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