kernel/relay.c

   1 /*
   2  * Public API and common code for kernel->userspace relay file support.
   3  *
   4  * See Documentation/filesystems/relay.txt for an overview.
   5  *
   6  * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
   7  * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
   8  *
   9  * Moved to kernel/relay.c by Paul Mundt, 2006.
  10  * November 2006 - CPU hotplug support by Mathieu Desnoyers
  11  *      (mathieu.desnoyers@polymtl.ca)
  12  *
  13  * This file is released under the GPL.
  14  */
  15 #include <linux/errno.h>
  16 #include <linux/stddef.h>
  17 #include <linux/slab.h>
  18 #include <linux/module.h>
  19 #include <linux/string.h>
  20 #include <linux/relay.h>
  21 #include <linux/vmalloc.h>
  22 #include <linux/mm.h>
  23 #include <linux/cpu.h>
  24 #include <linux/splice.h>
  25
  26 /* list of open channels, for cpu hotplug */
  27 static DEFINE_MUTEX(relay_channels_mutex);
  28 static LIST_HEAD(relay_channels);
  29
  30 /*
  31  * close() vm_op implementation for relay file mapping.
  32  */
  33 static void relay_file_mmap_close(struct vm_area_struct *vma)
  34 {
  35         struct rchan_buf *buf = vma->vm_private_data;
  36         buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  37 }
  38
  39 /*
  40  * fault() vm_op implementation for relay file mapping.
  41  */
  42 static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  43 {
  44         struct page *page;
  45         struct rchan_buf *buf = vma->vm_private_data;
  46         pgoff_t pgoff = vmf->pgoff;
  47
  48         if (!buf)
  49                 return VM_FAULT_OOM;
  50
  51         page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
  52         if (!page)
  53                 return VM_FAULT_SIGBUS;
  54         get_page(page);
  55         vmf->page = page;
  56
  57         return 0;
  58 }
  59
  60 /*
  61  * vm_ops for relay file mappings.
  62  */
  63 static const struct vm_operations_struct relay_file_mmap_ops = {
  64         .fault = relay_buf_fault,
  65         .close = relay_file_mmap_close,
  66 };
  67
  68 /*
  69  * allocate an array of pointers of struct page
  70  */
  71 static struct page **relay_alloc_page_array(unsigned int n_pages)
  72 {
  73         struct page **array;
  74         size_t pa_size = n_pages * sizeof(struct page *);
  75
  76         if (pa_size > PAGE_SIZE) {
  77                 array = vmalloc(pa_size);
  78                 if (array)
  79                         memset(array, 0, pa_size);
  80         } else {
  81                 array = kzalloc(pa_size, GFP_KERNEL);
  82         }
  83         return array;
  84 }
  85
  86 /*
  87  * free an array of pointers of struct page
  88  */
  89 static void relay_free_page_array(struct page **array)
  90 {
  91         if (is_vmalloc_addr(array))
  92                 vfree(array);
  93         else
  94                 kfree(array);
  95 }
  96
  97 /**
  98  *      relay_mmap_buf: - mmap channel buffer to process address space
  99  *      @buf: relay channel buffer
 100  *      @vma: vm_area_struct describing memory to be mapped
 101  *
 102  *      Returns 0 if ok, negative on error
 103  *
 104  *      Caller should already have grabbed mmap_sem.
 105  */
 106 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
 107 {
 108         unsigned long length = vma->vm_end - vma->vm_start;
 109         struct file *filp = vma->vm_file;
 110
 111         if (!buf)
 112                 return -EBADF;
 113
 114         if (length != (unsigned long)buf->chan->alloc_size)
 115                 return -EINVAL;
 116
 117         vma->vm_ops = &relay_file_mmap_ops;
 118         vma->vm_flags |= VM_DONTEXPAND;
 119         vma->vm_private_data = buf;
 120         buf->chan->cb->buf_mapped(buf, filp);
 121
 122         return 0;
 123 }
 124
 125 /**
 126  *      relay_alloc_buf - allocate a channel buffer
 127  *      @buf: the buffer struct
 128  *      @size: total size of the buffer
 129  *
 130  *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 131  *      passed in size will get page aligned, if it isn't already.
 132  */
 133 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 134 {
 135         void *mem;
 136         unsigned int i, j, n_pages;
 137
 138         *size = PAGE_ALIGN(*size);
 139         n_pages = *size >> PAGE_SHIFT;
 140
 141         buf->page_array = relay_alloc_page_array(n_pages);
 142         if (!buf->page_array)
 143                 return NULL;
 144
 145         for (i = 0; i < n_pages; i++) {
 146                 buf->page_array[i] = alloc_page(GFP_KERNEL);
 147                 if (unlikely(!buf->page_array[i]))
 148                         goto depopulate;
 149                 set_page_private(buf->page_array[i], (unsigned long)buf);
 150         }
 151         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 152         if (!mem)
 153                 goto depopulate;
 154
 155         memset(mem, 0, *size);
 156         buf->page_count = n_pages;
 157         return mem;
 158
 159 depopulate:
 160         for (j = 0; j < i; j++)
 161                 __free_page(buf->page_array[j]);
 162         relay_free_page_array(buf->page_array);
 163         return NULL;
 164 }
 165
 166 /**
 167  *      relay_create_buf - allocate and initialize a channel buffer
 168  *      @chan: the relay channel
 169  *
 170  *      Returns channel buffer if successful, %NULL otherwise.
