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 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_online_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 /* 411 * relay_open_buf - create a new relay channel buffer 412 * 413 * used by relay_open() and CPU hotplug. 414 */ 415 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu) 416 { 417 struct rchan_buf *buf = NULL; 418 struct dentry *dentry; 419 char *tmpname; 420 421 if (chan->is_global) 422 return chan->buf[0]; 423 424 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL); 425 if (!tmpname) 426 goto end; 427 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu); 428 429 buf = relay_create_buf(chan); 430 if (!buf) 431 goto free_name; 432 433 buf->cpu = cpu; 434 __relay_reset(buf, 1); 435 436 /* Create file in fs */ 437 dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR, 438 buf, &chan->is_global); 439 if (!dentry) 440 goto free_buf; 441 442 buf->dentry = dentry; 443 444 if(chan->is_global) { 445 chan->buf[0] = buf; 446 buf->cpu = 0; 447 } 448 449 goto free_name; 450 451 free_buf: 452 relay_destroy_buf(buf); 453 buf = NULL; 454 free_name: 455 kfree(tmpname); 456 end: 457 return buf; 458 } 459 460 /** 461 * relay_close_buf - close a channel buffer 462 * @buf: channel buffer 463 * 464 * Marks the buffer finalized and restores the default callbacks. 465 * The channel buffer and channel buffer data structure are then freed 466 * automatically when the last reference is given up. 467 */ 468 static void relay_close_buf(struct rchan_buf *buf) 469 { 470 buf->finalized = 1; 471 del_timer_sync(&buf->timer); 472 kref_put(&buf->kref, relay_remove_buf); 473 } 474 475 static void setup_callbacks(struct rchan *chan, 476 struct rchan_callbacks *cb) 477 { 478 if (!cb) { 479 chan->cb = &default_channel_callbacks; 480 return; 481 } 482 483 if (!cb->subbuf_start) 484 cb->subbuf_start = subbuf_start_default_callback; 485 if (!cb->buf_mapped) 486 cb->buf_mapped = buf_mapped_default_callback; 487 if (!cb->buf_unmapped) 488 cb->buf_unmapped = buf_unmapped_default_callback; 489 if (!cb->create_buf_file) 490 cb->create_buf_file = create_buf_file_default_callback; 491 if (!cb->remove_buf_file) 492 cb->remove_buf_file = remove_buf_file_default_callback; 493 chan->cb = cb; 494 } 495 496 /** 497 * relay_hotcpu_callback - CPU hotplug callback 498 * @nb: notifier block 499 * @action: hotplug action to take 500 * @hcpu: CPU number 501 * 502 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD) 503 */ 504 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb, 505 unsigned long action, 506 void *hcpu) 507 { 508 unsigned int hotcpu = (unsigned long)hcpu; 509 struct rchan *chan; 510 511 switch(action) { 512 case CPU_UP_PREPARE: 513 case CPU_UP_PREPARE_FROZEN: 514 mutex_lock(&relay_channels_mutex); 515 list_for_each_entry(chan, &relay_channels, list) { 516 if (chan->buf[hotcpu]) 517 continue; 518 chan->buf[hotcpu] = relay_open_buf(chan, hotcpu); 519 if(!chan->buf[hotcpu]) { 520 printk(KERN_ERR 521 "relay_hotcpu_callback: cpu %d buffer " 522 "creation failed\n", hotcpu); 523 mutex_unlock(&relay_channels_mutex); 524 return NOTIFY_BAD; 525 } 526 } 527 mutex_unlock(&relay_channels_mutex); 528 break; 529 case CPU_DEAD: 530 case CPU_DEAD_FROZEN: 531 /* No need to flush the cpu : will be flushed upon 532 * final relay_flush() call. */ 533 break; 534 } 535 return NOTIFY_OK; 536 } 537 538 /** 539 * relay_open - create a new relay channel 540 * @base_filename: base name of files to create 541 * @parent: dentry of parent directory, %NULL for root directory 542 * @subbuf_size: size of sub-buffers 543 * @n_subbufs: number of sub-buffers 544 * @cb: client callback functions 545 * @private_data: user-defined data 546 * 547 * Returns channel pointer if successful, %NULL otherwise. 