SAFE public projects git trees. - safe/jmp/linux-2.6/blob - kernel/relay.c

   1 /*
   2  * Public API and common code for kernel->userspace relay file support.
   3  *
   4  * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
   5  *
   6  * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
   7  * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
   8  *
   9  * Moved to kernel/relay.c by Paul Mundt, 2006.
  10  *
  11  * This file is released under the GPL.
  12  */
  13 #include <linux/errno.h>
  14 #include <linux/stddef.h>
  15 #include <linux/slab.h>
  16 #include <linux/module.h>
  17 #include <linux/string.h>
  18 #include <linux/relay.h>
  19 #include <linux/vmalloc.h>
  20 #include <linux/mm.h>
  21
  22 /*
  23  * close() vm_op implementation for relay file mapping.
  24  */
  25 static void relay_file_mmap_close(struct vm_area_struct *vma)
  26 {
  27         struct rchan_buf *buf = vma->vm_private_data;
  28         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  29 }
  30
  31 /*
  32  * nopage() vm_op implementation for relay file mapping.
  33  */
  34 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
  35                                      unsigned long address,
  36                                      int *type)
  37 {
  38         struct page *page;
  39         struct rchan_buf *buf = vma->vm_private_data;
  40         unsigned long offset = address - vma->vm_start;
  41
  42         if (address > vma->vm_end)
  43                 return NOPAGE_SIGBUS; /* Disallow mremap */
  44         if (!buf)
  45                 return NOPAGE_OOM;
  46
  47         page = vmalloc_to_page(buf->start + offset);
  48         if (!page)
  49                 return NOPAGE_OOM;
  50         get_page(page);
  51
  52         if (type)
  53                 *type = VM_FAULT_MINOR;
  54
  55         return page;
  56 }
  57
  58 /*
  59  * vm_ops for relay file mappings.
  60  */
  61 static struct vm_operations_struct relay_file_mmap_ops = {
  62         .nopage = relay_buf_nopage,
  63         .close = relay_file_mmap_close,
  64 };
  65
  66 /**
  67  *      relay_mmap_buf: - mmap channel buffer to process address space
  68  *      @buf: relay channel buffer
  69  *      @vma: vm_area_struct describing memory to be mapped
  70  *
  71  *      Returns 0 if ok, negative on error
  72  *
  73  *      Caller should already have grabbed mmap_sem.
  74  */
  75 int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
  76 {
  77         unsigned long length = vma->vm_end - vma->vm_start;
  78         struct file *filp = vma->vm_file;
  79
  80         if (!buf)
  81                 return -EBADF;
  82
  83         if (length != (unsigned long)buf->chan->alloc_size)
  84                 return -EINVAL;
  85
  86         vma->vm_ops = &relay_file_mmap_ops;
  87         vma->vm_private_data = buf;
  88         buf->chan->cb->buf_mapped(buf, filp);
  89
  90         return 0;
  91 }
  92
  93 /**
  94  *      relay_alloc_buf - allocate a channel buffer
  95  *      @buf: the buffer struct
  96  *      @size: total size of the buffer
  97  *
  98  *      Returns a pointer to the resulting buffer, NULL if unsuccessful
  99  */
 100 static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size)
 101 {
 102         void *mem;
 103         unsigned int i, j, n_pages;
 104
 105         size = PAGE_ALIGN(size);
 106         n_pages = size >> PAGE_SHIFT;
 107
 108         buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
 109         if (!buf->page_array)
 110                 return NULL;
 111
 112         for (i = 0; i < n_pages; i++) {
 113                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 114                 if (unlikely(!buf->page_array[i]))
 115                         goto depopulate;
 116         }
 117         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 118         if (!mem)
 119                 goto depopulate;
 120
 121         memset(mem, 0, size);
 122         buf->page_count = n_pages;
 123         return mem;
 124
 125 depopulate:
 126         for (j = 0; j < i; j++)
 127                 __free_page(buf->page_array[j]);
 128         kfree(buf->page_array);
 129         return NULL;
 130 }
 131
 132 /**
 133  *      relay_create_buf - allocate and initialize a channel buffer
 134  *      @alloc_size: size of the buffer to allocate
 135  *      @n_subbufs: number of sub-buffers in the channel
 136  *
 137  *      Returns channel buffer if successful, NULL otherwise
 138  */
 139 struct rchan_buf *relay_create_buf(struct rchan *chan)
 140 {
 141         struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
 142         if (!buf)
 143                 return NULL;
 144
 145         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 146         if (!buf->padding)
 147                 goto free_buf;
 148
 149         buf->start = relay_alloc_buf(buf, chan->alloc_size);
 150         if (!buf->start)
 151                 goto free_buf;
 152
 153         buf->chan = chan;
 154         kref_get(&buf->chan->kref);
 155         return buf;
 156
 157 free_buf:
 158         kfree(buf->padding);
 159         kfree(buf);
 160         return NULL;
 161 }
 162
 163 /**
 164  *      relay_destroy_channel - free the channel struct
 165  *
 166  *      Should only be called from kref_put().