 171  */
 172 static struct rchan_buf *relay_create_buf(struct rchan *chan)
 173 {
 174         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 175         if (!buf)
 176                 return NULL;
 177
 178         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 179         if (!buf->padding)
 180                 goto free_buf;
 181
 182         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 183         if (!buf->start)
 184                 goto free_buf;
 185
 186         buf->chan = chan;
 187         kref_get(&buf->chan->kref);
 188         return buf;
 189
 190 free_buf:
 191         kfree(buf->padding);
 192         kfree(buf);
 193         return NULL;
 194 }
 195
 196 /**
 197  *      relay_destroy_channel - free the channel struct
 198  *      @kref: target kernel reference that contains the relay channel
 199  *
 200  *      Should only be called from kref_put().
 201  */
 202 static void relay_destroy_channel(struct kref *kref)
 203 {
 204         struct rchan *chan = container_of(kref, struct rchan, kref);
 205         kfree(chan);
 206 }
 207
 208 /**
 209  *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 210  *      @buf: the buffer struct
 211  */
 212 static void relay_destroy_buf(struct rchan_buf *buf)
 213 {
 214         struct rchan *chan = buf->chan;
 215         unsigned int i;
 216
 217         if (likely(buf->start)) {
 218                 vunmap(buf->start);
 219                 for (i = 0; i < buf->page_count; i++)
 220                         __free_page(buf->page_array[i]);
 221                 relay_free_page_array(buf->page_array);
 222         }
 223         chan->buf[buf->cpu] = NULL;
 224         kfree(buf->padding);
 225         kfree(buf);
 226         kref_put(&chan->kref, relay_destroy_channel);
 227 }
 228
 229 /**
 230  *      relay_remove_buf - remove a channel buffer
 231  *      @kref: target kernel reference that contains the relay buffer
 232  *
 233  *      Removes the file from the fileystem, which also frees the
 234  *      rchan_buf_struct and the channel buffer.  Should only be called from
 235  *      kref_put().
 236  */
 237 static void relay_remove_buf(struct kref *kref)
 238 {
 239         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 240         buf->chan->cb->remove_buf_file(buf->dentry);
 241         relay_destroy_buf(buf);
 242 }
 243
 244 /**
 245  *      relay_buf_empty - boolean, is the channel buffer empty?
 246  *      @buf: channel buffer
 247  *
 248  *      Returns 1 if the buffer is empty, 0 otherwise.
 249  */
 250 static int relay_buf_empty(struct rchan_buf *buf)
 251 {
 252         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 253 }
 254
 255 /**
 256  *      relay_buf_full - boolean, is the channel buffer full?
 257  *      @buf: channel buffer
 258  *
 259  *      Returns 1 if the buffer is full, 0 otherwise.
 260  */
 261 int relay_buf_full(struct rchan_buf *buf)
 262 {
 263         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 264         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 265 }
 266 EXPORT_SYMBOL_GPL(relay_buf_full);
 267
 268 /*
 269  * High-level relay kernel API and associated functions.
 270  */
 271
 272 /*
 273  * rchan_callback implementations defining default channel behavior.  Used
 274  * in place of corresponding NULL values in client callback struct.
 275  */
 276
 277 /*
 278  * subbuf_start() default callback.  Does nothing.
 279  */
 280 static int subbuf_start_default_callback (struct rchan_buf *buf,
 281                                           void *subbuf,
 282                                           void *prev_subbuf,
 283                                           size_t prev_padding)
 284 {
 285         if (relay_buf_full(buf))
 286                 return 0;
 287
 288         return 1;
 289 }
 290
 291 /*
 292  * buf_mapped() default callback.  Does nothing.
 293  */
 294 static void buf_mapped_default_callback(struct rchan_buf *buf,
 295                                         struct file *filp)
 296 {
 297 }
 298
 299 /*
 300  * buf_unmapped() default callback.  Does nothing.
 301  */
 302 static void buf_unmapped_default_callback(struct rchan_buf *buf,
 303                                           struct file *filp)
 304 {
 305 }
 306
 307 /*
 308  * create_buf_file_create() default callback.  Does nothing.
 309  */
 310 static struct dentry *create_buf_file_default_callback(const char *filename,
 311                                                        struct dentry *parent,
 312                                                        int mode,
 313                                                        struct rchan_buf *buf,
 314                                                        int *is_global)
 315 {
 316         return NULL;
 317 }
 318
 319 /*
 320  * remove_buf_file() default callback.  Does nothing.
 321  */
 322 static int remove_buf_file_default_callback(struct dentry *dentry)
 323 {
 324         return -EINVAL;
 325 }
 326
 327 /* relay channel default callbacks */
 328 static struct rchan_callbacks default_channel_callbacks = {
 329         .subbuf_start = subbuf_start_default_callback,
 330         .buf_mapped = buf_mapped_default_callback,
 331         .buf_unmapped = buf_unmapped_default_callback,
 332         .create_buf_file = create_buf_file_default_callback,
 333         .remove_buf_file = remove_buf_file_default_callback,
 334 };
 335
 336 /**
 337  *      wakeup_readers - wake up readers waiting on a channel
 338  *      @data: contains the channel buffer
 339  *
 340  *      This is the timer function used to defer reader waking.
 341  */
 342 static void wakeup_readers(unsigned long data)
 343 {
 344         struct rchan_buf *buf = (struct rchan_buf *)data;
 345         wake_up_interruptible(&buf->read_wait);
 346 }
 347
 348 /**
 349  *      __relay_reset - reset a channel buffer
 350  *      @buf: the channel buffer
 351  *      @init: 1 if this is a first-time initialization
 352  *
 353  *      See relay_reset() for description of effect.
