kernel/relay.c

   1 /*
   2  * Public API and common code for kernel->userspace relay file support.
   3  *
   4  * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
   5  *
   6  * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
   7  * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
   8  *
   9  * Moved to kernel/relay.c by Paul Mundt, 2006.
  10  * November 2006 - CPU hotplug support by Mathieu Desnoyers
  11  *      (mathieu.desnoyers@polymtl.ca)
  12  *
  13  * This file is released under the GPL.
  14  */
  15 #include <linux/errno.h>
  16 #include <linux/stddef.h>
  17 #include <linux/slab.h>
  18 #include <linux/module.h>
  19 #include <linux/string.h>
  20 #include <linux/relay.h>
  21 #include <linux/vmalloc.h>
  22 #include <linux/mm.h>
  23 #include <linux/cpu.h>
  24 #include <linux/splice.h>
  25
  26 /* list of open channels, for cpu hotplug */
  27 static DEFINE_MUTEX(relay_channels_mutex);
  28 static LIST_HEAD(relay_channels);
  29
  30 /*
  31  * close() vm_op implementation for relay file mapping.
  32  */
  33 static void relay_file_mmap_close(struct vm_area_struct *vma)
  34 {
  35         struct rchan_buf *buf = vma->vm_private_data;
  36         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  37 }
  38
  39 /*
  40  * nopage() vm_op implementation for relay file mapping.
  41  */
  42 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
  43                                      unsigned long address,
  44                                      int *type)
  45 {
  46         struct page *page;
  47         struct rchan_buf *buf = vma->vm_private_data;
  48         unsigned long offset = address - vma->vm_start;
  49
  50         if (address > vma->vm_end)
  51                 return NOPAGE_SIGBUS; /* Disallow mremap */
  52         if (!buf)
  53                 return NOPAGE_OOM;
  54
  55         page = vmalloc_to_page(buf->start + offset);
  56         if (!page)
  57                 return NOPAGE_OOM;
  58         get_page(page);
  59
  60         if (type)
  61                 *type = VM_FAULT_MINOR;
  62
  63         return page;
  64 }
  65
  66 /*
  67  * vm_ops for relay file mappings.
  68  */
  69 static struct vm_operations_struct relay_file_mmap_ops = {
  70         .nopage = relay_buf_nopage,
  71         .close = relay_file_mmap_close,
  72 };
  73
  74 /**
  75  *      relay_mmap_buf: - mmap channel buffer to process address space
  76  *      @buf: relay channel buffer
  77  *      @vma: vm_area_struct describing memory to be mapped
  78  *
  79  *      Returns 0 if ok, negative on error
  80  *
  81  *      Caller should already have grabbed mmap_sem.
  82  */
  83 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
  84 {
  85         unsigned long length = vma->vm_end - vma->vm_start;
  86         struct file *filp = vma->vm_file;
  87
  88         if (!buf)
  89                 return -EBADF;
  90
  91         if (length != (unsigned long)buf->chan->alloc_size)
  92                 return -EINVAL;
  93
  94         vma->vm_ops = &relay_file_mmap_ops;
  95         vma->vm_private_data = buf;
  96         buf->chan->cb->buf_mapped(buf, filp);
  97
  98         return 0;
  99 }
 100
 101 /**
 102  *      relay_alloc_buf - allocate a channel buffer
 103  *      @buf: the buffer struct
 104  *      @size: total size of the buffer
 105  *
 106  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 107  *      passed in size will get page aligned, if it isn't already.
 108  */
 109 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 110 {
 111         void *mem;
 112         unsigned int i, j, n_pages;
 113
 114         *size = PAGE_ALIGN(*size);
 115         n_pages = *size >> PAGE_SHIFT;
 116
 117         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
 118         if (!buf->page_array)
 119                 return NULL;
 120
 121         for (i = 0; i < n_pages; i++) {
 122                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 123                 if (unlikely(!buf->page_array[i]))
 124                         goto depopulate;
 125                 set_page_private(buf->page_array[i], (unsigned long)buf);
 126         }
 127         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 128         if (!mem)
 129                 goto depopulate;
 130
 131         memset(mem, 0, *size);
 132         buf->page_count = n_pages;
 133         return mem;
 134
 135 depopulate:
 136         for (j = 0; j < i; j++)
 137                 __free_page(buf->page_array[j]);
 138         kfree(buf->page_array);
 139         return NULL;
 140 }
 141
 142 /**
 143  *      relay_create_buf - allocate and initialize a channel buffer
 144  *      @chan: the relay channel
 145  *
 146  *      Returns channel buffer if successful, %NULL otherwise.
