git.oblomov.eu Git - linux-2.6/blob - 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 #include <linux/splice.h>
  25
  26 /* list of open channels, for cpu hotplug */
  27 static DEFINE_MUTEX(relay_channels_mutex);
  28 static LIST_HEAD(relay_channels);
  29
  30 /*
  31  * close() vm_op implementation for relay file mapping.
  32  */
  33 static void relay_file_mmap_close(struct vm_area_struct *vma)
  34 {
  35         struct rchan_buf *buf = vma->vm_private_data;
  36         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  37 }
  38
  39 /*
  40  * nopage() vm_op implementation for relay file mapping.
  41  */
  42 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
  43                                      unsigned long address,
  44                                      int *type)
  45 {
  46         struct page *page;
  47         struct rchan_buf *buf = vma->vm_private_data;
  48         unsigned long offset = address - vma->vm_start;
  49
  50         if (address > vma->vm_end)
  51                 return NOPAGE_SIGBUS; /* Disallow mremap */
  52         if (!buf)
  53                 return NOPAGE_OOM;
  54
  55         page = vmalloc_to_page(buf->start + offset);
  56         if (!page)
  57                 return NOPAGE_OOM;
  58         get_page(page);
  59
  60         if (type)
  61                 *type = VM_FAULT_MINOR;
  62
  63         return page;
  64 }
  65
  66 /*
  67  * vm_ops for relay file mappings.
  68  */
  69 static struct vm_operations_struct relay_file_mmap_ops = {
  70         .nopage = relay_buf_nopage,
  71         .close = relay_file_mmap_close,
  72 };
  73
  74 /**
  75  *      relay_mmap_buf: - mmap channel buffer to process address space
  76  *      @buf: relay channel buffer
  77  *      @vma: vm_area_struct describing memory to be mapped
  78  *
  79  *      Returns 0 if ok, negative on error
  80  *
  81  *      Caller should already have grabbed mmap_sem.
  82  */
  83 int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
  84 {
  85         unsigned long length = vma->vm_end - vma->vm_start;
  86         struct file *filp = vma->vm_file;
  87
  88         if (!buf)
  89                 return -EBADF;
  90
  91         if (length != (unsigned long)buf->chan->alloc_size)
  92                 return -EINVAL;
  93
  94         vma->vm_ops = &relay_file_mmap_ops;
  95         vma->vm_private_data = buf;
  96         buf->chan->cb->buf_mapped(buf, filp);
  97
  98         return 0;
  99 }
 100
 101 /**
 102  *      relay_alloc_buf - allocate a channel buffer
 103  *      @buf: the buffer struct
 104  *      @size: total size of the buffer
 105  *
 106  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 107  *      passed in size will get page aligned, if it isn't already.
 108  */
 109 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 110 {
 111         void *mem;
 112         unsigned int i, j, n_pages;
 113
 114         *size = PAGE_ALIGN(*size);
 115         n_pages = *size >> PAGE_SHIFT;
 116
 117         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
 118         if (!buf->page_array)
 119                 return NULL;
 120
 121         for (i = 0; i < n_pages; i++) {
 122                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 123                 if (unlikely(!buf->page_array[i]))
 124                         goto depopulate;
 125                 set_page_private(buf->page_array[i], (unsigned long)buf);
 126         }
 127         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 128         if (!mem)
 129                 goto depopulate;
 130
 131         memset(mem, 0, *size);
 132         buf->page_count = n_pages;
 133         return mem;
 134
 135 depopulate:
 136         for (j = 0; j < i; j++)
 137                 __free_page(buf->page_array[j]);
 138         kfree(buf->page_array);
 139         return NULL;
 140 }
 141
 142 /**
 143  *      relay_create_buf - allocate and initialize a channel buffer
 144  *      @chan: the relay channel
 145  *
 146  *      Returns channel buffer if successful, %NULL otherwise.
 147  */
 148 struct rchan_buf *relay_create_buf(struct rchan *chan)
 149 {
 150         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 151         if (!buf)
 152                 return NULL;
 153
 154         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 155         if (!buf->padding)
 156                 goto free_buf;
 157
 158         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 159         if (!buf->start)
 160                 goto free_buf;
 161
 162         buf->chan = chan;
 163         kref_get(&buf->chan->kref);
 164         return buf;
 165
 166 free_buf:
 167         kfree(buf->padding);
 168         kfree(buf);
 169         return NULL;
 170 }
 171
 172 /**
 173  *      relay_destroy_channel - free the channel struct
 174  *      @kref: target kernel reference that contains the relay channel
 175  *
 176  *      Should only be called from kref_put().