 167  */
 168 void relay_destroy_channel(struct kref *kref)
 169 {
 170         struct rchan *chan = container_of(kref, struct rchan, kref);
 171         kfree(chan);
 172 }
 173
 174 /**
 175  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 176  *      @buf: the buffer struct
 177  */
 178 void relay_destroy_buf(struct rchan_buf *buf)
 179 {
 180         struct rchan *chan = buf->chan;
 181         unsigned int i;
 182
 183         if (likely(buf->start)) {
 184                 vunmap(buf->start);
 185                 for (i = 0; i < buf->page_count; i++)
 186                         __free_page(buf->page_array[i]);
 187                 kfree(buf->page_array);
 188         }
 189         kfree(buf->padding);
 190         kfree(buf);
 191         kref_put(&chan->kref, relay_destroy_channel);
 192 }
 193
 194 /**
 195  *      relay_remove_buf - remove a channel buffer
 196  *
 197  *      Removes the file from the fileystem, which also frees the
 198  *      rchan_buf_struct and the channel buffer.  Should only be called from
 199  *      kref_put().
 200  */
 201 void relay_remove_buf(struct kref *kref)
 202 {
 203         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 204         buf->chan->cb->remove_buf_file(buf->dentry);
 205         relay_destroy_buf(buf);
 206 }
 207
 208 /**
 209  *      relay_buf_empty - boolean, is the channel buffer empty?
 210  *      @buf: channel buffer
 211  *
 212  *      Returns 1 if the buffer is empty, 0 otherwise.
 213  */
 214 int relay_buf_empty(struct rchan_buf *buf)
 215 {
 216         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 217 }
 218 EXPORT_SYMBOL_GPL(relay_buf_empty);
 219
 220 /**
 221  *      relay_buf_full - boolean, is the channel buffer full?
 222  *      @buf: channel buffer
 223  *
 224  *      Returns 1 if the buffer is full, 0 otherwise.
 225  */
 226 int relay_buf_full(struct rchan_buf *buf)
 227 {
 228         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 229         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 230 }
 231 EXPORT_SYMBOL_GPL(relay_buf_full);
 232
 233 /*
 234  * High-level relay kernel API and associated functions.
 235  */
 236
 237 /*
 238  * rchan_callback implementations defining default channel behavior.  Used
 239  * in place of corresponding NULL values in client callback struct.
 240  */
 241
 242 /*
 243  * subbuf_start() default callback.  Does nothing.
 244  */
 245 static int subbuf_start_default_callback (struct rchan_buf *buf,
 246                                           void *subbuf,
 247                                           void *prev_subbuf,
 248                                           size_t prev_padding)
 249 {
 250         if (relay_buf_full(buf))
 251                 return 0;
 252
 253         return 1;
 254 }
 255
 256 /*
 257  * buf_mapped() default callback.  Does nothing.
 258  */
 259 static void buf_mapped_default_callback(struct rchan_buf *buf,
 260                                         struct file *filp)
 261 {
 262 }
 263
 264 /*
 265  * buf_unmapped() default callback.  Does nothing.
 266  */
 267 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 268                                           struct file *filp)
 269 {
 270 }
 271
 272 /*
 273  * create_buf_file_create() default callback.  Does nothing.
 274  */
 275 static struct dentry *create_buf_file_default_callback(const char *filename,
 276                                                        struct dentry *parent,
 277                                                        int mode,
 278                                                        struct rchan_buf *buf,
 279                                                        int *is_global)
 280 {
 281         return NULL;
 282 }
 283
 284 /*
 285  * remove_buf_file() default callback.  Does nothing.