 147  */
 148 static struct rchan_buf *relay_create_buf(struct rchan *chan)
 149 {
 150         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 151         if (!buf)
 152                 return NULL;
 153
 154         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 155         if (!buf->padding)
 156                 goto free_buf;
 157
 158         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 159         if (!buf->start)
 160                 goto free_buf;
 161
 162         buf->chan = chan;
 163         kref_get(&buf->chan->kref);
 164         return buf;
 165
 166 free_buf:
 167         kfree(buf->padding);
 168         kfree(buf);
 169         return NULL;
 170 }
 171
 172 /**
 173  *      relay_destroy_channel - free the channel struct
 174  *      @kref: target kernel reference that contains the relay channel
 175  *
 176  *      Should only be called from kref_put().
 177  */
 178 static void relay_destroy_channel(struct kref *kref)
 179 {
 180         struct rchan *chan = container_of(kref, struct rchan, kref);
 181         kfree(chan);
 182 }
 183
 184 /**
 185  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 186  *      @buf: the buffer struct
 187  */
 188 static void relay_destroy_buf(struct rchan_buf *buf)
 189 {
 190         struct rchan *chan = buf->chan;
 191         unsigned int i;
 192
 193         if (likely(buf->start)) {
 194                 vunmap(buf->start);
 195                 for (i = 0; i < buf->page_count; i++)
 196                         __free_page(buf->page_array[i]);
 197                 kfree(buf->page_array);
 198         }
 199         chan->buf[buf->cpu] = NULL;
 200         kfree(buf->padding);
 201         kfree(buf);
 202         kref_put(&chan->kref, relay_destroy_channel);
 203 }
 204
 205 /**
 206  *      relay_remove_buf - remove a channel buffer
 207  *      @kref: target kernel reference that contains the relay buffer
 208  *
 209  *      Removes the file from the fileystem, which also frees the
 210  *      rchan_buf_struct and the channel buffer.  Should only be called from
 211  *      kref_put().
 212  */
 213 static void relay_remove_buf(struct kref *kref)
 214 {
 215         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 216         buf->chan->cb->remove_buf_file(buf->dentry);
 217         relay_destroy_buf(buf);
 218 }
 219
 220 /**
 221  *      relay_buf_empty - boolean, is the channel buffer empty?
 222  *      @buf: channel buffer
 223  *
 224  *      Returns 1 if the buffer is empty, 0 otherwise.
 225  */
 226 static int relay_buf_empty(struct rchan_buf *buf)
 227 {
 228         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 229 }
 230
 231 /**
 232  *      relay_buf_full - boolean, is the channel buffer full?
 233  *      @buf: channel buffer
 234  *
 235  *      Returns 1 if the buffer is full, 0 otherwise.
 236  */
 237 int relay_buf_full(struct rchan_buf *buf)
 238 {
 239         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 240         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 241 }
 242 EXPORT_SYMBOL_GPL(relay_buf_full);
 243
 244 /*
 245  * High-level relay kernel API and associated functions.
 246  */
 247
 248 /*
 249  * rchan_callback implementations defining default channel behavior.  Used
 250  * in place of corresponding NULL values in client callback struct.
 251  */
 252
 253 /*
 254  * subbuf_start() default callback.  Does nothing.
 255  */
 256 static int subbuf_start_default_callback (struct rchan_buf *buf,
 257                                           void *subbuf,
 258                                           void *prev_subbuf,
 259                                           size_t prev_padding)
 260 {
 261         if (relay_buf_full(buf))
 262                 return 0;
 263
 264         return 1;
 265 }
 266
 267 /*
 268  * buf_mapped() default callback.  Does nothing.
 269  */
 270 static void buf_mapped_default_callback(struct rchan_buf *buf,
 271                                         struct file *filp)
 272 {
 273 }
 274
 275 /*
 276  * buf_unmapped() default callback.  Does nothing.
 277  */
 278 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 279                                           struct file *filp)
 280 {
 281 }
 282
 283 /*
 284  * create_buf_file_create() default callback.  Does nothing.
 285  */
 286 static struct dentry *create_buf_file_default_callback(const char *filename,
 287                                                        struct dentry *parent,
 288                                                        int mode,
 289                                                        struct rchan_buf *buf,
 290                                                        int *is_global)
 291 {
 292         return NULL;
 293 }
 294
 295 /*
 296  * remove_buf_file() default callback.  Does nothing.