 177  */
 178 void relay_destroy_channel(struct kref *kref)
 179 {
 180         struct rchan *chan = container_of(kref, struct rchan, kref);
 181         kfree(chan);
 182 }
 183
 184 /**
 185  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 186  *      @buf: the buffer struct
 187  */
 188 void relay_destroy_buf(struct rchan_buf *buf)
 189 {
 190         struct rchan *chan = buf->chan;
 191         unsigned int i;
 192
 193         if (likely(buf->start)) {
 194                 vunmap(buf->start);
 195                 for (i = 0; i < buf->page_count; i++)
 196                         __free_page(buf->page_array[i]);
 197                 kfree(buf->page_array);
 198         }
 199         chan->buf[buf->cpu] = NULL;
 200         kfree(buf->padding);
 201         kfree(buf);
 202         kref_put(&chan->kref, relay_destroy_channel);
 203 }
 204
 205 /**
 206  *      relay_remove_buf - remove a channel buffer
 207  *      @kref: target kernel reference that contains the relay buffer
 208  *
 209  *      Removes the file from the fileystem, which also frees the
 210  *      rchan_buf_struct and the channel buffer.  Should only be called from
 211  *      kref_put().
 212  */
 213 void relay_remove_buf(struct kref *kref)
 214 {
 215         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 216         buf->chan->cb->remove_buf_file(buf->dentry);
 217         relay_destroy_buf(buf);
 218 }
 219
 220 /**
 221  *      relay_buf_empty - boolean, is the channel buffer empty?
 222  *      @buf: channel buffer
 223  *
 224  *      Returns 1 if the buffer is empty, 0 otherwise.
 225  */
 226 int relay_buf_empty(struct rchan_buf *buf)
 227 {
 228         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 229 }
 230 EXPORT_SYMBOL_GPL(relay_buf_empty);
 231
 232 /**
 233  *      relay_buf_full - boolean, is the channel buffer full?
 234  *      @buf: channel buffer
 235  *
 236  *      Returns 1 if the buffer is full, 0 otherwise.
 237  */
 238 int relay_buf_full(struct rchan_buf *buf)
 239 {
 240         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 241         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 242 }
 243 EXPORT_SYMBOL_GPL(relay_buf_full);
 244
 245 /*
 246  * High-level relay kernel API and associated functions.
 247  */
 248
 249 /*
 250  * rchan_callback implementations defining default channel behavior.  Used
 251  * in place of corresponding NULL values in client callback struct.
 252  */
 253
 254 /*
 255  * subbuf_start() default callback.  Does nothing.
 256  */
 257 static int subbuf_start_default_callback (struct rchan_buf *buf,
 258                                           void *subbuf,
 259                                           void *prev_subbuf,
 260                                           size_t prev_padding)
 261 {
 262         if (relay_buf_full(buf))
 263                 return 0;
 264
 265         return 1;
 266 }
 267
 268 /*
 269  * buf_mapped() default callback.  Does nothing.
 270  */
 271 static void buf_mapped_default_callback(struct rchan_buf *buf,
 272                                         struct file *filp)
 273 {
 274 }
 275
 276 /*
 277  * buf_unmapped() default callback.  Does nothing.
 278  */
 279 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 280                                           struct file *filp)
 281 {
 282 }
 283
 284 /*
 285  * create_buf_file_create() default callback.  Does nothing.
 286  */
 287 static struct dentry *create_buf_file_default_callback(const char *filename,
 288                                                        struct dentry *parent,
 289                                                        int mode,
 290                                                        struct rchan_buf *buf,
 291                                                        int *is_global)
 292 {
 293         return NULL;
 294 }
 295
 296 /*
 297  * remove_buf_file() default callback.  Does nothing.
 298  */
 299 static int remove_buf_file_default_callback(struct dentry *dentry)
 300 {
 301         return -EINVAL;
 302 }
 303
 304 /* relay channel default callbacks */
 305 static struct rchan_callbacks default_channel_callbacks = {
 306         .subbuf_start = subbuf_start_default_callback,
 307         .buf_mapped = buf_mapped_default_callback,
 308         .buf_unmapped = buf_unmapped_default_callback,
 309         .create_buf_file = create_buf_file_default_callback,
 310         .remove_buf_file = remove_buf_file_default_callback,
 311 };
 312
 313 /**
 314  *      wakeup_readers - wake up readers waiting on a channel
 315  *      @data: contains the channel buffer
 316  *
 317  *      This is the timer function used to defer reader waking.