 354  */
 355 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 356 {
 357         size_t i;
 358
 359         if (init) {
 360                 init_waitqueue_head(&buf->read_wait);
 361                 kref_init(&buf->kref);
 362                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 363         } else
 364                 del_timer_sync(&buf->timer);
 365
 366         buf->subbufs_produced = 0;
 367         buf->subbufs_consumed = 0;
 368         buf->bytes_consumed = 0;
 369         buf->finalized = 0;
 370         buf->data = buf->start;
 371         buf->offset = 0;
 372
 373         for (i = 0; i < buf->chan->n_subbufs; i++)
 374                 buf->padding[i] = 0;
 375
 376         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 377 }
 378
 379 /**
 380  *      relay_reset - reset the channel
 381  *      @chan: the channel
 382  *
 383  *      This has the effect of erasing all data from all channel buffers
 384  *      and restarting the channel in its initial state.  The buffers
 385  *      are not freed, so any mappings are still in effect.
 386  *
 387  *      NOTE. Care should be taken that the channel isn't actually
 388  *      being used by anything when this call is made.
 389  */
 390 void relay_reset(struct rchan *chan)
 391 {
 392         unsigned int i;
 393
 394         if (!chan)
 395                 return;
 396
 397         if (chan->is_global && chan->buf[0]) {
 398                 __relay_reset(chan->buf[0], 0);
 399                 return;
 400         }
 401
 402         mutex_lock(&relay_channels_mutex);
 403         for_each_possible_cpu(i)
 404                 if (chan->buf[i])
 405                         __relay_reset(chan->buf[i], 0);
 406         mutex_unlock(&relay_channels_mutex);
 407 }
 408 EXPORT_SYMBOL_GPL(relay_reset);
 409
 410 static inline void relay_set_buf_dentry(struct rchan_buf *buf,
 411                                         struct dentry *dentry)
 412 {
 413         buf->dentry = dentry;
 414         buf->dentry->d_inode->i_size = buf->early_bytes;
 415 }
 416
 417 static struct dentry *relay_create_buf_file(struct rchan *chan,
 418                                             struct rchan_buf *buf,
 419                                             unsigned int cpu)
 420 {
 421         struct dentry *dentry;
 422         char *tmpname;
 423
 424         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 425         if (!tmpname)
 426                 return NULL;
 427         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 428
 429         /* Create file in fs */
 430         dentry = chan->cb->create_buf_file(tmpname, chan->parent,
 431                                            S_IRUSR, buf,
 432                                            &chan->is_global);
 433
 434         kfree(tmpname);
 435
 436         return dentry;
 437 }
 438
 439 /*
 440  *      relay_open_buf - create a new relay channel buffer
 441  *
 442  *      used by relay_open() and CPU hotplug.
 443  */
 444 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 445 {
 446         struct rchan_buf *buf = NULL;
 447         struct dentry *dentry;
 448
 449         if (chan->is_global)
 450                 return chan->buf[0];
 451
 452         buf = relay_create_buf(chan);
 453         if (!buf)
 454                 return NULL;
 455
 456         if (chan->has_base_filename) {
 457                 dentry = relay_create_buf_file(chan, buf, cpu);
 458                 if (!dentry)
 459                         goto free_buf;
 460                 relay_set_buf_dentry(buf, dentry);
 461         }
 462
 463         buf->cpu = cpu;
 464         __relay_reset(buf, 1);
 465
 466         if(chan->is_global) {
 467                 chan->buf[0] = buf;
 468                 buf->cpu = 0;
 469         }
 470
 471         return buf;
 472
 473 free_buf:
 474         relay_destroy_buf(buf);
 475         return NULL;
 476 }
 477
 478 /**
 479  *      relay_close_buf - close a channel buffer
 480  *      @buf: channel buffer
 481  *
 482  *      Marks the buffer finalized and restores the default callbacks.
 483  *      The channel buffer and channel buffer data structure are then freed
 484  *      automatically when the last reference is given up.
