.
 647  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 648  *      not the total consumed.
 649  *
 650  *      NOTE. Kernel clients don't need to call this function if the channel
 651  *      mode is 'overwrite'.
 652  */
 653 void relay_subbufs_consumed(struct rchan *chan,
 654                             unsigned int cpu,
 655                             size_t subbufs_consumed)
 656 {
 657         struct rchan_buf *buf;
 658
 659         if (!chan)
 660                 return;
 661
 662         if (cpu >= NR_CPUS || !chan->buf[cpu])
 663                 return;
 664
 665         buf = chan->buf[cpu];
 666         buf->subbufs_consumed += subbufs_consumed;
 667         if (buf->subbufs_consumed > buf->subbufs_produced)
 668                 buf->subbufs_consumed = buf->subbufs_produced;
 669 }
 670 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 671
 672 /**
 673  *      relay_close - close the channel
 674  *      @chan: the channel
 675  *
 676  *      Closes all channel buffers and frees the channel.
 677  */
 678 void relay_close(struct rchan *chan)
 679 {
 680         unsigned int i;
 681
 682         if (!chan)
 683                 return;
 684
 685         mutex_lock(&relay_channels_mutex);
 686         if (chan->is_global && chan->buf[0])
 687                 relay_close_buf(chan->buf[0]);
 688         else
 689                 for_each_possible_cpu(i)
 690                         if (chan->buf[i])
 691                                 relay_close_buf(chan->buf[i]);
 692
 693         if (chan->last_toobig)
 694                 printk(KERN_WARNING "relay: one or more items not logged "
 695                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 696                        chan->last_toobig, chan->subbuf_size);
 697
 698         list_del(&chan->list);
 699         kref_put(&chan->kref, relay_destroy_channel);
 700         mutex_unlock(&relay_channels_mutex);
 701 }
 702 EXPORT_SYMBOL_GPL(relay_close);
 703
 704 /**
 705  *      relay_flush - close the channel
 706  *      @chan: the channel
 707  *
 708  *      Flushes all channel buffers, i.e. forces buffer switch.
 709  */
 710 void relay_flush(struct rchan *chan)
 711 {
 712         unsigned int i;
 713
 714         if (!chan)
 715                 return;
 716
 717         if (chan->is_global && chan->buf[0]) {
 718                 relay_switch_subbuf(chan->buf[0], 0);
 719                 return;
 720         }
 721
 722         mutex_lock(&relay_channels_mutex);
 723         for_each_possible_cpu(i)
 724                 if (chan->buf[i])
 725                         relay_switch_subbuf(chan->buf[i], 0);
 726         mutex_unlock(&relay_channels_mutex);
 727 }
 728 EXPORT_SYMBOL_GPL(relay_flush);
 729
 730 /**
 731  *      relay_file_open - open file op for relay files
 732  *      @inode: the inode
 733  *      @filp: the file
 734  *
 735  *      Increments the channel buffer refcount.
 736  */
 737 static int relay_file_open(struct inode *inode, struct file *filp)
 738 {
 739         struct rchan_buf *buf = inode->i_private;
 740         kref_get(&buf->kref);
 741         filp->private_data = buf;
 742
 743         return 0;
 744 }
 745
 746 /**
 747  *      relay_file_mmap - mmap file op for relay files
 748  *      @filp: the file
 749  *      @vma: the vma describing what to map
 750  *
 751  *      Calls upon relay_mmap_buf() to map the file into user space.
 752  */
 753 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 754 {
 755         struct rchan_buf *buf = filp->private_data;
 756         return relay_mmap_buf(buf, vma);
 757 }
 758
 759 /**
 760  *      relay_file_poll - poll file op for relay files
 761  *      @filp: the file
 762  *      @wait: poll table
 763  *
 764  *      Poll implemention.
 765  */
 766 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 767 {
 768         unsigned int mask = 0;
 769         struct rchan_buf *buf = filp->private_data;
 770
 771         if (buf->finalized)
 772                 return POLLERR;
 773
 774         if (filp->f_mode & FMODE_READ) {
 775                 poll_wait(filp, &buf->read_wait, wait);
 776                 if (!relay_buf_empty(buf))
 777                         mask |= POLLIN | POLLRDNORM;
 778         }
 779
 780         return mask;
 781 }
 782
 783 /**
 784  *      relay_file_release - release file op for relay files
 785  *      @inode: the inode
 786  *      @filp: the file
 787  *
 788  *      Decrements the channel refcount, as the filesystem is
 789  *      no longer using it.