 318  */
 319 static void wakeup_readers(unsigned long data)
 320 {
 321         struct rchan_buf *buf = (struct rchan_buf *)data;
 322         wake_up_interruptible(&buf->read_wait);
 323 }
 324
 325 /**
 326  *      __relay_reset - reset a channel buffer
 327  *      @buf: the channel buffer
 328  *      @init: 1 if this is a first-time initialization
 329  *
 330  *      See relay_reset() for description of effect.
 331  */
 332 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 333 {
 334         size_t i;
 335
 336         if (init) {
 337                 init_waitqueue_head(&buf->read_wait);
 338                 kref_init(&buf->kref);
 339                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 340         } else
 341                 del_timer_sync(&buf->timer);
 342
 343         buf->subbufs_produced = 0;
 344         buf->subbufs_consumed = 0;
 345         buf->bytes_consumed = 0;
 346         buf->finalized = 0;
 347         buf->data = buf->start;
 348         buf->offset = 0;
 349
 350         for (i = 0; i < buf->chan->n_subbufs; i++)
 351                 buf->padding[i] = 0;
 352
 353         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 354 }
 355
 356 /**
 357  *      relay_reset - reset the channel
 358  *      @chan: the channel
 359  *
 360  *      This has the effect of erasing all data from all channel buffers
 361  *      and restarting the channel in its initial state.  The buffers
 362  *      are not freed, so any mappings are still in effect.
 363  *
 364  *      NOTE. Care should be taken that the channel isn't actually
 365  *      being used by anything when this call is made.
 366  */
 367 void relay_reset(struct rchan *chan)
 368 {
 369         unsigned int i;
 370
 371         if (!chan)
 372                 return;
 373
 374         if (chan->is_global && chan->buf[0]) {
 375                 __relay_reset(chan->buf[0], 0);
 376                 return;
 377         }
 378
 379         mutex_lock(&relay_channels_mutex);
 380         for_each_online_cpu(i)
 381                 if (chan->buf[i])
 382                         __relay_reset(chan->buf[i], 0);
 383         mutex_unlock(&relay_channels_mutex);
 384 }
 385 EXPORT_SYMBOL_GPL(relay_reset);
 386
 387 /*
 388  *      relay_open_buf - create a new relay channel buffer
 389  *
 390  *      used by relay_open() and CPU hotplug.
 391  */
 392 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 393 {
 394         struct rchan_buf *buf = NULL;
 395         struct dentry *dentry;
 396         char *tmpname;
 397
 398         if (chan->is_global)
 399                 return chan->buf[0];
 400
 401         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 402         if (!tmpname)
 403                 goto end;
 404         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 405
 406         buf = relay_create_buf(chan);
 407         if (!buf)
 408                 goto free_name;
 409
 410         buf->cpu = cpu;
 411         __relay_reset(buf, 1);
 412
 413         /* Create file in fs */
 414         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
 415                                            buf, &chan->is_global);
 416         if (!dentry)
 417                 goto free_buf;
 418
 419         buf->dentry = dentry;
 420
 421         if(chan->is_global) {
 422                 chan->buf[0] = buf;
 423                 buf->cpu = 0;
 424         }
 425
 426         goto free_name;
 427
 428 free_buf:
 429         relay_destroy_buf(buf);
 430 free_name:
 431         kfree(tmpname);
 432 end:
 433         return buf;
 434 }
 435
 436 /**
 437  *      relay_close_buf - close a channel buffer
 438  *      @buf: channel buffer
 439  *
 440  *      Marks the buffer finalized and restores the default callbacks.
 441  *      The channel buffer and channel buffer data structure are then freed
 442  *      automatically when the last reference is given up.