 297  */
 298 static int remove_buf_file_default_callback(struct dentry *dentry)
 299 {
 300         return -EINVAL;
 301 }
 302
 303 /* relay channel default callbacks */
 304 static struct rchan_callbacks default_channel_callbacks = {
 305         .subbuf_start = subbuf_start_default_callback,
 306         .buf_mapped = buf_mapped_default_callback,
 307         .buf_unmapped = buf_unmapped_default_callback,
 308         .create_buf_file = create_buf_file_default_callback,
 309         .remove_buf_file = remove_buf_file_default_callback,
 310 };
 311
 312 /**
 313  *      wakeup_readers - wake up readers waiting on a channel
 314  *      @data: contains the channel buffer
 315  *
 316  *      This is the timer function used to defer reader waking.
 317  */
 318 static void wakeup_readers(unsigned long data)
 319 {
 320         struct rchan_buf *buf = (struct rchan_buf *)data;
 321         wake_up_interruptible(&buf->read_wait);
 322 }
 323
 324 /**
 325  *      __relay_reset - reset a channel buffer
 326  *      @buf: the channel buffer
 327  *      @init: 1 if this is a first-time initialization
 328  *
 329  *      See relay_reset() for description of effect.
 330  */
 331 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 332 {
 333         size_t i;
 334
 335         if (init) {
 336                 init_waitqueue_head(&buf->read_wait);
 337                 kref_init(&buf->kref);
 338                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 339         } else
 340                 del_timer_sync(&buf->timer);
 341
 342         buf->subbufs_produced = 0;
 343         buf->subbufs_consumed = 0;
 344         buf->bytes_consumed = 0;
 345         buf->finalized = 0;
 346         buf->data = buf->start;
 347         buf->offset = 0;
 348
 349         for (i = 0; i < buf->chan->n_subbufs; i++)
 350                 buf->padding[i] = 0;
 351
 352         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 353 }
 354
 355 /**
 356  *      relay_reset - reset the channel
 357  *      @chan: the channel
 358  *
 359  *      This has the effect of erasing all data from all channel buffers
 360  *      and restarting the channel in its initial state.  The buffers
 361  *      are not freed, so any mappings are still in effect.
 362  *
 363  *      NOTE. Care should be taken that the channel isn't actually
 364  *      being used by anything when this call is made.
 365  */
 366 void relay_reset(struct rchan *chan)
 367 {
 368         unsigned int i;
 369
 370         if (!chan)
 371                 return;
 372
 373         if (chan->is_global && chan->buf[0]) {
 374                 __relay_reset(chan->buf[0], 0);
 375                 return;
 376         }
 377
 378         mutex_lock(&relay_channels_mutex);
 379         for_each_online_cpu(i)
 380                 if (chan->buf[i])
 381                         __relay_reset(chan->buf[i], 0);
 382         mutex_unlock(&relay_channels_mutex);
 383 }
 384 EXPORT_SYMBOL_GPL(relay_reset);
 385
 386 /*
 387  *      relay_open_buf - create a new relay channel buffer
 388  *
 389  *      used by relay_open() and CPU hotplug.
 390  */
 391 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 392 {
 393         struct rchan_buf *buf = NULL;
 394         struct dentry *dentry;
 395         char *tmpname;
 396
 397         if (chan->is_global)
 398                 return chan->buf[0];
 399
 400         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 401         if (!tmpname)
 402                 goto end;
 403         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 404
 405         buf = relay_create_buf(chan);
 406         if (!buf)
 407                 goto free_name;
 408
 409         buf->cpu = cpu;
 410         __relay_reset(buf, 1);
 411
 412         /* Create file in fs */
 413         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
 414                                            buf, &chan->is_global);
 415         if (!dentry)
 416                 goto free_buf;
 417
 418         buf->dentry = dentry;
 419
 420         if(chan->is_global) {
 421                 chan->buf[0] = buf;
 422                 buf->cpu = 0;
 423         }
 424
 425         goto free_name;
 426
 427 free_buf:
 428         relay_destroy_buf(buf);
 429 free_name:
 430         kfree(tmpname);
 431 end:
 432         return buf;
 433 }
 434
 435 /**
 436  *      relay_close_buf - close a channel buffer
 437  *      @buf: channel buffer
 438  *
 439  *      Marks the buffer finalized and restores the default callbacks.
 440  *      The channel buffer and channel buffer data structure are then freed
 441  *      automatically when the last reference is given up.
