linux/kernel/relay.c
<<
>>
Prefs
   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 */
  27static DEFINE_MUTEX(relay_channels_mutex);
  28static LIST_HEAD(relay_channels);
  29
  30/*
  31 * close() vm_op implementation for relay file mapping.
  32 */
  33static 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 */
  42static 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 */
  63static 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 */
  71static struct page **relay_alloc_page_array(unsigned int n_pages)
  72{
  73        const size_t pa_size = n_pages * sizeof(struct page *);
  74        if (pa_size > PAGE_SIZE)
  75                return vzalloc(pa_size);
  76        return kzalloc(pa_size, GFP_KERNEL);
  77}
  78
  79/*
  80 * free an array of pointers of struct page
  81 */
  82static void relay_free_page_array(struct page **array)
  83{
  84        if (is_vmalloc_addr(array))
  85                vfree(array);
  86        else
  87                kfree(array);
  88}
  89
  90/**
  91 *      relay_mmap_buf: - mmap channel buffer to process address space
  92 *      @buf: relay channel buffer
  93 *      @vma: vm_area_struct describing memory to be mapped
  94 *
  95 *      Returns 0 if ok, negative on error
  96 *
  97 *      Caller should already have grabbed mmap_sem.
  98 */
  99static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
 100{
 101        unsigned long length = vma->vm_end - vma->vm_start;
 102        struct file *filp = vma->vm_file;
 103
 104        if (!buf)
 105                return -EBADF;
 106
 107        if (length != (unsigned long)buf->chan->alloc_size)
 108                return -EINVAL;
 109
 110        vma->vm_ops = &relay_file_mmap_ops;
 111        vma->vm_flags |= VM_DONTEXPAND;
 112        vma->vm_private_data = buf;
 113        buf->chan->cb->buf_mapped(buf, filp);
 114
 115        return 0;
 116}
 117
 118/**
 119 *      relay_alloc_buf - allocate a channel buffer
 120 *      @buf: the buffer struct
 121 *      @size: total size of the buffer
 122 *
 123 *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 124 *      passed in size will get page aligned, if it isn't already.
 125 */
 126static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 127{
 128        void *mem;
 129        unsigned int i, j, n_pages;
 130
 131        *size = PAGE_ALIGN(*size);
 132        n_pages = *size >> PAGE_SHIFT;
 133
 134        buf->page_array = relay_alloc_page_array(n_pages);
 135        if (!buf->page_array)
 136                return NULL;
 137
 138        for (i = 0; i < n_pages; i++) {
 139                buf->page_array[i] = alloc_page(GFP_KERNEL);
 140                if (unlikely(!buf->page_array[i]))
 141                        goto depopulate;
 142                set_page_private(buf->page_array[i], (unsigned long)buf);
 143        }
 144        mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
 145        if (!mem)
 146                goto depopulate;
 147
 148        memset(mem, 0, *size);
 149        buf->page_count = n_pages;
 150        return mem;
 151
 152depopulate:
 153        for (j = 0; j < i; j++)
 154                __free_page(buf->page_array[j]);
 155        relay_free_page_array(buf->page_array);
 156        return NULL;
 157}
 158
 159/**
 160 *      relay_create_buf - allocate and initialize a channel buffer
 161 *      @chan: the relay channel
 162 *
 163 *      Returns channel buffer if successful, %NULL otherwise.
 164 */
 165static struct rchan_buf *relay_create_buf(struct rchan *chan)
 166{
 167        struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
 168        if (!buf)
 169                return NULL;
 170
 171        buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
 172        if (!buf->padding)
 173                goto free_buf;
 174
 175        buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 176        if (!buf->start)
 177                goto free_buf;
 178
 179        buf->chan = chan;
 180        kref_get(&buf->chan->kref);
 181        return buf;
 182
 183free_buf:
 184        kfree(buf->padding);
 185        kfree(buf);
 186        return NULL;
 187}
 188
 189/**
 190 *      relay_destroy_channel - free the channel struct
 191 *      @kref: target kernel reference that contains the relay channel
 192 *
 193 *      Should only be called from kref_put().
 194 */
 195static void relay_destroy_channel(struct kref *kref)
 196{
 197        struct rchan *chan = container_of(kref, struct rchan, kref);
 198        kfree(chan);
 199}
 200
 201/**
 202 *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 203 *      @buf: the buffer struct
 204 */
 205static void relay_destroy_buf(struct rchan_buf *buf)
 206{
 207        struct rchan *chan = buf->chan;
 208        unsigned int i;
 209
 210        if (likely(buf->start)) {
 211                vunmap(buf->start);
 212                for (i = 0; i < buf->page_count; i++)
 213                        __free_page(buf->page_array[i]);
 214                relay_free_page_array(buf->page_array);
 215        }
 216        chan->buf[buf->cpu] = NULL;
 217        kfree(buf->padding);
 218        kfree(buf);
 219        kref_put(&chan->kref, relay_destroy_channel);
 220}
 221
 222/**
 223 *      relay_remove_buf - remove a channel buffer
 224 *      @kref: target kernel reference that contains the relay buffer
 225 *
 226 *      Removes the file from the fileystem, which also frees the
 227 *      rchan_buf_struct and the channel buffer.  Should only be called from
 228 *      kref_put().
