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