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 int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
43{
44 struct page *page;
45 struct rchan_buf *buf = vma->vm_private_data;
46 pgoff_t pgoff = vmf->pgoff;
47
48 if (!buf)
49 return VM_FAULT_OOM;
50
51 page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
52 if (!page)
53 return VM_FAULT_SIGBUS;
54 get_page(page);
55 vmf->page = page;
56
57 return 0;
58}
59
60/*
61 * vm_ops for relay file mappings.
62 */
63static const struct vm_operations_struct relay_file_mmap_ops = {
64 .fault = relay_buf_fault,
65 .close = relay_file_mmap_close,
66};
67
68/*
69 * allocate an array of pointers of struct page
70 */
71static struct page **relay_alloc_page_array(unsigned int n_pages)
72{
73 const size_t pa_size = n_pages * sizeof(struct page *);
74 if (pa_size > PAGE_SIZE)
75 return vzalloc(pa_size);
76 return kzalloc(pa_size, GFP_KERNEL);
77}
78
79/*
80 * free an array of pointers of struct page
81 */
82static void relay_free_page_array(struct page **array)
83{
84 if (is_vmalloc_addr(array))
85 vfree(array);
86 else
87 kfree(array);
88}
89
90/**
91 * relay_mmap_buf: - mmap channel buffer to process address space
92 * @buf: relay channel buffer
93 * @vma: vm_area_struct describing memory to be mapped
94 *
95 * Returns 0 if ok, negative on error
96 *
97 * Caller should already have grabbed mmap_sem.
98 */
99static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
100{
101 unsigned long length = vma->vm_end - vma->vm_start;
102 struct file *filp = vma->vm_file;
103
104 if (!buf)
105 return -EBADF;
106
107 if (length != (unsigned long)buf->chan->alloc_size)
108 return -EINVAL;
109
110 vma->vm_ops = &relay_file_mmap_ops;
111 vma->vm_flags |= VM_DONTEXPAND;
112 vma->vm_private_data = buf;
113 buf->chan->cb->buf_mapped(buf, filp);
114
115 return 0;
116}
117
118/**
119 * relay_alloc_buf - allocate a channel buffer
120 * @buf: the buffer struct
121 * @size: total size of the buffer
122 *
123 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
124 * passed in size will get page aligned, if it isn't already.
125 */
126static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
127{
128 void *mem;
129 unsigned int i, j, n_pages;
130
131 *size = PAGE_ALIGN(*size);
132 n_pages = *size >> PAGE_SHIFT;
133
134 buf->page_array = relay_alloc_page_array(n_pages);
135 if (!buf->page_array)
136 return NULL;
137
138 for (i = 0; i < n_pages; i++) {
139 buf->page_array[i] = alloc_page(GFP_KERNEL);
140 if (unlikely(!buf->page_array[i]))
141 goto depopulate;
142 set_page_private(buf->page_array[i], (unsigned long)buf);
143 }
144 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
145 if (!mem)
146 goto depopulate;
147
148 memset(mem, 0, *size);
149 buf->page_count = n_pages;
150 return mem;
151
152depopulate:
153 for (j = 0; j < i; j++)
154 __free_page(buf->page_array[j]);
155 relay_free_page_array(buf->page_array);
156 return NULL;
157}
158
159/**
160 * relay_create_buf - allocate and initialize a channel buffer
161 * @chan: the relay channel
162 *
163 * Returns channel buffer if successful, %NULL otherwise.
164 */
165static struct rchan_buf *relay_create_buf(struct rchan *chan)
166{
167 struct rchan_buf *buf;
168
169 if (chan->n_subbufs > UINT_MAX / sizeof(size_t *))
170 return NULL;
171
172 buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
173 if (!buf)
174 return NULL;
175 buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
176 if (!buf->padding)
177 goto free_buf;
178
179 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
180 if (!buf->start)
181 goto free_buf;
182
183 buf->chan = chan;
184 kref_get(&buf->chan->kref);
185 return buf;
186
187free_buf:
188 kfree(buf->padding);
189 kfree(buf);
190 return NULL;
191}
192
193/**
194 * relay_destroy_channel - free the channel struct
195 * @kref: target kernel reference that contains the relay channel
196 *
197 * Should only be called from kref_put().
