git.oblomov.eu Git - linux-2.6/blob - kernel/relay.c

   1 /*
   2  * Public API and common code for kernel->userspace relay file support.
   3  *
   4  * See Documentation/filesystems/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  * 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_flags |= VM_DONTEXPAND;
  96         vma->vm_private_data = buf;
  97         buf->chan->cb->buf_mapped(buf, filp);
  98
  99         return 0;
 100 }
 101
 102 /**
 103  *      relay_alloc_buf - allocate a channel buffer
 104  *      @buf: the buffer struct
 105  *      @size: total size of the buffer
 106  *
 107  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 108  *      passed in size will get page aligned, if it isn't already.
 109  */
 110 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 111 {
 112         void *mem;
 113         unsigned int i, j, n_pages;
 114
 115         *size = PAGE_ALIGN(*size);
 116         n_pages = *size >> PAGE_SHIFT;
 117
 118         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
 119         if (!buf->page_array)
 120                 return NULL;
 121
 122         for (i = 0; i < n_pages; i++) {
 123                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 124                 if (unlikely(!buf->page_array[i]))
 125                         goto depopulate;
 126                 set_page_private(buf->page_array[i], (unsigned long)buf);
 127         }
 128         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 129         if (!mem)
 130                 goto depopulate;
 131
 132         memset(mem, 0, *size);
 133         buf->page_count = n_pages;
 134         return mem;
 135
 136 depopulate:
 137         for (j = 0; j < i; j++)
 138                 __free_page(buf->page_array[j]);
 139         kfree(buf->page_array);
 140         return NULL;
 141 }
 142
 143 /**
 144  *      relay_create_buf - allocate and initialize a channel buffer
 145  *      @chan: the relay channel
 146  *
 147  *      Returns channel buffer if successful, %NULL otherwise.
 148  */
 149 static struct rchan_buf *relay_create_buf(struct rchan *chan)
 150 {
 151         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 152         if (!buf)
 153                 return NULL;
 154
 155         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 156         if (!buf->padding)
 157                 goto free_buf;
 158
 159         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 160         if (!buf->start)
 161                 goto free_buf;
 162
 163         buf->chan = chan;
 164         kref_get(&buf->chan->kref);
 165         return buf;
 166
 167 free_buf:
 168         kfree(buf->padding);
 169         kfree(buf);
 170         return NULL;
 171 }
 172
 173 /**
 174  *      relay_destroy_channel - free the channel struct
 175  *      @kref: target kernel reference that contains the relay channel
 176  *
 177  *      Should only be called from kref_put().
 178  */
 179 static void relay_destroy_channel(struct kref *kref)
 180 {
 181         struct rchan *chan = container_of(kref, struct rchan, kref);
 182         kfree(chan);
 183 }
 184
 185 /**
 186  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 187  *      @buf: the buffer struct
 188  */
 189 static void relay_destroy_buf(struct rchan_buf *buf)
 190 {
 191         struct rchan *chan = buf->chan;
 192         unsigned int i;
 193
 194         if (likely(buf->start)) {
 195                 vunmap(buf->start);
 196                 for (i = 0; i < buf->page_count; i++)
 197                         __free_page(buf->page_array[i]);
 198                 kfree(buf->page_array);
 199         }
 200         chan->buf[buf->cpu] = NULL;
 201         kfree(buf->padding);
 202         kfree(buf);
 203         kref_put(&chan->kref, relay_destroy_channel);
 204 }
 205
 206 /**
 207  *      relay_remove_buf - remove a channel buffer
 208  *      @kref: target kernel reference that contains the relay buffer
 209  *
 210  *      Removes the file from the fileystem, which also frees the
 211  *      rchan_buf_struct and the channel buffer.  Should only be called from
 212  *      kref_put().
 213  */
 214 static void relay_remove_buf(struct kref *kref)
 215 {
 216         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 217         buf->chan->cb->remove_buf_file(buf->dentry);
 218         relay_destroy_buf(buf);
 219 }
 220
 221 /**
 222  *      relay_buf_empty - boolean, is the channel buffer empty?
