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  *      @data: contains the channel buffer
 314  *
 315  *      This is the timer function used to defer reader waking.
 316  */
 317 static void wakeup_readers(unsigned long data)
 318 {
 319         struct rchan_buf *buf = (struct rchan_buf *)data;
 320         wake_up_interruptible(&buf->read_wait);
 321 }
 322
 323 /**
 324  *      __relay_reset - reset a channel buffer
 325  *      @buf: the channel buffer
 326  *      @init: 1 if this is a first-time initialization
 327  *
 328  *      See relay_reset() for description of effect.
 329  */
 330 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 331 {
 332         size_t i;
 333
 334         if (init) {
 335                 init_waitqueue_head(&buf->read_wait);
 336                 kref_init(&buf->kref);
 337                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 338         } else
 339                 del_timer_sync(&buf->timer);
 340
 341         buf->subbufs_produced = 0;
 342         buf->subbufs_consumed = 0;
 343         buf->bytes_consumed = 0;
 344         buf->finalized = 0;
 345         buf->data = buf->start;
 346         buf->offset = 0;
 347
 348         for (i = 0; i < buf->chan->n_subbufs; i++)
 349                 buf->padding[i] = 0;
 350
 351         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 352 }
 353
 354 /**
 355  *      relay_reset - reset the channel
 356  *      @chan: the channel
 357  *
 358  *      This has the effect of erasing all data from all channel buffers
 359  *      and restarting the channel in its initial state.  The buffers
 360  *      are not freed, so any mappings are still in effect.
 361  *
 362  *      NOTE. Care should be taken that the channel isn't actually
 363  *      being used by anything when this call is made.
 364  */
 365 void relay_reset(struct rchan *chan)
 366 {
 367         unsigned int i;
 368
 369         if (!chan)
 370                 return;
 371
 372         if (chan->is_global && chan->buf[0]) {
 373                 __relay_reset(chan->buf[0], 0);
 374                 return;
 375         }
 376
 377         mutex_lock(&relay_channels_mutex);
 378         for_each_online_cpu(i)
 379                 if (chan->buf[i])
 380                         __relay_reset(chan->buf[i], 0);
 381         mutex_unlock(&relay_channels_mutex);
 382 }
 383 EXPORT_SYMBOL_GPL(relay_reset);
 384
 385 /*
 386  *      relay_open_buf - create a new relay channel buffer
 387  *
 388  *      used by relay_open() and CPU hotplug.
 389  */
 390 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 391 {
 392         struct rchan_buf *buf = NULL;
 393         struct dentry *dentry;
 394         char *tmpname;
 395
 396         if (chan->is_global)
 397                 return chan->buf[0];
 398
 399         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 400         if (!tmpname)
 401                 goto end;
 402         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 403
 404         buf = relay_create_buf(chan);
 405         if (!buf)
 406                 goto free_name;
 407
 408         buf->cpu = cpu;
 409         __relay_reset(buf, 1);
 410
 411         /* Create file in fs */
 412         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
 413                                            buf, &chan->is_global);
 414         if (!dentry)
 415                 goto free_buf;
 416
 417         buf->dentry = dentry;
 418
 419         if(chan->is_global) {
 420                 chan->buf[0] = buf;
 421                 buf->cpu = 0;
 422         }
 423
 424         goto free_name;
 425
 426 free_buf:
 427         relay_destroy_buf(buf);
 428 free_name:
 429         kfree(tmpname);
 430 end:
 431         return buf;
 432 }
 433
 434 /**
 435  *      relay_close_buf - close a channel buffer
 436  *      @buf: channel buffer
 437  *
 438  *      Marks the buffer finalized and restores the default callbacks.
 439  *      The channel buffer and channel buffer data structure are then freed
 440  *      automatically when the last reference is given up.