548 * 549 * Creates a channel buffer for each cpu using the sizes and 550 * attributes specified. The created channel buffer files 551 * will be named base_filename0...base_filenameN-1. File 552 * permissions will be %S_IRUSR. 553 */ 554 struct rchan *relay_open(const char *base_filename, 555 struct dentry *parent, 556 size_t subbuf_size, 557 size_t n_subbufs, 558 struct rchan_callbacks *cb, 559 void *private_data) 560 { 561 unsigned int i; 562 struct rchan *chan; 563 if (!base_filename) 564 return NULL; 565 566 if (!(subbuf_size && n_subbufs)) 567 return NULL; 568 569 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL); 570 if (!chan) 571 return NULL; 572 573 chan->version = RELAYFS_CHANNEL_VERSION; 574 chan->n_subbufs = n_subbufs; 575 chan->subbuf_size = subbuf_size; 576 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs); 577 chan->parent = parent; 578 chan->private_data = private_data; 579 strlcpy(chan->base_filename, base_filename, NAME_MAX); 580 setup_callbacks(chan, cb); 581 kref_init(&chan->kref); 582 583 mutex_lock(&relay_channels_mutex); 584 for_each_online_cpu(i) { 585 chan->buf[i] = relay_open_buf(chan, i); 586 if (!chan->buf[i]) 587 goto free_bufs; 588 } 589 list_add(&chan->list, &relay_channels); 590 mutex_unlock(&relay_channels_mutex); 591 592 return chan; 593 594 free_bufs: 595 for_each_online_cpu(i) { 596 if (!chan->buf[i]) 597 break; 598 relay_close_buf(chan->buf[i]); 599 } 600 601 kref_put(&chan->kref, relay_destroy_channel); 602 mutex_unlock(&relay_channels_mutex); 603 return NULL; 604 } 605 EXPORT_SYMBOL_GPL(relay_open); 606 607 /** 608 * relay_switch_subbuf - switch to a new sub-buffer 609 * @buf: channel buffer 610 * @length: size of current event 611 * 612 * Returns either the length passed in or 0 if full. 613 * 614 * Performs sub-buffer-switch tasks such as invoking callbacks, 615 * updating padding counts, waking up readers, etc. 616 */ 617 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) 618 { 619 void *old, *new; 620 size_t old_subbuf, new_subbuf; 621 622 if (unlikely(length > buf->chan->subbuf_size)) 623 goto toobig; 624 625 if (buf->offset != buf->chan->subbuf_size + 1) { 626 buf->prev_padding = buf->chan->subbuf_size - buf->offset; 627 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; 628 buf->padding[old_subbuf] = buf->prev_padding; 629 buf->subbufs_produced++; 630 buf->dentry->d_inode->i_size += buf->chan->subbuf_size - 631 buf->padding[old_subbuf]; 632 smp_mb(); 633 if (waitqueue_active(&buf->read_wait)) 634 /* 635 * Calling wake_up_interruptible() from here 636 * will deadlock if we happen to be logging 637 * from the scheduler (trying to re-grab 638 * rq->lock), so defer it. 639 */ 640 __mod_timer(&buf->timer, jiffies + 1); 641 } 642 643 old = buf->data; 644 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; 645 new = buf->start + new_subbuf * buf->chan->subbuf_size; 646 buf->offset = 0; 647 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) { 648 buf->offset = buf->chan->subbuf_size + 1; 649 return 0; 650 } 651 buf->data = new; 652 buf->padding[new_subbuf] = 0; 653 654 if (unlikely(length + buf->offset > buf->chan->subbuf_size)) 655 goto toobig; 656 657 return length; 658 659 toobig: 660 buf->chan->last_toobig = length; 661 return 0; 662 } 663 EXPORT_SYMBOL_GPL(relay_switch_subbuf); 664 665 /** 666 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count 667 * @chan: the channel 668 * @cpu: the cpu associated with the channel buffer to update 669 * @subbufs_consumed: number of sub-buffers to add to current buf's count 670 * 671 * Adds to the channel buffer's consumed sub-buffer count. 672 * subbufs_consumed should be the number of sub-buffers newly consumed, 673 * not the total consumed. 674 * 675 * NOTE. Kernel clients don't need to call this function if the channel 676 * mode is 'overwrite'. 