 223  *      @buf: channel buffer
 224  *
 225  *      Returns 1 if the buffer is empty, 0 otherwise.
 226  */
 227 static int relay_buf_empty(struct rchan_buf *buf)
 228 {
 229         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 230 }
 231
 232 /**
 233  *      relay_buf_full - boolean, is the channel buffer full?
 234  *      @buf: channel buffer
 235  *
 236  *      Returns 1 if the buffer is full, 0 otherwise.
 237  */
 238 int relay_buf_full(struct rchan_buf *buf)
 239 {
 240         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 241         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 242 }
 243 EXPORT_SYMBOL_GPL(relay_buf_full);
 244
 245 /*
 246  * High-level relay kernel API and associated functions.
 247  */
 248
 249 /*
 250  * rchan_callback implementations defining default channel behavior.  Used
 251  * in place of corresponding NULL values in client callback struct.
 252  */
 253
 254 /*
 255  * subbuf_start() default callback.  Does nothing.
 256  */
 257 static int subbuf_start_default_callback (struct rchan_buf *buf,
 258                                           void *subbuf,
 259                                           void *prev_subbuf,
 260                                           size_t prev_padding)
 261 {
 262         if (relay_buf_full(buf))
 263                 return 0;
 264
 265         return 1;
 266 }
 267
 268 /*
 269  * buf_mapped() default callback.  Does nothing.
 270  */
 271 static void buf_mapped_default_callback(struct rchan_buf *buf,
 272                                         struct file *filp)
 273 {
 274 }
 275
 276 /*
 277  * buf_unmapped() default callback.  Does nothing.
 278  */
 279 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 280                                           struct file *filp)
 281 {
 282 }
 283
 284 /*
 285  * create_buf_file_create() default callback.  Does nothing.
 286  */
 287 static struct dentry *create_buf_file_default_callback(const char *filename,
 288                                                        struct dentry *parent,
 289                                                        int mode,
 290                                                        struct rchan_buf *buf,
 291                                                        int *is_global)
 292 {
 293         return NULL;
 294 }
 295
 296 /*
 297  * remove_buf_file() default callback.  Does nothing.
 298  */
 299 static int remove_buf_file_default_callback(struct dentry *dentry)
 300 {
 301         return -EINVAL;
 302 }
 303
 304 /* relay channel default callbacks */
 305 static struct rchan_callbacks default_channel_callbacks = {
 306         .subbuf_start = subbuf_start_default_callback,
 307         .buf_mapped = buf_mapped_default_callback,
 308         .buf_unmapped = buf_unmapped_default_callback,
 309         .create_buf_file = create_buf_file_default_callback,
 310         .remove_buf_file = remove_buf_file_default_callback,
 311 };
 312
 313 /**
 314  *      wakeup_readers - wake up readers waiting on a channel
 315  *      @data: contains the channel buffer
 316  *
 317  *      This is the timer function used to defer reader waking.
 318  */
 319 static void wakeup_readers(unsigned long data)
 320 {
 321         struct rchan_buf *buf = (struct rchan_buf *)data;
 322         wake_up_interruptible(&buf->read_wait);
 323 }
 324
 325 /**
 326  *      __relay_reset - reset a channel buffer
 327  *      @buf: the channel buffer
 328  *      @init: 1 if this is a first-time initialization
 329  *
 330  *      See relay_reset() for description of effect.
 331  */
 332 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 333 {
 334         size_t i;
 335
 336         if (init) {
 337                 init_waitqueue_head(&buf->read_wait);
 338                 kref_init(&buf->kref);
 339                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 340         } else
 341                 del_timer_sync(&buf->timer);
 342
 343         buf->subbufs_produced = 0;
 344         buf->subbufs_consumed = 0;
 345         buf->bytes_consumed = 0;
 346         buf->finalized = 0;
 347         buf->data = buf->start;
 348         buf->offset = 0;
 349
 350         for (i = 0; i < buf->chan->n_subbufs; i++)
 351                 buf->padding[i] = 0;
 352
 353         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 354 }
 355
 356 /**
 357  *      relay_reset - reset the channel
 358  *      @chan: the channel
 359  *
 360  *      This has the effect of erasing all data from all channel buffers
 361  *      and restarting the channel in its initial state.  The buffers
 362  *      are not freed, so any mappings are still in effect.