 441  */
 442 static void relay_close_buf(struct rchan_buf *buf)
 443 {
 444         buf->finalized = 1;
 445         del_timer_sync(&buf->timer);
 446         kref_put(&buf->kref, relay_remove_buf);
 447 }
 448
 449 static void setup_callbacks(struct rchan *chan,
 450                                    struct rchan_callbacks *cb)
 451 {
 452         if (!cb) {
 453                 chan->cb = &default_channel_callbacks;
 454                 return;
 455         }
 456
 457         if (!cb->subbuf_start)
 458                 cb->subbuf_start = subbuf_start_default_callback;
 459         if (!cb->buf_mapped)
 460                 cb->buf_mapped = buf_mapped_default_callback;
 461         if (!cb->buf_unmapped)
 462                 cb->buf_unmapped = buf_unmapped_default_callback;
 463         if (!cb->create_buf_file)
 464                 cb->create_buf_file = create_buf_file_default_callback;
 465         if (!cb->remove_buf_file)
 466                 cb->remove_buf_file = remove_buf_file_default_callback;
 467         chan->cb = cb;
 468 }
 469
 470 /**
 471  *      relay_hotcpu_callback - CPU hotplug callback
 472  *      @nb: notifier block
 473  *      @action: hotplug action to take
 474  *      @hcpu: CPU number
 475  *
 476  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 477  */
 478 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 479                                 unsigned long action,
 480                                 void *hcpu)
 481 {
 482         unsigned int hotcpu = (unsigned long)hcpu;
 483         struct rchan *chan;
 484
 485         switch(action) {
 486         case CPU_UP_PREPARE:
 487         case CPU_UP_PREPARE_FROZEN:
 488                 mutex_lock(&relay_channels_mutex);
 489                 list_for_each_entry(chan, &relay_channels, list) {
 490                         if (chan->buf[hotcpu])
 491                                 continue;
 492                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 493                         if(!chan->buf[hotcpu]) {
 494                                 printk(KERN_ERR
 495                                         "relay_hotcpu_callback: cpu %d buffer "
 496                                         "creation failed\n", hotcpu);
 497                                 mutex_unlock(&relay_channels_mutex);
 498                                 return NOTIFY_BAD;
 499                         }
 500                 }
 501                 mutex_unlock(&relay_channels_mutex);
 502                 break;
 503         case CPU_DEAD:
 504         case CPU_DEAD_FROZEN:
 505                 /* No need to flush the cpu : will be flushed upon
 506                  * final relay_flush() call. */
 507                 break;
 508         }
 509         return NOTIFY_OK;
 510 }
 511
 512 /**
 513  *      relay_open - create a new relay channel
 514  *      @base_filename: base name of files to create
 515  *      @parent: dentry of parent directory, %NULL for root directory
 516  *      @subbuf_size: size of sub-buffers
 517  *      @n_subbufs: number of sub-buffers
 518  *      @cb: client callback functions
 519  *      @private_data: user-defined data
 520  *
 521  *      Returns channel pointer if successful, %NULL otherwise.
 522  *
 523  *      Creates a channel buffer for each cpu using the sizes and
 524  *      attributes specified.  The created channel buffer files
 525  *      will be named base_filename0...base_filenameN-1.  File
 526  *      permissions will be %S_IRUSR.
 527  */
 528 struct rchan *relay_open(const char *base_filename,
 529                          struct dentry *parent,
 530                          size_t subbuf_size,
 531                          size_t n_subbufs,
 532                          struct rchan_callbacks *cb,
 533                          void *private_data)
 534 {
 535         unsigned int i;
 536         struct rchan *chan;
 537         if (!base_filename)
 538                 return NULL;
 539
 540         if (!(subbuf_size && n_subbufs))
 541                 return NULL;
 542
 543         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 544         if (!chan)
 545                 return NULL;
 546
 547         chan->version = RELAYFS_CHANNEL_VERSION;
 548         chan->n_subbufs = n_subbufs;
 549         chan->subbuf_size = subbuf_size;
 550         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 551         chan->parent = parent;
 552         chan->private_data = private_data;
 553         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 554         setup_callbacks(chan, cb);
 555         kref_init(&chan->kref);
 556
 557         mutex_lock(&relay_channels_mutex);
 558         for_each_online_cpu(i) {
 559                 chan->buf[i] = relay_open_buf(chan, i);
 560                 if (!chan->buf[i])
 561                         goto free_bufs;
 562         }
 563         list_add(&chan->list, &relay_channels);
 564         mutex_unlock(&relay_channels_mutex);
 565
 566         return chan;
 567
 568 free_bufs:
 569         for_each_online_cpu(i) {
 570                 if (!chan->buf[i])
 571                         break;
 572                 relay_close_buf(chan->buf[i]);
 573         }
 574
 575         kref_put(&chan->kref, relay_destroy_channel);
 576         mutex_unlock(&relay_channels_mutex);
 577         return NULL;
 578 }
 579 EXPORT_SYMBOL_GPL(relay_open);
 580
 581 /**
 582  *      relay_switch_subbuf - switch to a new sub-buffer
 583  *      @buf: channel buffer
 584  *      @length: size of current event
 585  *
 586  *      Returns either the length passed in or 0 if full.
