kernel/relay.c

   1 /*
   2  * Public API and common code for kernel->userspace relay file support.
   3  *
   4  * See Documentation/filesystems/relay.txt for an overview.
   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/export.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  * fault() vm_op implementation for relay file mapping.
  41  */
  42 static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  43 {
  44         struct page *page;
  45         struct rchan_buf *buf = vma->vm_private_data;
  46         pgoff_t pgoff = vmf->pgoff;
  47
  48         if (!buf)
  49                 return VM_FAULT_OOM;
  50
  51         page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
  52         if (!page)
  53                 return VM_FAULT_SIGBUS;
  54         get_page(page);
  55         vmf->page = page;
  56
  57         return 0;
  58 }
  59
  60 /*
  61  * vm_ops for relay file mappings.
  62  */
  63 static const struct vm_operations_struct relay_file_mmap_ops = {
  64         .fault = relay_buf_fault,
  65         .close = relay_file_mmap_close,
  66 };
  67
  68 /*
  69  * allocate an array of pointers of struct page
  70  */
  71 static struct page **relay_alloc_page_array(unsigned int n_pages)
  72 {
  73         const size_t pa_size = n_pages * sizeof(struct page *);
  74         if (pa_size > PAGE_SIZE)
  75                 return vzalloc(pa_size);
  76         return kzalloc(pa_size, GFP_KERNEL);
  77 }
  78
  79 /*
  80  * free an array of pointers of struct page
  81  */
  82 static void relay_free_page_array(struct page **array)
  83 {
  84         kvfree(array);
  85 }
  86
  87 /**
  88  *      relay_mmap_buf: - mmap channel buffer to process address space
  89  *      @buf: relay channel buffer
  90  *      @vma: vm_area_struct describing memory to be mapped
  91  *
  92  *      Returns 0 if ok, negative on error
  93  *
  94  *      Caller should already have grabbed mmap_sem.
  95  */
  96 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
  97 {
  98         unsigned long length = vma->vm_end - vma->vm_start;
  99         struct file *filp = vma->vm_file;
 100
 101         if (!buf)
 102                 return -EBADF;
 103
 104         if (length != (unsigned long)buf->chan->alloc_size)
 105                 return -EINVAL;
 106
 107         vma->vm_ops = &relay_file_mmap_ops;
 108         vma->vm_flags |= VM_DONTEXPAND;
 109         vma->vm_private_data = buf;
 110         buf->chan->cb->buf_mapped(buf, filp);
 111
 112         return 0;
 113 }
 114
 115 /**
 116  *      relay_alloc_buf - allocate a channel buffer
 117  *      @buf: the buffer struct
 118  *      @size: total size of the buffer
 119  *
 120  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 121  *      passed in size will get page aligned, if it isn't already.
 122  */
 123 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 124 {
 125         void *mem;
 126         unsigned int i, j, n_pages;
 127
 128         *size = PAGE_ALIGN(*size);
 129         n_pages = *size >> PAGE_SHIFT;
 130
 131         buf->page_array = relay_alloc_page_array(n_pages);
 132         if (!buf->page_array)
 133                 return NULL;
 134
 135         for (i = 0; i < n_pages; i++) {
 136                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 137                 if (unlikely(!buf->page_array[i]))
 138                         goto depopulate;
 139                 set_page_private(buf->page_array[i], (unsigned long)buf);
 140         }
 141         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 142         if (!mem)
 143                 goto depopulate;
 144
 145         memset(mem, 0, *size);
 146         buf->page_count = n_pages;
 147         return mem;
 148
 149 depopulate:
 150         for (j = 0; j < i; j++)
 151                 __free_page(buf->page_array[j]);
 152         relay_free_page_array(buf->page_array);
 153         return NULL;
 154 }
 155
 156 /**
 157  *      relay_create_buf - allocate and initialize a channel buffer
 158  *      @chan: the relay channel
 159  *
 160  *      Returns channel buffer if successful, %NULL otherwise.
 161  */
 162 static struct rchan_buf *relay_create_buf(struct rchan *chan)
 163 {
 164         struct rchan_buf *buf;
 165
 166         if (chan->n_subbufs > UINT_MAX / sizeof(size_t *))
 167                 return NULL;
 168
 169         buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 170         if (!buf)
 171                 return NULL;
 172         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 173         if (!buf->padding)
 174                 goto free_buf;
 175
 176         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 177         if (!buf->start)
 178                 goto free_buf;
 179
 180         buf->chan = chan;
 181         kref_get(&buf->chan->kref);
 182         return buf;
 183
 184 free_buf:
 185         kfree(buf->padding);
 186         kfree(buf);
 187         return NULL;
 188 }
 189
 190 /**
 191  *      relay_destroy_channel - free the channel struct
 192  *      @kref: target kernel reference that contains the relay channel
 193  *
 194  *      Should only be called from kref_put().
 195  */
 196 static void relay_destroy_channel(struct kref *kref)
 197 {
 198         struct rchan *chan = container_of(kref, struct rchan, kref);
 199         kfree(chan);
 200 }
 201
 202 /**
 203  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 204  *      @buf: the buffer struct
 205  */
 206 static void relay_destroy_buf(struct rchan_buf *buf)
 207 {
 208         struct rchan *chan = buf->chan;
 209         unsigned int i;
 210
 211         if (likely(buf->start)) {
 212                 vunmap(buf->start);
 213                 for (i = 0; i < buf->page_count; i++)
 214                         __free_page(buf->page_array[i]);
 215                 relay_free_page_array(buf->page_array);
 216         }
 217         *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
 218         kfree(buf->padding);
 219         kfree(buf);
 220         kref_put(&chan->kref, relay_destroy_channel);
 221 }
 222
 223 /**
 224  *      relay_remove_buf - remove a channel buffer
 225  *      @kref: target kernel reference that contains the relay buffer
 226  *
 227  *      Removes the file from the filesystem, which also frees the
 228  *      rchan_buf_struct and the channel buffer.  Should only be called from
 229  *      kref_put().