 363  *
 364  *      NOTE. Care should be taken that the channel isn't actually
 365  *      being used by anything when this call is made.
 366  */
 367 void relay_reset(struct rchan *chan)
 368 {
 369         unsigned int i;
 370
 371         if (!chan)
 372                 return;
 373
 374         if (chan->is_global && chan->buf[0]) {
 375                 __relay_reset(chan->buf[0], 0);
 376                 return;
 377         }
 378
 379         mutex_lock(&relay_channels_mutex);
 380         for_each_online_cpu(i)
 381                 if (chan->buf[i])
 382                         __relay_reset(chan->buf[i], 0);
 383         mutex_unlock(&relay_channels_mutex);
 384 }
 385 EXPORT_SYMBOL_GPL(relay_reset);
 386
 387 /*
 388  *      relay_open_buf - create a new relay channel buffer
 389  *
 390  *      used by relay_open() and CPU hotplug.
 391  */
 392 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 393 {
 394         struct rchan_buf *buf = NULL;
 395         struct dentry *dentry;
 396         char *tmpname;
 397
 398         if (chan->is_global)
 399                 return chan->buf[0];
 400
 401         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 402         if (!tmpname)
 403                 goto end;
 404         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 405
 406         buf = relay_create_buf(chan);
 407         if (!buf)
 408                 goto free_name;
 409
 410         buf->cpu = cpu;
 411         __relay_reset(buf, 1);
 412
 413         /* Create file in fs */
 414         dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
 415                                            buf, &chan->is_global);
 416         if (!dentry)
 417                 goto free_buf;
 418
 419         buf->dentry = dentry;
 420
 421         if(chan->is_global) {
 422                 chan->buf[0] = buf;
 423                 buf->cpu = 0;
 424         }
 425
 426         goto free_name;
 427
 428 free_buf:
 429         relay_destroy_buf(buf);
 430         buf = NULL;
 431 free_name:
 432         kfree(tmpname);
 433 end:
 434         return buf;
 435 }
 436
 437 /**
 438  *      relay_close_buf - close a channel buffer
 439  *      @buf: channel buffer
 440  *
 441  *      Marks the buffer finalized and restores the default callbacks.
 442  *      The channel buffer and channel buffer data structure are then freed
 443  *      automatically when the last reference is given up.
 444  */
 445 static void relay_close_buf(struct rchan_buf *buf)
 446 {
 447         buf->finalized = 1;
 448         del_timer_sync(&buf->timer);
 449         kref_put(&buf->kref, relay_remove_buf);
 450 }
 451
 452 static void setup_callbacks(struct rchan *chan,
 453                                    struct rchan_callbacks *cb)
 454 {
 455         if (!cb) {
 456                 chan->cb = &default_channel_callbacks;
 457                 return;
 458         }
 459
 460         if (!cb->subbuf_start)
 461                 cb->subbuf_start = subbuf_start_default_callback;
 462         if (!cb->buf_mapped)
 463                 cb->buf_mapped = buf_mapped_default_callback;
 464         if (!cb->buf_unmapped)
 465                 cb->buf_unmapped = buf_unmapped_default_callback;
 466         if (!cb->create_buf_file)
 467                 cb->create_buf_file = create_buf_file_default_callback;
 468         if (!cb->remove_buf_file)
 469                 cb->remove_buf_file = remove_buf_file_default_callback;
 470         chan->cb = cb;
 471 }
 472
 473 /**
 474  *      relay_hotcpu_callback - CPU hotplug callback
 475  *      @nb: notifier block
 476  *      @action: hotplug action to take
 477  *      @hcpu: CPU number
 478  *
 479  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 480  */
 481 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 482                                 unsigned long action,
 483                                 void *hcpu)
 484 {
 485         unsigned int hotcpu = (unsigned long)hcpu;
 486         struct rchan *chan;
 487
 488         switch(action) {
 489         case CPU_UP_PREPARE:
 490         case CPU_UP_PREPARE_FROZEN:
 491                 mutex_lock(&relay_channels_mutex);
 492                 list_for_each_entry(chan, &relay_channels, list) {
 493                         if (chan->buf[hotcpu])
 494                                 continue;
 495                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 496                         if(!chan->buf[hotcpu]) {
 497                                 printk(KERN_ERR
 498                                         "relay_hotcpu_callback: cpu %d buffer "
 499                                         "creation failed\n", hotcpu);
 500                                 mutex_unlock(&relay_channels_mutex);
 501                                 return NOTIFY_BAD;
 502                         }
 503                 }
 504                 mutex_unlock(&relay_channels_mutex);
 505                 break;
 506         case CPU_DEAD:
 507         case CPU_DEAD_FROZEN:
 508                 /* No need to flush the cpu : will be flushed upon
 509                  * final relay_flush() call. */
 510                 break;
 511         }
 512         return NOTIFY_OK;
 513 }
 514
 515 /**
 516  *      relay_open - create a new relay channel
 517  *      @base_filename: base name of files to create
 518  *      @parent: dentry of parent directory, %NULL for root directory
 519  *      @subbuf_size: size of sub-buffers
 520  *      @n_subbufs: number of sub-buffers
 521  *      @cb: client callback functions
 522  *      @private_data: user-defined data
 523  *
 524  *      Returns channel pointer if successful, %NULL otherwise.
 525  *
 526  *      Creates a channel buffer for each cpu using the sizes and
 527  *      attributes specified.  The created channel buffer files
 528  *      will be named base_filename0...base_filenameN-1.  File
 529  *      permissions will be %S_IRUSR.
 530  */
 531 struct rchan *relay_open(const char *base_filename,
 532                          struct dentry *parent,
 533                          size_t subbuf_size,
 534                          size_t n_subbufs,
 535                          struct rchan_callbacks *cb,
 536                          void *private_data)
 537 {
 538         unsigned int i;
 539         struct rchan *chan;
 540         if (!base_filename)
 541                 return NULL;
 542
 543         if (!(subbuf_size && n_subbufs))
 544                 return NULL;
 545
 546         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 547         if (!chan)
 548                 return NULL;
 549
 550         chan->version = RELAYFS_CHANNEL_VERSION;
 551         chan->n_subbufs = n_subbufs;
 552         chan->subbuf_size = subbuf_size;
 553         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 554         chan->parent = parent;
 555         chan->private_data = private_data;
 556         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 557         setup_callbacks(chan, cb);
 558         kref_init(&chan->kref);
 559
 560         mutex_lock(&relay_channels_mutex);
 561         for_each_online_cpu(i) {
 562                 chan->buf[i] = relay_open_buf(chan, i);
 563                 if (!chan->buf[i])
 564                         goto free_bufs;
 565         }
 566         list_add(&chan->list, &relay_channels);
 567         mutex_unlock(&relay_channels_mutex);
 568
 569         return chan;
 570
 571 free_bufs:
 572         for_each_online_cpu(i) {
 573                 if (!chan->buf[i])
 574                         break;
 575                 relay_close_buf(chan->buf[i]);
 576         }
 577
 578         kref_put(&chan->kref, relay_destroy_channel);
 579         mutex_unlock(&relay_channels_mutex);
 580         return NULL;
 581 }
 582 EXPORT_SYMBOL_GPL(relay_open);
 583
 584 /**
 585  *      relay_switch_subbuf - switch to a new sub-buffer
 586  *      @buf: channel buffer
 587  *      @length: size of current event
 588  *
 589  *      Returns either the length passed in or 0 if full.
 590  *
 591  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 592  *      updating padding counts, waking up readers, etc.