 587  *
 588  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 589  *      updating padding counts, waking up readers, etc.
 590  */
 591 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 592 {
 593         void *old, *new;
 594         size_t old_subbuf, new_subbuf;
 595
 596         if (unlikely(length > buf->chan->subbuf_size))
 597                 goto toobig;
 598
 599         if (buf->offset != buf->chan->subbuf_size + 1) {
 600                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 601                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 602                 buf->padding[old_subbuf] = buf->prev_padding;
 603                 buf->subbufs_produced++;
 604                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
 605                         buf->padding[old_subbuf];
 606                 smp_mb();
 607                 if (waitqueue_active(&buf->read_wait))
 608                         /*
 609                          * Calling wake_up_interruptible() from here
 610                          * will deadlock if we happen to be logging
 611                          * from the scheduler (trying to re-grab
 612                          * rq->lock), so defer it.
 613                          */
 614                         __mod_timer(&buf->timer, jiffies + 1);
 615         }
 616
 617         old = buf->data;
 618         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 619         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 620         buf->offset = 0;
 621         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 622                 buf->offset = buf->chan->subbuf_size + 1;
 623                 return 0;
 624         }
 625         buf->data = new;
 626         buf->padding[new_subbuf] = 0;
 627
 628         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 629                 goto toobig;
 630
 631         return length;
 632
 633 toobig:
 634         buf->chan->last_toobig = length;
 635         return 0;
 636 }
 637 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 638
 639 /**
 640  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 641  *      @chan: the channel
 642  *      @cpu: the cpu associated with the channel buffer to update
 643  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 644  *
 645  *      Adds to the channel buffer's consumed sub-buffer count.
 646  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 647  *      not the total consumed.
 648  *
 649  *      NOTE. Kernel clients don't need to call this function if the channel
 650  *      mode is 'overwrite'.
 651  */
 652 void relay_subbufs_consumed(struct rchan *chan,
 653                             unsigned int cpu,
 654                             size_t subbufs_consumed)
 655 {
 656         struct rchan_buf *buf;
 657
 658         if (!chan)
 659                 return;
 660
 661         if (cpu >= NR_CPUS || !chan->buf[cpu])
 662                 return;
 663
 664         buf = chan->buf[cpu];
 665         buf->subbufs_consumed += subbufs_consumed;
 666         if (buf->subbufs_consumed > buf->subbufs_produced)
 667                 buf->subbufs_consumed = buf->subbufs_produced;
 668 }
 669 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 670
 671 /**
 672  *      relay_close - close the channel
 673  *      @chan: the channel
 674  *
 675  *      Closes all channel buffers and frees the channel.
 676  */
 677 void relay_close(struct rchan *chan)
 678 {
 679         unsigned int i;
 680
 681         if (!chan)
 682                 return;
 683
 684         mutex_lock(&relay_channels_mutex);
 685         if (chan->is_global && chan->buf[0])
 686                 relay_close_buf(chan->buf[0]);
 687         else
 688                 for_each_possible_cpu(i)
 689                         if (chan->buf[i])
 690                                 relay_close_buf(chan->buf[i]);
 691
 692         if (chan->last_toobig)
 693                 printk(KERN_WARNING "relay: one or more items not logged "
 694                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 695                        chan->last_toobig, chan->subbuf_size);
 696
 697         list_del(&chan->list);
 698         kref_put(&chan->kref, relay_destroy_channel);
 699         mutex_unlock(&relay_channels_mutex);
 700 }
 701 EXPORT_SYMBOL_GPL(relay_close);
 702
 703 /**
 704  *      relay_flush - close the channel
 705  *      @chan: the channel
 706  *
 707  *      Flushes all channel buffers, i.e. forces buffer switch.