 230  */
 231 static void relay_remove_buf(struct kref *kref)
 232 {
 233         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 234         relay_destroy_buf(buf);
 235 }
 236
 237 /**
 238  *      relay_buf_empty - boolean, is the channel buffer empty?
 239  *      @buf: channel buffer
 240  *
 241  *      Returns 1 if the buffer is empty, 0 otherwise.
 242  */
 243 static int relay_buf_empty(struct rchan_buf *buf)
 244 {
 245         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 246 }
 247
 248 /**
 249  *      relay_buf_full - boolean, is the channel buffer full?
 250  *      @buf: channel buffer
 251  *
 252  *      Returns 1 if the buffer is full, 0 otherwise.
 253  */
 254 int relay_buf_full(struct rchan_buf *buf)
 255 {
 256         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 257         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 258 }
 259 EXPORT_SYMBOL_GPL(relay_buf_full);
 260
 261 /*
 262  * High-level relay kernel API and associated functions.
 263  */
 264
 265 /*
 266  * rchan_callback implementations defining default channel behavior.  Used
 267  * in place of corresponding NULL values in client callback struct.
 268  */
 269
 270 /*
 271  * subbuf_start() default callback.  Does nothing.
 272  */
 273 static int subbuf_start_default_callback (struct rchan_buf *buf,
 274                                           void *subbuf,
 275                                           void *prev_subbuf,
 276                                           size_t prev_padding)
 277 {
 278         if (relay_buf_full(buf))
 279                 return 0;
 280
 281         return 1;
 282 }
 283
 284 /*
 285  * buf_mapped() default callback.  Does nothing.
 286  */
 287 static void buf_mapped_default_callback(struct rchan_buf *buf,
 288                                         struct file *filp)
 289 {
 290 }
 291
 292 /*
 293  * buf_unmapped() default callback.  Does nothing.
 294  */
 295 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 296                                           struct file *filp)
 297 {
 298 }
 299
 300 /*
 301  * create_buf_file_create() default callback.  Does nothing.
 302  */
 303 static struct dentry *create_buf_file_default_callback(const char *filename,
 304                                                        struct dentry *parent,
 305                                                        umode_t mode,
 306                                                        struct rchan_buf *buf,
 307                                                        int *is_global)
 308 {
 309         return NULL;
 310 }
 311
 312 /*
 313  * remove_buf_file() default callback.  Does nothing.
 314  */
 315 static int remove_buf_file_default_callback(struct dentry *dentry)
 316 {
 317         return -EINVAL;
 318 }
 319
 320 /* relay channel default callbacks */
 321 static struct rchan_callbacks default_channel_callbacks = {
 322         .subbuf_start = subbuf_start_default_callback,
 323         .buf_mapped = buf_mapped_default_callback,
 324         .buf_unmapped = buf_unmapped_default_callback,
 325         .create_buf_file = create_buf_file_default_callback,
 326         .remove_buf_file = remove_buf_file_default_callback,
 327 };
 328
 329 /**
 330  *      wakeup_readers - wake up readers waiting on a channel
 331  *      @data: contains the channel buffer
 332  *
 333  *      This is the timer function used to defer reader waking.
 334  */
 335 static void wakeup_readers(unsigned long data)
 336 {
 337         struct rchan_buf *buf = (struct rchan_buf *)data;
 338         wake_up_interruptible(&buf->read_wait);
 339 }
 340
 341 /**
 342  *      __relay_reset - reset a channel buffer
 343  *      @buf: the channel buffer
 344  *      @init: 1 if this is a first-time initialization
 345  *
 346  *      See relay_reset() for description of effect.
 347  */
 348 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 349 {
 350         size_t i;
 351
 352         if (init) {
 353                 init_waitqueue_head(&buf->read_wait);
 354                 kref_init(&buf->kref);
 355                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 356         } else
 357                 del_timer_sync(&buf->timer);
 358
 359         buf->subbufs_produced = 0;
 360         buf->subbufs_consumed = 0;
 361         buf->bytes_consumed = 0;
 362         buf->finalized = 0;
 363         buf->data = buf->start;
 364         buf->offset = 0;
 365
 366         for (i = 0; i < buf->chan->n_subbufs; i++)
 367                 buf->padding[i] = 0;
 368
 369         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 370 }
 371
 372 /**
 373  *      relay_reset - reset the channel
 374  *      @chan: the channel
 375  *
 376  *      This has the effect of erasing all data from all channel buffers
 377  *      and restarting the channel in its initial state.  The buffers
 378  *      are not freed, so any mappings are still in effect.
 379  *
 380  *      NOTE. Care should be taken that the channel isn't actually
 381  *      being used by anything when this call is made.