 593  */
 594 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 595 {
 596         void *old, *new;
 597         size_t old_subbuf, new_subbuf;
 598
 599         if (unlikely(length > buf->chan->subbuf_size))
 600                 goto toobig;
 601
 602         if (buf->offset != buf->chan->subbuf_size + 1) {
 603                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 604                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 605                 buf->padding[old_subbuf] = buf->prev_padding;
 606                 buf->subbufs_produced++;
 607                 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
 608                         buf->padding[old_subbuf];
 609                 smp_mb();
 610                 if (waitqueue_active(&buf->read_wait))
 611                         /*
 612                          * Calling wake_up_interruptible() from here
 613                          * will deadlock if we happen to be logging
 614                          * from the scheduler (trying to re-grab
 615                          * rq->lock), so defer it.
 616                          */
 617                         __mod_timer(&buf->timer, jiffies + 1);
 618         }
 619
 620         old = buf->data;
 621         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 622         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 623         buf->offset = 0;
 624         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 625                 buf->offset = buf->chan->subbuf_size + 1;
 626                 return 0;
 627         }
 628         buf->data = new;
 629         buf->padding[new_subbuf] = 0;
 630
 631         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 632                 goto toobig;
 633
 634         return length;
 635
 636 toobig:
 637         buf->chan->last_toobig = length;
 638         return 0;
 639 }
 640 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 641
 642 /**
 643  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 644  *      @chan: the channel
 645  *      @cpu: the cpu associated with the channel buffer to update
 646  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 647  *
 648  *      Adds to the channel buffer's consumed sub-buffer count.
 649  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 650  *      not the total consumed.
 651  *
 652  *      NOTE. Kernel clients don't need to call this function if the channel
 653  *      mode is 'overwrite'.
 654  */
 655 void relay_subbufs_consumed(struct rchan *chan,
 656                             unsigned int cpu,
 657                             size_t subbufs_consumed)
 658 {
 659         struct rchan_buf *buf;
 660
 661         if (!chan)
 662                 return;
 663
 664         if (cpu >= NR_CPUS || !chan->buf[cpu])
 665                 return;
 666
 667         buf = chan->buf[cpu];
 668         buf->subbufs_consumed += subbufs_consumed;
 669         if (buf->subbufs_consumed > buf->subbufs_produced)
 670                 buf->subbufs_consumed = buf->subbufs_produced;
 671 }
 672 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 673
 674 /**
 675  *      relay_close - close the channel
 676  *      @chan: the channel
 677  *
 678  *      Closes all channel buffers and frees the channel.
 679  */
 680 void relay_close(struct rchan *chan)
 681 {
 682         unsigned int i;
 683
 684         if (!chan)
 685                 return;
 686
 687         mutex_lock(&relay_channels_mutex);
 688         if (chan->is_global && chan->buf[0])
 689                 relay_close_buf(chan->buf[0]);
 690         else
 691                 for_each_possible_cpu(i)
 692                         if (chan->buf[i])
 693                                 relay_close_buf(chan->buf[i]);
 694
 695         if (chan->last_toobig)
 696                 printk(KERN_WARNING "relay: one or more items not logged "
 697                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 698                        chan->last_toobig, chan->subbuf_size);
 699
 700         list_del(&chan->list);
 701         kref_put(&chan->kref, relay_destroy_channel);
 702         mutex_unlock(&relay_channels_mutex);
 703 }
 704 EXPORT_SYMBOL_GPL(relay_close);
 705
 706 /**
 707  *      relay_flush - close the channel
 708  *      @chan: the channel
 709  *
 710  *      Flushes all channel buffers, i.e. forces buffer switch.
 711  */
 712 void relay_flush(struct rchan *chan)
 713 {
 714         unsigned int i;
 715
 716         if (!chan)
 717                 return;
 718
 719         if (chan->is_global && chan->buf[0]) {
 720                 relay_switch_subbuf(chan->buf[0], 0);
 721                 return;
 722         }
 723
 724         mutex_lock(&relay_channels_mutex);
 725         for_each_possible_cpu(i)
 726                 if (chan->buf[i])
 727                         relay_switch_subbuf(chan->buf[i], 0);
 728         mutex_unlock(&relay_channels_mutex);
 729 }
 730 EXPORT_SYMBOL_GPL(relay_flush);
 731
 732 /**
 733  *      relay_file_open - open file op for relay files
 734  *      @inode: the inode
 735  *      @filp: the file
 736  *
 737  *      Increments the channel buffer refcount.