 708  */
 709 void relay_flush(struct rchan *chan)
 710 {
 711         unsigned int i;
 712
 713         if (!chan)
 714                 return;
 715
 716         if (chan->is_global && chan->buf[0]) {
 717                 relay_switch_subbuf(chan->buf[0], 0);
 718                 return;
 719         }
 720
 721         mutex_lock(&relay_channels_mutex);
 722         for_each_possible_cpu(i)
 723                 if (chan->buf[i])
 724                         relay_switch_subbuf(chan->buf[i], 0);
 725         mutex_unlock(&relay_channels_mutex);
 726 }
 727 EXPORT_SYMBOL_GPL(relay_flush);
 728
 729 /**
 730  *      relay_file_open - open file op for relay files
 731  *      @inode: the inode
 732  *      @filp: the file
 733  *
 734  *      Increments the channel buffer refcount.
 735  */
 736 static int relay_file_open(struct inode *inode, struct file *filp)
 737 {
 738         struct rchan_buf *buf = inode->i_private;
 739         kref_get(&buf->kref);
 740         filp->private_data = buf;
 741
 742         return 0;
 743 }
 744
 745 /**
 746  *      relay_file_mmap - mmap file op for relay files
 747  *      @filp: the file
 748  *      @vma: the vma describing what to map
 749  *
 750  *      Calls upon relay_mmap_buf() to map the file into user space.
 751  */
 752 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 753 {
 754         struct rchan_buf *buf = filp->private_data;
 755         return relay_mmap_buf(buf, vma);
 756 }
 757
 758 /**
 759  *      relay_file_poll - poll file op for relay files
 760  *      @filp: the file
 761  *      @wait: poll table
 762  *
 763  *      Poll implemention.
 764  */
 765 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 766 {
 767         unsigned int mask = 0;
 768         struct rchan_buf *buf = filp->private_data;
 769
 770         if (buf->finalized)
 771                 return POLLERR;
 772
 773         if (filp->f_mode & FMODE_READ) {
 774                 poll_wait(filp, &buf->read_wait, wait);
 775                 if (!relay_buf_empty(buf))
 776                         mask |= POLLIN | POLLRDNORM;
 777         }
 778
 779         return mask;
 780 }
 781
 782 /**
 783  *      relay_file_release - release file op for relay files
 784  *      @inode: the inode
 785  *      @filp: the file
 786  *
 787  *      Decrements the channel refcount, as the filesystem is
 788  *      no longer using it.
 789  */
 790 static int relay_file_release(struct inode *inode, struct file *filp)
 791 {
 792         struct rchan_buf *buf = filp->private_data;
 793         kref_put(&buf->kref, relay_remove_buf);
 794
 795         return 0;
 796 }
 797
 798 /*
 799  *      relay_file_read_consume - update the consumed count for the buffer
 800  */
 801 static void relay_file_read_consume(struct rchan_buf *buf,
 802                                     size_t read_pos,
 803                                     size_t bytes_consumed)
 804 {
 805         size_t subbuf_size = buf->chan->subbuf_size;
 806         size_t n_subbufs = buf->chan->n_subbufs;
 807         size_t read_subbuf;
 808
 809         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 810                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 811                 buf->bytes_consumed = 0;
 812         }
 813
 814         buf->bytes_consumed += bytes_consumed;
 815         if (!read_pos)
 816                 read_subbuf = buf->subbufs_consumed % n_subbufs;
 817         else
 818                 read_subbuf = read_pos / buf->chan->subbuf_size;
 819         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 820                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 821                     (buf->offset == subbuf_size))
 822                         return;
 823                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 824                 buf->bytes_consumed = 0;
 825         }
 826 }
 827
 828 /*
 829  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 830  */
 831 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 832 {
 833         size_t subbuf_size = buf->chan->subbuf_size;
 834         size_t n_subbufs = buf->chan->n_subbufs;
 835         size_t produced = buf->subbufs_produced;
 836         size_t consumed = buf->subbufs_consumed;
 837
 838         relay_file_read_consume(buf, read_pos, 0);
 839
 840         if (unlikely(buf->offset > subbuf_size)) {
 841                 if (produced == consumed)
 842                         return 0;
 843                 return 1;
 844         }
 845
 846         if (unlikely(produced - consumed >= n_subbufs)) {
 847                 consumed = produced - n_subbufs + 1;
 848                 buf->subbufs_consumed = consumed;
 849                 buf->bytes_consumed = 0;