 382  */
 383 void relay_reset(struct rchan *chan)
 384 {
 385         struct rchan_buf *buf;
 386         unsigned int i;
 387
 388         if (!chan)
 389                 return;
 390
 391         if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
 392                 __relay_reset(buf, 0);
 393                 return;
 394         }
 395
 396         mutex_lock(&relay_channels_mutex);
 397         for_each_possible_cpu(i)
 398                 if ((buf = *per_cpu_ptr(chan->buf, i)))
 399                         __relay_reset(buf, 0);
 400         mutex_unlock(&relay_channels_mutex);
 401 }
 402 EXPORT_SYMBOL_GPL(relay_reset);
 403
 404 static inline void relay_set_buf_dentry(struct rchan_buf *buf,
 405                                         struct dentry *dentry)
 406 {
 407         buf->dentry = dentry;
 408         d_inode(buf->dentry)->i_size = buf->early_bytes;
 409 }
 410
 411 static struct dentry *relay_create_buf_file(struct rchan *chan,
 412                                             struct rchan_buf *buf,
 413                                             unsigned int cpu)
 414 {
 415         struct dentry *dentry;
 416         char *tmpname;
 417
 418         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 419         if (!tmpname)
 420                 return NULL;
 421         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 422
 423         /* Create file in fs */
 424         dentry = chan->cb->create_buf_file(tmpname, chan->parent,
 425                                            S_IRUSR, buf,
 426                                            &chan->is_global);
 427
 428         kfree(tmpname);
 429
 430         return dentry;
 431 }
 432
 433 /*
 434  *      relay_open_buf - create a new relay channel buffer
 435  *
 436  *      used by relay_open() and CPU hotplug.
 437  */
 438 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 439 {
 440         struct rchan_buf *buf = NULL;
 441         struct dentry *dentry;
 442
 443         if (chan->is_global)
 444                 return *per_cpu_ptr(chan->buf, 0);
 445
 446         buf = relay_create_buf(chan);
 447         if (!buf)
 448                 return NULL;
 449
 450         if (chan->has_base_filename) {
 451                 dentry = relay_create_buf_file(chan, buf, cpu);
 452                 if (!dentry)
 453                         goto free_buf;
 454                 relay_set_buf_dentry(buf, dentry);
 455         } else {
 456                 /* Only retrieve global info, nothing more, nothing less */
 457                 dentry = chan->cb->create_buf_file(NULL, NULL,
 458                                                    S_IRUSR, buf,
 459                                                    &chan->is_global);
 460                 if (WARN_ON(dentry))
 461                         goto free_buf;
 462         }
 463
 464         buf->cpu = cpu;
 465         __relay_reset(buf, 1);
 466
 467         if(chan->is_global) {
 468                 *per_cpu_ptr(chan->buf, 0) = buf;
 469                 buf->cpu = 0;
 470         }
 471
 472         return buf;
 473
 474 free_buf:
 475         relay_destroy_buf(buf);
 476         return NULL;
 477 }
 478
 479 /**
 480  *      relay_close_buf - close a channel buffer
 481  *      @buf: channel buffer
 482  *
 483  *      Marks the buffer finalized and restores the default callbacks.
 484  *      The channel buffer and channel buffer data structure are then freed
 485  *      automatically when the last reference is given up.
 486  */
 487 static void relay_close_buf(struct rchan_buf *buf)
 488 {
 489         buf->finalized = 1;
 490         del_timer_sync(&buf->timer);
 491         buf->chan->cb->remove_buf_file(buf->dentry);
 492         kref_put(&buf->kref, relay_remove_buf);
 493 }
 494
 495 static void setup_callbacks(struct rchan *chan,
 496                                    struct rchan_callbacks *cb)
 497 {
 498         if (!cb) {
 499                 chan->cb = &default_channel_callbacks;
 500                 return;
 501         }
 502
 503         if (!cb->subbuf_start)
 504                 cb->subbuf_start = subbuf_start_default_callback;
 505         if (!cb->buf_mapped)
 506                 cb->buf_mapped = buf_mapped_default_callback;
 507         if (!cb->buf_unmapped)
 508                 cb->buf_unmapped = buf_unmapped_default_callback;
 509         if (!cb->create_buf_file)
 510                 cb->create_buf_file = create_buf_file_default_callback;
 511         if (!cb->remove_buf_file)
 512                 cb->remove_buf_file = remove_buf_file_default_callback;
 513         chan->cb = cb;
 514 }
 515
 516 /**
 517  *      relay_hotcpu_callback - CPU hotplug callback
 518  *      @nb: notifier block
 519  *      @action: hotplug action to take
 520  *      @hcpu: CPU number
 521  *
 522  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 523  */
 524 static int relay_hotcpu_callback(struct notifier_block *nb,
 525                                 unsigned long action,
 526                                 void *hcpu)
 527 {
 528         unsigned int hotcpu = (unsigned long)hcpu;
 529         struct rchan *chan;
 530         struct rchan_buf *buf;
 531
 532         switch(action) {
 533         case CPU_UP_PREPARE:
 534         case CPU_UP_PREPARE_FROZEN:
 535                 mutex_lock(&relay_channels_mutex);
 536                 list_for_each_entry(chan, &relay_channels, list) {
 537                         if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
 538                                 continue;
 539                         buf = relay_open_buf(chan, hotcpu);
 540                         if (!buf) {
 541                                 printk(KERN_ERR
 542                                         "relay_hotcpu_callback: cpu %d buffer "
 543                                         "creation failed\n", hotcpu);
 544                                 mutex_unlock(&relay_channels_mutex);
 545                                 return notifier_from_errno(-ENOMEM);
 546                         }
 547                         *per_cpu_ptr(chan->buf, hotcpu) = buf;
 548                 }
 549                 mutex_unlock(&relay_channels_mutex);
 550                 break;
 551         case CPU_DEAD:
 552         case CPU_DEAD_FROZEN:
 553                 /* No need to flush the cpu : will be flushed upon
 554                  * final relay_flush() call. */
 555                 break;
 556         }
 557         return NOTIFY_OK;
 558 }
 559
 560 /**
 561  *      relay_open - create a new relay channel
 562  *      @base_filename: base name of files to create, %NULL for buffering only
 563  *      @parent: dentry of parent directory, %NULL for root directory or buffer
 564  *      @subbuf_size: size of sub-buffers
 565  *      @n_subbufs: number of sub-buffers
 566  *      @cb: client callback functions
 567  *      @private_data: user-defined data
 568  *
 569  *      Returns channel pointer if successful, %NULL otherwise.
