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