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