 570  *
 571  *      Creates a channel buffer for each cpu using the sizes and
 572  *      attributes specified.  The created channel buffer files
 573  *      will be named base_filename0...base_filenameN-1.  File
 574  *      permissions will be %S_IRUSR.
 575  *
 576  *      If opening a buffer (@parent = NULL) that you later wish to register
 577  *      in a filesystem, call relay_late_setup_files() once the @parent dentry
 578  *      is available.
 579  */
 580 struct rchan *relay_open(const char *base_filename,
 581                          struct dentry *parent,
 582                          size_t subbuf_size,
 583                          size_t n_subbufs,
 584                          struct rchan_callbacks *cb,
 585                          void *private_data)
 586 {
 587         unsigned int i;
 588         struct rchan *chan;
 589         struct rchan_buf *buf;
 590
 591         if (!(subbuf_size && n_subbufs))
 592                 return NULL;
 593         if (subbuf_size > UINT_MAX / n_subbufs)
 594                 return NULL;
 595
 596         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 597         if (!chan)
 598                 return NULL;
 599
 600         chan->buf = alloc_percpu(struct rchan_buf *);
 601         chan->version = RELAYFS_CHANNEL_VERSION;
 602         chan->n_subbufs = n_subbufs;
 603         chan->subbuf_size = subbuf_size;
 604         chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
 605         chan->parent = parent;
 606         chan->private_data = private_data;
 607         if (base_filename) {
 608                 chan->has_base_filename = 1;
 609                 strlcpy(chan->base_filename, base_filename, NAME_MAX);
 610         }
 611         setup_callbacks(chan, cb);
 612         kref_init(&chan->kref);
 613
 614         mutex_lock(&relay_channels_mutex);
 615         for_each_online_cpu(i) {
 616                 buf = relay_open_buf(chan, i);
 617                 if (!buf)
 618                         goto free_bufs;
 619                 *per_cpu_ptr(chan->buf, i) = buf;
 620         }
 621         list_add(&chan->list, &relay_channels);
 622         mutex_unlock(&relay_channels_mutex);
 623
 624         return chan;
 625
 626 free_bufs:
 627         for_each_possible_cpu(i) {
 628                 if ((buf = *per_cpu_ptr(chan->buf, i)))
 629                         relay_close_buf(buf);
 630         }
 631
 632         kref_put(&chan->kref, relay_destroy_channel);
 633         mutex_unlock(&relay_channels_mutex);
 634         kfree(chan);
 635         return NULL;
 636 }
 637 EXPORT_SYMBOL_GPL(relay_open);
 638
 639 struct rchan_percpu_buf_dispatcher {
 640         struct rchan_buf *buf;
 641         struct dentry *dentry;
 642 };
 643
 644 /* Called in atomic context. */
 645 static void __relay_set_buf_dentry(void *info)
 646 {
 647         struct rchan_percpu_buf_dispatcher *p = info;
 648
 649         relay_set_buf_dentry(p->buf, p->dentry);
 650 }
 651
 652 /**
 653  *      relay_late_setup_files - triggers file creation
 654  *      @chan: channel to operate on
 655  *      @base_filename: base name of files to create
 656  *      @parent: dentry of parent directory, %NULL for root directory
 657  *
 658  *      Returns 0 if successful, non-zero otherwise.
 659  *
 660  *      Use to setup files for a previously buffer-only channel created
 661  *      by relay_open() with a NULL parent dentry.
 662  *
 663  *      For example, this is useful for perfomring early tracing in kernel,
 664  *      before VFS is up and then exposing the early results once the dentry
 665  *      is available.
 666  */
 667 int relay_late_setup_files(struct rchan *chan,
 668                            const char *base_filename,
 669                            struct dentry *parent)
 670 {
 671         int err = 0;
 672         unsigned int i, curr_cpu;
 673         unsigned long flags;
 674         struct dentry *dentry;
 675         struct rchan_buf *buf;
 676         struct rchan_percpu_buf_dispatcher disp;
 677
 678         if (!chan || !base_filename)
 679                 return -EINVAL;
 680
 681         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 682
 683         mutex_lock(&relay_channels_mutex);
 684         /* Is chan already set up? */
 685         if (unlikely(chan->has_base_filename)) {
 686                 mutex_unlock(&relay_channels_mutex);
 687                 return -EEXIST;
 688         }
 689         chan->has_base_filename = 1;
 690         chan->parent = parent;
 691
 692         if (chan->is_global) {
 693                 err = -EINVAL;
 694                 buf = *per_cpu_ptr(chan->buf, 0);
 695                 if (!WARN_ON_ONCE(!buf)) {
 696                         dentry = relay_create_buf_file(chan, buf, 0);
 697                         if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
 698                                 relay_set_buf_dentry(buf, dentry);
 699                                 err = 0;
 700                         }
 701                 }
 702                 mutex_unlock(&relay_channels_mutex);
 703                 return err;
 704         }
 705
 706         curr_cpu = get_cpu();
 707         /*
 708          * The CPU hotplug notifier ran before us and created buffers with
 709          * no files associated. So it's safe to call relay_setup_buf_file()
 710          * on all currently online CPUs.