 738  */
 739 static int relay_file_open(struct inode *inode, struct file *filp)
 740 {
 741         struct rchan_buf *buf = inode->i_private;
 742         kref_get(&buf->kref);
 743         filp->private_data = buf;
 744
 745         return 0;
 746 }
 747
 748 /**
 749  *      relay_file_mmap - mmap file op for relay files
 750  *      @filp: the file
 751  *      @vma: the vma describing what to map
 752  *
 753  *      Calls upon relay_mmap_buf() to map the file into user space.
 754  */
 755 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 756 {
 757         struct rchan_buf *buf = filp->private_data;
 758         return relay_mmap_buf(buf, vma);
 759 }
 760
 761 /**
 762  *      relay_file_poll - poll file op for relay files
 763  *      @filp: the file
 764  *      @wait: poll table
 765  *
 766  *      Poll implemention.
 767  */
 768 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 769 {
 770         unsigned int mask = 0;
 771         struct rchan_buf *buf = filp->private_data;
 772
 773         if (buf->finalized)
 774                 return POLLERR;
 775
 776         if (filp->f_mode & FMODE_READ) {
 777                 poll_wait(filp, &buf->read_wait, wait);
 778                 if (!relay_buf_empty(buf))
 779                         mask |= POLLIN | POLLRDNORM;
 780         }
 781
 782         return mask;
 783 }
 784
 785 /**
 786  *      relay_file_release - release file op for relay files
 787  *      @inode: the inode
 788  *      @filp: the file
 789  *
 790  *      Decrements the channel refcount, as the filesystem is
 791  *      no longer using it.
 792  */
 793 static int relay_file_release(struct inode *inode, struct file *filp)
 794 {
 795         struct rchan_buf *buf = filp->private_data;
 796         kref_put(&buf->kref, relay_remove_buf);
 797
 798         return 0;
 799 }
 800
 801 /*
 802  *      relay_file_read_consume - update the consumed count for the buffer
 803  */
 804 static void relay_file_read_consume(struct rchan_buf *buf,
 805                                     size_t read_pos,
 806                                     size_t bytes_consumed)
 807 {
 808         size_t subbuf_size = buf->chan->subbuf_size;
 809         size_t n_subbufs = buf->chan->n_subbufs;
 810         size_t read_subbuf;
 811
 812         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 813                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 814                 buf->bytes_consumed = 0;
 815         }
 816
 817         buf->bytes_consumed += bytes_consumed;
 818         if (!read_pos)
 819                 read_subbuf = buf->subbufs_consumed % n_subbufs;
 820         else
 821                 read_subbuf = read_pos / buf->chan->subbuf_size;
 822         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 823                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 824                     (buf->offset == subbuf_size))
 825                         return;
 826                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 827                 buf->bytes_consumed = 0;
 828         }
 829 }
 830
 831 /*
 832  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 833  */
 834 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 835 {
 836         size_t subbuf_size = buf->chan->subbuf_size;
 837         size_t n_subbufs = buf->chan->n_subbufs;
 838         size_t produced = buf->subbufs_produced;
 839         size_t consumed = buf->subbufs_consumed;
 840
 841         relay_file_read_consume(buf, read_pos, 0);
 842
 843         if (unlikely(buf->offset > subbuf_size)) {
 844                 if (produced == consumed)
 845                         return 0;
 846                 return 1;
 847         }
 848
 849         if (unlikely(produced - consumed >= n_subbufs)) {
 850                 consumed = produced - n_subbufs + 1;
 851                 buf->subbufs_consumed = consumed;
 852                 buf->bytes_consumed = 0;
 853         }
 854
 855         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 856         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 857
 858         if (consumed > produced)
 859                 produced += n_subbufs * subbuf_size;
 860
 861         if (consumed == produced)
 862                 return 0;
 863
 864         return 1;
 865 }
 866
 867 /**
 868  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
 869  *      @read_pos: file read position
 870  *      @buf: relay channel buffer
 871  */
 872 static size_t relay_file_read_subbuf_avail(size_t read_pos,
 873                                            struct rchan_buf *buf)
 874 {