 485  */
 486 static void relay_close_buf(struct rchan_buf *buf)
 487 {
 488         buf->finalized = 1;
 489         del_timer_sync(&buf->timer);
 490         kref_put(&buf->kref, relay_remove_buf);
 491 }
 492
 493 static void setup_callbacks(struct rchan *chan,
 494                                    struct rchan_callbacks *cb)
 495 {
 496         if (!cb) {
 497                 chan->cb = &default_channel_callbacks;
 498                 return;
 499         }
 500
 501         if (!cb->subbuf_start)
 502                 cb->subbuf_start = subbuf_start_default_callback;
 503         if (!cb->buf_mapped)
 504                 cb->buf_mapped = buf_mapped_default_callback;
 505         if (!cb->buf_unmapped)
 506                 cb->buf_unmapped = buf_unmapped_default_callback;
 507         if (!cb->create_buf_file)
 508                 cb->create_buf_file = create_buf_file_default_callback;
 509         if (!cb->remove_buf_file)
 510                 cb->remove_buf_file = remove_buf_file_default_callback;
 511         chan->cb = cb;
 512 }
 513
 514 /**
 515  *      relay_hotcpu_callback - CPU hotplug callback
 516  *      @nb: notifier block
 517  *      @action: hotplug action to take
 518  *      @hcpu: CPU number
 519  *
 520  *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 521  */
 522 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 523                                 unsigned long action,
 524                                 void *hcpu)
 525 {
 526         unsigned int hotcpu = (unsigned long)hcpu;
 527         struct rchan *chan;
 528
 529         switch(action) {
 530         case CPU_UP_PREPARE:
 531         case CPU_UP_PREPARE_FROZEN:
 532                 mutex_lock(&relay_channels_mutex);
 533                 list_for_each_entry(chan, &relay_channels, list) {
 534                         if (chan->buf[hotcpu])
 535                                 continue;
 536                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 537                         if(!chan->buf[hotcpu]) {
 538                                 printk(KERN_ERR
 539                                         "relay_hotcpu_callback: cpu %d buffer "
 540                                         "creation failed\n", hotcpu);
 541                                 mutex_unlock(&relay_channels_mutex);
 542                                 return notifier_from_errno(-ENOMEM);
 543                         }
 544                 }
 545                 mutex_unlock(&relay_channels_mutex);
 546                 break;
 547         case CPU_DEAD:
 548         case CPU_DEAD_FROZEN:
 549                 /* No need to flush the cpu : will be flushed upon
 550                  * final relay_flush() call. */
 551                 break;
 552         }
 553         return NOTIFY_OK;
 554 }
 555
 556 /**
 557  *      relay_open - create a new relay channel
 558  *      @base_filename: base name of files to create, %NULL for buffering only
 559  *      @parent: dentry of parent directory, %NULL for root directory or buffer
 560  *      @subbuf_size: size of sub-buffers
 561  *      @n_subbufs: number of sub-buffers
 562  *      @cb: client callback functions
 563  *      @private_data: user-defined data
 564  *
 565  *      Returns channel pointer if successful, %NULL otherwise.
 566  *
 567  *      Creates a channel buffer for each cpu using the sizes and
 568  *      attributes specified.  The created channel buffer files
 569  *      will be named base_filename0...base_filenameN-1.  File
 570  *      permissions will be %S_IRUSR.
 571  */
 572 struct rchan *relay_open(const char *base_filename,
 573                          struct dentry *parent,
 574                          size_t subbuf_size,
 575                          size_t n_subbufs,
 576                          struct rchan_callbacks *cb,
 577                          void *private_data)
 578 {
 579         unsigned int i;
 580         struct rchan *chan;
 581
 582         if (!(subbuf_size && n_subbufs))
 583                 return NULL;
 584
 585         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 586         if (!chan)
 587                 return NULL;
 588
 589         chan->version = RELAYFS_CHANNEL_VERSION;
 590         chan->n_subbufs = n_subbufs;
 591         chan->subbuf_size = subbuf_size;
 592         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 593         chan->parent = parent;
 594         chan->private_data = private_data;
 595         if (base_filename) {
 596                 chan->has_base_filename = 1;
 597                 strlcpy(chan->base_filename, base_filename, NAME_MAX);
 598         }
 599         setup_callbacks(chan, cb);
 600         kref_init(&chan->kref);
 601
 602         mutex_lock(&relay_channels_mutex);
 603         for_each_online_cpu(i) {
 604                 chan->buf[i] = relay_open_buf(chan, i);
 605                 if (!chan->buf[i])
 606                         goto free_bufs;
 607         }
 608         list_add(&chan->list, &relay_channels);
 609         mutex_unlock(&relay_channels_mutex);
 610
 611         return chan;
 612
 613 free_bufs:
 614         for_each_possible_cpu(i) {
 615                 if (chan->buf[i])
 616                         relay_close_buf(chan->buf[i]);
 617         }
 618
 619         kref_put(&chan->kref, relay_destroy_channel);
 620         mutex_unlock(&relay_channels_mutex);
 621         return NULL;
 622 }
 623 EXPORT_SYMBOL_GPL(relay_open);
 624
 625 struct rchan_percpu_buf_dispatcher {
 626         struct rchan_buf *buf;
 627         struct dentry *dentry;
 628 };
 629
 630 /* Called in atomic context. */
 631 static void __relay_set_buf_dentry(void *info)
 632 {
 633         struct rchan_percpu_buf_dispatcher *p = info;
 634
 635         relay_set_buf_dentry(p->buf, p->dentry);
 636 }
 637
 638 /**
 639  *      relay_late_setup_files - triggers file creation
 640  *      @chan: channel to operate on
 641  *      @base_filename: base name of files to create
 642  *      @parent: dentry of parent directory, %NULL for root directory
 643  *
 644  *      Returns 0 if successful, non-zero otherwise.
 645  *
 646  *      Use to setup files for a previously buffer-only channel.
 647  *      Useful to do early tracing in kernel, before VFS is up, for example.
 648  */
 649 int relay_late_setup_files(struct rchan *chan,
 650                            const char *base_filename,
 651                            struct dentry *parent)
 652 {
 653         int err = 0;
 654         unsigned int i, curr_cpu;
 655         unsigned long flags;
 656         struct dentry *dentry;
 657         struct rchan_percpu_buf_dispatcher disp;
 658
 659         if (!chan || !base_filename)
 660                 return -EINVAL;
 661
 662         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 663
 664         mutex_lock(&relay_channels_mutex);
 665         /* Is chan already set up? */
 666         if (unlikely(chan->has_base_filename)) {
 667                 mutex_unlock(&relay_channels_mutex);
 668                 return -EEXIST;
 669         }
 670         chan->has_base_filename = 1;
 671         chan->parent = parent;
 672         curr_cpu = get_cpu();
 673         /*
 674          * The CPU hotplug notifier ran before us and created buffers with
 675          * no files associated. So it's safe to call relay_setup_buf_file()
 676          * on all currently online CPUs.