 850         }
 851
 852         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 853         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 854
 855         if (consumed > produced)
 856                 produced += n_subbufs * subbuf_size;
 857
 858         if (consumed == produced)
 859                 return 0;
 860
 861         return 1;
 862 }
 863
 864 /**
 865  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
 866  *      @read_pos: file read position
 867  *      @buf: relay channel buffer
 868  */
 869 static size_t relay_file_read_subbuf_avail(size_t read_pos,
 870                                            struct rchan_buf *buf)
 871 {
 872         size_t padding, avail = 0;
 873         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 874         size_t subbuf_size = buf->chan->subbuf_size;
 875
 876         write_subbuf = (buf->data - buf->start) / subbuf_size;
 877         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 878         read_subbuf = read_pos / subbuf_size;
 879         read_offset = read_pos % subbuf_size;
 880         padding = buf->padding[read_subbuf];
 881
 882         if (read_subbuf == write_subbuf) {
 883                 if (read_offset + padding < write_offset)
 884                         avail = write_offset - (read_offset + padding);
 885         } else
 886                 avail = (subbuf_size - padding) - read_offset;
 887
 888         return avail;
 889 }
 890
 891 /**
 892  *      relay_file_read_start_pos - find the first available byte to read
 893  *      @read_pos: file read position
 894  *      @buf: relay channel buffer
 895  *
 896  *      If the @read_pos is in the middle of padding, return the
 897  *      position of the first actually available byte, otherwise
 898  *      return the original value.
 899  */
 900 static size_t relay_file_read_start_pos(size_t read_pos,
 901                                         struct rchan_buf *buf)
 902 {
 903         size_t read_subbuf, padding, padding_start, padding_end;
 904         size_t subbuf_size = buf->chan->subbuf_size;
 905         size_t n_subbufs = buf->chan->n_subbufs;
 906         size_t consumed = buf->subbufs_consumed % n_subbufs;
 907
 908         if (!read_pos)
 909                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
 910         read_subbuf = read_pos / subbuf_size;
 911         padding = buf->padding[read_subbuf];
 912         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 913         padding_end = (read_subbuf + 1) * subbuf_size;
 914         if (read_pos >= padding_start && read_pos < padding_end) {
 915                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 916                 read_pos = read_subbuf * subbuf_size;
 917         }
 918
 919         return read_pos;
 920 }
 921
 922 /**
 923  *      relay_file_read_end_pos - return the new read position
 924  *      @read_pos: file read position
 925  *      @buf: relay channel buffer
 926  *      @count: number of bytes to be read
 927  */
 928 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
 929                                       size_t read_pos,
 930                                       size_t count)
 931 {
 932         size_t read_subbuf, padding, end_pos;
 933         size_t subbuf_size = buf->chan->subbuf_size;
 934         size_t n_subbufs = buf->chan->n_subbufs;
 935
 936         read_subbuf = read_pos / subbuf_size;
 937         padding = buf->padding[read_subbuf];
 938         if (read_pos % subbuf_size + count + padding == subbuf_size)
 939                 end_pos = (read_subbuf + 1) * subbuf_size;
 940         else
 941                 end_pos = read_pos + count;
 942         if (end_pos >= subbuf_size * n_subbufs)
 943                 end_pos = 0;
 944
 945         return end_pos;
 946 }
 947
 948 /*
 949  *      subbuf_read_actor - read up to one subbuf's worth of data
 950  */
 951 static int subbuf_read_actor(size_t read_start,
 952                              struct rchan_buf *buf,
 953                              size_t avail,
 954                              read_descriptor_t *desc,
 955                              read_actor_t actor)
 956 {
 957         void *from;
 958         int ret = 0;
 959
 960         from = buf->start + read_start;
 961         ret = avail;
 962         if (copy_to_user(desc->arg.buf, from, avail)) {
 963                 desc->error = -EFAULT;
 964                 ret = 0;
 965         }
 966         desc->arg.data += ret;
 967         desc->written += ret;
 968         desc->count -= ret;
 969
 970         return ret;
 971 }
 972
 973 /*
 974  *      subbuf_send_actor - send up to one subbuf's worth of data
 975  */