 442  */
 443 static void relay_close_buf(struct rchan_buf *buf)
 444 {
 445         buf->finalized = 1;
 446         del_timer_sync(&buf->timer);
 447         kref_put(&buf->kref, relay_remove_buf);
 448 }
 449
 450 static void setup_callbacks(struct rchan *chan,
 451                                    struct rchan_callbacks *cb)
 452 {
 453         if (!cb) {
 454                 chan->cb = &default_channel_callbacks;
 455                 return;
 456         }
 457
 458         if (!cb->subbuf_start)
 459                 cb->subbuf_start = subbuf_start_default_callback;
 460         if (!cb->buf_mapped)
 461                 cb->buf_mapped = buf_mapped_default_callback;
 462         if (!cb->buf_unmapped)
 463                 cb->buf_unmapped = buf_unmapped_default_callback;
 464         if (!cb->create_buf_file)
 465                 cb->create_buf_file = create_buf_file_default_callback;
 466         if (!cb->remove_buf_file)
 467                 cb->remove_buf_file = remove_buf_file_default_callback;
 468         chan->cb = cb;
 469 }
 470
 471 /**
 472  *      relay_hotcpu_callback - CPU hotplug callback
 473  *      @nb: notifier block
 474  *      @action: hotplug action to take
 475  *      @hcpu: CPU number
 476  *
 477  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 478  */
 479 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 480                                 unsigned long action,
 481                                 void *hcpu)
 482 {
 483         unsigned int hotcpu = (unsigned long)hcpu;
 484         struct rchan *chan;
 485
 486         switch(action) {
 487         case CPU_UP_PREPARE:
 488         case CPU_UP_PREPARE_FROZEN:
 489                 mutex_lock(&relay_channels_mutex);
 490                 list_for_each_entry(chan, &relay_channels, list) {
 491                         if (chan->buf[hotcpu])
 492                                 continue;
 493                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 494                         if(!chan->buf[hotcpu]) {
 495                                 printk(KERN_ERR
 496                                         "relay_hotcpu_callback: cpu %d buffer "
 497                                         "creation failed\n", hotcpu);
 498                                 mutex_unlock(&relay_channels_mutex);
 499                                 return NOTIFY_BAD;
 500                         }
 501                 }
 502                 mutex_unlock(&relay_channels_mutex);
 503                 break;
 504         case CPU_DEAD:
 505         case CPU_DEAD_FROZEN:
 506                 /* No need to flush the cpu : will be flushed upon
 507                  * final relay_flush() call. */
 508                 break;
 509         }
 510         return NOTIFY_OK;
 511 }
 512
 513 /**
 514  *      relay_open - create a new relay channel
 515  *      @base_filename: base name of files to create
 516  *      @parent: dentry of parent directory, %NULL for root directory
 517  *      @subbuf_size: size of sub-buffers
 518  *      @n_subbufs: number of sub-buffers
 519  *      @cb: client callback functions
 520  *      @private_data: user-defined data
 521  *
 522  *      Returns channel pointer if successful, %NULL otherwise.
 523  *
 524  *      Creates a channel buffer for each cpu using the sizes and
 525  *      attributes specified.  The created channel buffer files
 526  *      will be named base_filename0...base_filenameN-1.  File
 527  *      permissions will be %S_IRUSR.
 528  */
 529 struct rchan *relay_open(const char *base_filename,
 530                          struct dentry *parent,
 531                          size_t subbuf_size,
 532                          size_t n_subbufs,
 533                          struct rchan_callbacks *cb,
 534                          void *private_data)
 535 {
 536         unsigned int i;
 537         struct rchan *chan;
 538         if (!base_filename)
 539                 return NULL;
 540
 541         if (!(subbuf_size && n_subbufs))
 542                 return NULL;
 543
 544         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 545         if (!chan)
 546                 return NULL;
 547
 548         chan->version = RELAYFS_CHANNEL_VERSION;
 549         chan->n_subbufs = n_subbufs;
 550         chan->subbuf_size = subbuf_size;
 551         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 552         chan->parent = parent;
 553         chan->private_data = private_data;
 554         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 555         setup_callbacks(chan, cb);
 556         kref_init(&chan->kref);
 557
 558         mutex_lock(&relay_channels_mutex);
 559         for_each_online_cpu(i) {
 560                 chan->buf[i] = relay_open_buf(chan, i);
 561                 if (!chan->buf[i])
 562                         goto free_bufs;
 563         }
 564         list_add(&chan->list, &relay_channels);
 565         mutex_unlock(&relay_channels_mutex);
 566
 567         return chan;
 568
 569 free_bufs:
 570         for_each_online_cpu(i) {
 571                 if (!chan->buf[i])
 572                         break;
 573                 relay_close_buf(chan->buf[i]);
 574         }
 575
 576         kref_put(&chan->kref, relay_destroy_channel);
 577         mutex_unlock(&relay_channels_mutex);
 578         return NULL;
 579 }
 580 EXPORT_SYMBOL_GPL(relay_open);
 581
 582 /**
 583  *      relay_switch_subbuf - switch to a new sub-buffer
 584  *      @buf: channel buffer
 585  *      @length: size of current event
 586  *
 587  *      Returns either the length passed in or 0 if full.