198 */
199static void relay_destroy_channel(struct kref *kref)
200{
201 struct rchan *chan = container_of(kref, struct rchan, kref);
202 kfree(chan);
203}
204
205/**
206 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
207 * @buf: the buffer struct
208 */
209static void relay_destroy_buf(struct rchan_buf *buf)
210{
211 struct rchan *chan = buf->chan;
212 unsigned int i;
213
214 if (likely(buf->start)) {
215 vunmap(buf->start);
216 for (i = 0; i < buf->page_count; i++)
217 __free_page(buf->page_array[i]);
218 relay_free_page_array(buf->page_array);
219 }
220 chan->buf[buf->cpu] = NULL;
221 kfree(buf->padding);
222 kfree(buf);
223 kref_put(&chan->kref, relay_destroy_channel);
224}
225
226/**
227 * relay_remove_buf - remove a channel buffer
228 * @kref: target kernel reference that contains the relay buffer
229 *
230 * Removes the file from the fileystem, which also frees the
231 * rchan_buf_struct and the channel buffer. Should only be called from
232 * kref_put().
233 */
234static void relay_remove_buf(struct kref *kref)
235{
236 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
237 buf->chan->cb->remove_buf_file(buf->dentry);
238 relay_destroy_buf(buf);
239}
240
241/**
242 * relay_buf_empty - boolean, is the channel buffer empty?
243 * @buf: channel buffer
244 *
245 * Returns 1 if the buffer is empty, 0 otherwise.
246 */
247static int relay_buf_empty(struct rchan_buf *buf)
248{
249 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
250}
251
252/**
253 * relay_buf_full - boolean, is the channel buffer full?
254 * @buf: channel buffer
255 *
256 * Returns 1 if the buffer is full, 0 otherwise.
257 */
258int relay_buf_full(struct rchan_buf *buf)
259{
260 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
261 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
262}
263EXPORT_SYMBOL_GPL(relay_buf_full);
264
265/*
266 * High-level relay kernel API and associated functions.
267 */
268
269/*
270 * rchan_callback implementations defining default channel behavior. Used
271 * in place of corresponding NULL values in client callback struct.
272 */
273
274/*
275 * subbuf_start() default callback. Does nothing.
276 */
277static int subbuf_start_default_callback (struct rchan_buf *buf,
278 void *subbuf,
279 void *prev_subbuf,
280 size_t prev_padding)
281{
282 if (relay_buf_full(buf))
283 return 0;
284
285 return 1;
286}
287
288/*
289 * buf_mapped() default callback. Does nothing.
290 */
291static void buf_mapped_default_callback(struct rchan_buf *buf,
292 struct file *filp)
293{
294}
295
296/*
297 * buf_unmapped() default callback. Does nothing.
298 */
299static void buf_unmapped_default_callback(struct rchan_buf *buf,
300 struct file *filp)
301{
302}
303
304/*
305 * create_buf_file_create() default callback. Does nothing.
306 */
307static struct dentry *create_buf_file_default_callback(const char *filename,
308 struct dentry *parent,
309 umode_t mode,
310 struct rchan_buf *buf,
311 int *is_global)
312{
313 return NULL;
314}
315
316/*
317 * remove_buf_file() default callback. Does nothing.
318 */
319static int remove_buf_file_default_callback(struct dentry *dentry)
320{
321 return -EINVAL;
322}
323
324/* relay channel default callbacks */
325static struct rchan_callbacks default_channel_callbacks = {
326 .subbuf_start = subbuf_start_default_callback,
327 .buf_mapped = buf_mapped_default_callback,
328 .buf_unmapped = buf_unmapped_default_callback,
329 .create_buf_file = create_buf_file_default_callback,
330 .remove_buf_file = remove_buf_file_default_callback,
331};
332
333/**
334 * wakeup_readers - wake up readers waiting on a channel
335 * @data: contains the channel buffer
336 *
337 * This is the timer function used to defer reader waking.