 229 */
 230static void relay_remove_buf(struct kref *kref)
 231{
 232        struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
 233        buf->chan->cb->remove_buf_file(buf->dentry);
 234        relay_destroy_buf(buf);
 235}
 236
 237/**
 238 *      relay_buf_empty - boolean, is the channel buffer empty?
 239 *      @buf: channel buffer
 240 *
 241 *      Returns 1 if the buffer is empty, 0 otherwise.
 242 */
 243static int relay_buf_empty(struct rchan_buf *buf)
 244{
 245        return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 246}
 247
 248/**
 249 *      relay_buf_full - boolean, is the channel buffer full?
 250 *      @buf: channel buffer
 251 *
 252 *      Returns 1 if the buffer is full, 0 otherwise.
 253 */
 254int relay_buf_full(struct rchan_buf *buf)
 255{
 256        size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
 257        return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 258}
 259EXPORT_SYMBOL_GPL(relay_buf_full);
 260
 261/*
 262 * High-level relay kernel API and associated functions.
 263 */
 264
 265/*
 266 * rchan_callback implementations defining default channel behavior.  Used
 267 * in place of corresponding NULL values in client callback struct.
 268 */
 269
 270/*
 271 * subbuf_start() default callback.  Does nothing.
 272 */
 273static int subbuf_start_default_callback (struct rchan_buf *buf,
 274                                          void *subbuf,
 275                                          void *prev_subbuf,
 276                                          size_t prev_padding)
 277{
 278        if (relay_buf_full(buf))
 279                return 0;
 280
 281        return 1;
 282}
 283
 284/*
 285 * buf_mapped() default callback.  Does nothing.
 286 */
 287static void buf_mapped_default_callback(struct rchan_buf *buf,
 288                                        struct file *filp)
 289{
 290}
 291
 292/*
 293 * buf_unmapped() default callback.  Does nothing.
 294 */
 295static void buf_unmapped_default_callback(struct rchan_buf *buf,
 296                                          struct file *filp)
 297{
 298}
 299
 300/*
 301 * create_buf_file_create() default callback.  Does nothing.
 302 */
 303static struct dentry *create_buf_file_default_callback(const char *filename,
 304                                                       struct dentry *parent,
 305                                                       int mode,
 306                                                       struct rchan_buf *buf,
 307                                                       int *is_global)
 308{
 309        return NULL;
 310}
 311
 312/*
 313 * remove_buf_file() default callback.  Does nothing.
 314 */
 315static int remove_buf_file_default_callback(struct dentry *dentry)
 316{
 317        return -EINVAL;
 318}
 319
 320/* relay channel default callbacks */
 321static struct rchan_callbacks default_channel_callbacks = {
 322        .subbuf_start = subbuf_start_default_callback,
 323        .buf_mapped = buf_mapped_default_callback,
 324        .buf_unmapped = buf_unmapped_default_callback,
 325        .create_buf_file = create_buf_file_default_callback,
 326        .remove_buf_file = remove_buf_file_default_callback,
 327};
 328
 329/**
 330 *      wakeup_readers - wake up readers waiting on a channel
 331 *      @data: contains the channel buffer
 332 *
 333 *      This is the timer function used to defer reader waking.
 334 */
 335static void wakeup_readers(unsigned long data)
 336{
 337        struct rchan_buf *buf = (struct rchan_buf *)data;
 338        wake_up_interruptible(&buf->read_wait);
 339}
 340
 341/**
 342 *      __relay_reset - reset a channel buffer
 343 *      @buf: the channel buffer
 344 *      @init: 1 if this is a first-time initialization
 345 *
 346 *      See relay_reset() for description of effect.
 347 */
 348static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 349{
 350        size_t i;
 351
 352        if (init) {
 353                init_waitqueue_head(&buf->read_wait);
 354                kref_init(&buf->kref);
 355                setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
 356        } else
 357                del_timer_sync(&buf->timer);
 358
 359        buf->subbufs_produced = 0;
 360        buf->subbufs_consumed = 0;
 361        buf->bytes_consumed = 0;
 362        buf->finalized = 0;
 363        buf->data = buf->start;
 364        buf->offset = 0;
 365
 366        for (i = 0; i < buf->chan->n_subbufs; i++)
 367                buf->padding[i] = 0;
 368
 369        buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 370}
 371
 372/**
 373 *      relay_reset - reset the channel
 374 *      @chan: the channel
 375 *
 376 *      This has the effect of erasing all data from all channel buffers
 377 *      and restarting the channel in its initial state.  The buffers
 378 *      are not freed, so any mappings are still in effect.
 379 *
 380 *      NOTE. Care should be taken that the channel isn't actually
 381 *      being used by anything when this call is made.