 286  */
 287 static int remove_buf_file_default_callback(struct dentry *dentry)
 288 {
 289         return -EINVAL;
 290 }
 291
 292 /* relay channel default callbacks */
 293 static struct rchan_callbacks default_channel_callbacks = {
 294         .subbuf_start = subbuf_start_default_callback,
 295         .buf_mapped = buf_mapped_default_callback,
 296         .buf_unmapped = buf_unmapped_default_callback,
 297         .create_buf_file = create_buf_file_default_callback,
 298         .remove_buf_file = remove_buf_file_default_callback,
 299 };
 300
 301 /**
 302  *      wakeup_readers - wake up readers waiting on a channel
 303  *      @private: the channel buffer
 304  *
 305  *      This is the work function used to defer reader waking.  The
 306  *      reason waking is deferred is that calling directly from write
 307  *      causes problems if you're writing from say the scheduler.
 308  */
 309 static void wakeup_readers(void *private)
 310 {
 311         struct rchan_buf *buf = private;
 312         wake_up_interruptible(&buf->read_wait);
 313 }
 314
 315 /**
 316  *      __relay_reset - reset a channel buffer
 317  *      @buf: the channel buffer
 318  *      @init: 1 if this is a first-time initialization
 319  *
 320  *      See relay_reset for description of effect.
 321  */
 322 static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
 323 {
 324         size_t i;
 325
 326         if (init) {
 327                 init_waitqueue_head(&buf->read_wait);
 328                 kref_init(&buf->kref);
 329                 INIT_WORK(&buf->wake_readers, NULL, NULL);
 330         } else {
 331                 cancel_delayed_work(&buf->wake_readers);
 332                 flush_scheduled_work();
 333         }
 334
 335         buf->subbufs_produced = 0;
 336         buf->subbufs_consumed = 0;
 337         buf->bytes_consumed = 0;
 338         buf->finalized = 0;
 339         buf->data = buf->start;
 340         buf->offset = 0;
 341
 342         for (i = 0; i < buf->chan->n_subbufs; i++)
 343                 buf->padding[i] = 0;
 344
 345         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 346 }
 347
 348 /**
 349  *      relay_reset - reset the channel
 350  *      @chan: the channel
 351  *
 352  *      This has the effect of erasing all data from all channel buffers
 353  *      and restarting the channel in its initial state.  The buffers
 354  *      are not freed, so any mappings are still in effect.
 355  *
 356  *      NOTE: Care should be taken that the channel isn't actually
 357  *      being used by anything when this call is made.
 358  */
 359 void relay_reset(struct rchan *chan)
 360 {
 361         unsigned int i;
 362         struct rchan_buf *prev = NULL;
 363
 364         if (!chan)
 365                 return;
 366
 367         for (i = 0; i < NR_CPUS; i++) {
 368                 if (!chan->buf[i] || chan->buf[i] == prev)
 369                         break;
 370                 __relay_reset(chan->buf[i], 0);
 371                 prev = chan->buf[i];
 372         }
 373 }
 374 EXPORT_SYMBOL_GPL(relay_reset);
 375
 376 /**
 377  *      relay_open_buf - create a new relay channel buffer
 378  *
 379  *      Internal - used by relay_open().
 380  */
 381 static struct rchan_buf *relay_open_buf(struct rchan *chan,
 382                                         const char *filename,
 383                                         struct dentry *parent,
 384                                         int *is_global)
 385 {
 386         struct rchan_buf *buf;
 387         struct dentry *dentry;
 388
 389         if (*is_global)
 390                 return chan->buf[0];
 391
 392         buf = relay_create_buf(chan);
 393         if (!buf)
 394                 return NULL;
 395
 396         /* Create file in fs */
 397         dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
 398                                            buf, is_global);
 399         if (!dentry) {
 400                 relay_destroy_buf(buf);
 401                 return NULL;
 402         }
 403
 404         buf->dentry = dentry;
 405         __relay_reset(buf, 1);
 406
 407         return buf;
 408 }
 409
 410 /**
 411  *      relay_close_buf - close a channel buffer
 412  *      @buf: channel buffer
 413  *
 414  *      Marks the buffer finalized and restores the default callbacks.