677 */ 678 void relay_subbufs_consumed(struct rchan *chan, 679 unsigned int cpu, 680 size_t subbufs_consumed) 681 { 682 struct rchan_buf *buf; 683 684 if (!chan) 685 return; 686 687 if (cpu >= NR_CPUS || !chan->buf[cpu]) 688 return; 689 690 buf = chan->buf[cpu]; 691 buf->subbufs_consumed += subbufs_consumed; 692 if (buf->subbufs_consumed > buf->subbufs_produced) 693 buf->subbufs_consumed = buf->subbufs_produced; 694 } 695 EXPORT_SYMBOL_GPL(relay_subbufs_consumed); 696 697 /** 698 * relay_close - close the channel 699 * @chan: the channel 700 * 701 * Closes all channel buffers and frees the channel. 702 */ 703 void relay_close(struct rchan *chan) 704 { 705 unsigned int i; 706 707 if (!chan) 708 return; 709 710 mutex_lock(&relay_channels_mutex); 711 if (chan->is_global && chan->buf[0]) 712 relay_close_buf(chan->buf[0]); 713 else 714 for_each_possible_cpu(i) 715 if (chan->buf[i]) 716 relay_close_buf(chan->buf[i]); 717 718 if (chan->last_toobig) 719 printk(KERN_WARNING "relay: one or more items not logged " 720 "[item size (%Zd) > sub-buffer size (%Zd)]\n", 721 chan->last_toobig, chan->subbuf_size); 722 723 list_del(&chan->list); 724 kref_put(&chan->kref, relay_destroy_channel); 725 mutex_unlock(&relay_channels_mutex); 726 } 727 EXPORT_SYMBOL_GPL(relay_close); 728 729 /** 730 * relay_flush - close the channel 731 * @chan: the channel 732 * 733 * Flushes all channel buffers, i.e. forces buffer switch. 734 */ 735 void relay_flush(struct rchan *chan) 736 { 737 unsigned int i; 738 739 if (!chan) 740 return; 741 742 if (chan->is_global && chan->buf[0]) { 743 relay_switch_subbuf(chan->buf[0], 0); 744 return; 745 } 746 747 mutex_lock(&relay_channels_mutex); 748 for_each_possible_cpu(i) 749 if (chan->buf[i]) 750 relay_switch_subbuf(chan->buf[i], 0); 751 mutex_unlock(&relay_channels_mutex); 752 } 753 EXPORT_SYMBOL_GPL(relay_flush); 754 755 /** 756 * relay_file_open - open file op for relay files 757 * @inode: the inode 758 * @filp: the file 759 * 760 * Increments the channel buffer refcount. 761 */ 762 static int relay_file_open(struct inode *inode, struct file *filp) 763 { 764 struct rchan_buf *buf = inode->i_private; 765 kref_get(&buf->kref); 766 filp->private_data = buf; 767 768 return nonseekable_open(inode, filp); 769 } 770 771 /** 772 * relay_file_mmap - mmap file op for relay files 773 * @filp: the file 774 * @vma: the vma describing what to map 775 * 776 * Calls upon relay_mmap_buf() to map the file into user space. 777 */ 778 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma) 779 { 780 struct rchan_buf *buf = filp->private_data; 781 return relay_mmap_buf(buf, vma); 782 } 783 784 /** 785 * relay_file_poll - poll file op for relay files 786 * @filp: the file 787 * @wait: poll table 788 * 789 * Poll implemention. 790 */ 791 static unsigned int relay_file_poll(struct file *filp, poll_table *wait) 792 { 793 unsigned int mask = 0; 794 struct rchan_buf *buf = filp->private_data; 795 796 if (buf->finalized) 797 return POLLERR; 798 799 if (filp->f_mode & FMODE_READ) { 800 poll_wait(filp, &buf->read_wait, wait); 801 if (!relay_buf_empty(buf)) 802 mask |= POLLIN | POLLRDNORM; 803 } 804 805 return mask; 806 } 807 808 /** 809 * relay_file_release - release file op for relay files 810 * @inode: the inode 811 * @filp: the file 812 * 813 * Decrements the channel refcount, as the filesystem is 814 * no longer using it. 815 */ 816 static int relay_file_release(struct inode *inode, struct file *filp) 817 { 818 struct rchan_buf *buf = filp->private_data; 819 kref_put(&buf->kref, relay_remove_buf); 820 821 return 0; 822 } 823 824 /* 825 * relay_file_read_consume - update the consumed count for the buffer 826 */ 827 static void relay_file_read_consume(struct rchan_buf *buf, 828 size_t read_pos, 829 size_t bytes_consumed) 830 { 831 size_t