 711          */
 712         for_each_online_cpu(i) {
 713                 buf = *per_cpu_ptr(chan->buf, i);
 714                 if (unlikely(!buf)) {
 715                         WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
 716                         err = -EINVAL;
 717                         break;
 718                 }
 719
 720                 dentry = relay_create_buf_file(chan, buf, i);
 721                 if (unlikely(!dentry)) {
 722                         err = -EINVAL;
 723                         break;
 724                 }
 725
 726                 if (curr_cpu == i) {
 727                         local_irq_save(flags);
 728                         relay_set_buf_dentry(buf, dentry);
 729                         local_irq_restore(flags);
 730                 } else {
 731                         disp.buf = buf;
 732                         disp.dentry = dentry;
 733                         smp_mb();
 734                         /* relay_channels_mutex must be held, so wait. */
 735                         err = smp_call_function_single(i,
 736                                                        __relay_set_buf_dentry,
 737                                                        &disp, 1);
 738                 }
 739                 if (unlikely(err))
 740                         break;
 741         }
 742         put_cpu();
 743         mutex_unlock(&relay_channels_mutex);
 744
 745         return err;
 746 }
 747 EXPORT_SYMBOL_GPL(relay_late_setup_files);
 748
 749 /**
 750  *      relay_switch_subbuf - switch to a new sub-buffer
 751  *      @buf: channel buffer
 752  *      @length: size of current event
 753  *
 754  *      Returns either the length passed in or 0 if full.
 755  *
 756  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 757  *      updating padding counts, waking up readers, etc.
 758  */
 759 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 760 {
 761         void *old, *new;
 762         size_t old_subbuf, new_subbuf;
 763
 764         if (unlikely(length > buf->chan->subbuf_size))
 765                 goto toobig;
 766
 767         if (buf->offset != buf->chan->subbuf_size + 1) {
 768                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 769                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 770                 buf->padding[old_subbuf] = buf->prev_padding;
 771                 buf->subbufs_produced++;
 772                 if (buf->dentry)
 773                         d_inode(buf->dentry)->i_size +=
 774                                 buf->chan->subbuf_size -
 775                                 buf->padding[old_subbuf];
 776                 else
 777                         buf->early_bytes += buf->chan->subbuf_size -
 778                                             buf->padding[old_subbuf];
 779                 smp_mb();
 780                 if (waitqueue_active(&buf->read_wait))
 781                         /*
 782                          * Calling wake_up_interruptible() from here
 783                          * will deadlock if we happen to be logging
 784                          * from the scheduler (trying to re-grab
 785                          * rq->lock), so defer it.
 786                          */
 787                         mod_timer(&buf->timer, jiffies + 1);
 788         }
 789
 790         old = buf->data;
 791         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 792         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 793         buf->offset = 0;
 794         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 795                 buf->offset = buf->chan->subbuf_size + 1;
 796                 return 0;
 797         }
 798         buf->data = new;
 799         buf->padding[new_subbuf] = 0;
 800
 801         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 802                 goto toobig;
 803
 804         return length;
 805
 806 toobig:
 807         buf->chan->last_toobig = length;
 808         return 0;
 809 }
 810 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 811
 812 /**
 813  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 814  *      @chan: the channel
 815  *      @cpu: the cpu associated with the channel buffer to update
 816  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 817  *
 818  *      Adds to the channel buffer's consumed sub-buffer count.
 819  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 820  *      not the total consumed.
 821  *
 822  *      NOTE. Kernel clients don't need to call this function if the channel
 823  *      mode is 'overwrite'.
 824  */
 825 void relay_subbufs_consumed(struct rchan *chan,
 826                             unsigned int cpu,
 827                             size_t subbufs_consumed)
 828 {
 829         struct rchan_buf *buf;
 830
 831         if (!chan)
 832                 return;
 833
 834         buf = *per_cpu_ptr(chan->buf, cpu);
 835         if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
 836                 return;
 837
 838         if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
 839                 buf->subbufs_consumed = buf->subbufs_produced;
 840         else
 841                 buf->subbufs_consumed += subbufs_consumed;
 842 }
 843 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 844
 845 /**
 846  *      relay_close - close the channel
 847  *      @chan: the channel
 848  *
 849  *      Closes all channel buffers and frees the channel.
 850  */
 851 void relay_close(struct rchan *chan)
 852 {
 853         struct rchan_buf *buf;
 854         unsigned int i;
 855
 856         if (!chan)
 857                 return;
 858
 859         mutex_lock(&relay_channels_mutex);
 860         if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
 861                 relay_close_buf(buf);
 862         else
 863                 for_each_possible_cpu(i)
 864                         if ((buf = *per_cpu_ptr(chan->buf, i)))
 865                                 relay_close_buf(buf);
 866
 867         if (chan->last_toobig)
 868                 printk(KERN_WARNING "relay: one or more items not logged "
 869                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 870                        chan->last_toobig, chan->subbuf_size);
 871
 872         list_del(&chan->list);
 873         kref_put(&chan->kref, relay_destroy_channel);
 874         mutex_unlock(&relay_channels_mutex);
 875 }
 876 EXPORT_SYMBOL_GPL(relay_close);
 877
 878 /**
 879  *      relay_flush - close the channel
 880  *      @chan: the channel
 881  *
 882  *      Flushes all channel buffers, i.e. forces buffer switch.
