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