 415  *      The channel buffer and channel buffer data structure are then freed
 416  *      automatically when the last reference is given up.
 417  */
 418 static inline void relay_close_buf(struct rchan_buf *buf)
 419 {
 420         buf->finalized = 1;
 421         cancel_delayed_work(&buf->wake_readers);
 422         flush_scheduled_work();
 423         kref_put(&buf->kref, relay_remove_buf);
 424 }
 425
 426 static inline void setup_callbacks(struct rchan *chan,
 427                                    struct rchan_callbacks *cb)
 428 {
 429         if (!cb) {
 430                 chan->cb = &default_channel_callbacks;
 431                 return;
 432         }
 433
 434         if (!cb->subbuf_start)
 435                 cb->subbuf_start = subbuf_start_default_callback;
 436         if (!cb->buf_mapped)
 437                 cb->buf_mapped = buf_mapped_default_callback;
 438         if (!cb->buf_unmapped)
 439                 cb->buf_unmapped = buf_unmapped_default_callback;
 440         if (!cb->create_buf_file)
 441                 cb->create_buf_file = create_buf_file_default_callback;
 442         if (!cb->remove_buf_file)
 443                 cb->remove_buf_file = remove_buf_file_default_callback;
 444         chan->cb = cb;
 445 }
 446
 447 /**
 448  *      relay_open - create a new relay channel
 449  *      @base_filename: base name of files to create
 450  *      @parent: dentry of parent directory, NULL for root directory
 451  *      @subbuf_size: size of sub-buffers
 452  *      @n_subbufs: number of sub-buffers
 453  *      @cb: client callback functions
 454  *
 455  *      Returns channel pointer if successful, NULL otherwise.
 456  *
 457  *      Creates a channel buffer for each cpu using the sizes and
 458  *      attributes specified.  The created channel buffer files
 459  *      will be named base_filename0...base_filenameN-1.  File
 460  *      permissions will be S_IRUSR.
 461  */
 462 struct rchan *relay_open(const char *base_filename,
 463                          struct dentry *parent,
 464                          size_t subbuf_size,
 465                          size_t n_subbufs,
 466                          struct rchan_callbacks *cb)
 467 {
 468         unsigned int i;
 469         struct rchan *chan;
 470         char *tmpname;
 471         int is_global = 0;
 472
 473         if (!base_filename)
 474                 return NULL;
 475
 476         if (!(subbuf_size && n_subbufs))
 477                 return NULL;
 478
 479         chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
 480         if (!chan)
 481                 return NULL;
 482
 483         chan->version = RELAYFS_CHANNEL_VERSION;
 484         chan->n_subbufs = n_subbufs;
 485         chan->subbuf_size = subbuf_size;
 486         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 487         setup_callbacks(chan, cb);
 488         kref_init(&chan->kref);
 489
 490         tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 491         if (!tmpname)
 492                 goto free_chan;
 493
 494         for_each_online_cpu(i) {
 495                 sprintf(tmpname, "%s%d", base_filename, i);
 496                 chan->buf[i] = relay_open_buf(chan, tmpname, parent,
 497                                               &is_global);
 498                 if (!chan->buf[i])
 499                         goto free_bufs;
 500
 501                 chan->buf[i]->cpu = i;
 502         }
 503
 504         kfree(tmpname);
 505         return chan;
 506
 507 free_bufs:
 508         for (i = 0; i < NR_CPUS; i++) {
 509                 if (!chan->buf[i])
 510                         break;
 511                 relay_close_buf(chan->buf[i]);
 512                 if (is_global)
 513                         break;
 514         }
 515         kfree(tmpname);
 516
 517 free_chan:
 518         kref_put(&chan->kref, relay_destroy_channel);
 519         return NULL;
 520 }
 521 EXPORT_SYMBOL_GPL(relay_open);
 522
 523 /**
 524  *      relay_switch_subbuf - switch to a new sub-buffer
 525  *      @buf: channel buffer
 526  *      @length: size of current event
 527  *
 528  *      Returns either the length passed in or 0 if full.
 529  *
 530  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 531  *      updating padding counts, waking up readers, etc.