subbuf_size = buf->chan->subbuf_size; 832 size_t n_subbufs = buf->chan->n_subbufs; 833 size_t read_subbuf; 834 835 if (buf->bytes_consumed + bytes_consumed > subbuf_size) { 836 relay_subbufs_consumed(buf->chan, buf->cpu, 1); 837 buf->bytes_consumed = 0; 838 } 839 840 buf->bytes_consumed += bytes_consumed; 841 if (!read_pos) 842 read_subbuf = buf->subbufs_consumed % n_subbufs; 843 else 844 read_subbuf = read_pos / buf->chan->subbuf_size; 845 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) { 846 if ((read_subbuf == buf->subbufs_produced % n_subbufs) && 847 (buf->offset == subbuf_size)) 848 return; 849 relay_subbufs_consumed(buf->chan, buf->cpu, 1); 850 buf->bytes_consumed = 0; 851 } 852 } 853 854 /* 855 * relay_file_read_avail - boolean, are there unconsumed bytes available? 856 */ 857 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos) 858 { 859 size_t subbuf_size = buf->chan->subbuf_size; 860 size_t n_subbufs = buf->chan->n_subbufs; 861 size_t produced = buf->subbufs_produced; 862 size_t consumed = buf->subbufs_consumed; 863 864 relay_file_read_consume(buf, read_pos, 0); 865 866 if (unlikely(buf->offset > subbuf_size)) { 867 if (produced == consumed) 868 return 0; 869 return 1; 870 } 871 872 if (unlikely(produced - consumed >= n_subbufs)) { 873 consumed = produced - n_subbufs + 1; 874 buf->subbufs_consumed = consumed; 875 buf->bytes_consumed = 0; 876 } 877 878 produced = (produced % n_subbufs) * subbuf_size + buf->offset; 879 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed; 880 881 if (consumed > produced) 882 produced += n_subbufs * subbuf_size; 883 884 if (consumed == produced) 885 return 0; 886 887 return 1; 888 } 889 890 /** 891 * relay_file_read_subbuf_avail - return bytes available in sub-buffer 892 * @read_pos: file read position 893 * @buf: relay channel buffer 894 */ 895 static size_t relay_file_read_subbuf_avail(size_t read_pos, 896 struct rchan_buf *buf) 897 { 898 size_t padding, avail = 0; 899 size_t read_subbuf, read_offset, write_subbuf, write_offset; 900 size_t subbuf_size = buf->chan->subbuf_size; 901 902 write_subbuf = (buf->data - buf->start) / subbuf_size; 903 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset; 904 read_subbuf = read_pos / subbuf_size; 905 read_offset = read_pos % subbuf_size; 906 padding = buf->padding[read_subbuf]; 907 908 if (read_subbuf == write_subbuf) { 909 if (read_offset + padding < write_offset) 910 avail = write_offset - (read_offset + padding); 911 } else 912 avail = (subbuf_size - padding) - read_offset; 913 914 return avail; 915 } 916 917 /** 918 * relay_file_read_start_pos - find the first available byte to read 919 * @read_pos: file read position 920 * @buf: relay channel buffer 921 * 922 * If the @read_pos is in the middle of padding, return the 923 * position of the first actually available byte, otherwise 924 * return the original value. 925 */ 926 static size_t relay_file_read_start_pos(size_t read_pos, 927 struct rchan_buf *buf) 928 { 929 size_t read_subbuf, padding, padding_start, padding_end; 930 size_t subbuf_size = buf->chan->subbuf_size; 931 size_t n_subbufs = buf->chan->n_subbufs; 932 size_t consumed = buf->subbufs_consumed % n_subbufs; 933 934 if (!read_pos) 935 read_pos = consumed * subbuf_size + buf->bytes_consumed; 936 read_subbuf = read_pos / subbuf_size; 937 padding = buf->padding[read_subbuf]; 938 padding_start = (read_subbuf + 1) * subbuf_size - padding; 939 padding_end = (read_subbuf + 1) * subbuf_size; 940 if (read_pos >= padding_start && read_pos < padding_end) { 941 read_subbuf = (read_subbuf + 1) % n_subbufs; 942 read_pos = read_subbuf * subbuf_size; 943 } 944 945 return read_pos; 946 } 947 948 /** 949 * relay_file_read_end_pos - return the new read position 950 * @read_pos: file read position 951 * @buf: relay channel buffer 952 * @count: number of bytes to be read 953 */ 954 static size_t relay_file_read_end_pos(struct rchan_buf *buf, 955 size_t read_pos, 956 size_t count) 957 { 958 size_t read_subbuf, padding, end_pos; 959 size_t subbuf_size = buf->chan->subbuf_size; 960 size_t n_subbufs = buf->chan->n_subbufs; 961 962 read_subbuf = read_pos / subbuf_size; 963 padding = buf->padding[read_subbuf]; 964 if (read_pos % subbuf_size + count + padding == subbuf_size) 965 end_pos = (read_subbuf + 1) * subbuf_size; 966 else 967 end_pos = read_pos + count; 968 if (end_pos >= subbuf_size * n_subbufs) 969 end_pos = 0; 970 971 return end_pos; 972 } 973 974 /* 975 * subbuf_read_actor - read up to one subbuf's worth of data 976 */ 977 static int subbuf_read_actor(size_t read_start, 978 struct rchan_buf *buf, 979 size_t avail, 980 read_descriptor_t *desc, 981 read_actor_t actor) 982 { 983 void *from; 984 int ret = 0; 985 986 from = buf->start + read_start; 987 ret = avail; 988 if (copy_to_user(desc->arg.buf, from, avail)) { 989 desc->error = -EFAULT; 990 ret = 0; 991 } 992 desc->arg.data += ret; 993 desc->written += ret; 994 desc->count -= ret; 995 996 return ret; 997 } 998 999 typedef int (*subbuf_actor_t) (size_t read_start, 1000 struct rchan_buf *buf, 1001 size_t avail, 1002 read_descriptor_t *desc, 1003 read_actor_t actor); 1004 1005 /* 1006 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries 1007 */ 1008 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos, 1009 subbuf_actor_t subbuf_actor, 1010 read_actor_t actor, 1011 read_descriptor_t *desc) 1012 { 1013 struct rchan_buf *buf = filp->private_data; 1014 size_t read_start, avail; 1015 int ret; 1016 1017 if (!desc->count) 1018 return 0; 1019 1020 mutex_lock(&filp->f_path.dentry->d_inode->i_mutex); 1021 do { 1022 if (!relay_file_read_avail(buf, *ppos)) 1023 break; 1024 1025 read_start = relay_file_read_start_pos(*ppos, buf); 1026 avail = relay_file_read_subbuf_avail(read_start, buf); 1027 if (!avail) 1028 break; 1029 1030 avail = min(desc->count, avail); 1031 ret = subbuf_actor(read_start, buf, avail, desc, actor); 1032 if (desc->error < 0) 1033 break; 1034 1035 if (ret) { 1036 relay_file_read_consume(buf, read_start, ret); 1037 *ppos = relay_file_read_end_pos(buf, read_start, ret); 1038 } 1039 } while (desc->count && ret); 1040 mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex); 1041 1042 return desc->written; 1043 } 1044 1045 static ssize_t relay_file_read(struct file *filp, 1046 char __user *buffer, 1047 size_t count, 1048 loff_t *ppos) 1049 { 1050 read_descriptor_t desc; 1051 desc.written = 0; 1052 desc.count = count; 1053 desc.arg.buf = buffer; 1054 desc.error = 0; 1055 return relay_file_read_subbufs(filp, ppos, subbuf_read_actor, 1056 NULL, &desc); 1057 } 1058 1059 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed) 1060 { 1061 rbuf->bytes_consumed += bytes_consumed; 1062 1063 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) { 1064 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1); 1065 rbuf->bytes_consumed %= rbuf->chan->subbuf_size; 1066 } 1067 } 1068 1069 static void relay_pipe_buf_release(struct pipe_inode_info *pipe, 1070 struct pipe_buffer *buf) 1071 { 1072 struct rchan_buf *rbuf; 1073 1074 rbuf = (struct rchan_buf *)page_private(buf->page); 1075 relay_consume_bytes(rbuf, buf->private); 1076 } 1077 1078 static struct pipe_buf_operations relay_pipe_buf_ops = { 1079 .can_merge = 0, 1080 .map = generic_pipe_buf_map, 1081 .unmap = generic_pipe_buf_unmap, 1082 .confirm = generic_pipe_buf_confirm, 1083 .release = relay_pipe_buf_release, 1084 .steal = generic_pipe_buf_steal, 1085 .get = generic_pipe_buf_get, 1086 }; 1087 1088 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i) 1089 { 1090 } 1091 1092 /* 1093 * subbuf_splice_actor - splice up to one subbuf's worth of data 1094 */ 1095 