 677          */
 678         for_each_online_cpu(i) {
 679                 if (unlikely(!chan->buf[i])) {
 680                         WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
 681                         err = -EINVAL;
 682                         break;
 683                 }
 684
 685                 dentry = relay_create_buf_file(chan, chan->buf[i], i);
 686                 if (unlikely(!dentry)) {
 687                         err = -EINVAL;
 688                         break;
 689                 }
 690
 691                 if (curr_cpu == i) {
 692                         local_irq_save(flags);
 693                         relay_set_buf_dentry(chan->buf[i], dentry);
 694                         local_irq_restore(flags);
 695                 } else {
 696                         disp.buf = chan->buf[i];
 697                         disp.dentry = dentry;
 698                         smp_mb();
 699                         /* relay_channels_mutex must be held, so wait. */
 700                         err = smp_call_function_single(i,
 701                                                        __relay_set_buf_dentry,
 702                                                        &disp, 1);
 703                 }
 704                 if (unlikely(err))
 705                         break;
 706         }
 707         put_cpu();
 708         mutex_unlock(&relay_channels_mutex);
 709
 710         return err;
 711 }
 712
 713 /**
 714  *      relay_switch_subbuf - switch to a new sub-buffer
 715  *      @buf: channel buffer
 716  *      @length: size of current event
 717  *
 718  *      Returns either the length passed in or 0 if full.
 719  *
 720  *      Performs sub-buffer-switch tasks such as invoking callbacks,
 721  *      updating padding counts, waking up readers, etc.
 722  */
 723 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 724 {
 725         void *old, *new;
 726         size_t old_subbuf, new_subbuf;
 727
 728         if (unlikely(length > buf->chan->subbuf_size))
 729                 goto toobig;
 730
 731         if (buf->offset != buf->chan->subbuf_size + 1) {
 732                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 733                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 734                 buf->padding[old_subbuf] = buf->prev_padding;
 735                 buf->subbufs_produced++;
 736                 if (buf->dentry)
 737                         buf->dentry->d_inode->i_size +=
 738                                 buf->chan->subbuf_size -
 739                                 buf->padding[old_subbuf];
 740                 else
 741                         buf->early_bytes += buf->chan->subbuf_size -
 742                                             buf->padding[old_subbuf];
 743                 smp_mb();
 744                 if (waitqueue_active(&buf->read_wait))
 745                         /*
 746                          * Calling wake_up_interruptible() from here
 747                          * will deadlock if we happen to be logging
 748                          * from the scheduler (trying to re-grab
 749                          * rq->lock), so defer it.
 750                          */
 751                         mod_timer(&buf->timer, jiffies + 1);
 752         }
 753
 754         old = buf->data;
 755         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 756         new = buf->start + new_subbuf * buf->chan->subbuf_size;
 757         buf->offset = 0;
 758         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 759                 buf->offset = buf->chan->subbuf_size + 1;
 760                 return 0;
 761         }
 762         buf->data = new;
 763         buf->padding[new_subbuf] = 0;
 764
 765         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 766                 goto toobig;
 767
 768         return length;
 769
 770 toobig:
 771         buf->chan->last_toobig = length;
 772         return 0;
 773 }
 774 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 775
 776 /**
 777  *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 778  *      @chan: the channel
 779  *      @cpu: the cpu associated with the channel buffer to update
 780  *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 781  *
 782  *      Adds to the channel buffer's consumed sub-buffer count.
 783  *      subbufs_consumed should be the number of sub-buffers newly consumed,
 784  *      not the total consumed.
 785  *
 786  *      NOTE. Kernel clients don't need to call this function if the channel
 787  *      mode is 'overwrite'.
 788  */
 789 void relay_subbufs_consumed(struct rchan *chan,
 790                             unsigned int cpu,
 791                             size_t subbufs_consumed)
 792 {
 793         struct rchan_buf *buf;
 794
 795         if (!chan)
 796                 return;
 797
 798         if (cpu >= NR_CPUS || !chan->buf[cpu] ||
 799                                         subbufs_consumed > chan->n_subbufs)
 800                 return;
 801
 802         buf = chan->buf[cpu];
 803         if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
 804                 buf->subbufs_consumed = buf->subbufs_produced;
 805         else
 806                 buf->subbufs_consumed += subbufs_consumed;
 807 }
 808 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 809
 810 /**
 811  *      relay_close - close the channel
 812  *      @chan: the channel
 813  *
 814  *      Closes all channel buffers and frees the channel.
 815  */
 816 void relay_close(struct rchan *chan)
 817 {
 818         unsigned int i;
 819
 820         if (!chan)
 821                 return;
 822
 823         mutex_lock(&relay_channels_mutex);
 824         if (chan->is_global && chan->buf[0])
 825                 relay_close_buf(chan->buf[0]);
 826         else
 827                 for_each_possible_cpu(i)
 828                         if (chan->buf[i])
 829                                 relay_close_buf(chan->buf[i]);
 830
 831         if (chan->last_toobig)
 832                 printk(KERN_WARNING "relay: one or more items not logged "
 833                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 834                        chan->last_toobig, chan->subbuf_size);
 835
 836         list_del(&chan->list);
 837         kref_put(&chan->kref, relay_destroy_channel);
 838         mutex_unlock(&relay_channels_mutex);
 839 }
 840 EXPORT_SYMBOL_GPL(relay_close);
 841
 842 /**
 843  *      relay_flush - close the channel
 844  *      @chan: the channel
 845  *
 846  *      Flushes all channel buffers, i.e. forces buffer switch.