 382 */
 383void relay_reset(struct rchan *chan)
 384{
 385        unsigned int i;
 386
 387        if (!chan)
 388                return;
 389
 390        if (chan->is_global && chan->buf[0]) {
 391                __relay_reset(chan->buf[0], 0);
 392                return;
 393        }
 394
 395        mutex_lock(&relay_channels_mutex);
 396        for_each_possible_cpu(i)
 397                if (chan->buf[i])
 398                        __relay_reset(chan->buf[i], 0);
 399        mutex_unlock(&relay_channels_mutex);
 400}
 401EXPORT_SYMBOL_GPL(relay_reset);
 402
 403static inline void relay_set_buf_dentry(struct rchan_buf *buf,
 404                                        struct dentry *dentry)
 405{
 406        buf->dentry = dentry;
 407        buf->dentry->d_inode->i_size = buf->early_bytes;
 408}
 409
 410static struct dentry *relay_create_buf_file(struct rchan *chan,
 411                                            struct rchan_buf *buf,
 412                                            unsigned int cpu)
 413{
 414        struct dentry *dentry;
 415        char *tmpname;
 416
 417        tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
 418        if (!tmpname)
 419                return NULL;
 420        snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 421
 422        /* Create file in fs */
 423        dentry = chan->cb->create_buf_file(tmpname, chan->parent,
 424                                           S_IRUSR, buf,
 425                                           &chan->is_global);
 426
 427        kfree(tmpname);
 428
 429        return dentry;
 430}
 431
 432/*
 433 *      relay_open_buf - create a new relay channel buffer
 434 *
 435 *      used by relay_open() and CPU hotplug.
 436 */
 437static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 438{
 439        struct rchan_buf *buf = NULL;
 440        struct dentry *dentry;
 441
 442        if (chan->is_global)
 443                return chan->buf[0];
 444
 445        buf = relay_create_buf(chan);
 446        if (!buf)
 447                return NULL;
 448
 449        if (chan->has_base_filename) {
 450                dentry = relay_create_buf_file(chan, buf, cpu);
 451                if (!dentry)
 452                        goto free_buf;
 453                relay_set_buf_dentry(buf, dentry);
 454        }
 455
 456        buf->cpu = cpu;
 457        __relay_reset(buf, 1);
 458
 459        if(chan->is_global) {
 460                chan->buf[0] = buf;
 461                buf->cpu = 0;
 462        }
 463
 464        return buf;
 465
 466free_buf:
 467        relay_destroy_buf(buf);
 468        return NULL;
 469}
 470
 471/**
 472 *      relay_close_buf - close a channel buffer
 473 *      @buf: channel buffer
 474 *
 475 *      Marks the buffer finalized and restores the default callbacks.
 476 *      The channel buffer and channel buffer data structure are then freed
 477 *      automatically when the last reference is given up.
 478 */
 479static void relay_close_buf(struct rchan_buf *buf)
 480{
 481        buf->finalized = 1;
 482        del_timer_sync(&buf->timer);
 483        kref_put(&buf->kref, relay_remove_buf);
 484}
 485
 486static void setup_callbacks(struct rchan *chan,
 487                                   struct rchan_callbacks *cb)
 488{
 489        if (!cb) {
 490                chan->cb = &default_channel_callbacks;
 491                return;
 492        }
 493
 494        if (!cb->subbuf_start)
 495                cb->subbuf_start = subbuf_start_default_callback;
 496        if (!cb->buf_mapped)
 497                cb->buf_mapped = buf_mapped_default_callback;
 498        if (!cb->buf_unmapped)
 499                cb->buf_unmapped = buf_unmapped_default_callback;
 500        if (!cb->create_buf_file)
 501                cb->create_buf_file = create_buf_file_default_callback;
 502        if (!cb->remove_buf_file)
 503                cb->remove_buf_file = remove_buf_file_default_callback;
 504        chan->cb = cb;
 505}
 506
 507/**
 508 *      relay_hotcpu_callback - CPU hotplug callback
 509 *      @nb: notifier block
 510 *      @action: hotplug action to take
 511 *      @hcpu: CPU number
 512 *
 513 *      Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
 514 */
 515static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
 516                                unsigned long action,
 517                                void *hcpu)
 518{
 519        unsigned int hotcpu = (unsigned long)hcpu;
 520        struct rchan *chan;
 521
 522        switch(action) {
 523        case CPU_UP_PREPARE:
 524        case CPU_UP_PREPARE_FROZEN:
 525                mutex_lock(&relay_channels_mutex);
 526                list_for_each_entry(chan, &relay_channels, list) {
 527                        if (chan->buf[hotcpu])
 528                                continue;
 529                        chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
 530                        if(!chan->buf[hotcpu]) {
 531                                printk(KERN_ERR
 532                                        "relay_hotcpu_callback: cpu %d buffer "
 533                                        "creation failed\n", hotcpu);
 534                                mutex_unlock(&relay_channels_mutex);
 535                                return notifier_from_errno(-ENOMEM);
 536                        }
 537                }
 538                mutex_unlock(&relay_channels_mutex);
 539                break;
 540        case CPU_DEAD:
 541        case CPU_DEAD_FROZEN:
 542                /* No need to flush the cpu : will be flushed upon
 543                 * final relay_flush() call. */
 544                break;
 545        }
 546        return NOTIFY_OK;
 547}
 548
 549/**
 550 *      relay_open - create a new relay channel
 551 *      @base_filename: base name of files to create, %NULL for buffering only
 552 *      @parent: dentry of parent directory, %NULL for root directory or buffer
 553 *      @subbuf_size: size of sub-buffers
 554 *      @n_subbufs: number of sub-buffers
 555 *      @cb: client callback functions
 556 *      @private_data: user-defined data
 557 *
 558 *      Returns channel pointer if successful, %NULL otherwise.