static int subbuf_splice_actor(struct file *in, 1096 loff_t *ppos, 1097 struct pipe_inode_info *pipe, 1098 size_t len, 1099 unsigned int flags, 1100 int *nonpad_ret) 1101 { 1102 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret; 1103 struct rchan_buf *rbuf = in->private_data; 1104 unsigned int subbuf_size = rbuf->chan->subbuf_size; 1105 uint64_t pos = (uint64_t) *ppos; 1106 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size; 1107 size_t read_start = (size_t) do_div(pos, alloc_size); 1108 size_t read_subbuf = read_start / subbuf_size; 1109 size_t padding = rbuf->padding[read_subbuf]; 1110 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding; 1111 struct page *pages[PIPE_BUFFERS]; 1112 struct partial_page partial[PIPE_BUFFERS]; 1113 struct splice_pipe_desc spd = { 1114 .pages = pages, 1115 .nr_pages = 0, 1116 .partial = partial, 1117 .flags = flags, 1118 .ops = &relay_pipe_buf_ops, 1119 .spd_release = relay_page_release, 1120 }; 1121 1122 if (rbuf->subbufs_produced == rbuf->subbufs_consumed) 1123 return 0; 1124 1125 /* 1126 * Adjust read len, if longer than what is available 1127 */ 1128 if (len > (subbuf_size - read_start % subbuf_size)) 1129 len = subbuf_size - read_start % subbuf_size; 1130 1131 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT; 1132 pidx = (read_start / PAGE_SIZE) % subbuf_pages; 1133 poff = read_start & ~PAGE_MASK; 1134 nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS); 1135 1136 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) { 1137 unsigned int this_len, this_end, private; 1138 unsigned int cur_pos = read_start + total_len; 1139 1140 if (!len) 1141 break; 1142 1143 this_len = min_t(unsigned long, len, PAGE_SIZE - poff); 1144 private = this_len; 1145 1146 spd.pages[spd.nr_pages] = rbuf->page_array[pidx]; 1147 spd.partial[spd.nr_pages].offset = poff; 1148 1149 this_end = cur_pos + this_len; 1150 if (this_end >= nonpad_end) { 1151 this_len = nonpad_end - cur_pos; 1152 private = this_len + padding; 1153 } 1154 spd.partial[spd.nr_pages].len = this_len; 1155 spd.partial[spd.nr_pages].private = private; 1156 1157 len -= this_len; 1158 total_len += this_len; 1159 poff = 0; 1160 pidx = (pidx + 1) % subbuf_pages; 1161 1162 if (this_end >= nonpad_end) { 1163 spd.nr_pages++; 1164 break; 1165 } 1166 } 1167 1168 if (!spd.nr_pages) 1169 return 0; 1170 1171 ret = *nonpad_ret = splice_to_pipe(pipe, &spd); 1172 if (ret < 0 || ret < total_len) 1173 return ret; 1174 1175 if (read_start + ret == nonpad_end) 1176 ret += padding; 1177 1178 return ret; 1179 } 1180 1181 static ssize_t relay_file_splice_read(struct file *in, 1182 loff_t *ppos, 1183 struct pipe_inode_info *pipe, 1184 size_t len, 1185 unsigned int flags) 1186 { 1187 ssize_t spliced; 1188 int ret; 1189 int nonpad_ret = 0; 1190 1191 ret = 0; 1192 spliced = 0; 1193 1194 while (len && !spliced) { 1195 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret); 1196 if (ret < 0) 1197 break; 1198 else if (!ret) { 1199 if (spliced) 1200 break; 1201 if (flags & SPLICE_F_NONBLOCK) { 1202 ret = -EAGAIN; 1203 break; 1204 } 1205 } 1206 1207 *ppos += ret; 1208 if (ret > len) 1209 len = 0; 1210 else 1211 len -= ret; 1212 spliced += nonpad_ret; 1213 nonpad_ret = 0; 1214 } 1215 1216 if (spliced) 1217 return spliced; 1218 1219 return ret; 1220 } 1221 1222 const struct file_operations relay_file_operations = { 1223 .open = relay_file_open, 1224 .poll = relay_file_poll, 1225 .mmap = relay_file_mmap, 1226 .read = relay_file_read, 1227 .llseek = no_llseek, 1228 .release = relay_file_release, 1229 .splice_read = relay_file_splice_read, 1230 }; 1231 EXPORT_SYMBOL_GPL(relay_file_operations); 1232 1233 static __init int relay_init(void) 1234 { 1235 1236 hotcpu_notifier(relay_hotcpu_callback, 0); 1237 return 0; 1238 } 1239 1240 module_init(relay_init); 1241