 790  */
 791 static int relay_file_release(struct inode *inode, struct file *filp)
 792 {
 793         struct rchan_buf *buf = filp->private_data;
 794         kref_put(&buf->kref, relay_remove_buf);
 795
 796         return 0;
 797 }
 798
 799 /*
 800  *      relay_file_read_consume - update the consumed count for the buffer
 801  */
 802 static void relay_file_read_consume(struct rchan_buf *buf,
 803                                     size_t read_pos,
 804                                     size_t bytes_consumed)
 805 {
 806         size_t subbuf_size = buf->chan->subbuf_size;
 807         size_t n_subbufs = buf->chan->n_subbufs;
 808         size_t read_subbuf;
 809
 810         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 811                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 812                 buf->bytes_consumed = 0;
 813         }
 814
 815         buf->bytes_consumed += bytes_consumed;
 816         read_subbuf = read_pos / buf->chan->subbuf_size;
 817         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 818                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 819                     (buf->offset == subbuf_size))
 820                         return;
 821                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 822                 buf->bytes_consumed = 0;
 823         }
 824 }
 825
 826 /*
 827  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 828  */
 829 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 830 {
 831         size_t subbuf_size = buf->chan->subbuf_size;
 832         size_t n_subbufs = buf->chan->n_subbufs;
 833         size_t produced = buf->subbufs_produced;
 834         size_t consumed = buf->subbufs_consumed;
 835
 836         relay_file_read_consume(buf, read_pos, 0);
 837
 838         if (unlikely(buf->offset > subbuf_size)) {
 839                 if (produced == consumed)
 840                         return 0;
 841                 return 1;
 842         }
 843
 844         if (unlikely(produced - consumed >= n_subbufs)) {
 845                 consumed = (produced / n_subbufs) * n_subbufs;
 846                 buf->subbufs_consumed = consumed;
 847         }
 848
 849         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 850         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 851
 852         if (consumed > produced)
 853                 produced += n_subbufs * subbuf_size;
 854
 855         if (consumed == produced)
 856                 return 0;
 857
 858         return 1;
 859 }
 860
 861 /**
 862  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
 863  *      @read_pos: file read position
 864  *      @buf: relay channel buffer
 865  */
 866 static size_t relay_file_read_subbuf_avail(size_t read_pos,
 867                                            struct rchan_buf *buf)
 868 {
 869         size_t padding, avail = 0;
 870         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 871         size_t subbuf_size = buf->chan->subbuf_size;
 872
 873         write_subbuf = (buf->data - buf->start) / subbuf_size;
 874         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 875         read_subbuf = read_pos / subbuf_size;
 876         read_offset = read_pos % subbuf_size;
 877         padding = buf->padding[read_subbuf];
 878
 879         if (read_subbuf == write_subbuf) {
 880                 if (read_offset + padding < write_offset)
 881                         avail = write_offset - (read_offset + padding);
 882         } else
 883                 avail = (subbuf_size - padding) - read_offset;
 884
 885         return avail;
 886 }
 887
 888 /**
 889  *      relay_file_read_start_pos - find the first available byte to read
 890  *      @read_pos: file read position
 891  *      @buf: relay channel buffer
 892  *
 893  *      If the @read_pos is in the middle of padding, return the
 894  *      position of the first actually available byte, otherwise
 895  *      return the original value.
 896  */
 897 static size_t relay_file_read_start_pos(size_t read_pos,
 898                                         struct rchan_buf *buf)
 899 {
 900         size_t read_subbuf, padding, padding_start, padding_end;
 901         size_t subbuf_size = buf->chan->subbuf_size;
 902         size_t n_subbufs = buf->chan->n_subbufs;
 903
 904         read_subbuf = read_pos / subbuf_size;
 905         padding = buf->padding[read_subbuf];
 906         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 907         padding_end = (read_subbuf + 1) * subbuf_size;
 908         if (read_pos >= padding_start && read_pos < padding_end) {
 909                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 910                 read_pos = read_subbuf * subbuf_size;
 911         }
 912
 913         return read_pos;
 914 }
 915
 916 /**
 917  *      relay_file_read_end_pos - return the new read position
 918  *      @read_pos: file read position
 919  *      @buf: relay channel buffer
 920  *      @count: number of bytes to be read
 921  */
 922 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
 923                                       size_t read_pos,
 924                                       size_t count)
 925 {
 926         size_t read_subbuf, padding, end_pos;
 927         size_t subbuf_size = buf->chan->subbuf_size;
 928         size_t n_subbufs = buf->chan->n_subbufs;
 929
 930         read_subbuf = read_pos / subbuf_size;
 931         padding = buf->padding[read_subbuf];
 932         if (read_pos % subbuf_size + count + padding == subbuf_size)
 933                 end_pos = (read_subbuf + 1) * subbuf_size;
 934         else
 935                 end_pos = read_pos + count;