 443  */
 444 static void relay_close_buf(struct rchan_buf *buf)
 445 {
 446         buf->finalized = 1;
 447         del_timer_sync(&buf->timer);
 448         kref_put(&buf->kref, relay_remove_buf);
 449 }
 450
 451 static void setup_callbacks(struct rchan *chan,
 452                                    struct rchan_callbacks *cb)
 453 {
 454         if (!cb) {
 455                 chan->cb = &default_channel_callbacks;
 456                 return;
 457         }
 458
 459         if (!cb->subbuf_start)
 460                 cb->subbuf_start = subbuf_start_default_callback;
 461         if (!cb->buf_mapped)
 462                 cb->buf_mapped = buf_mapped_default_callback;
 463         if (!cb->buf_unmapped)
 464                 cb->buf_unmapped = buf_unmapped_default_callback;
 465         if (!cb->create_buf_file)
 466                 cb->create_buf_file = create_buf_file_default_callback;
 467         if (!cb->remove_buf_file)
 468                 cb->remove_buf_file = remove_buf_file_default_callback;
 469         chan->cb = cb;
 470 }
 471
 472 /**
 473  *      relay_hotcpu_callback - CPU hotplug callback
 474  *      @nb: notifier block
 475  *      @action: hotplug action to take
 476  *      @hcpu: CPU number
 477  *
 478  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 479  */
 480 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 481                                 unsigned long action,
 482                                 void *hcpu)
 483 {
 484         unsigned int hotcpu = (unsigned long)hcpu;
 485         struct rchan *chan;
 486
 487         switch(action) {
 488         case CPU_UP_PREPARE:
 489         case CPU_UP_PREPARE_FROZEN:
 490                 mutex_lock(&relay_channels_mutex);
 491                 list_for_each_entry(chan, &relay_channels, list) {
 492                         if (chan->buf[hotcpu])
 493                                 continue;
 494                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 495                         if(!chan->buf[hotcpu]) {
 496                                 printk(KERN_ERR
 497                                         "relay_hotcpu_callback: cpu %d buffer "
 498                                         "creation failed\n", hotcpu);
 499                                 mutex_unlock(&relay_channels_mutex);
 500                                 return NOTIFY_BAD;
 501                         }
 502                 }
 503                 mutex_unlock(&relay_channels_mutex);
 504                 break;
 505         case CPU_DEAD:
 506         case CPU_DEAD_FROZEN:
 507                 /* No need to flush the cpu : will be flushed upon
 508                  * final relay_flush() call. */
 509                 break;
 510         }
 511         return NOTIFY_OK;
 512 }
 513
 514 /**
 515  *      relay_open - create a new relay channel
 516  *      @base_filename: base name of files to create
 517  *      @parent: dentry of parent directory, %NULL for root directory
 518  *      @subbuf_size: size of sub-buffers
 519  *      @n_subbufs: number of sub-buffers
 520  *      @cb: client callback functions
 521  *      @private_data: user-defined data
 522  *
 523  *      Returns channel pointer if successful, %NULL otherwise.
 524  *
 525  *      Creates a channel buffer for each cpu using the sizes and
 526  *      attributes specified.  The created channel buffer files
 527  *      will be named base_filename0...base_filenameN-1.  File
 528  *      permissions will be %S_IRUSR.
 529  */
 530 struct rchan *relay_open(const char *base_filename,
 531                          struct dentry *parent,
 532                          size_t subbuf_size,
 533                          size_t n_subbufs,
 534                          struct rchan_callbacks *cb,
 535                          void *private_data)
 536 {
 537         unsigned int i;
 538         struct rchan *chan;
 539         if (!base_filename)
 540                 return NULL;
 541
 542         if (!(subbuf_size && n_subbufs))
 543                 return NULL;
 544
 545         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 546         if (!chan)
 547                 return NULL;
 548
 549         chan->version = RELAYFS_CHANNEL_VERSION;
 550         chan->n_subbufs = n_subbufs;
 551         chan->subbuf_size = subbuf_size;
 552         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 553         chan->parent = parent;
 554         chan->private_data = private_data;
 555         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 556         setup_callbacks(chan, cb);
 557         kref_init(&chan->kref);
 558
 559         mutex_lock(&relay_channels_mutex);
 560         for_each_online_cpu(i) {
 561                 chan->buf[i] = relay_open_buf(chan, i);
 562                 if (!chan->buf[i])
 563                         goto free_bufs;
 564         }
 565         list_add(&chan->list, &relay_channels);
 566         mutex_unlock(&relay_channels_mutex);
 567
 568         return chan;
 569
 570 free_bufs:
 571         for_each_online_cpu(i) {
 572                 if (!chan->buf[i])
 573                         break;
 574                 relay_close_buf(chan->buf[i]);
 575         }
 576
 577         kref_put(&chan->kref, relay_destroy_channel);
 578         mutex_unlock(&relay_channels_mutex);
 579         return NULL;
 580 }
 581 EXPORT_SYMBOL_GPL(relay_open);
 582
 583 /**
 584  *      relay_switch_subbuf - switch to a new sub-buffer
 585  *      @buf: channel buffer
 586  *      @length: size of current event
 587  *
 588  *      Returns either the length passed in or 0 if full.
 589  *
 590  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 591  *      updating padding counts, waking up readers, etc.
 592  */
 593 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 594 {
 595         void *old, *new;
 596         size_t old_subbuf, new_subbuf;
 597
 598         if (unlikely(length > buf->chan->subbuf_size))
 599                 goto toobig;
 600
 601         if (buf->offset != buf->chan->subbuf_size + 1) {
 602                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 603                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 604                 buf->padding[old_subbuf] = buf->prev_padding;
 605                 buf->subbufs_produced++;
 606                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
 607                         buf->padding[old_subbuf];
 608                 smp_mb();
 609                 if (waitqueue_active(&buf->read_wait))
 610                         /*
 611                          * Calling wake_up_interruptible() from here
 612                          * will deadlock if we happen to be logging
 613                          * from the scheduler (trying to re-grab
 614                          * rq->lock), so defer it.