 559 *
 560 *      Creates a channel buffer for each cpu using the sizes and
 561 *      attributes specified.  The created channel buffer files
 562 *      will be named base_filename0...base_filenameN-1.  File
 563 *      permissions will be %S_IRUSR.
 564 */
 565struct rchan *relay_open(const char *base_filename,
 566                         struct dentry *parent,
 567                         size_t subbuf_size,
 568                         size_t n_subbufs,
 569                         struct rchan_callbacks *cb,
 570                         void *private_data)
 571{
 572        unsigned int i;
 573        struct rchan *chan;
 574
 575        if (!(subbuf_size && n_subbufs))
 576                return NULL;
 577
 578        chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 579        if (!chan)
 580                return NULL;
 581
 582        chan->version = RELAYFS_CHANNEL_VERSION;
 583        chan->n_subbufs = n_subbufs;
 584        chan->subbuf_size = subbuf_size;
 585        chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
 586        chan->parent = parent;
 587        chan->private_data = private_data;
 588        if (base_filename) {
 589                chan->has_base_filename = 1;
 590                strlcpy(chan->base_filename, base_filename, NAME_MAX);
 591        }
 592        setup_callbacks(chan, cb);
 593        kref_init(&chan->kref);
 594
 595        mutex_lock(&relay_channels_mutex);
 596        for_each_online_cpu(i) {
 597                chan->buf[i] = relay_open_buf(chan, i);
 598                if (!chan->buf[i])
 599                        goto free_bufs;
 600        }
 601        list_add(&chan->list, &relay_channels);
 602        mutex_unlock(&relay_channels_mutex);
 603
 604        return chan;
 605
 606free_bufs:
 607        for_each_possible_cpu(i) {
 608                if (chan->buf[i])
 609                        relay_close_buf(chan->buf[i]);
 610        }
 611
 612        kref_put(&chan->kref, relay_destroy_channel);
 613        mutex_unlock(&relay_channels_mutex);
 614        return NULL;
 615}
 616EXPORT_SYMBOL_GPL(relay_open);
 617
 618struct rchan_percpu_buf_dispatcher {
 619        struct rchan_buf *buf;
 620        struct dentry *dentry;
 621};
 622
 623/* Called in atomic context. */
 624static void __relay_set_buf_dentry(void *info)
 625{
 626        struct rchan_percpu_buf_dispatcher *p = info;
 627
 628        relay_set_buf_dentry(p->buf, p->dentry);
 629}
 630
 631/**
 632 *      relay_late_setup_files - triggers file creation
 633 *      @chan: channel to operate on
 634 *      @base_filename: base name of files to create
 635 *      @parent: dentry of parent directory, %NULL for root directory
 636 *
 637 *      Returns 0 if successful, non-zero otherwise.
 638 *
 639 *      Use to setup files for a previously buffer-only channel.
 640 *      Useful to do early tracing in kernel, before VFS is up, for example.
 641 */
 642int relay_late_setup_files(struct rchan *chan,
 643                           const char *base_filename,
 644                           struct dentry *parent)
 645{
 646        int err = 0;
 647        unsigned int i, curr_cpu;
 648        unsigned long flags;
 649        struct dentry *dentry;
 650        struct rchan_percpu_buf_dispatcher disp;
 651
 652        if (!chan || !base_filename)
 653                return -EINVAL;
 654
 655        strlcpy(chan->base_filename, base_filename, NAME_MAX);
 656
 657        mutex_lock(&relay_channels_mutex);
 658        /* Is chan already set up? */
 659        if (unlikely(chan->has_base_filename)) {
 660                mutex_unlock(&relay_channels_mutex);
 661                return -EEXIST;
 662        }
 663        chan->has_base_filename = 1;
 664        chan->parent = parent;
 665        curr_cpu = get_cpu();
 666        /*
 667         * The CPU hotplug notifier ran before us and created buffers with
 668         * no files associated. So it's safe to call relay_setup_buf_file()
 669         * on all currently online CPUs.
 670         */
 671        for_each_online_cpu(i) {
 672                if (unlikely(!chan->buf[i])) {
 673                        WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
 674                        err = -EINVAL;
 675                        break;
 676                }
 677
 678                dentry = relay_create_buf_file(chan, chan->buf[i], i);
 679                if (unlikely(!dentry)) {
 680                        err = -EINVAL;
 681                        break;
 682                }
 683
 684                if (curr_cpu == i) {
 685                        local_irq_save(flags);
 686                        relay_set_buf_dentry(chan->buf[i], dentry);
 687                        local_irq_restore(flags);
 688                } else {
 689                        disp.buf = chan->buf[i];
 690                        disp.dentry = dentry;
 691                        smp_mb();
 692                        /* relay_channels_mutex must be held, so wait. */
 693                        err = smp_call_function_single(i,
 694                                                       __relay_set_buf_dentry,
 695                                                       &disp, 1);
 696                }
 697                if (unlikely(err))
 698                        break;
 699        }
 700        put_cpu();
 701        mutex_unlock(&relay_channels_mutex);
 702
 703        return err;
 704}
 705
 706/**
 707 *      relay_switch_subbuf - switch to a new sub-buffer
 708 *      @buf: channel buffer
 709 *      @length: size of current event
 710 *
 711 *      Returns either the length passed in or 0 if full.