 588  *
 589  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 590  *      updating padding counts, waking up readers, etc.
 591  */
 592 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 593 {
 594         void *old, *new;
 595         size_t old_subbuf, new_subbuf;
 596
 597         if (unlikely(length > buf->chan->subbuf_size))
 598                 goto toobig;
 599
 600         if (buf->offset != buf->chan->subbuf_size + 1) {
 601                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 602                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 603                 buf->padding[old_subbuf] = buf->prev_padding;
 604                 buf->subbufs_produced++;
 605                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
 606                         buf->padding[old_subbuf];
 607                 smp_mb();
 608                 if (waitqueue_active(&buf->read_wait))
 609                         /*
 610                          * Calling wake_up_interruptible() from here
 611                          * will deadlock if we happen to be logging
 612                          * from the scheduler (trying to re-grab
 613                          * rq->lock), so defer it.
 614                          */
 615                         __mod_timer(&buf->timer, jiffies + 1);
 616         }
 617
 618         old = buf->data;
 619         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 620         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 621         buf->offset = 0;
 622         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 623                 buf->offset = buf->chan->subbuf_size + 1;
 624                 return 0;
 625         }
 626         buf->data = new;
 627         buf->padding[new_subbuf] = 0;
 628
 629         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 630                 goto toobig;
 631
 632         return length;
 633
 634 toobig:
 635         buf->chan->last_toobig = length;
 636         return 0;
 637 }
 638 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 639
 640 /**
 641  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 642  *      @chan: the channel
 643  *      @cpu: the cpu associated with the channel buffer to update
 644  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 645  *
 646  *      Adds to the channel buffer's consumed sub-buffer count.
 647  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 648  *      not the total consumed.
 649  *
 650  *      NOTE. Kernel clients don't need to call this function if the channel
 651  *      mode is 'overwrite'.
 652  */
 653 void relay_subbufs_consumed(struct rchan *chan,
 654                             unsigned int cpu,
 655                             size_t subbufs_consumed)
 656 {
 657         struct rchan_buf *buf;
 658
 659         if (!chan)
 660                 return;
 661
 662         if (cpu >= NR_CPUS || !chan->buf[cpu])
 663                 return;
 664
 665         buf = chan->buf[cpu];
 666         buf->subbufs_consumed += subbufs_consumed;
 667         if (buf->subbufs_consumed > buf->subbufs_produced)
 668                 buf->subbufs_consumed = buf->subbufs_produced;
 669 }
 670 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 671
 672 /**
 673  *      relay_close - close the channel
 674  *      @chan: the channel
 675  *
 676  *      Closes all channel buffers and frees the channel.
 677  */
 678 void relay_close(struct rchan *chan)
 679 {
 680         unsigned int i;
 681
 682         if (!chan)
 683                 return;
 684
 685         mutex_lock(&relay_channels_mutex);
 686         if (chan->is_global && chan->buf[0])
 687                 relay_close_buf(chan->buf[0]);
 688         else
 689                 for_each_possible_cpu(i)
 690                         if (chan->buf[i])
 691                                 relay_close_buf(chan->buf[i]);
 692
 693         if (chan->last_toobig)
 694                 printk(KERN_WARNING "relay: one or more items not logged "
 695                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 696                        chan->last_toobig, chan->subbuf_size);
 697
 698         list_del(&chan->list);
 699         kref_put(&chan->kref, relay_destroy_channel);
 700         mutex_unlock(&relay_channels_mutex);
 701 }
 702 EXPORT_SYMBOL_GPL(relay_close);
 703
 704 /**
 705  *      relay_flush - close the channel
 706  *      @chan: the channel
 707  *
 708  *      Flushes all channel buffers, i.e. forces buffer switch.
 709  */
 710 void relay_flush(struct rchan *chan)
 711 {
 712         unsigned int i;
 713
 714         if (!chan)
 715                 return;
 716
 717         if (chan->is_global && chan->buf[0]) {
 718                 relay_switch_subbuf(chan->buf[0], 0);
 719                 return;
 720         }
 721
 722         mutex_lock(&relay_channels_mutex);
 723         for_each_possible_cpu(i)
 724                 if (chan->buf[i])
 725                         relay_switch_subbuf(chan->buf[i], 0);
 726         mutex_unlock(&relay_channels_mutex);
 727 }
 728 EXPORT_SYMBOL_GPL(relay_flush);
 729
 730 /**
 731  *      relay_file_open - open file op for relay files
 732  *      @inode: the inode
 733  *      @filp: the file
 734  *
 735  *      Increments the channel buffer refcount.