 615                          */
 616                         __mod_timer(&buf->timer, jiffies + 1);
 617         }
 618
 619         old = buf->data;
 620         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 621         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 622         buf->offset = 0;
 623         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 624                 buf->offset = buf->chan->subbuf_size + 1;
 625                 return 0;
 626         }
 627         buf->data = new;
 628         buf->padding[new_subbuf] = 0;
 629
 630         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 631                 goto toobig;
 632
 633         return length;
 634
 635 toobig:
 636         buf->chan->last_toobig = length;
 637         return 0;
 638 }
 639 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 640
 641 /**
 642  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 643  *      @chan: the channel
 644  *      @cpu: the cpu associated with the channel buffer to update
 645  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 646  *
 647  *      Adds to the channel buffer's consumed sub-buffer count.
 648  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 649  *      not the total consumed.
 650  *
 651  *      NOTE. Kernel clients don't need to call this function if the channel
 652  *      mode is 'overwrite'.
 653  */
 654 void relay_subbufs_consumed(struct rchan *chan,
 655                             unsigned int cpu,
 656                             size_t subbufs_consumed)
 657 {
 658         struct rchan_buf *buf;
 659
 660         if (!chan)
 661                 return;
 662
 663         if (cpu >= NR_CPUS || !chan->buf[cpu])
 664                 return;
 665
 666         buf = chan->buf[cpu];
 667         buf->subbufs_consumed += subbufs_consumed;
 668         if (buf->subbufs_consumed > buf->subbufs_produced)
 669                 buf->subbufs_consumed = buf->subbufs_produced;
 670 }
 671 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 672
 673 /**
 674  *      relay_close - close the channel
 675  *      @chan: the channel
 676  *
 677  *      Closes all channel buffers and frees the channel.
 678  */
 679 void relay_close(struct rchan *chan)
 680 {
 681         unsigned int i;
 682
 683         if (!chan)
 684                 return;
 685
 686         mutex_lock(&relay_channels_mutex);
 687         if (chan->is_global && chan->buf[0])
 688                 relay_close_buf(chan->buf[0]);
 689         else
 690                 for_each_possible_cpu(i)
 691                         if (chan->buf[i])
 692                                 relay_close_buf(chan->buf[i]);
 693
 694         if (chan->last_toobig)
 695                 printk(KERN_WARNING "relay: one or more items not logged "
 696                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 697                        chan->last_toobig, chan->subbuf_size);
 698
 699         list_del(&chan->list);
 700         kref_put(&chan->kref, relay_destroy_channel);
 701         mutex_unlock(&relay_channels_mutex);
 702 }
 703 EXPORT_SYMBOL_GPL(relay_close);
 704
 705 /**
 706  *      relay_flush - close the channel
 707  *      @chan: the channel
 708  *
 709  *      Flushes all channel buffers, i.e. forces buffer switch.
 710  */
 711 void relay_flush(struct rchan *chan)
 712 {
 713         unsigned int i;
 714
 715         if (!chan)
 716                 return;
 717
 718         if (chan->is_global && chan->buf[0]) {
 719                 relay_switch_subbuf(chan->buf[0], 0);
 720                 return;
 721         }
 722
 723         mutex_lock(&relay_channels_mutex);
 724         for_each_possible_cpu(i)
 725                 if (chan->buf[i])
 726                         relay_switch_subbuf(chan->buf[i], 0);
 727         mutex_unlock(&relay_channels_mutex);
 728 }
 729 EXPORT_SYMBOL_GPL(relay_flush);
 730
 731 /**
 732  *      relay_file_open - open file op for relay files
 733  *      @inode: the inode
 734  *      @filp: the file
 735  *
 736  *      Increments the channel buffer refcount.
 737  */
 738 static int relay_file_open(struct inode *inode, struct file *filp)
 739 {
 740         struct rchan_buf *buf = inode->i_private;
 741         kref_get(&buf->kref);
 742         filp->private_data = buf;
 743
 744         return 0;
 745 }
 746
 747 /**
 748  *      relay_file_mmap - mmap file op for relay files
 749  *      @filp: the file
 750  *      @vma: the vma describing what to map
 751  *
 752  *      Calls upon relay_mmap_buf() to map the file into user space.