 532  */
 533 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 534 {
 535         void *old, *new;
 536         size_t old_subbuf, new_subbuf;
 537
 538         if (unlikely(length > buf->chan->subbuf_size))
 539                 goto toobig;
 540
 541         if (buf->offset != buf->chan->subbuf_size + 1) {
 542                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 543                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 544                 buf->padding[old_subbuf] = buf->prev_padding;
 545                 buf->subbufs_produced++;
 546                 if (waitqueue_active(&buf->read_wait)) {
 547                         PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
 548                         schedule_delayed_work(&buf->wake_readers, 1);
 549                 }
 550         }
 551
 552         old = buf->data;
 553         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 554         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 555         buf->offset = 0;
 556         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 557                 buf->offset = buf->chan->subbuf_size + 1;
 558                 return 0;
 559         }
 560         buf->data = new;
 561         buf->padding[new_subbuf] = 0;
 562
 563         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 564                 goto toobig;
 565
 566         return length;
 567
 568 toobig:
 569         buf->chan->last_toobig = length;
 570         return 0;
 571 }
 572 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 573
 574 /**
 575  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 576  *      @chan: the channel
 577  *      @cpu: the cpu associated with the channel buffer to update
 578  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 579  *
 580  *      Adds to the channel buffer's consumed sub-buffer count.
 581  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 582  *      not the total consumed.
 583  *
 584  *      NOTE: kernel clients don't need to call this function if the channel
 585  *      mode is 'overwrite'.
 586  */
 587 void relay_subbufs_consumed(struct rchan *chan,
 588                             unsigned int cpu,
 589                             size_t subbufs_consumed)
 590 {
 591         struct rchan_buf *buf;
 592
 593         if (!chan)
 594                 return;
 595
 596         if (cpu >= NR_CPUS || !chan->buf[cpu])
 597                 return;
 598
 599         buf = chan->buf[cpu];
 600         buf->subbufs_consumed += subbufs_consumed;
 601         if (buf->subbufs_consumed > buf->subbufs_produced)
 602                 buf->subbufs_consumed = buf->subbufs_produced;
 603 }
 604 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 605
 606 /**
 607  *      relay_close - close the channel
 608  *      @chan: the channel
 609  *
 610  *      Closes all channel buffers and frees the channel.
 611  */
 612 void relay_close(struct rchan *chan)
 613 {
 614         unsigned int i;
 615         struct rchan_buf *prev = NULL;
 616
 617         if (!chan)
 618                 return;
 619
 620         for (i = 0; i < NR_CPUS; i++) {
 621                 if (!chan->buf[i] || chan->buf[i] == prev)
 622                         break;
 623                 relay_close_buf(chan->buf[i]);
 624                 prev = chan->buf[i];
 625         }
 626
 627         if (chan->last_toobig)
 628                 printk(KERN_WARNING "relay: one or more items not logged "
 629                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 630                        chan->last_toobig, chan->subbuf_size);
 631
 632         kref_put(&chan->kref, relay_destroy_channel);
 633 }
 634 EXPORT_SYMBOL_GPL(relay_close);
 635
 636 /**
 637  *      relay_flush - close the channel
 638  *      @chan: the channel
 639  *
 640  *      Flushes all channel buffers i.e. forces buffer switch.
 641  */
 642 void relay_flush(struct rchan *chan)
 643 {
 644         unsigned int i;
 645         struct rchan_buf *prev = NULL;
 646
 647         if (!chan)
 648                 return;
 649
 650         for (i = 0; i < NR_CPUS; i++) {
 651                 if (!chan->buf[i] || chan->buf[i] == prev)
 652                         break;
 653                 relay_switch_subbuf(chan->buf[i], 0);
 654                 prev = chan->buf[i];
 655         }
 656 }
 657 EXPORT_SYMBOL_GPL(relay_flush);
 658
 659 /**
 660  *      relay_file_open - open file op for relay files
 661  *      @inode: the inode
 662  *      @filp: the file
 663  *
 664  *      Increments the channel buffer refcount.
 665  */
 666 static int relay_file_open(struct inode *inode, struct file *filp)
 667 {
 668         struct rchan_buf *buf = inode->u.generic_ip;
 669         kref_get(&buf->kref);
 670         filp->private_data = buf;
 671
 672         return 0;
 673 }
 674
 675 /**
 676  *      relay_file_mmap - mmap file op for relay files
 677  *      @filp: the file
 678  *      @vma: the vma describing what to map
 679  *
 680  *      Calls upon relay_mmap_buf to map the file into user space.