 883  */
 884 void relay_flush(struct rchan *chan)
 885 {
 886         struct rchan_buf *buf;
 887         unsigned int i;
 888
 889         if (!chan)
 890                 return;
 891
 892         if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
 893                 relay_switch_subbuf(buf, 0);
 894                 return;
 895         }
 896
 897         mutex_lock(&relay_channels_mutex);
 898         for_each_possible_cpu(i)
 899                 if ((buf = *per_cpu_ptr(chan->buf, i)))
 900                         relay_switch_subbuf(buf, 0);
 901         mutex_unlock(&relay_channels_mutex);
 902 }
 903 EXPORT_SYMBOL_GPL(relay_flush);
 904
 905 /**
 906  *      relay_file_open - open file op for relay files
 907  *      @inode: the inode
 908  *      @filp: the file
 909  *
 910  *      Increments the channel buffer refcount.
 911  */
 912 static int relay_file_open(struct inode *inode, struct file *filp)
 913 {
 914         struct rchan_buf *buf = inode->i_private;
 915         kref_get(&buf->kref);
 916         filp->private_data = buf;
 917
 918         return nonseekable_open(inode, filp);
 919 }
 920
 921 /**
 922  *      relay_file_mmap - mmap file op for relay files
 923  *      @filp: the file
 924  *      @vma: the vma describing what to map
 925  *
 926  *      Calls upon relay_mmap_buf() to map the file into user space.
 927  */
 928 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 929 {
 930         struct rchan_buf *buf = filp->private_data;
 931         return relay_mmap_buf(buf, vma);
 932 }
 933
 934 /**
 935  *      relay_file_poll - poll file op for relay files
 936  *      @filp: the file
 937  *      @wait: poll table
 938  *
 939  *      Poll implemention.
 940  */
 941 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 942 {
 943         unsigned int mask = 0;
 944         struct rchan_buf *buf = filp->private_data;
 945
 946         if (buf->finalized)
 947                 return POLLERR;
 948
 949         if (filp->f_mode & FMODE_READ) {
 950                 poll_wait(filp, &buf->read_wait, wait);
 951                 if (!relay_buf_empty(buf))
 952                         mask |= POLLIN | POLLRDNORM;
 953         }
 954
 955         return mask;
 956 }
 957
 958 /**
 959  *      relay_file_release - release file op for relay files
 960  *      @inode: the inode
 961  *      @filp: the file
 962  *
 963  *      Decrements the channel refcount, as the filesystem is
 964  *      no longer using it.
 965  */
 966 static int relay_file_release(struct inode *inode, struct file *filp)
 967 {
 968         struct rchan_buf *buf = filp->private_data;
 969         kref_put(&buf->kref, relay_remove_buf);
 970
 971         return 0;
 972 }
 973
 974 /*
 975  *      relay_file_read_consume - update the consumed count for the buffer
 976  */
 977 static void relay_file_read_consume(struct rchan_buf *buf,
 978                                     size_t read_pos,
 979                                     size_t bytes_consumed)
 980 {
 981         size_t subbuf_size = buf->chan->subbuf_size;
 982         size_t n_subbufs = buf->chan->n_subbufs;
 983         size_t read_subbuf;
 984
 985         if (buf->subbufs_produced == buf->subbufs_consumed &&
 986             buf->offset == buf->bytes_consumed)
 987                 return;
 988
 989         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 990                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 991                 buf->bytes_consumed = 0;
 992         }
 993
 994         buf->bytes_consumed += bytes_consumed;
 995         if (!read_pos)
 996                 read_subbuf = buf->subbufs_consumed % n_subbufs;
 997         else
 998                 read_subbuf = read_pos / buf->chan->subbuf_size;
 999         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
1000                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
1001                     (buf->offset == subbuf_size))
1002                         return;
1003                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
1004                 buf->bytes_consumed = 0;
1005         }
1006 }
1007
1008 /*
1009  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
1010  */
1011 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
1012 {
1013         size_t subbuf_size = buf->chan->subbuf_size;
1014         size_t n_subbufs = buf->chan->n_subbufs;
1015         size_t produced = buf->subbufs_produced;
1016         size_t consumed = buf->subbufs_consumed;
1017
1018         relay_file_read_consume(buf, read_pos, 0);
1019
1020         consumed = buf->subbufs_consumed;
1021
1022         if (unlikely(buf->offset > subbuf_size)) {
1023                 if (produced == consumed)
1024                         return 0;
1025                 return 1;
1026         }
1027
1028         if (unlikely(produced - consumed >= n_subbufs)) {
1029                 consumed = produced - n_subbufs + 1;
1030                 buf->subbufs_consumed = consumed;
1031                 buf->bytes_consumed = 0;
1032         }
1033
1034         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
1035         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
1036
1037         if (consumed > produced)
1038                 produced += n_subbufs * subbuf_size;
1039
1040         if (consumed == produced) {
1041                 if (buf->offset == subbuf_size &&
1042                     buf->subbufs_produced > buf->subbufs_consumed)
1043                         return 1;
1044                 return 0;
1045         }
1046
1047         return 1;
1048 }
1049
1050 /**
1051  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
1052  *      @read_pos: file read position
1053  *      @buf: relay channel buffer
1054  */
1055 static size_t relay_file_read_subbuf_avail(size_t read_pos,
1056                                            struct rchan_buf *buf)
1057 {
1058         size_t padding, avail = 0;
1059         size_t read_subbuf, read_offset, write_subbuf, write_offset;
1060         size_t subbuf_size = buf->chan->subbuf_size;
1061
1062         write_subbuf = (buf->data - buf->start) / subbuf_size;
1063         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1064         read_subbuf = read_pos / subbuf_size;
1065         read_offset = read_pos % subbuf_size;
1066         padding = buf->padding[read_subbuf];
1067
1068         if (read_subbuf == write_subbuf) {
1069                 if (read_offset + padding < write_offset)
1070                         avail = write_offset - (read_offset + padding);
1071         } else
1072                 avail = (subbuf_size - padding) - read_offset;
1073
1074         return avail;
1075 }
1076
1077 /**
1078  *      relay_file_read_start_pos - find the first available byte to read
1079  *      @read_pos: file read position
1080  *      @buf: relay channel buffer
1081  *
1082  *      If the @read_pos is in the middle of padding, return the
1083  *      position of the first actually available byte, otherwise
1084  *      return the original value.