 753  */
 754 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 755 {
 756         struct rchan_buf *buf = filp->private_data;
 757         return relay_mmap_buf(buf, vma);
 758 }
 759
 760 /**
 761  *      relay_file_poll - poll file op for relay files
 762  *      @filp: the file
 763  *      @wait: poll table
 764  *
 765  *      Poll implemention.
 766  */
 767 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 768 {
 769         unsigned int mask = 0;
 770         struct rchan_buf *buf = filp->private_data;
 771
 772         if (buf->finalized)
 773                 return POLLERR;
 774
 775         if (filp->f_mode & FMODE_READ) {
 776                 poll_wait(filp, &buf->read_wait, wait);
 777                 if (!relay_buf_empty(buf))
 778                         mask |= POLLIN | POLLRDNORM;
 779         }
 780
 781         return mask;
 782 }
 783
 784 /**
 785  *      relay_file_release - release file op for relay files
 786  *      @inode: the inode
 787  *      @filp: the file
 788  *
 789  *      Decrements the channel refcount, as the filesystem is
 790  *      no longer using it.
 791  */
 792 static int relay_file_release(struct inode *inode, struct file *filp)
 793 {
 794         struct rchan_buf *buf = filp->private_data;
 795         kref_put(&buf->kref, relay_remove_buf);
 796
 797         return 0;
 798 }
 799
 800 /*
 801  *      relay_file_read_consume - update the consumed count for the buffer
 802  */
 803 static void relay_file_read_consume(struct rchan_buf *buf,
 804                                     size_t read_pos,
 805                                     size_t bytes_consumed)
 806 {
 807         size_t subbuf_size = buf->chan->subbuf_size;
 808         size_t n_subbufs = buf->chan->n_subbufs;
 809         size_t read_subbuf;
 810
 811         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 812                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 813                 buf->bytes_consumed = 0;
 814         }
 815
 816         buf->bytes_consumed += bytes_consumed;
 817         if (!read_pos)
 818                 read_subbuf = buf->subbufs_consumed % n_subbufs;
 819         else
 820                 read_subbuf = read_pos / buf->chan->subbuf_size;
 821         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 822                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 823                     (buf->offset == subbuf_size))
 824                         return;
 825                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 826                 buf->bytes_consumed = 0;
 827         }
 828 }
 829
 830 /*
 831  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 832  */
 833 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 834 {
 835         size_t subbuf_size = buf->chan->subbuf_size;
 836         size_t n_subbufs = buf->chan->n_subbufs;
 837         size_t produced = buf->subbufs_produced;
 838         size_t consumed = buf->subbufs_consumed;
 839
 840         relay_file_read_consume(buf, read_pos, 0);
 841
 842         if (unlikely(buf->offset > subbuf_size)) {
 843                 if (produced == consumed)
 844                         return 0;
 845                 return 1;
 846         }
 847
 848         if (unlikely(produced - consumed >= n_subbufs)) {
 849                 consumed = produced - n_subbufs + 1;
 850                 buf->subbufs_consumed = consumed;
 851                 buf->bytes_consumed = 0;
 852         }
 853
 854         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 855         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 856
 857         if (consumed > produced)
 858                 produced += n_subbufs * subbuf_size;
 859
 860         if (consumed == produced)
 861                 return 0;
 862
 863         return 1;
 864 }
 865
 866 /**
 867  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
 868  *      @read_pos: file read position
 869  *      @buf: relay channel buffer
 870  */
 871 static size_t relay_file_read_subbuf_avail(size_t read_pos,
 872                                            struct rchan_buf *buf)
 873 {
 874         size_t padding, avail = 0;
 875         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 876         size_t subbuf_size = buf->chan->subbuf_size;
 877
 878         write_subbuf = (buf->data - buf->start) / subbuf_size;
 879         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 880         read_subbuf = read_pos / subbuf_size;
 881         read_offset = read_pos % subbuf_size;
 882         padding = buf->padding[read_subbuf];
 883
 884         if (read_subbuf == write_subbuf) {
 885                 if (read_offset + padding < write_offset)
 886                         avail = write_offset - (read_offset + padding);
 887         } else
 888                 avail = (subbuf_size - padding) - read_offset;
 889
 890         return avail;
 891 }
 892
 893 /**
 894  *      relay_file_read_start_pos - find the first available byte to read
 895  *      @read_pos: file read position
 896  *      @buf: relay channel buffer
 897  *
 898  *      If the @read_pos is in the middle of padding, return the
 899  *      position of the first actually available byte, otherwise
 900  *      return the original value.