 681  */
 682 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 683 {
 684         struct rchan_buf *buf = filp->private_data;
 685         return relay_mmap_buf(buf, vma);
 686 }
 687
 688 /**
 689  *      relay_file_poll - poll file op for relay files
 690  *      @filp: the file
 691  *      @wait: poll table
 692  *
 693  *      Poll implemention.
 694  */
 695 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 696 {
 697         unsigned int mask = 0;
 698         struct rchan_buf *buf = filp->private_data;
 699
 700         if (buf->finalized)
 701                 return POLLERR;
 702
 703         if (filp->f_mode & FMODE_READ) {
 704                 poll_wait(filp, &buf->read_wait, wait);
 705                 if (!relay_buf_empty(buf))
 706                         mask |= POLLIN | POLLRDNORM;
 707         }
 708
 709         return mask;
 710 }
 711
 712 /**
 713  *      relay_file_release - release file op for relay files
 714  *      @inode: the inode
 715  *      @filp: the file
 716  *
 717  *      Decrements the channel refcount, as the filesystem is
 718  *      no longer using it.
 719  */
 720 static int relay_file_release(struct inode *inode, struct file *filp)
 721 {
 722         struct rchan_buf *buf = filp->private_data;
 723         kref_put(&buf->kref, relay_remove_buf);
 724
 725         return 0;
 726 }
 727
 728 /**
 729  *      relay_file_read_consume - update the consumed count for the buffer
 730  */
 731 static void relay_file_read_consume(struct rchan_buf *buf,
 732                                     size_t read_pos,
 733                                     size_t bytes_consumed)
 734 {
 735         size_t subbuf_size = buf->chan->subbuf_size;
 736         size_t n_subbufs = buf->chan->n_subbufs;
 737         size_t read_subbuf;
 738
 739         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 740                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 741                 buf->bytes_consumed = 0;
 742         }
 743
 744         buf->bytes_consumed += bytes_consumed;
 745         read_subbuf = read_pos / buf->chan->subbuf_size;
 746         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 747                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 748                     (buf->offset == subbuf_size))
 749                         return;
 750                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 751                 buf->bytes_consumed = 0;
 752         }
 753 }
 754
 755 /**
 756  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 757  */
 758 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 759 {
 760         size_t bytes_produced, bytes_consumed, write_offset;
 761         size_t subbuf_size = buf->chan->subbuf_size;
 762         size_t n_subbufs = buf->chan->n_subbufs;
 763         size_t produced = buf->subbufs_produced % n_subbufs;
 764         size_t consumed = buf->subbufs_consumed % n_subbufs;
 765
 766         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 767
 768         if (consumed > produced) {
 769                 if ((produced > n_subbufs) &&
 770                     (produced + n_subbufs - consumed <= n_subbufs))
 771                         produced += n_subbufs;
 772         } else if (consumed == produced) {
 773                 if (buf->offset > subbuf_size) {
 774                         produced += n_subbufs;
 775                         if (buf->subbufs_produced == buf->subbufs_consumed)
 776                                 consumed += n_subbufs;
 777                 }
 778         }
 779
 780         if (buf->offset > subbuf_size)
 781                 bytes_produced = (produced - 1) * subbuf_size + write_offset;
 782         else
 783                 bytes_produced = produced * subbuf_size + write_offset;
 784         bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;
 785
 786         if (bytes_produced == bytes_consumed)
 787                 return 0;
 788
 789         relay_file_read_consume(buf, read_pos, 0);
 790
 791         return 1;
 792 }
 793
 794 /**
 795  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
 796  */
 797 static size_t relay_file_read_subbuf_avail(size_t read_pos,
 798                                            struct rchan_buf *buf)
 799 {
 800         size_t padding, avail = 0;
 801         size_t read_subbuf, read_offset, write_subbuf, write_offset;
 802         size_t subbuf_size = buf->chan->subbuf_size;
 803
 804         write_subbuf = (buf->data - buf->start) / subbuf_size;
 805         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
 806         read_subbuf = read_pos / subbuf_size;
 807         read_offset = read_pos % subbuf_size;
 808         padding = buf->padding[read_subbuf];
 809
 810         if (read_subbuf == write_subbuf) {
 811                 if (read_offset + padding < write_offset)
 812                         avail = write_offset - (read_offset + padding);
 813         } else
 814                 avail = (subbuf_size - padding) - read_offset;
 815
 816         return avail;
 817 }
 818
 819 /**
 820  *      relay_file_read_start_pos - find the first available byte to read
 821  *
 822  *      If the read_pos is in the middle of padding, return the
 823  *      position of the first actually available byte, otherwise
 824  *      return the original value.