 736  */
 737 static int relay_file_open(struct inode *inode, struct file *filp)
 738 {
 739         struct rchan_buf *buf = inode->i_private;
 740         kref_get(&buf->kref);
 741         filp->private_data = buf;
 742
 743         return 0;
 744 }
 745
 746 /**
 747  *      relay_file_mmap - mmap file op for relay files
 748  *      @filp: the file
 749  *      @vma: the vma describing what to map
 750  *
 751  *      Calls upon relay_mmap_buf() to map the file into user space.
 752  */
 753 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 754 {
 755         struct rchan_buf *buf = filp->private_data;
 756         return relay_mmap_buf(buf, vma);
 757 }
 758
 759 /**
 760  *      relay_file_poll - poll file op for relay files
 761  *      @filp: the file
 762  *      @wait: poll table
 763  *
 764  *      Poll implemention.
 765  */
 766 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 767 {
 768         unsigned int mask = 0;
 769         struct rchan_buf *buf = filp->private_data;
 770
 771         if (buf->finalized)
 772                 return POLLERR;
 773
 774         if (filp->f_mode & FMODE_READ) {
 775                 poll_wait(filp, &buf->read_wait, wait);
 776                 if (!relay_buf_empty(buf))
 777                         mask |= POLLIN | POLLRDNORM;
 778         }
 779
 780         return mask;
 781 }
 782
 783 /**
 784  *      relay_file_release - release file op for relay files
 785  *      @inode: the inode
 786  *      @filp: the file
 787  *
 788  *      Decrements the channel refcount, as the filesystem is
 789  *      no longer using it.
 790  */
 791 static int relay_file_release(struct inode *inode, struct file *filp)
 792 {
 793         struct rchan_buf *buf = filp->private_data;
 794         kref_put(&buf->kref, relay_remove_buf);
 795
 796         return 0;
 797 }
 798
 799 /*
 800  *      relay_file_read_consume - update the consumed count for the buffer
 801  */
 802 static void relay_file_read_consume(struct rchan_buf *buf,
 803                                     size_t read_pos,
 804                                     size_t bytes_consumed)
 805 {
 806         size_t subbuf_size = buf->chan->subbuf_size;
 807         size_t n_subbufs = buf->chan->n_subbufs;
 808         size_t read_subbuf;
 809
 810         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 811                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 812                 buf->bytes_consumed = 0;
 813         }
 814
 815         buf->bytes_consumed += bytes_consumed;
 816         if (!read_pos)
 817                 read_subbuf = buf->subbufs_consumed % n_subbufs;
 818         else
 819                 read_subbuf = read_pos / buf->chan->subbuf_size;
 820         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 821                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 822                     (buf->offset == subbuf_size))
 823                         return;
 824                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 825                 buf->bytes_consumed = 0;
 826         }
 827 }
 828
 829 /*
 830  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 831  */
 832 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 833 {
 834         size_t subbuf_size = buf->chan->subbuf_size;
 835         size_t n_subbufs = buf->chan->n_subbufs;
 836         size_t produced = buf->subbufs_produced;
 837         size_t consumed = buf->subbufs_consumed;
 838
 839         relay_file_read_consume(buf, read_pos, 0);
 840
 841         if (unlikely(buf->offset > subbuf_size)) {
 842                 if (produced == consumed)
 843                         return 0;
 844                 return 1;
 845         }
 846
 847         if (unlikely(produced - consumed >= n_subbufs)) {
 848                 consumed = produced - n_subbufs + 1;
 849                 buf->subbufs_consumed = consumed;
 850                 buf->bytes_consumed = 0;
 851         }
 852
 853         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 854         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 855
 856         if (consumed > produced)
 857                 produced += n_subbufs * subbuf_size;
 858
 859         if (consumed == produced)
 860                 return 0;
 861
 862         return 1;
 863 }
 864
 865 /**
 866  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
 867  *      @read_pos: file read position
 868  *      @buf: relay channel buffer
 869  */
 870 static size_t relay_file_read_subbuf_avail(size_t read_pos,
 871                                            struct rchan_buf *buf)
 872 {
 873         size_t padding, avail = 0;
 874         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 875         size_t subbuf_size = buf->chan->subbuf_size;
 876
 877         write_subbuf = (buf->data - buf->start) / subbuf_size;
 878         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 879         read_subbuf = read_pos / subbuf_size;
 880         read_offset = read_pos % subbuf_size;
 881         padding = buf->padding[read_subbuf];
 882
 883         if (read_subbuf == write_subbuf) {
 884                 if (read_offset + padding < write_offset)
 885                         avail = write_offset - (read_offset + padding);
 886         } else
 887                 avail = (subbuf_size - padding) - read_offset;
 888
 889         return avail;
 890 }
 891
 892 /**
 893  *      relay_file_read_start_pos - find the first available byte to read
 894  *      @read_pos: file read position
 895  *      @buf: relay channel buffer
 896  *
 897  *      If the @read_pos is in the middle of padding, return the
 898  *      position of the first actually available byte, otherwise
 899  *      return the original value.