 901  */
 902 static size_t relay_file_read_start_pos(size_t read_pos,
 903                                         struct rchan_buf *buf)
 904 {
 905         size_t read_subbuf, padding, padding_start, padding_end;
 906         size_t subbuf_size = buf->chan->subbuf_size;
 907         size_t n_subbufs = buf->chan->n_subbufs;
 908         size_t consumed = buf->subbufs_consumed % n_subbufs;
 909
 910         if (!read_pos)
 911                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
 912         read_subbuf = read_pos / subbuf_size;
 913         padding = buf->padding[read_subbuf];
 914         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 915         padding_end = (read_subbuf + 1) * subbuf_size;
 916         if (read_pos >= padding_start && read_pos < padding_end) {
 917                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 918                 read_pos = read_subbuf * subbuf_size;
 919         }
 920
 921         return read_pos;
 922 }
 923
 924 /**
 925  *      relay_file_read_end_pos - return the new read position
 926  *      @read_pos: file read position
 927  *      @buf: relay channel buffer
 928  *      @count: number of bytes to be read
 929  */
 930 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
 931                                       size_t read_pos,
 932                                       size_t count)
 933 {
 934         size_t read_subbuf, padding, end_pos;
 935         size_t subbuf_size = buf->chan->subbuf_size;
 936         size_t n_subbufs = buf->chan->n_subbufs;
 937
 938         read_subbuf = read_pos / subbuf_size;
 939         padding = buf->padding[read_subbuf];
 940         if (read_pos % subbuf_size + count + padding == subbuf_size)
 941                 end_pos = (read_subbuf + 1) * subbuf_size;
 942         else
 943                 end_pos = read_pos + count;
 944         if (end_pos >= subbuf_size * n_subbufs)
 945                 end_pos = 0;
 946
 947         return end_pos;
 948 }
 949
 950 /*
 951  *      subbuf_read_actor - read up to one subbuf's worth of data
 952  */
 953 static int subbuf_read_actor(size_t read_start,
 954                              struct rchan_buf *buf,
 955                              size_t avail,
 956                              read_descriptor_t *desc,
 957                              read_actor_t actor)
 958 {
 959         void *from;
 960         int ret = 0;
 961
 962         from = buf->start + read_start;
 963         ret = avail;
 964         if (copy_to_user(desc->arg.buf, from, avail)) {
 965                 desc->error = -EFAULT;
 966                 ret = 0;
 967         }
 968         desc->arg.data += ret;
 969         desc->written += ret;
 970         desc->count -= ret;
 971
 972         return ret;
 973 }
 974
 975 typedef int (*subbuf_actor_t) (size_t read_start,
 976                                struct rchan_buf *buf,
 977                                size_t avail,
 978                                read_descriptor_t *desc,
 979                                read_actor_t actor);
 980
 981 /*
 982  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
 983  */
 984 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
 985                                         subbuf_actor_t subbuf_actor,
 986                                         read_actor_t actor,
 987                                         read_descriptor_t *desc)
 988 {
 989         struct rchan_buf *buf = filp->private_data;
 990         size_t read_start, avail;
 991         int ret;
 992
 993         if (!desc->count)
 994                 return 0;
 995
 996         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
 997         do {
 998                 if (!relay_file_read_avail(buf, *ppos))
 999                         break;
1000
1001                 read_start = relay_file_read_start_pos(*ppos, buf);
1002                 avail = relay_file_read_subbuf_avail(read_start, buf);
1003                 if (!avail)
1004                         break;
1005
1006                 avail = min(desc->count, avail);
1007                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1008                 if (desc->error < 0)
1009                         break;
1010
1011                 if (ret) {
1012                         relay_file_read_consume(buf, read_start, ret);
1013                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1014                 }
1015         } while (desc->count && ret);
1016         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1017
1018         return desc->written;
1019 }
1020
1021 static ssize_t relay_file_read(struct file *filp,
1022                                char __user *buffer,
1023                                size_t count,
1024                                loff_t *ppos)
1025 {
1026         read_descriptor_t desc;
1027         desc.written = 0;
1028         desc.count = count;
1029         desc.arg.buf = buffer;
1030         desc.error = 0;
1031         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1032                                        NULL, &desc);
1033 }
1034
1035 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1036 {
1037         rbuf->bytes_consumed += bytes_consumed;
1038
1039         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1040                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1041                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1042         }
1043 }
1044
1045 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1046                                    struct pipe_buffer *buf)
1047 {
1048         struct rchan_buf *rbuf;
1049
1050         rbuf = (struct rchan_buf *)page_private(buf->page);
1051         relay_consume_bytes(rbuf, buf->private);