 847  */
 848 void relay_flush(struct rchan *chan)
 849 {
 850         unsigned int i;
 851
 852         if (!chan)
 853                 return;
 854
 855         if (chan->is_global && chan->buf[0]) {
 856                 relay_switch_subbuf(chan->buf[0], 0);
 857                 return;
 858         }
 859
 860         mutex_lock(&relay_channels_mutex);
 861         for_each_possible_cpu(i)
 862                 if (chan->buf[i])
 863                         relay_switch_subbuf(chan->buf[i], 0);
 864         mutex_unlock(&relay_channels_mutex);
 865 }
 866 EXPORT_SYMBOL_GPL(relay_flush);
 867
 868 /**
 869  *      relay_file_open - open file op for relay files
 870  *      @inode: the inode
 871  *      @filp: the file
 872  *
 873  *      Increments the channel buffer refcount.
 874  */
 875 static int relay_file_open(struct inode *inode, struct file *filp)
 876 {
 877         struct rchan_buf *buf = inode->i_private;
 878         kref_get(&buf->kref);
 879         filp->private_data = buf;
 880
 881         return nonseekable_open(inode, filp);
 882 }
 883
 884 /**
 885  *      relay_file_mmap - mmap file op for relay files
 886  *      @filp: the file
 887  *      @vma: the vma describing what to map
 888  *
 889  *      Calls upon relay_mmap_buf() to map the file into user space.
 890  */
 891 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 892 {
 893         struct rchan_buf *buf = filp->private_data;
 894         return relay_mmap_buf(buf, vma);
 895 }
 896
 897 /**
 898  *      relay_file_poll - poll file op for relay files
 899  *      @filp: the file
 900  *      @wait: poll table
 901  *
 902  *      Poll implemention.
 903  */
 904 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 905 {
 906         unsigned int mask = 0;
 907         struct rchan_buf *buf = filp->private_data;
 908
 909         if (buf->finalized)
 910                 return POLLERR;
 911
 912         if (filp->f_mode & FMODE_READ) {
 913                 poll_wait(filp, &buf->read_wait, wait);
 914                 if (!relay_buf_empty(buf))
 915                         mask |= POLLIN | POLLRDNORM;
 916         }
 917
 918         return mask;
 919 }
 920
 921 /**
 922  *      relay_file_release - release file op for relay files
 923  *      @inode: the inode
 924  *      @filp: the file
 925  *
 926  *      Decrements the channel refcount, as the filesystem is
 927  *      no longer using it.
 928  */
 929 static int relay_file_release(struct inode *inode, struct file *filp)
 930 {
 931         struct rchan_buf *buf = filp->private_data;
 932         kref_put(&buf->kref, relay_remove_buf);
 933
 934         return 0;
 935 }
 936
 937 /*
 938  *      relay_file_read_consume - update the consumed count for the buffer
 939  */
 940 static void relay_file_read_consume(struct rchan_buf *buf,
 941                                     size_t read_pos,
 942                                     size_t bytes_consumed)
 943 {
 944         size_t subbuf_size = buf->chan->subbuf_size;
 945         size_t n_subbufs = buf->chan->n_subbufs;
 946         size_t read_subbuf;
 947
 948         if (buf->subbufs_produced == buf->subbufs_consumed &&
 949             buf->offset == buf->bytes_consumed)
 950                 return;
 951
 952         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 953                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 954                 buf->bytes_consumed = 0;
 955         }
 956
 957         buf->bytes_consumed += bytes_consumed;
 958         if (!read_pos)
 959                 read_subbuf = buf->subbufs_consumed % n_subbufs;
 960         else
 961                 read_subbuf = read_pos / buf->chan->subbuf_size;
 962         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 963                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 964                     (buf->offset == subbuf_size))
 965                         return;
 966                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 967                 buf->bytes_consumed = 0;
 968         }
 969 }
 970
 971 /*
 972  *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 973  */
 974 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 975 {
 976         size_t subbuf_size = buf->chan->subbuf_size;
 977         size_t n_subbufs = buf->chan->n_subbufs;
 978         size_t produced = buf->subbufs_produced;
 979         size_t consumed = buf->subbufs_consumed;
 980
 981         relay_file_read_consume(buf, read_pos, 0);
 982
 983         consumed = buf->subbufs_consumed;
 984
 985         if (unlikely(buf->offset > subbuf_size)) {
 986                 if (produced == consumed)
 987                         return 0;
 988                 return 1;
 989         }
 990
 991         if (unlikely(produced - consumed >= n_subbufs)) {
 992                 consumed = produced - n_subbufs + 1;
 993                 buf->subbufs_consumed = consumed;
 994                 buf->bytes_consumed = 0;
 995         }
 996
 997         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 998         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 999
1000         if (consumed > produced)
1001                 produced += n_subbufs * subbuf_size;
1002
1003         if (consumed == produced) {
1004                 if (buf->offset == subbuf_size &&
1005                     buf->subbufs_produced > buf->subbufs_consumed)
1006                         return 1;
1007                 return 0;
1008         }
1009
1010         return 1;
1011 }
1012
1013 /**
1014  *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
1015  *      @read_pos: file read position
1016  *      @buf: relay channel buffer
1017  */
1018 static size_t relay_file_read_subbuf_avail(size_t read_pos,
1019                                            struct rchan_buf *buf)
1020 {
1021         size_t padding, avail = 0;
1022         size_t read_subbuf, read_offset, write_subbuf, write_offset;
1023         size_t subbuf_size = buf->chan->subbuf_size;
1024
1025         write_subbuf = (buf->data - buf->start) / subbuf_size;
1026         write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1027         read_subbuf = read_pos / subbuf_size;
1028         read_offset = read_pos % subbuf_size;
1029         padding = buf->padding[read_subbuf];
1030
1031         if (read_subbuf == write_subbuf) {
1032                 if (read_offset + padding < write_offset)
1033                         avail = write_offset - (read_offset + padding);
1034         } else
1035                 avail = (subbuf_size - padding) - read_offset;
1036
1037         return avail;
1038 }
1039
1040 /**
1041  *      relay_file_read_start_pos - find the first available byte to read
1042  *      @read_pos: file read position
1043  *      @buf: relay channel buffer
1044  *
1045  *      If the @read_pos is in the middle of padding, return the
1046  *      position of the first actually available byte, otherwise
1047  *      return the original value.
