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 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 vma->vm_flags |= 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 = NULL;
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
994 read_subbuf = read_pos / subbuf_size;
995 padding = buf->padding[read_subbuf];
996 padding_start = (read_subbuf + 1) * subbuf_size - padding;
997 padding_end = (read_subbuf + 1) * subbuf_size;
998 if (read_pos >= padding_start && read_pos < padding_end) {
999 read_subbuf = (read_subbuf + 1) % n_subbufs;
1000 read_pos = read_subbuf * subbuf_size;
1001 }
1002
1003 return read_pos;
1004}
1005
1006/**
1007 * relay_file_read_end_pos - return the new read position
1008 * @read_pos: file read position
1009 * @buf: relay channel buffer
1010 * @count: number of bytes to be read
1011 */
1012static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1013 size_t read_pos,
1014 size_t count)
1015{
1016 size_t read_subbuf, padding, end_pos;
1017 size_t subbuf_size = buf->chan->subbuf_size;
1018 size_t n_subbufs = buf->chan->n_subbufs;
1019
1020 read_subbuf = read_pos / subbuf_size;
1021 padding = buf->padding[read_subbuf];
1022 if (read_pos % subbuf_size + count + padding == subbuf_size)
1023 end_pos = (read_subbuf + 1) * subbuf_size;
1024 else
1025 end_pos = read_pos + count;
1026 if (end_pos >= subbuf_size * n_subbufs)
1027 end_pos = 0;
1028
1029 return end_pos;
1030}
1031
1032static ssize_t relay_file_read(struct file *filp,
1033 char __user *buffer,
1034 size_t count,
1035 loff_t *ppos)
1036{
1037 struct rchan_buf *buf = filp->private_data;
1038 size_t read_start, avail;
1039 size_t written = 0;
1040 int ret;
1041
1042 if (!count)
1043 return 0;
1044
1045 inode_lock(file_inode(filp));
1046 do {
1047 void *from;
1048
1049 if (!relay_file_read_avail(buf))
1050 break;
1051
1052 read_start = relay_file_read_start_pos(buf);
1053 avail = relay_file_read_subbuf_avail(read_start, buf);
1054 if (!avail)
1055 break;
1056
1057 avail = min(count, avail);
1058 from = buf->start + read_start;
1059 ret = avail;
1060 if (copy_to_user(buffer, from, avail))
1061 break;
1062
1063 buffer += ret;
1064 written += ret;
1065 count -= ret;
1066
1067 relay_file_read_consume(buf, read_start, ret);
1068 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1069 } while (count);
1070 inode_unlock(file_inode(filp));
1071
1072 return written;
1073}
1074
1075static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1076{
1077 rbuf->bytes_consumed += bytes_consumed;
1078
1079 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1080 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1081 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1082 }
1083}
1084
1085static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1086 struct pipe_buffer *buf)
1087{
1088 struct rchan_buf *rbuf;
1089
1090 rbuf = (struct rchan_buf *)page_private(buf->page);
1091 relay_consume_bytes(rbuf, buf->private);
1092}
1093
1094static const struct pipe_buf_operations relay_pipe_buf_ops = {
1095 .release = relay_pipe_buf_release,
1096 .try_steal = generic_pipe_buf_try_steal,
1097 .get = generic_pipe_buf_get,
1098};
1099
1100static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1101{
1102}
1103
1104/*
1105 * subbuf_splice_actor - splice up to one subbuf's worth of data
1106 */
1107static ssize_t subbuf_splice_actor(struct file *in,
1108 loff_t *ppos,
1109 struct pipe_inode_info *pipe,
1110 size_t len,
1111 unsigned int flags,
1112 int *nonpad_ret)
1113{
1114 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1115 struct rchan_buf *rbuf = in->private_data;
1116 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1117 uint64_t pos = (uint64_t) *ppos;
1118 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1119 size_t read_start = (size_t) do_div(pos, alloc_size);
1120 size_t read_subbuf = read_start / subbuf_size;
1121 size_t padding = rbuf->padding[read_subbuf];
1122 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1123 struct page *pages[PIPE_DEF_BUFFERS];
1124 struct partial_page partial[PIPE_DEF_BUFFERS];
1125 struct splice_pipe_desc spd = {
1126 .pages = pages,
1127 .nr_pages = 0,
1128 .nr_pages_max = PIPE_DEF_BUFFERS,
1129 .partial = partial,
1130 .ops = &relay_pipe_buf_ops,
1131 .spd_release = relay_page_release,
1132 };
1133 ssize_t ret;
1134
1135 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1136 return 0;
1137 if (splice_grow_spd(pipe, &spd))
1138 return -ENOMEM;
1139
1140 /*
1141 * Adjust read len, if longer than what is available
1142 */
1143 if (len > (subbuf_size - read_start % subbuf_size))
1144 len = subbuf_size - read_start % subbuf_size;
1145
1146 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1147 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1148 poff = read_start & ~PAGE_MASK;
1149 nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1150
1151 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1152 unsigned int this_len, this_end, private;
1153 unsigned int cur_pos = read_start + total_len;
1154
1155 if (!len)
1156 break;
1157
1158 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1159 private = this_len;
1160
1161 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1162 spd.partial[spd.nr_pages].offset = poff;
1163
1164 this_end = cur_pos + this_len;
1165 if (this_end >= nonpad_end) {
1166 this_len = nonpad_end - cur_pos;
1167 private = this_len + padding;
1168 }
1169 spd.partial[spd.nr_pages].len = this_len;
1170 spd.partial[spd.nr_pages].private = private;
1171
1172 len -= this_len;
1173 total_len += this_len;
1174 poff = 0;
1175 pidx = (pidx + 1) % subbuf_pages;
1176
1177 if (this_end >= nonpad_end) {
1178 spd.nr_pages++;
1179 break;
1180 }
1181 }
1182
1183 ret = 0;
1184 if (!spd.nr_pages)
1185 goto out;
1186
1187 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1188 if (ret < 0 || ret < total_len)
1189 goto out;
1190
1191 if (read_start + ret == nonpad_end)
1192 ret += padding;
1193
1194out:
1195 splice_shrink_spd(&spd);
1196 return ret;
1197}
1198
1199static ssize_t relay_file_splice_read(struct file *in,
1200 loff_t *ppos,
1201 struct pipe_inode_info *pipe,
1202 size_t len,
1203 unsigned int flags)
1204{
1205 ssize_t spliced;
1206 int ret;
1207 int nonpad_ret = 0;
1208
1209 ret = 0;
1210 spliced = 0;
1211
1212 while (len && !spliced) {
1213 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1214 if (ret < 0)
1215 break;
1216 else if (!ret) {
1217 if (flags & SPLICE_F_NONBLOCK)
1218 ret = -EAGAIN;
1219 break;
1220 }
1221
1222 *ppos += ret;
1223 if (ret > len)
1224 len = 0;
1225 else
1226 len -= ret;
1227 spliced += nonpad_ret;
1228 nonpad_ret = 0;
1229 }
1230
1231 if (spliced)
1232 return spliced;
1233
1234 return ret;
1235}
1236
1237const struct file_operations relay_file_operations = {
1238 .open = relay_file_open,
1239 .poll = relay_file_poll,
1240 .mmap = relay_file_mmap,
1241 .read = relay_file_read,
1242 .llseek = no_llseek,
1243 .release = relay_file_release,
1244 .splice_read = relay_file_splice_read,
1245};
1246EXPORT_SYMBOL_GPL(relay_file_operations);