338 */
339static void wakeup_readers(unsigned long data)
340{
341 struct rchan_buf *buf = (struct rchan_buf *)data;
342 wake_up_interruptible(&buf->read_wait);
343}
344
345/**
346 * __relay_reset - reset a channel buffer
347 * @buf: the channel buffer
348 * @init: 1 if this is a first-time initialization
349 *
350 * See relay_reset() for description of effect.
351 */
352static void __relay_reset(struct rchan_buf *buf, unsigned int init)
353{
354 size_t i;
355
356 if (init) {
357 init_waitqueue_head(&buf->read_wait);
358 kref_init(&buf->kref);
359 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
360 } else
361 del_timer_sync(&buf->timer);
362
363 buf->subbufs_produced = 0;
364 buf->subbufs_consumed = 0;
365 buf->bytes_consumed = 0;
366 buf->finalized = 0;
367 buf->data = buf->start;
368 buf->offset = 0;
369
370 for (i = 0; i < buf->chan->n_subbufs; i++)
371 buf->padding[i] = 0;
372
373 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
374}
375
376/**
377 * relay_reset - reset the channel
378 * @chan: the channel
379 *
380 * This has the effect of erasing all data from all channel buffers
381 * and restarting the channel in its initial state. The buffers
382 * are not freed, so any mappings are still in effect.
383 *
384 * NOTE. Care should be taken that the channel isn't actually
385 * being used by anything when this call is made.
386 */
387void relay_reset(struct rchan *chan)
388{
389 unsigned int i;
390
391 if (!chan)
392 return;
393
394 if (chan->is_global && chan->buf[0]) {
395 __relay_reset(chan->buf[0], 0);
396 return;
397 }
398
399 mutex_lock(&relay_channels_mutex);
400 for_each_possible_cpu(i)
401 if (chan->buf[i])
402 __relay_reset(chan->buf[i], 0);
403 mutex_unlock(&relay_channels_mutex);
404}
405EXPORT_SYMBOL_GPL(relay_reset);
406
407static inline void relay_set_buf_dentry(struct rchan_buf *buf,
408 struct dentry *dentry)
409{
410 buf->dentry = dentry;
411 buf->dentry->d_inode->i_size = buf->early_bytes;
412}
413
414static struct dentry *relay_create_buf_file(struct rchan *chan,
415 struct rchan_buf *buf,
416 unsigned int cpu)
417{
418 struct dentry *dentry;
419 char *tmpname;
420
421 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
422 if (!tmpname)
423 return NULL;
424 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
425
426 /* Create file in fs */
427 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
428 S_IRUSR, buf,
429 &chan->is_global);
430
431 kfree(tmpname);
432
433 return dentry;
434}
435
436/*
437 * relay_open_buf - create a new relay channel buffer
438 *
439 * used by relay_open() and CPU hotplug.
440 */
441static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
442{
443 struct rchan_buf *buf = NULL;
444 struct dentry *dentry;
445
446 if (chan->is_global)
447 return chan->buf[0];
448
449 buf = relay_create_buf(chan);
450 if (!buf)
451 return NULL;
452
453 if (chan->has_base_filename) {
454 dentry = relay_create_buf_file(chan, buf, cpu);
455 if (!dentry)
456 goto free_buf;
457 relay_set_buf_dentry(buf, dentry);
458 }
459
460 buf->cpu = cpu;
461 __relay_reset(buf, 1);
462
463 if(chan->is_global) {
464 chan->buf[0] = buf;
465 buf->cpu = 0;
466 }
467
468 return buf;
469
470free_buf:
471 relay_destroy_buf(buf);
472 return NULL;
473}
474
475/**
476 * relay_close_buf - close a channel buffer
477 * @buf: channel buffer
478 *
479 * Marks the buffer finalized and restores the default callbacks.