 712 *
 713 *      Performs sub-buffer-switch tasks such as invoking callbacks,
 714 *      updating padding counts, waking up readers, etc.
 715 */
 716size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 717{
 718        void *old, *new;
 719        size_t old_subbuf, new_subbuf;
 720
 721        if (unlikely(length > buf->chan->subbuf_size))
 722                goto toobig;
 723
 724        if (buf->offset != buf->chan->subbuf_size + 1) {
 725                buf->prev_padding = buf->chan->subbuf_size - buf->offset;
 726                old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 727                buf->padding[old_subbuf] = buf->prev_padding;
 728                buf->subbufs_produced++;
 729                if (buf->dentry)
 730                        buf->dentry->d_inode->i_size +=
 731                                buf->chan->subbuf_size -
 732                                buf->padding[old_subbuf];
 733                else
 734                        buf->early_bytes += buf->chan->subbuf_size -
 735                                            buf->padding[old_subbuf];
 736                smp_mb();
 737                if (waitqueue_active(&buf->read_wait))
 738                        /*
 739                         * Calling wake_up_interruptible() from here
 740                         * will deadlock if we happen to be logging
 741                         * from the scheduler (trying to re-grab
 742                         * rq->lock), so defer it.
 743                         */
 744                        mod_timer(&buf->timer, jiffies + 1);
 745        }
 746
 747        old = buf->data;
 748        new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 749        new = buf->start + new_subbuf * buf->chan->subbuf_size;
 750        buf->offset = 0;
 751        if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
 752                buf->offset = buf->chan->subbuf_size + 1;
 753                return 0;
 754        }
 755        buf->data = new;
 756        buf->padding[new_subbuf] = 0;
 757
 758        if (unlikely(length + buf->offset > buf->chan->subbuf_size))
 759                goto toobig;
 760
 761        return length;
 762
 763toobig:
 764        buf->chan->last_toobig = length;
 765        return 0;
 766}
 767EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 768
 769/**
 770 *      relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 771 *      @chan: the channel
 772 *      @cpu: the cpu associated with the channel buffer to update
 773 *      @subbufs_consumed: number of sub-buffers to add to current buf's count
 774 *
 775 *      Adds to the channel buffer's consumed sub-buffer count.
 776 *      subbufs_consumed should be the number of sub-buffers newly consumed,
 777 *      not the total consumed.
 778 *
 779 *      NOTE. Kernel clients don't need to call this function if the channel
 780 *      mode is 'overwrite'.
 781 */
 782void relay_subbufs_consumed(struct rchan *chan,
 783                            unsigned int cpu,
 784                            size_t subbufs_consumed)
 785{
 786        struct rchan_buf *buf;
 787
 788        if (!chan)
 789                return;
 790
 791        if (cpu >= NR_CPUS || !chan->buf[cpu] ||
 792                                        subbufs_consumed > chan->n_subbufs)
 793                return;
 794
 795        buf = chan->buf[cpu];
 796        if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
 797                buf->subbufs_consumed = buf->subbufs_produced;
 798        else
 799                buf->subbufs_consumed += subbufs_consumed;
 800}
 801EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 802
 803/**
 804 *      relay_close - close the channel
 805 *      @chan: the channel
 806 *
 807 *      Closes all channel buffers and frees the channel.
 808 */
 809void relay_close(struct rchan *chan)
 810{
 811        unsigned int i;
 812
 813        if (!chan)
 814                return;
 815
 816        mutex_lock(&relay_channels_mutex);
 817        if (chan->is_global && chan->buf[0])
 818                relay_close_buf(chan->buf[0]);
 819        else
 820                for_each_possible_cpu(i)
 821                        if (chan->buf[i])
 822                                relay_close_buf(chan->buf[i]);
 823
 824        if (chan->last_toobig)
 825                printk(KERN_WARNING "relay: one or more items not logged "
 826                       "[item size (%Zd) > sub-buffer size (%Zd)]\n",
 827                       chan->last_toobig, chan->subbuf_size);
 828
 829        list_del(&chan->list);
 830        kref_put(&chan->kref, relay_destroy_channel);
 831        mutex_unlock(&relay_channels_mutex);
 832}
 833EXPORT_SYMBOL_GPL(relay_close);
 834
 835/**
 836 *      relay_flush - close the channel
 837 *      @chan: the channel
 838 *
 839 *      Flushes all channel buffers, i.e. forces buffer switch.
 840 */
 841void relay_flush(struct rchan *chan)
 842{
 843        unsigned int i;
 844
 845        if (!chan)
 846                return;
 847
 848        if (chan->is_global && chan->buf[0]) {
 849                relay_switch_subbuf(chan->buf[0], 0);
 850                return;
 851        }
 852
 853        mutex_lock(&relay_channels_mutex);
 854        for_each_possible_cpu(i)
 855                if (chan->buf[i])
 856                        relay_switch_subbuf(chan->buf[i], 0);
 857        mutex_unlock(&relay_channels_mutex);
 858}
 859EXPORT_SYMBOL_GPL(relay_flush);
 860
 861/**
 862 *      relay_file_open - open file op for relay files
 863 *      @inode: the inode
 864 *      @filp: the file
 865 *
 866 *      Increments the channel buffer refcount.