 900  */
 901 static size_t relay_file_read_start_pos(size_t read_pos,
 902                                         struct rchan_buf *buf)
 903 {
 904         size_t read_subbuf, padding, padding_start, padding_end;
 905         size_t subbuf_size = buf->chan->subbuf_size;
 906         size_t n_subbufs = buf->chan->n_subbufs;
 907         size_t consumed = buf->subbufs_consumed % n_subbufs;
 908
 909         if (!read_pos)
 910                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
 911         read_subbuf = read_pos / subbuf_size;
 912         padding = buf->padding[read_subbuf];
 913         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 914         padding_end = (read_subbuf + 1) * subbuf_size;
 915         if (read_pos >= padding_start && read_pos < padding_end) {
 916                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 917                 read_pos = read_subbuf * subbuf_size;
 918         }
 919
 920         return read_pos;
 921 }
 922
 923 /**
 924  *      relay_file_read_end_pos - return the new read position
 925  *      @read_pos: file read position
 926  *      @buf: relay channel buffer
 927  *      @count: number of bytes to be read
 928  */
 929 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
 930                                       size_t read_pos,
 931                                       size_t count)
 932 {
 933         size_t read_subbuf, padding, end_pos;
 934         size_t subbuf_size = buf->chan->subbuf_size;
 935         size_t n_subbufs = buf->chan->n_subbufs;
 936
 937         read_subbuf = read_pos / subbuf_size;
 938         padding = buf->padding[read_subbuf];
 939         if (read_pos % subbuf_size + count + padding == subbuf_size)
 940                 end_pos = (read_subbuf + 1) * subbuf_size;
 941         else
 942                 end_pos = read_pos + count;
 943         if (end_pos >= subbuf_size * n_subbufs)
 944                 end_pos = 0;
 945
 946         return end_pos;
 947 }
 948
 949 /*
 950  *      subbuf_read_actor - read up to one subbuf's worth of data
 951  */
 952 static int subbuf_read_actor(size_t read_start,
 953                              struct rchan_buf *buf,
 954                              size_t avail,
 955                              read_descriptor_t *desc,
 956                              read_actor_t actor)
 957 {
 958         void *from;
 959         int ret = 0;
 960
 961         from = buf->start + read_start;
 962         ret = avail;
 963         if (copy_to_user(desc->arg.buf, from, avail)) {
 964                 desc->error = -EFAULT;
 965                 ret = 0;
 966         }
 967         desc->arg.data += ret;
 968         desc->written += ret;
 969         desc->count -= ret;
 970
 971         return ret;
 972 }
 973
 974 typedef int (*subbuf_actor_t) (size_t read_start,
 975                                struct rchan_buf *buf,
 976                                size_t avail,
 977                                read_descriptor_t *desc,
 978                                read_actor_t actor);
 979
 980 /*
 981  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
 982  */
 983 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
 984                                         subbuf_actor_t subbuf_actor,
 985                                         read_actor_t actor,
 986                                         read_descriptor_t *desc)
 987 {
 988         struct rchan_buf *buf = filp->private_data;
 989         size_t read_start, avail;
 990         int ret;
 991
 992         if (!desc->count)
 993                 return 0;
 994
 995         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
 996         do {
 997                 if (!relay_file_read_avail(buf, *ppos))
 998                         break;
 999
1000                 read_start = relay_file_read_start_pos(*ppos, buf);
1001                 avail = relay_file_read_subbuf_avail(read_start, buf);
1002                 if (!avail)
1003                         break;
1004
1005                 avail = min(desc->count, avail);
1006                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1007                 if (desc->error < 0)
1008                         break;
1009
1010                 if (ret) {
1011                         relay_file_read_consume(buf, read_start, ret);
1012                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1013                 }
1014         } while (desc->count && ret);
1015         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1016
1017         return desc->written;
1018 }
1019
1020 static ssize_t relay_file_read(struct file *filp,
1021                                char __user *buffer,
1022                                size_t count,
1023                                loff_t *ppos)
1024 {
1025         read_descriptor_t desc;
1026         desc.written = 0;
1027         desc.count = count;
1028         desc.arg.buf = buffer;
1029         desc.error = 0;
1030         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1031                                        NULL, &desc);
1032 }
1033
1034 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1035 {