1085  */
1086 static size_t relay_file_read_start_pos(size_t read_pos,
1087                                         struct rchan_buf *buf)
1088 {
1089         size_t read_subbuf, padding, padding_start, padding_end;
1090         size_t subbuf_size = buf->chan->subbuf_size;
1091         size_t n_subbufs = buf->chan->n_subbufs;
1092         size_t consumed = buf->subbufs_consumed % n_subbufs;
1093
1094         if (!read_pos)
1095                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
1096         read_subbuf = read_pos / subbuf_size;
1097         padding = buf->padding[read_subbuf];
1098         padding_start = (read_subbuf + 1) * subbuf_size - padding;
1099         padding_end = (read_subbuf + 1) * subbuf_size;
1100         if (read_pos >= padding_start && read_pos < padding_end) {
1101                 read_subbuf = (read_subbuf + 1) % n_subbufs;
1102                 read_pos = read_subbuf * subbuf_size;
1103         }
1104
1105         return read_pos;
1106 }
1107
1108 /**
1109  *      relay_file_read_end_pos - return the new read position
1110  *      @read_pos: file read position
1111  *      @buf: relay channel buffer
1112  *      @count: number of bytes to be read
1113  */
1114 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1115                                       size_t read_pos,
1116                                       size_t count)
1117 {
1118         size_t read_subbuf, padding, end_pos;
1119         size_t subbuf_size = buf->chan->subbuf_size;
1120         size_t n_subbufs = buf->chan->n_subbufs;
1121
1122         read_subbuf = read_pos / subbuf_size;
1123         padding = buf->padding[read_subbuf];
1124         if (read_pos % subbuf_size + count + padding == subbuf_size)
1125                 end_pos = (read_subbuf + 1) * subbuf_size;
1126         else
1127                 end_pos = read_pos + count;
1128         if (end_pos >= subbuf_size * n_subbufs)
1129                 end_pos = 0;
1130
1131         return end_pos;
1132 }
1133
1134 /*
1135  *      subbuf_read_actor - read up to one subbuf's worth of data
1136  */
1137 static int subbuf_read_actor(size_t read_start,
1138                              struct rchan_buf *buf,
1139                              size_t avail,
1140                              read_descriptor_t *desc)
1141 {
1142         void *from;
1143         int ret = 0;
1144
1145         from = buf->start + read_start;
1146         ret = avail;
1147         if (copy_to_user(desc->arg.buf, from, avail)) {
1148                 desc->error = -EFAULT;
1149                 ret = 0;
1150         }
1151         desc->arg.data += ret;
1152         desc->written += ret;
1153         desc->count -= ret;
1154
1155         return ret;
1156 }
1157
1158 typedef int (*subbuf_actor_t) (size_t read_start,
1159                                struct rchan_buf *buf,
1160                                size_t avail,
1161                                read_descriptor_t *desc);
1162
1163 /*
1164  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1165  */
1166 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1167                                         subbuf_actor_t subbuf_actor,
1168                                         read_descriptor_t *desc)
1169 {
1170         struct rchan_buf *buf = filp->private_data;
1171         size_t read_start, avail;
1172         int ret;
1173
1174         if (!desc->count)
1175                 return 0;
1176
1177         inode_lock(file_inode(filp));
1178         do {
1179                 if (!relay_file_read_avail(buf, *ppos))
1180                         break;
1181
1182                 read_start = relay_file_read_start_pos(*ppos, buf);
1183                 avail = relay_file_read_subbuf_avail(read_start, buf);
1184                 if (!avail)
1185                         break;
1186
1187                 avail = min(desc->count, avail);
1188                 ret = subbuf_actor(read_start, buf, avail, desc);
1189                 if (desc->error < 0)
1190                         break;
1191
1192                 if (ret) {
1193                         relay_file_read_consume(buf, read_start, ret);
1194                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1195                 }
1196         } while (desc->count && ret);
1197         inode_unlock(file_inode(filp));
1198
1199         return desc->written;
1200 }
1201
1202 static ssize_t relay_file_read(struct file *filp,
1203                                char __user *buffer,
1204                                size_t count,
1205                                loff_t *ppos)
1206 {
1207         read_descriptor_t desc;
1208         desc.written = 0;
1209         desc.count = count;
1210         desc.arg.buf = buffer;
1211         desc.error = 0;
1212         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor, &desc);
1213 }
1214
1215 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1216 {
1217         rbuf->bytes_consumed += bytes_consumed;
1218
1219         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1220                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1221                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1222         }
1223 }
1224
1225 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1226                                    struct pipe_buffer *buf)
1227 {
1228         struct rchan_buf *rbuf;
1229
1230         rbuf = (struct rchan_buf *)page_private(buf->page);
1231         relay_consume_bytes(rbuf, buf->private);
1232 }
1233
1234 static const struct pipe_buf_operations relay_pipe_buf_ops = {
1235         .can_merge = 0,
1236         .confirm = generic_pipe_buf_confirm,
1237         .release = relay_pipe_buf_release,
1238         .steal = generic_pipe_buf_steal,
1239         .get = generic_pipe_buf_get,