 867 */
 868static int relay_file_open(struct inode *inode, struct file *filp)
 869{
 870        struct rchan_buf *buf = inode->i_private;
 871        kref_get(&buf->kref);
 872        filp->private_data = buf;
 873
 874        return nonseekable_open(inode, filp);
 875}
 876
 877/**
 878 *      relay_file_mmap - mmap file op for relay files
 879 *      @filp: the file
 880 *      @vma: the vma describing what to map
 881 *
 882 *      Calls upon relay_mmap_buf() to map the file into user space.
 883 */
 884static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 885{
 886        struct rchan_buf *buf = filp->private_data;
 887        return relay_mmap_buf(buf, vma);
 888}
 889
 890/**
 891 *      relay_file_poll - poll file op for relay files
 892 *      @filp: the file
 893 *      @wait: poll table
 894 *
 895 *      Poll implemention.
 896 */
 897static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 898{
 899        unsigned int mask = 0;
 900        struct rchan_buf *buf = filp->private_data;
 901
 902        if (buf->finalized)
 903                return POLLERR;
 904
 905        if (filp->f_mode & FMODE_READ) {
 906                poll_wait(filp, &buf->read_wait, wait);
 907                if (!relay_buf_empty(buf))
 908                        mask |= POLLIN | POLLRDNORM;
 909        }
 910
 911        return mask;
 912}
 913
 914/**
 915 *      relay_file_release - release file op for relay files
 916 *      @inode: the inode
 917 *      @filp: the file
 918 *
 919 *      Decrements the channel refcount, as the filesystem is
 920 *      no longer using it.
 921 */
 922static int relay_file_release(struct inode *inode, struct file *filp)
 923{
 924        struct rchan_buf *buf = filp->private_data;
 925        kref_put(&buf->kref, relay_remove_buf);
 926
 927        return 0;
 928}
 929
 930/*
 931 *      relay_file_read_consume - update the consumed count for the buffer
 932 */
 933static void relay_file_read_consume(struct rchan_buf *buf,
 934                                    size_t read_pos,
 935                                    size_t bytes_consumed)
 936{
 937        size_t subbuf_size = buf->chan->subbuf_size;
 938        size_t n_subbufs = buf->chan->n_subbufs;
 939        size_t read_subbuf;
 940
 941        if (buf->subbufs_produced == buf->subbufs_consumed &&
 942            buf->offset == buf->bytes_consumed)
 943                return;
 944
 945        if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
 946                relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 947                buf->bytes_consumed = 0;
 948        }
 949
 950        buf->bytes_consumed += bytes_consumed;
 951        if (!read_pos)
 952                read_subbuf = buf->subbufs_consumed % n_subbufs;
 953        else
 954                read_subbuf = read_pos / buf->chan->subbuf_size;
 955        if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
 956                if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
 957                    (buf->offset == subbuf_size))
 958                        return;
 959                relay_subbufs_consumed(buf->chan, buf->cpu, 1);
 960                buf->bytes_consumed = 0;
 961        }
 962}
 963
 964/*
 965 *      relay_file_read_avail - boolean, are there unconsumed bytes available?
 966 */
 967static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 968{
 969        size_t subbuf_size = buf->chan->subbuf_size;
 970        size_t n_subbufs = buf->chan->n_subbufs;
 971        size_t produced = buf->subbufs_produced;
 972        size_t consumed = buf->subbufs_consumed;
 973
 974        relay_file_read_consume(buf, read_pos, 0);
 975
 976        consumed = buf->subbufs_consumed;
 977
 978        if (unlikely(buf->offset > subbuf_size)) {
 979                if (produced == consumed)
 980                        return 0;
 981                return 1;
 982        }
 983
 984        if (unlikely(produced - consumed >= n_subbufs)) {
 985                consumed = produced - n_subbufs + 1;
 986                buf->subbufs_consumed = consumed;
 987                buf->bytes_consumed = 0;
 988        }
 989
 990        produced = (produced % n_subbufs) * subbuf_size + buf->offset;
 991        consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 992
 993        if (consumed > produced)
 994                produced += n_subbufs * subbuf_size;
 995
 996        if (consumed == produced) {
 997                if (buf->offset == subbuf_size &&
 998                    buf->subbufs_produced > buf->subbufs_consumed)
 999                        return 1;
1000                return 0;
1001        }
1002
1003        return 1;
1004}
1005
1006/**
1007 *      relay_file_read_subbuf_avail - return bytes available in sub-buffer
1008 *      @read_pos: file read position
1009 *      @buf: relay channel buffer
1010 */
1011static size_t relay_file_read_subbuf_avail(size_t read_pos,
1012                                           struct rchan_buf *buf)
1013{
1014        size_t padding, avail = 0;
1015        size_t read_subbuf, read_offset, write_subbuf, write_offset;
1016        size_t subbuf_size = buf->chan->subbuf_size;
1017
1018        write_subbuf = (buf->data - buf->start) / subbuf_size;
1019        write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1020        read_subbuf = read_pos / subbuf_size;
1021        read_offset = read_pos % subbuf_size;
1022        padding = buf->padding[read_subbuf];
1023
1024        if (read_subbuf == write_subbuf) {
1025                if (read_offset + padding < write_offset)
1026                        avail = write_offset - (read_offset + padding);
1027        } else
1028                avail = (subbuf_size - padding) - read_offset;
1029
1030        return avail;
1031}
1032
1033/**
1034 *      relay_file_read_start_pos - find the first available byte to read
1035 *      @read_pos: file read position
1036 *      @buf: relay channel buffer
1037 *
1038 *      If the @read_pos is in the middle of padding, return the
1039 *      position of the first actually available byte, otherwise
1040 *      return the original value.