 976 static int subbuf_send_actor(size_t read_start,
 977                              struct rchan_buf *buf,
 978                              size_t avail,
 979                              read_descriptor_t *desc,
 980                              read_actor_t actor)
 981 {
 982         unsigned long pidx, poff;
 983         unsigned int subbuf_pages;
 984         int ret = 0;
 985
 986         subbuf_pages = buf->chan->alloc_size >> PAGE_SHIFT;
 987         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
 988         poff = read_start & ~PAGE_MASK;
 989         while (avail) {
 990                 struct page *p = buf->page_array[pidx];
 991                 unsigned int len;
 992
 993                 len = PAGE_SIZE - poff;
 994                 if (len > avail)
 995                         len = avail;
 996
 997                 len = actor(desc, p, poff, len);
 998                 if (desc->error)
 999                         break;
1000
1001                 avail -= len;
1002                 ret += len;
1003                 poff = 0;
1004                 pidx = (pidx + 1) % subbuf_pages;
1005         }
1006
1007         return ret;
1008 }
1009
1010 typedef int (*subbuf_actor_t) (size_t read_start,
1011                                struct rchan_buf *buf,
1012                                size_t avail,
1013                                read_descriptor_t *desc,
1014                                read_actor_t actor);
1015
1016 /*
1017  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1018  */
1019 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1020                                         subbuf_actor_t subbuf_actor,
1021                                         read_actor_t actor,
1022                                         read_descriptor_t *desc)
1023 {
1024         struct rchan_buf *buf = filp->private_data;
1025         size_t read_start, avail;
1026         int ret;
1027
1028         if (!desc->count)
1029                 return 0;
1030
1031         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1032         do {
1033                 if (!relay_file_read_avail(buf, *ppos))
1034                         break;
1035
1036                 read_start = relay_file_read_start_pos(*ppos, buf);
1037                 avail = relay_file_read_subbuf_avail(read_start, buf);
1038                 if (!avail)
1039                         break;
1040
1041                 avail = min(desc->count, avail);
1042                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1043                 if (desc->error < 0)
1044                         break;
1045
1046                 if (ret) {
1047                         relay_file_read_consume(buf, read_start, ret);
1048                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1049                 }
1050         } while (desc->count && ret);
1051         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1052
1053         return desc->written;
1054 }
1055
1056 static ssize_t relay_file_read(struct file *filp,
1057                                char __user *buffer,
1058                                size_t count,
1059                                loff_t *ppos)
1060 {
1061         read_descriptor_t desc;
1062         desc.written = 0;
1063         desc.count = count;
1064         desc.arg.buf = buffer;
1065         desc.error = 0;
1066         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1067                                        NULL, &desc);
1068 }
1069
1070 static ssize_t relay_file_sendfile(struct file *filp,
1071                                    loff_t *ppos,
1072                                    size_t count,
1073                                    read_actor_t actor,
1074                                    void *target)
1075 {
1076         read_descriptor_t desc;
1077         desc.written = 0;
1078         desc.count = count;
1079         desc.arg.data = target;
1080         desc.error = 0;
1081         return relay_file_read_subbufs(filp, ppos, subbuf_send_actor,
1082                                        actor, &desc);
1083 }
1084
1085 const struct file_operations relay_file_operations = {
1086         .open           = relay_file_open,
1087         .poll           = relay_file_poll,
1088         .mmap           = relay_file_mmap,
1089         .read           = relay_file_read,
1090         .llseek         = no_llseek,
1091         .release        = relay_file_release,
1092         .sendfile       = relay_file_sendfile,
1093 };
1094 EXPORT_SYMBOL_GPL(relay_file_operations);
1095
1096 static __init int relay_init(void)
1097 {
1098
1099         hotcpu_notifier(relay_hotcpu_callback, 0);
1100         return 0;
1101 }
1102
1103 module_init(relay_init);