1048  */
1049 static size_t relay_file_read_start_pos(size_t read_pos,
1050                                         struct rchan_buf *buf)
1051 {
1052         size_t read_subbuf, padding, padding_start, padding_end;
1053         size_t subbuf_size = buf->chan->subbuf_size;
1054         size_t n_subbufs = buf->chan->n_subbufs;
1055         size_t consumed = buf->subbufs_consumed % n_subbufs;
1056
1057         if (!read_pos)
1058                 read_pos = consumed * subbuf_size + buf->bytes_consumed;
1059         read_subbuf = read_pos / subbuf_size;
1060         padding = buf->padding[read_subbuf];
1061         padding_start = (read_subbuf + 1) * subbuf_size - padding;
1062         padding_end = (read_subbuf + 1) * subbuf_size;
1063         if (read_pos >= padding_start && read_pos < padding_end) {
1064                 read_subbuf = (read_subbuf + 1) % n_subbufs;
1065                 read_pos = read_subbuf * subbuf_size;
1066         }
1067
1068         return read_pos;
1069 }
1070
1071 /**
1072  *      relay_file_read_end_pos - return the new read position
1073  *      @read_pos: file read position
1074  *      @buf: relay channel buffer
1075  *      @count: number of bytes to be read
1076  */
1077 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1078                                       size_t read_pos,
1079                                       size_t count)
1080 {
1081         size_t read_subbuf, padding, end_pos;
1082         size_t subbuf_size = buf->chan->subbuf_size;
1083         size_t n_subbufs = buf->chan->n_subbufs;
1084
1085         read_subbuf = read_pos / subbuf_size;
1086         padding = buf->padding[read_subbuf];
1087         if (read_pos % subbuf_size + count + padding == subbuf_size)
1088                 end_pos = (read_subbuf + 1) * subbuf_size;
1089         else
1090                 end_pos = read_pos + count;
1091         if (end_pos >= subbuf_size * n_subbufs)
1092                 end_pos = 0;
1093
1094         return end_pos;
1095 }
1096
1097 /*
1098  *      subbuf_read_actor - read up to one subbuf's worth of data
1099  */
1100 static int subbuf_read_actor(size_t read_start,
1101                              struct rchan_buf *buf,
1102                              size_t avail,
1103                              read_descriptor_t *desc,
1104                              read_actor_t actor)
1105 {
1106         void *from;
1107         int ret = 0;
1108
1109         from = buf->start + read_start;
1110         ret = avail;
1111         if (copy_to_user(desc->arg.buf, from, avail)) {
1112                 desc->error = -EFAULT;
1113                 ret = 0;
1114         }
1115         desc->arg.data += ret;
1116         desc->written += ret;
1117         desc->count -= ret;
1118
1119         return ret;
1120 }
1121
1122 typedef int (*subbuf_actor_t) (size_t read_start,
1123                                struct rchan_buf *buf,
1124                                size_t avail,
1125                                read_descriptor_t *desc,
1126                                read_actor_t actor);
1127
1128 /*
1129  *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1130  */
1131 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1132                                         subbuf_actor_t subbuf_actor,
1133                                         read_actor_t actor,
1134                                         read_descriptor_t *desc)
1135 {
1136         struct rchan_buf *buf = filp->private_data;
1137         size_t read_start, avail;
1138         int ret;
1139
1140         if (!desc->count)
1141                 return 0;
1142
1143         mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1144         do {
1145                 if (!relay_file_read_avail(buf, *ppos))
1146                         break;
1147
1148                 read_start = relay_file_read_start_pos(*ppos, buf);
1149                 avail = relay_file_read_subbuf_avail(read_start, buf);
1150                 if (!avail)
1151                         break;
1152
1153                 avail = min(desc->count, avail);
1154                 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1155                 if (desc->error < 0)
1156                         break;
1157
1158                 if (ret) {
1159                         relay_file_read_consume(buf, read_start, ret);
1160                         *ppos = relay_file_read_end_pos(buf, read_start, ret);
1161                 }
1162         } while (desc->count && ret);
1163         mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1164
1165         return desc->written;
1166 }
1167
1168 static ssize_t relay_file_read(struct file *filp,
1169                                char __user *buffer,
1170                                size_t count,
1171                                loff_t *ppos)
1172 {
1173         read_descriptor_t desc;
1174         desc.written = 0;
1175         desc.count = count;
1176         desc.arg.buf = buffer;
1177         desc.error = 0;
1178         return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1179                                        NULL, &desc);
1180 }
1181
1182 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1183 {
1184         rbuf->bytes_consumed += bytes_consumed;
1185
1186         if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1187                 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1188                 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1189         }
1190 }
1191
1192 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1193                                    struct pipe_buffer *buf)
1194 {
1195         struct rchan_buf *rbuf;
1196
1197         rbuf = (struct rchan_buf *)page_private(buf->page);
1198         relay_consume_bytes(rbuf, buf->private);
1199 }
1200
1201 static const struct pipe_buf_operations relay_pipe_buf_ops = {
1202         .can_merge = 0,
1203         .map = generic_pipe_buf_map,
1204         .unmap = generic_pipe_buf_unmap,