1036         rbuf->bytes_consumed += bytes_consumed;
1037
1038         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1039                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1040                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1041         }
1042 }
1043
1044 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1045                                    struct pipe_buffer *buf)
1046 {
1047         struct rchan_buf *rbuf;
1048
1049         rbuf = (struct rchan_buf *)page_private(buf->page);
1050         relay_consume_bytes(rbuf, buf->private);
1051 }
1052
1053 static struct pipe_buf_operations relay_pipe_buf_ops = {
1054         .can_merge = 0,
1055         .map = generic_pipe_buf_map,
1056         .unmap = generic_pipe_buf_unmap,
1057         .confirm = generic_pipe_buf_confirm,
1058         .release = relay_pipe_buf_release,
1059         .steal = generic_pipe_buf_steal,
1060         .get = generic_pipe_buf_get,
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, 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         };
1091
1092         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1093                 return 0;
1094
1095         /*
1096          * Adjust read len, if longer than what is available
1097          */
1098         if (len > (subbuf_size - read_start % subbuf_size))
1099                 len = subbuf_size - read_start % subbuf_size;
1100
1101         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1102         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1103         poff = read_start & ~PAGE_MASK;
1104
1105         for (total_len = 0; spd.nr_pages < subbuf_pages; spd.nr_pages++) {
1106                 unsigned int this_len, this_end, private;
1107                 unsigned int cur_pos = read_start + total_len;
1108
1109                 if (!len)
1110                         break;
1111
1112                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1113                 private = this_len;
1114
1115                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1116                 spd.partial[spd.nr_pages].offset = poff;
1117
1118                 this_end = cur_pos + this_len;
1119                 if (this_end >= nonpad_end) {
1120                         this_len = nonpad_end - cur_pos;
1121                         private = this_len + padding;
1122                 }
1123                 spd.partial[spd.nr_pages].len = this_len;
1124                 spd.partial[spd.nr_pages].private = private;
1125
1126                 len -= this_len;
1127                 total_len += this_len;
1128                 poff = 0;
1129                 pidx = (pidx + 1) % subbuf_pages;
1130
1131                 if (this_end >= nonpad_end) {
1132                         spd.nr_pages++;
1133                         break;
1134                 }
1135         }
1136
1137         if (!spd.nr_pages)
1138                 return 0;
1139
1140         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1141         if (ret < 0 || ret < total_len)
1142                 return ret;
1143
1144         if (read_start + ret == nonpad_end)
1145                 ret += padding;
1146
1147         return ret;
1148 }
1149
1150 static ssize_t relay_file_splice_read(struct file *in,
1151                                       loff_t *ppos,
1152                                       struct pipe_inode_info *pipe,
1153                                       size_t len,
1154                                       unsigned int flags)
1155 {
1156         ssize_t spliced;
1157         int ret;
1158         int nonpad_ret = 0;
1159
1160         ret = 0;
1161         spliced = 0;
1162
1163         while (len) {
1164                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1165                 if (ret < 0)
1166                         break;
1167                 else if (!ret) {
1168                         if (spliced)
1169                                 break;
1170                         if (flags & SPLICE_F_NONBLOCK) {
1171                                 ret = -EAGAIN;
1172                                 break;
1173                         }
1174                 }
1175
1176                 *ppos += ret;
1177                 if (ret > len)
1178                         len = 0;
1179                 else
1180                         len -= ret;
1181                 spliced += nonpad_ret;
1182                 nonpad_ret = 0;
1183         }
1184
1185         if (spliced)
1186                 return spliced;
1187
1188         return ret;
1189 }
1190
1191 const struct file_operations relay_file_operations = {
1192         .open           = relay_file_open,
1193         .poll           = relay_file_poll,
1194         .mmap           = relay_file_mmap,
1195         .read           = relay_file_read,
1196         .llseek         = no_llseek,
1197         .release        = relay_file_release,
1198         .splice_read    = relay_file_splice_read,
1199 };
1200 EXPORT_SYMBOL_GPL(relay_file_operations);
1201
1202 static __init int relay_init(void)
1203 {
1204
1205         hotcpu_notifier(relay_hotcpu_callback, 0);
1206         return 0;
1207 }
1208
1209 module_init(relay_init);