1052 }
1053
1054 static struct pipe_buf_operations relay_pipe_buf_ops = {
1055         .can_merge = 0,
1056         .map = generic_pipe_buf_map,
1057         .unmap = generic_pipe_buf_unmap,
1058         .confirm = generic_pipe_buf_confirm,
1059         .release = relay_pipe_buf_release,
1060         .steal = generic_pipe_buf_steal,
1061         .get = generic_pipe_buf_get,
1062 };
1063
1064 /**
1065  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1066  */
1067 static int subbuf_splice_actor(struct file *in,
1068                                loff_t *ppos,
1069                                struct pipe_inode_info *pipe,
1070                                size_t len,
1071                                unsigned int flags,
1072                                int *nonpad_ret)
1073 {
1074         unsigned int pidx, poff, total_len, subbuf_pages, ret;
1075         struct rchan_buf *rbuf = in->private_data;
1076         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1077         size_t read_start = ((size_t)*ppos) % rbuf->chan->alloc_size;
1078         size_t read_subbuf = read_start / subbuf_size;
1079         size_t padding = rbuf->padding[read_subbuf];
1080         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1081         struct page *pages[PIPE_BUFFERS];
1082         struct partial_page partial[PIPE_BUFFERS];
1083         struct splice_pipe_desc spd = {
1084                 .pages = pages,
1085                 .nr_pages = 0,
1086                 .partial = partial,
1087                 .flags = flags,
1088                 .ops = &relay_pipe_buf_ops,
1089         };
1090
1091         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1092                 return 0;
1093
1094         /*
1095          * Adjust read len, if longer than what is available
1096          */
1097         if (len > (subbuf_size - read_start % subbuf_size))
1098                 len = subbuf_size - read_start % subbuf_size;
1099
1100         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1101         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1102         poff = read_start & ~PAGE_MASK;
1103
1104         for (total_len = 0; spd.nr_pages < subbuf_pages; spd.nr_pages++) {
1105                 unsigned int this_len, this_end, private;
1106                 unsigned int cur_pos = read_start + total_len;
1107
1108                 if (!len)
1109                         break;
1110
1111                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1112                 private = this_len;
1113
1114                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1115                 spd.partial[spd.nr_pages].offset = poff;
1116
1117                 this_end = cur_pos + this_len;
1118                 if (this_end >= nonpad_end) {
1119                         this_len = nonpad_end - cur_pos;
1120                         private = this_len + padding;
1121                 }
1122                 spd.partial[spd.nr_pages].len = this_len;
1123                 spd.partial[spd.nr_pages].private = private;
1124
1125                 len -= this_len;
1126                 total_len += this_len;
1127                 poff = 0;
1128                 pidx = (pidx + 1) % subbuf_pages;
1129
1130                 if (this_end >= nonpad_end) {
1131                         spd.nr_pages++;
1132                         break;
1133                 }
1134         }
1135
1136         if (!spd.nr_pages)
1137                 return 0;
1138
1139         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1140         if (ret < 0 || ret < total_len)
1141                 return ret;
1142
1143         if (read_start + ret == nonpad_end)
1144                 ret += padding;
1145
1146         return ret;
1147 }
1148
1149 static ssize_t relay_file_splice_read(struct file *in,
1150                                       loff_t *ppos,
1151                                       struct pipe_inode_info *pipe,
1152                                       size_t len,
1153                                       unsigned int flags)
1154 {
1155         ssize_t spliced;
1156         int ret;
1157         int nonpad_ret = 0;
1158
1159         ret = 0;
1160         spliced = 0;
1161
1162         while (len) {
1163                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1164                 if (ret < 0)
1165                         break;
1166                 else if (!ret) {
1167                         if (spliced)
1168                                 break;
1169                         if (flags & SPLICE_F_NONBLOCK) {
1170                                 ret = -EAGAIN;
1171                                 break;
1172                         }
1173                 }
1174
1175                 *ppos += ret;
1176                 if (ret > len)
1177                         len = 0;
1178                 else
1179                         len -= ret;
1180                 spliced += nonpad_ret;
1181                 nonpad_ret = 0;
1182         }
1183
1184         if (spliced)
1185                 return spliced;
1186
1187         return ret;
1188 }
1189
1190 const struct file_operations relay_file_operations = {
1191         .open           = relay_file_open,
1192         .poll           = relay_file_poll,
1193         .mmap           = relay_file_mmap,
1194         .read           = relay_file_read,
1195         .llseek         = no_llseek,
1196         .release        = relay_file_release,
1197         .splice_read    = relay_file_splice_read,
1198 };
1199 EXPORT_SYMBOL_GPL(relay_file_operations);
1200
1201 static __init int relay_init(void)
1202 {
1203
1204         hotcpu_notifier(relay_hotcpu_callback, 0);
1205         return 0;
1206 }
1207
1208 module_init(relay_init);