1205         .confirm = generic_pipe_buf_confirm,
1206         .release = relay_pipe_buf_release,
1207         .steal = generic_pipe_buf_steal,
1208         .get = generic_pipe_buf_get,
1209 };
1210
1211 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1212 {
1213 }
1214
1215 /*
1216  *      subbuf_splice_actor - splice up to one subbuf's worth of data
1217  */
1218 static ssize_t subbuf_splice_actor(struct file *in,
1219                                loff_t *ppos,
1220                                struct pipe_inode_info *pipe,
1221                                size_t len,
1222                                unsigned int flags,
1223                                int *nonpad_ret)
1224 {
1225         unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1226         struct rchan_buf *rbuf = in->private_data;
1227         unsigned int subbuf_size = rbuf->chan->subbuf_size;
1228         uint64_t pos = (uint64_t) *ppos;
1229         uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1230         size_t read_start = (size_t) do_div(pos, alloc_size);
1231         size_t read_subbuf = read_start / subbuf_size;
1232         size_t padding = rbuf->padding[read_subbuf];
1233         size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1234         struct page *pages[PIPE_DEF_BUFFERS];
1235         struct partial_page partial[PIPE_DEF_BUFFERS];
1236         struct splice_pipe_desc spd = {
1237                 .pages = pages,
1238                 .nr_pages = 0,
1239                 .partial = partial,
1240                 .flags = flags,
1241                 .ops = &relay_pipe_buf_ops,
1242                 .spd_release = relay_page_release,
1243         };
1244         ssize_t ret;
1245
1246         if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1247                 return 0;
1248         if (splice_grow_spd(pipe, &spd))
1249                 return -ENOMEM;
1250
1251         /*
1252          * Adjust read len, if longer than what is available
1253          */
1254         if (len > (subbuf_size - read_start % subbuf_size))
1255                 len = subbuf_size - read_start % subbuf_size;
1256
1257         subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1258         pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1259         poff = read_start & ~PAGE_MASK;
1260         nr_pages = min_t(unsigned int, subbuf_pages, pipe->buffers);
1261
1262         for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1263                 unsigned int this_len, this_end, private;
1264                 unsigned int cur_pos = read_start + total_len;
1265
1266                 if (!len)
1267                         break;
1268
1269                 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1270                 private = this_len;
1271
1272                 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1273                 spd.partial[spd.nr_pages].offset = poff;
1274
1275                 this_end = cur_pos + this_len;
1276                 if (this_end >= nonpad_end) {
1277                         this_len = nonpad_end - cur_pos;
1278                         private = this_len + padding;
1279                 }
1280                 spd.partial[spd.nr_pages].len = this_len;
1281                 spd.partial[spd.nr_pages].private = private;
1282
1283                 len -= this_len;
1284                 total_len += this_len;
1285                 poff = 0;
1286                 pidx = (pidx + 1) % subbuf_pages;
1287
1288                 if (this_end >= nonpad_end) {
1289                         spd.nr_pages++;
1290                         break;
1291                 }
1292         }
1293
1294         ret = 0;
1295         if (!spd.nr_pages)
1296                 goto out;
1297
1298         ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1299         if (ret < 0 || ret < total_len)
1300                 goto out;
1301
1302         if (read_start + ret == nonpad_end)
1303                 ret += padding;
1304
1305 out:
1306         splice_shrink_spd(pipe, &spd);
1307         return ret;
1308 }
1309
1310 static ssize_t relay_file_splice_read(struct file *in,
1311                                       loff_t *ppos,
1312                                       struct pipe_inode_info *pipe,
1313                                       size_t len,
1314                                       unsigned int flags)
1315 {
1316         ssize_t spliced;
1317         int ret;
1318         int nonpad_ret = 0;
1319
1320         ret = 0;
1321         spliced = 0;
1322
1323         while (len && !spliced) {
1324                 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1325                 if (ret < 0)
1326                         break;
1327                 else if (!ret) {
1328                         if (flags & SPLICE_F_NONBLOCK)
1329                                 ret = -EAGAIN;
1330                         break;
1331                 }
1332
1333                 *ppos += ret;
1334                 if (ret > len)
1335                         len = 0;
1336                 else
1337                         len -= ret;
1338                 spliced += nonpad_ret;
1339                 nonpad_ret = 0;
1340         }
1341
1342         if (spliced)
1343                 return spliced;
1344
1345         return ret;
1346 }
1347
1348 const struct file_operations relay_file_operations = {
1349         .open           = relay_file_open,
1350         .poll           = relay_file_poll,
1351         .mmap           = relay_file_mmap,
1352         .read           = relay_file_read,
1353         .llseek         = no_llseek,
1354         .release        = relay_file_release,
1355         .splice_read    = relay_file_splice_read,
1356 };
1357 EXPORT_SYMBOL_GPL(relay_file_operations);
1358
1359 static __init int relay_init(void)
1360 {
1361
1362         hotcpu_notifier(relay_hotcpu_callback, 0);
1363         return 0;
1364 }
1365
1366 early_initcall(relay_init);