480 * The channel buffer and channel buffer data structure are then freed
481 * automatically when the last reference is given up.
482 */
483static void relay_close_buf(struct rchan_buf *buf)
484{
485 buf->finalized = 1;
486 del_timer_sync(&buf->timer);
487 kref_put(&buf->kref, relay_remove_buf);
488}
489
490static void setup_callbacks(struct rchan *chan,
491 struct rchan_callbacks *cb)
492{
493 if (!cb) {
494 chan->cb = &default_channel_callbacks;
495 return;
496 }
497
498 if (!cb->subbuf_start)
499 cb->subbuf_start = subbuf_start_default_callback;
500 if (!cb->buf_mapped)
501 cb->buf_mapped = buf_mapped_default_callback;
502 if (!cb->buf_unmapped)
503 cb->buf_unmapped = buf_unmapped_default_callback;
504 if (!cb->create_buf_file)
505 cb->create_buf_file = create_buf_file_default_callback;
506 if (!cb->remove_buf_file)
507 cb->remove_buf_file = remove_buf_file_default_callback;
508 chan->cb = cb;
509}
510
511/**
512 * relay_hotcpu_callback - CPU hotplug callback
513 * @nb: notifier block
514 * @action: hotplug action to take
515 * @hcpu: CPU number
516 *
517 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
518 */
519static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
520 unsigned long action,
521 void *hcpu)
522{
523 unsigned int hotcpu = (unsigned long)hcpu;
524 struct rchan *chan;
525
526 switch(action) {
527 case CPU_UP_PREPARE:
528 case CPU_UP_PREPARE_FROZEN:
529 mutex_lock(&relay_channels_mutex);
530 list_for_each_entry(chan, &relay_channels, list) {
531 if (chan->buf[hotcpu])
532 continue;
533 chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
534 if(!chan->buf[hotcpu]) {
535 printk(KERN_ERR
536 "relay_hotcpu_callback: cpu %d buffer "
537 "creation failed\n", hotcpu);
538 mutex_unlock(&relay_channels_mutex);
539 return notifier_from_errno(-ENOMEM);
540 }
541 }
542 mutex_unlock(&relay_channels_mutex);
543 break;
544 case CPU_DEAD:
545 case CPU_DEAD_FROZEN:
546 /* No need to flush the cpu : will be flushed upon
547 * final relay_flush() call. */
548 break;
549 }
550 return NOTIFY_OK;
551}
552
553/**
554 * relay_open - create a new relay channel
555 * @base_filename: base name of files to create, %NULL for buffering only
556 * @parent: dentry of parent directory, %NULL for root directory or buffer
557 * @subbuf_size: size of sub-buffers
558 * @n_subbufs: number of sub-buffers
559 * @cb: client callback functions
560 * @private_data: user-defined data
561 *
562 * Returns channel pointer if successful, %NULL otherwise.
563 *
564 * Creates a channel buffer for each cpu using the sizes and
565 * attributes specified. The created channel buffer files
566 * will be named base_filename0...base_filenameN-1. File
567 * permissions will be %S_IRUSR.