 825  */
 826 static size_t relay_file_read_start_pos(size_t read_pos,
 827                                         struct rchan_buf *buf)
 828 {
 829         size_t read_subbuf, padding, padding_start, padding_end;
 830         size_t subbuf_size = buf->chan->subbuf_size;
 831         size_t n_subbufs = buf->chan->n_subbufs;
 832
 833         read_subbuf = read_pos / subbuf_size;
 834         padding = buf->padding[read_subbuf];
 835         padding_start = (read_subbuf + 1) * subbuf_size - padding;
 836         padding_end = (read_subbuf + 1) * subbuf_size;
 837         if (read_pos >= padding_start && read_pos < padding_end) {
 838                 read_subbuf = (read_subbuf + 1) % n_subbufs;
 839                 read_pos = read_subbuf * subbuf_size;
 840         }
 841
 842         return read_pos;
 843 }
 844
 845 /**
 846  *      relay_file_read_end_pos - return the new read position
 847  */
 848 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
 849                                       size_t read_pos,
 850                                       size_t count)
 851 {
 852         size_t read_subbuf, padding, end_pos;
 853         size_t subbuf_size = buf->chan->subbuf_size;
 854         size_t n_subbufs = buf->chan->n_subbufs;
 855
 856         read_subbuf = read_pos / subbuf_size;
 857         padding = buf->padding[read_subbuf];
 858         if (read_pos % subbuf_size + count + padding == subbuf_size)
 859                 end_pos = (read_subbuf + 1) * subbuf_size;
 860         else
 861                 end_pos = read_pos + count;
 862         if (end_pos >= subbuf_size * n_subbufs)
 863                 end_pos = 0;
 864
 865         return end_pos;
 866 }
 867
 868 /**
 869  *      relay_file_read - read file op for relay files
 870  *      @filp: the file
 871  *      @buffer: the userspace buffer
 872  *      @count: number of bytes to read
 873  *      @ppos: position to read from
 874  *
 875  *      Reads count bytes or the number of bytes available in the
 876  *      current sub-buffer being read, whichever is smaller.
 877  */
 878 static ssize_t relay_file_read(struct file *filp,
 879                                char __user *buffer,
 880                                size_t count,
 881                                loff_t *ppos)
 882 {
 883         struct rchan_buf *buf = filp->private_data;
 884         struct inode *inode = filp->f_dentry->d_inode;
 885         size_t read_start, avail;
 886         ssize_t ret = 0;
 887         void *from;
 888
 889         mutex_lock(&inode->i_mutex);
 890         if(!relay_file_read_avail(buf, *ppos))
 891                 goto out;
 892
 893         read_start = relay_file_read_start_pos(*ppos, buf);
 894         avail = relay_file_read_subbuf_avail(read_start, buf);
 895         if (!avail)
 896                 goto out;
 897
 898         from = buf->start + read_start;
 899         ret = count = min(count, avail);
 900         if (copy_to_user(buffer, from, count)) {
 901                 ret = -EFAULT;
 902                 goto out;
 903         }
 904         relay_file_read_consume(buf, read_start, count);
 905         *ppos = relay_file_read_end_pos(buf, read_start, count);
 906 out:
 907         mutex_unlock(&inode->i_mutex);
 908         return ret;
 909 }
 910
 911 struct file_operations relay_file_operations = {
 912         .open           = relay_file_open,
 913         .poll           = relay_file_poll,
 914         .mmap           = relay_file_mmap,
 915         .read           = relay_file_read,
 916         .llseek         = no_llseek,
 917         .release        = relay_file_release,
 918 };
 919 EXPORT_SYMBOL_GPL(relay_file_operations);