 875         size_t padding, avail = 0;
 876         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 877         size_t subbuf_size = buf->chan->subbuf_size;
 878
 879         write_subbuf = (buf->data - buf->start) / subbuf_size;
 880         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 881         read_subbuf = read_pos / subbuf_size;
 882         read_offset = read_pos % subbuf_size;
 883         padding = buf->padding[read_subbuf];
 884
 885         if (read_subbuf == write_subbuf) {
 886                 if (read_offset + padding < write_offset)
 887                         avail = write_offset - (read_offset + padding);
 888         } else
 889                 avail = (subbuf_size - padding) - read_offset;
 890
 891         return avail;
 892 }
 893
 894 /**
 895  *      relay_file_read_start_pos - find the first available byte to read
 896  *      @read_pos: file read position
 897  *      @buf: relay channel buffer
 898  *
 899  *      If the @read_pos is in the middle of padding, return the
 900  *      position of the first actually available byte, otherwise
 901  *      return the original value.
 902  */
 903 static size_t relay_file_read_start_pos(size_t read_pos,
 904                                         struct rchan_buf *buf)
 905 {
 906         size_t read_subbuf, padding, padding_start, padding_end;
 907         size_t subbuf_size = buf->chan->subbuf_size;
 908         size_t n_subbufs = buf->chan->n_subbufs;
 909         size_t consumed = buf->subbufs_consumed % n_subbufs;
 910
 911         if (!read_pos)
 912                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
 913         read_subbuf = read_pos / subbuf_size;
 914         padding = buf->padding[read_subbuf];
 915         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 916         padding_end = (read_subbuf + 1) * subbuf_size;
 917         if (read_pos >= padding_start && read_pos < padding_end) {
 918                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 919                 read_pos = read_subbuf * subbuf_size;
 920         }
 921
 922         return read_pos;
 923 }
 924
 925 /**
 926  *      relay_file_read_end_pos - return the new read position
 927  *      @read_pos: file read position
 928  *      @buf: relay channel buffer
 929  *      @count: number of bytes to be read
 930  */
 931 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
 932                                       size_t read_pos,
 933                                       size_t count)
 934 {
 935         size_t read_subbuf, padding, end_pos;
 936         size_t subbuf_size = buf->chan->subbuf_size;
 937         size_t n_subbufs = buf->chan->n_subbufs;
 938
 939         read_subbuf = read_pos / subbuf_size;
 940         padding = buf->padding[read_subbuf];
 941         if (read_pos % subbuf_size + count + padding == subbuf_size)
 942                 end_pos = (read_subbuf + 1) * subbuf_size;
 943         else
 944                 end_pos = read_pos + count;
 945         if (end_pos >= subbuf_size * n_subbufs)
 946                 end_pos = 0;
 947
 948         return end_pos;
 949 }
 950
 951 /*
 952  *      subbuf_read_actor - read up to one subbuf's worth of data
 953  */
 954 static int subbuf_read_actor(size_t read_start,
 955                              struct rchan_buf *buf,
 956                              size_t avail,
 957                              read_descriptor_t *desc,
 958                              read_actor_t actor)
 959 {
 960         void *from;
 961         int ret = 0;
 962
 963         from = buf->start + read_start;
 964         ret = avail;
 965         if (copy_to_user(desc->arg.buf, from, avail)) {
 966                 desc->error = -EFAULT;
 967                 ret = 0;
 968         }
 969         desc->arg.data += ret;
 970         desc->written += ret;
 971         desc->count -= ret;
 972
 973         return ret;
 974 }
 975
 976 typedef int (*subbuf_actor_t) (size_t read_start,
 977                                struct rchan_buf *buf,
 978                                size_t avail,
 979                                read_descriptor_t *desc,
 980                                read_actor_t actor);
 981
 982 /*
 983  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
 984  */
 985 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
 986                                         subbuf_actor_t subbuf_actor,
 987                                         read_actor_t actor,
 988                                         read_descriptor_t *desc)
 989 {
 990         struct rchan_buf *buf = filp->private_data;