1041 */
1042static size_t relay_file_read_start_pos(size_t read_pos,
1043                                        struct rchan_buf *buf)
1044{
1045        size_t read_subbuf, padding, padding_start, padding_end;
1046        size_t subbuf_size = buf->chan->subbuf_size;
1047        size_t n_subbufs = buf->chan->n_subbufs;
1048        size_t consumed = buf->subbufs_consumed % n_subbufs;
1049
1050        if (!read_pos)
1051                read_pos = consumed * subbuf_size + buf->bytes_consumed;
1052        read_subbuf = read_pos / subbuf_size;
1053        padding = buf->padding[read_subbuf];
1054        padding_start = (read_subbuf + 1) * subbuf_size - padding;
1055        padding_end = (read_subbuf + 1) * subbuf_size;
1056        if (read_pos >= padding_start && read_pos < padding_end) {
1057                read_subbuf = (read_subbuf + 1) % n_subbufs;
1058                read_pos = read_subbuf * subbuf_size;
1059        }
1060
1061        return read_pos;
1062}
1063
1064/**
1065 *      relay_file_read_end_pos - return the new read position
1066 *      @read_pos: file read position
1067 *      @buf: relay channel buffer
1068 *      @count: number of bytes to be read
1069 */
1070static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1071                                      size_t read_pos,
1072                                      size_t count)
1073{
1074        size_t read_subbuf, padding, end_pos;
1075        size_t subbuf_size = buf->chan->subbuf_size;
1076        size_t n_subbufs = buf->chan->n_subbufs;
1077
1078        read_subbuf = read_pos / subbuf_size;
1079        padding = buf->padding[read_subbuf];
1080        if (read_pos % subbuf_size + count + padding == subbuf_size)
1081                end_pos = (read_subbuf + 1) * subbuf_size;
1082        else
1083                end_pos = read_pos + count;
1084        if (end_pos >= subbuf_size * n_subbufs)
1085                end_pos = 0;
1086
1087        return end_pos;
1088}
1089
1090/*
1091 *      subbuf_read_actor - read up to one subbuf's worth of data
1092 */
1093static int subbuf_read_actor(size_t read_start,
1094                             struct rchan_buf *buf,
1095                             size_t avail,
1096                             read_descriptor_t *desc,
1097                             read_actor_t actor)
1098{
1099        void *from;
1100        int ret = 0;
1101
1102        from = buf->start + read_start;
1103        ret = avail;
1104        if (copy_to_user(desc->arg.buf, from, avail)) {
1105                desc->error = -EFAULT;
1106                ret = 0;
1107        }
1108        desc->arg.data += ret;
1109        desc->written += ret;
1110        desc->count -= ret;
1111
1112        return ret;
1113}
1114
1115typedef int (*subbuf_actor_t) (size_t read_start,
1116                               struct rchan_buf *buf,
1117                               size_t avail,
1118                               read_descriptor_t *desc,
1119                               read_actor_t actor);
1120
1121/*
1122 *      relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1123 */
1124static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1125                                        subbuf_actor_t subbuf_actor,
1126                                        read_actor_t actor,
1127                                        read_descriptor_t *desc)
1128{
1129        struct rchan_buf *buf = filp->private_data;
1130        size_t read_start, avail;
1131        int ret;
1132
1133        if (!desc->count)
1134                return 0;
1135
1136        mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1137        do {
1138                if (!relay_file_read_avail(buf, *ppos))
1139                        break;
1140
1141                read_start = relay_file_read_start_pos(*ppos, buf);
1142                avail = relay_file_read_subbuf_avail(read_start, buf);
1143                if (!avail)
1144                        break;
1145
1146                avail = min(desc->count, avail);
1147                ret = subbuf_actor(read_start, buf, avail, desc, actor);
1148                if (desc->error < 0)
1149                        break;
1150
1151                if (ret) {
1152                        relay_file_read_consume(buf, read_start, ret);
1153                        *ppos = relay_file_read_end_pos(buf, read_start, ret);
1154                }
1155        } while (desc->count && ret);
1156        mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1157
1158        return desc->written;
1159}
1160
1161static ssize_t relay_file_read(struct file *filp,
1162                               char __user *buffer,
1163                               size_t count,
1164                               loff_t *ppos)
1165{
1166        read_descriptor_t desc;
1167        desc.written = 0;
1168        desc.count = count;
1169        desc.arg.buf = buffer;
1170        desc.error = 0;
1171        return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1172                                       NULL, &desc);
1173}
1174
1175static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1176{
1177        rbuf->bytes_consumed += bytes_consumed;
1178
1179        if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1180                relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1181                rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1182        }
1183}
1184
1185static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1186                                   struct pipe_buffer *buf)
1187{
1188        struct rchan_buf *rbuf;
1189
1190        rbuf = (struct rchan_buf *)page_private(buf->page);
1191        relay_consume_bytes(rbuf, buf->private);
1192}
1193
1194static const struct pipe_buf_operations relay_pipe_buf_ops = {
1195        .can_merge = 0,
1196        .map = generic_pipe_buf_map,
1197        .unmap = generic_pipe_buf_unmap,