1240 };
1241
1242 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1243 {
1244 }
1245
1246 /*
1247  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1248  */
1249 static ssize_t subbuf_splice_actor(struct file *in,
1250                                loff_t *ppos,
1251                                struct pipe_inode_info *pipe,
1252                                size_t len,
1253                                unsigned int flags,
1254                                int *nonpad_ret)
1255 {
1256         unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1257         struct rchan_buf *rbuf = in->private_data;
1258         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1259         uint64_t pos = (uint64_t) *ppos;
1260         uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1261         size_t read_start = (size_t) do_div(pos, alloc_size);
1262         size_t read_subbuf = read_start / subbuf_size;
1263         size_t padding = rbuf->padding[read_subbuf];
1264         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1265         struct page *pages[PIPE_DEF_BUFFERS];
1266         struct partial_page partial[PIPE_DEF_BUFFERS];
1267         struct splice_pipe_desc spd = {
1268                 .pages = pages,
1269                 .nr_pages = 0,
1270                 .nr_pages_max = PIPE_DEF_BUFFERS,
1271                 .partial = partial,
1272                 .flags = flags,
1273                 .ops = &relay_pipe_buf_ops,
1274                 .spd_release = relay_page_release,
1275         };
1276         ssize_t ret;
1277
1278         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1279                 return 0;
1280         if (splice_grow_spd(pipe, &spd))
1281                 return -ENOMEM;
1282
1283         /*
1284          * Adjust read len, if longer than what is available
1285          */
1286         if (len > (subbuf_size - read_start % subbuf_size))
1287                 len = subbuf_size - read_start % subbuf_size;
1288
1289         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1290         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1291         poff = read_start & ~PAGE_MASK;
1292         nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1293
1294         for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1295                 unsigned int this_len, this_end, private;
1296                 unsigned int cur_pos = read_start + total_len;
1297
1298                 if (!len)
1299                         break;
1300
1301                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1302                 private = this_len;
1303
1304                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1305                 spd.partial[spd.nr_pages].offset = poff;
1306
1307                 this_end = cur_pos + this_len;
1308                 if (this_end >= nonpad_end) {
1309                         this_len = nonpad_end - cur_pos;
1310                         private = this_len + padding;
1311                 }
1312                 spd.partial[spd.nr_pages].len = this_len;
1313                 spd.partial[spd.nr_pages].private = private;
1314
1315                 len -= this_len;
1316                 total_len += this_len;
1317                 poff = 0;
1318                 pidx = (pidx + 1) % subbuf_pages;
1319
1320                 if (this_end >= nonpad_end) {
1321                         spd.nr_pages++;
1322                         break;
1323                 }
1324         }
1325
1326         ret = 0;
1327         if (!spd.nr_pages)
1328                 goto out;
1329
1330         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1331         if (ret < 0 || ret < total_len)
1332                 goto out;
1333
1334         if (read_start + ret == nonpad_end)
1335                 ret += padding;
1336
1337 out:
1338         splice_shrink_spd(&spd);
1339         return ret;
1340 }
1341
1342 static ssize_t relay_file_splice_read(struct file *in,
1343                                       loff_t *ppos,
1344                                       struct pipe_inode_info *pipe,
1345                                       size_t len,
1346                                       unsigned int flags)
1347 {
1348         ssize_t spliced;
1349         int ret;
1350         int nonpad_ret = 0;
1351
1352         ret = 0;
1353         spliced = 0;
1354
1355         while (len && !spliced) {
1356                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1357                 if (ret < 0)
1358                         break;
1359                 else if (!ret) {
1360                         if (flags & SPLICE_F_NONBLOCK)
1361                                 ret = -EAGAIN;
1362                         break;
1363                 }
1364
1365                 *ppos += ret;
1366                 if (ret > len)
1367                         len = 0;
1368                 else
1369                         len -= ret;
1370                 spliced += nonpad_ret;
1371                 nonpad_ret = 0;
1372         }
1373
1374         if (spliced)
1375                 return spliced;
1376
1377         return ret;
1378 }
1379
1380 const struct file_operations relay_file_operations = {
1381         .open           = relay_file_open,
1382         .poll           = relay_file_poll,
1383         .mmap           = relay_file_mmap,
1384         .read           = relay_file_read,
1385         .llseek         = no_llseek,
1386         .release        = relay_file_release,
1387         .splice_read    = relay_file_splice_read,
1388 };
1389 EXPORT_SYMBOL_GPL(relay_file_operations);
1390
1391 static __init int relay_init(void)
1392 {
1393
1394         hotcpu_notifier(relay_hotcpu_callback, 0);
1395         return 0;
1396 }
1397
1398 early_initcall(relay_init);