 991         size_t read_start, avail;
 992         int ret;
 993
 994         if (!desc->count)
 995                 return 0;
 996
 997         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
 998         do {
 999                 if (!relay_file_read_avail(buf, *ppos))
1000                         break;
1001
1002                 read_start = relay_file_read_start_pos(*ppos, buf);
1003                 avail = relay_file_read_subbuf_avail(read_start, buf);
1004                 if (!avail)
1005                         break;
1006
1007                 avail = min(desc->count, avail);
1008                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1009                 if (desc->error < 0)
1010                         break;
1011
1012                 if (ret) {
1013                         relay_file_read_consume(buf, read_start, ret);
1014                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1015                 }
1016         } while (desc->count && ret);
1017         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1018
1019         return desc->written;
1020 }
1021
1022 static ssize_t relay_file_read(struct file *filp,
1023                                char __user *buffer,
1024                                size_t count,
1025                                loff_t *ppos)
1026 {
1027         read_descriptor_t desc;
1028         desc.written = 0;
1029         desc.count = count;
1030         desc.arg.buf = buffer;
1031         desc.error = 0;
1032         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1033                                        NULL, &desc);
1034 }
1035
1036 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1037 {
1038         rbuf->bytes_consumed += bytes_consumed;
1039
1040         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1041                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1042                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1043         }
1044 }
1045
1046 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1047                                    struct pipe_buffer *buf)
1048 {
1049         struct rchan_buf *rbuf;
1050
1051         rbuf = (struct rchan_buf *)page_private(buf->page);
1052         relay_consume_bytes(rbuf, buf->private);
1053 }
1054
1055 static struct pipe_buf_operations relay_pipe_buf_ops = {
1056         .can_merge = 0,
1057         .map = generic_pipe_buf_map,
1058         .unmap = generic_pipe_buf_unmap,
1059         .confirm = generic_pipe_buf_confirm,
1060         .release = relay_pipe_buf_release,
1061         .steal = generic_pipe_buf_steal,
1062         .get = generic_pipe_buf_get,
1063 };
1064
1065 /*
1066  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1067  */
1068 static int subbuf_splice_actor(struct file *in,
1069                                loff_t *ppos,
1070                                struct pipe_inode_info *pipe,
1071                                size_t len,
1072                                unsigned int flags,
1073                                int *nonpad_ret)
1074 {
1075         unsigned int pidx, poff, total_len, subbuf_pages, ret;
1076         struct rchan_buf *rbuf = in->private_data;
1077         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1078         uint64_t pos = (uint64_t) *ppos;
1079         uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1080         size_t read_start = (size_t) do_div(pos, alloc_size);
1081         size_t read_subbuf = read_start / subbuf_size;
1082         size_t padding = rbuf->padding[read_subbuf];
1083         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1084         struct page *pages[PIPE_BUFFERS];
1085         struct partial_page partial[PIPE_BUFFERS];
1086         struct splice_pipe_desc spd = {
1087                 .pages = pages,
1088                 .nr_pages = 0,
1089                 .partial = partial,
1090                 .flags = flags,
1091                 .ops = &relay_pipe_buf_ops,
1092         };
1093
1094         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1095                 return 0;
1096
1097         /*
1098          * Adjust read len, if longer than what is available
1099          */
1100         if (len > (subbuf_size - read_start % subbuf_size))
1101                 len = subbuf_size - read_start % subbuf_size;
1102
1103         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1104         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1105         poff = read_start & ~PAGE_MASK;
1106
1107         for (total_len = 0; spd.nr_pages < subbuf_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);