 936         if (end_pos >= subbuf_size * n_subbufs)
 937                 end_pos = 0;
 938
 939         return end_pos;
 940 }
 941
 942 /*
 943  *      subbuf_read_actor - read up to one subbuf's worth of data
 944  */
 945 static int subbuf_read_actor(size_t read_start,
 946                              struct rchan_buf *buf,
 947                              size_t avail,
 948                              read_descriptor_t *desc,
 949                              read_actor_t actor)
 950 {
 951         void *from;
 952         int ret = 0;
 953
 954         from = buf->start + read_start;
 955         ret = avail;
 956         if (copy_to_user(desc->arg.buf, from, avail)) {
 957                 desc->error = -EFAULT;
 958                 ret = 0;
 959         }
 960         desc->arg.data += ret;
 961         desc->written += ret;
 962         desc->count -= ret;
 963
 964         return ret;
 965 }
 966
 967 /*
 968  *      subbuf_send_actor - send up to one subbuf's worth of data
 969  */
 970 static int subbuf_send_actor(size_t read_start,
 971                              struct rchan_buf *buf,
 972                              size_t avail,
 973                              read_descriptor_t *desc,
 974                              read_actor_t actor)
 975 {
 976         unsigned long pidx, poff;
 977         unsigned int subbuf_pages;
 978         int ret = 0;
 979
 980         subbuf_pages = buf->chan->alloc_size >> PAGE_SHIFT;
 981         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
 982         poff = read_start & ~PAGE_MASK;
 983         while (avail) {
 984                 struct page *p = buf->page_array[pidx];
 985                 unsigned int len;
 986
 987                 len = PAGE_SIZE - poff;
 988                 if (len > avail)
 989                         len = avail;
 990
 991                 len = actor(desc, p, poff, len);
 992                 if (desc->error)
 993                         break;
 994
 995                 avail -= len;
 996                 ret += len;
 997                 poff = 0;
 998                 pidx = (pidx + 1) % subbuf_pages;
 999         }
1000
1001         return ret;
1002 }
1003
1004 typedef int (*subbuf_actor_t) (size_t read_start,
1005                                struct rchan_buf *buf,
1006                                size_t avail,
1007                                read_descriptor_t *desc,
1008                                read_actor_t actor);
1009
1010 /*
1011  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1012  */
1013 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1014                                         subbuf_actor_t subbuf_actor,
1015                                         read_actor_t actor,
1016                                         read_descriptor_t *desc)
1017 {
1018         struct rchan_buf *buf = filp->private_data;
1019         size_t read_start, avail;
1020         int ret;
1021
1022         if (!desc->count)
1023                 return 0;
1024
1025         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1026         do {
1027                 if (!relay_file_read_avail(buf, *ppos))
1028                         break;
1029
1030                 read_start = relay_file_read_start_pos(*ppos, buf);
1031                 avail = relay_file_read_subbuf_avail(read_start, buf);
1032                 if (!avail)
1033                         break;
1034
1035                 avail = min(desc->count, avail);
1036                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1037                 if (desc->error < 0)
1038                         break;
1039
1040                 if (ret) {
1041                         relay_file_read_consume(buf, read_start, ret);
1042                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1043                 }
1044         } while (desc->count && ret);
1045         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1046
1047         return desc->written;
1048 }
1049
1050 static ssize_t relay_file_read(struct file *filp,
1051                                char __user *buffer,
1052                                size_t count,
1053                                loff_t *ppos)
1054 {
1055         read_descriptor_t desc;
1056         desc.written = 0;
1057         desc.count = count;
1058         desc.arg.buf = buffer;
1059         desc.error = 0;
1060         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1061                                        NULL, &desc);
1062 }
1063
1064 static ssize_t relay_file_sendfile(struct file *filp,
1065                                    loff_t *ppos,
1066                                    size_t count,
1067                                    read_actor_t actor,
1068                                    void *target)
1069 {
1070         read_descriptor_t desc;
1071         desc.written = 0;
1072         desc.count = count;
1073         desc.arg.data = target;
1074         desc.error = 0;
1075         return relay_file_read_subbufs(filp, ppos, subbuf_send_actor,
1076                                        actor, &desc);
1077 }
1078
1079 const struct file_operations relay_file_operations = {
1080         .open           = relay_file_open,
1081         .poll           = relay_file_poll,
1082         .mmap           = relay_file_mmap,
1083         .read           = relay_file_read,
1084         .llseek         = no_llseek,
1085         .release        = relay_file_release,
1086         .sendfile       = relay_file_sendfile,
1087 };
1088 EXPORT_SYMBOL_GPL(relay_file_operations);
1089
1090 static __init int relay_init(void)
1091 {
1092
1093         hotcpu_notifier(relay_hotcpu_callback, 0);
1094         return 0;
1095 }
1096
1097 module_init(relay_init);