1198        .confirm = generic_pipe_buf_confirm,
1199        .release = relay_pipe_buf_release,
1200        .steal = generic_pipe_buf_steal,
1201        .get = generic_pipe_buf_get,
1202};
1203
1204static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1205{
1206}
1207
1208/*
1209 *      subbuf_splice_actor - splice up to one subbuf's worth of data
1210 */
1211static ssize_t subbuf_splice_actor(struct file *in,
1212                               loff_t *ppos,
1213                               struct pipe_inode_info *pipe,
1214                               size_t len,
1215                               unsigned int flags,
1216                               int *nonpad_ret)
1217{
1218        unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1219        struct rchan_buf *rbuf = in->private_data;
1220        unsigned int subbuf_size = rbuf->chan->subbuf_size;
1221        uint64_t pos = (uint64_t) *ppos;
1222        uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1223        size_t read_start = (size_t) do_div(pos, alloc_size);
1224        size_t read_subbuf = read_start / subbuf_size;
1225        size_t padding = rbuf->padding[read_subbuf];
1226        size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1227        struct page *pages[PIPE_DEF_BUFFERS];
1228        struct partial_page partial[PIPE_DEF_BUFFERS];
1229        struct splice_pipe_desc spd = {
1230                .pages = pages,
1231                .nr_pages = 0,
1232                .partial = partial,
1233                .flags = flags,
1234                .ops = &relay_pipe_buf_ops,
1235                .spd_release = relay_page_release,
1236        };
1237        ssize_t ret;
1238
1239        if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1240                return 0;
1241        if (splice_grow_spd(pipe, &spd))
1242                return -ENOMEM;
1243
1244        /*
1245         * Adjust read len, if longer than what is available
1246         */
1247        if (len > (subbuf_size - read_start % subbuf_size))
1248                len = subbuf_size - read_start % subbuf_size;
1249
1250        subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1251        pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1252        poff = read_start & ~PAGE_MASK;
1253        nr_pages = min_t(unsigned int, subbuf_pages, pipe->buffers);
1254
1255        for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1256                unsigned int this_len, this_end, private;
1257                unsigned int cur_pos = read_start + total_len;
1258
1259                if (!len)
1260                        break;
1261
1262                this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1263                private = this_len;
1264
1265                spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1266                spd.partial[spd.nr_pages].offset = poff;
1267
1268                this_end = cur_pos + this_len;
1269                if (this_end >= nonpad_end) {
1270                        this_len = nonpad_end - cur_pos;
1271                        private = this_len + padding;
1272                }
1273                spd.partial[spd.nr_pages].len = this_len;
1274                spd.partial[spd.nr_pages].private = private;
1275
1276                len -= this_len;
1277                total_len += this_len;
1278                poff = 0;
1279                pidx = (pidx + 1) % subbuf_pages;
1280
1281                if (this_end >= nonpad_end) {
1282                        spd.nr_pages++;
1283                        break;
1284                }
1285        }
1286
1287        ret = 0;
1288        if (!spd.nr_pages)
1289                goto out;
1290
1291        ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1292        if (ret < 0 || ret < total_len)
1293                goto out;
1294
1295        if (read_start + ret == nonpad_end)
1296                ret += padding;
1297
1298out:
1299        splice_shrink_spd(pipe, &spd);
1300        return ret;
1301}
1302
1303static ssize_t relay_file_splice_read(struct file *in,
1304                                      loff_t *ppos,
1305                                      struct pipe_inode_info *pipe,
1306                                      size_t len,
1307                                      unsigned int flags)
1308{
1309        ssize_t spliced;
1310        int ret;
1311        int nonpad_ret = 0;
1312
1313        ret = 0;
1314        spliced = 0;
1315
1316        while (len && !spliced) {
1317                ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1318                if (ret < 0)
1319                        break;
1320                else if (!ret) {
1321                        if (flags & SPLICE_F_NONBLOCK)
1322                                ret = -EAGAIN;
1323                        break;
1324                }
1325
1326                *ppos += ret;
1327                if (ret > len)
1328                        len = 0;
1329                else
1330                        len -= ret;
1331                spliced += nonpad_ret;
1332                nonpad_ret = 0;
1333        }
1334
1335        if (spliced)
1336                return spliced;
1337
1338        return ret;
1339}
1340
1341const struct file_operations relay_file_operations = {
1342        .open           = relay_file_open,
1343        .poll           = relay_file_poll,
1344        .mmap           = relay_file_mmap,
1345        .read           = relay_file_read,
1346        .llseek         = no_llseek,
1347        .release        = relay_file_release,
1348        .splice_read    = relay_file_splice_read,
1349};
1350EXPORT_SYMBOL_GPL(relay_file_operations);
1351
1352static __init int relay_init(void)
1353{
1354
1355        hotcpu_notifier(relay_hotcpu_callback, 0);
1356        return 0;
1357}
1358
1359early_initcall(relay_init);
1360
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.