568 */
569struct rchan *relay_open(const char *base_filename,
570 struct dentry *parent,
571 size_t subbuf_size,
572 size_t n_subbufs,
573 struct rchan_callbacks *cb,
574 void *private_data)
575{
576 unsigned int i;
577 struct rchan *chan;
578
579 if (!(subbuf_size && n_subbufs))
580 return NULL;
581 if (subbuf_size > UINT_MAX / n_subbufs)
582 return NULL;
583
584 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
585 if (!chan)
586 return NULL;
587
588 chan->version = RELAYFS_CHANNEL_VERSION;
589 chan->n_subbufs = n_subbufs;
590 chan->subbuf_size = subbuf_size;
591 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
592 chan->parent = parent;
593 chan->private_data = private_data;
594 if (base_filename) {
595 chan->has_base_filename = 1;
596 strlcpy(chan->base_filename, base_filename, NAME_MAX);
597 }
598 setup_callbacks(chan, cb);
599 kref_init(&chan->kref);
600
601 mutex_lock(&relay_channels_mutex);
602 for_each_online_cpu(i) {
603 chan->buf[i] = relay_open_buf(chan, i);
604 if (!chan->buf[i])
605 goto free_bufs;
606 }
607 list_add(&chan->list, &relay_channels);
608 mutex_unlock(&relay_channels_mutex);
609
610 return chan;
611
612free_bufs:
613 for_each_possible_cpu(i) {
614 if (chan->buf[i])
615 relay_close_buf(chan->buf[i]);
616 }
617
618 kref_put(&chan->kref, relay_destroy_channel);
619 mutex_unlock(&relay_channels_mutex);
620 return NULL;
621}
622EXPORT_SYMBOL_GPL(relay_open);
623
624struct rchan_percpu_buf_dispatcher {
625 struct rchan_buf *buf;
626 struct dentry *dentry;
627};
628
629/* Called in atomic context. */
630static void __relay_set_buf_dentry(void *info)
631{
632 struct rchan_percpu_buf_dispatcher *p = info;
633
634 relay_set_buf_dentry(p->buf, p->dentry);
635}
636
637/**
638 * relay_late_setup_files - triggers file creation
639 * @chan: channel to operate on
640 * @base_filename: base name of files to create
641 * @parent: dentry of parent directory, %NULL for root directory
642 *
643 * Returns 0 if successful, non-zero otherwise.
644 *
645 * Use to setup files for a previously buffer-only channel.
646 * Useful to do early tracing in kernel, before VFS is up, for example.
647 */
648int relay_late_setup_files(struct rchan *chan,
649 const char *base_filename,
650 struct dentry *parent)
651{
652 int err = 0;
653 unsigned int i, curr_cpu;
654 unsigned long flags;
655 struct dentry *dentry;
656 struct rchan_percpu_buf_dispatcher disp;
657
658 if (!chan || !base_filename)
659 return -EINVAL;
660
661 strlcpy(chan->base_filename, base_filename, NAME_MAX);
662
663 mutex_lock(&relay_channels_mutex);
664 /* Is chan already set up? */
665 if (unlikely(chan->has_base_filename)) {
666 mutex_unlock(&relay_channels_mutex);
667 return -EEXIST;
668 }
669 chan->has_base_filename = 1;
670 chan->parent = parent;
671 curr_cpu = get_cpu();
672 /*
673 * The CPU hotplug notifier ran before us and created buffers with
674 * no files associated. So it's safe to call relay_setup_buf_file()
675 * on all currently online CPUs.
676 */
677 for_each_online_cpu(i) {
678 if (unlikely(!chan->buf[i])) {
679 WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
680 err = -EINVAL;
681 break;
682 }
683
684 dentry = relay_create_buf_file(chan, chan->buf[i], i);
685 if (unlikely(!dentry)) {
686 err = -EINVAL;
687 break;
688 }
689
690 if (curr_cpu == i) {
691 local_irq_save(flags);
692 relay_set_buf_dentry(chan->buf[i], dentry);
693 local_irq_restore(flags);
694 } else {
695 disp.buf = chan->buf[i];
696 disp.dentry = dentry;
697 smp_mb();
698 /* relay_channels_mutex must be held, so wait. */
699 err = smp_call_function_single(i,
700 __relay_set_buf_dentry,
701 &disp, 1);
702 }
703 if (unlikely(err))
704 break;
705 }
706 put_cpu();
707 mutex_unlock(&relay_channels_mutex);
708
709 return err;
710}
711
712/**
713 * relay_switch_subbuf - switch to a new sub-buffer
714 * @buf: channel buffer
715 * @length: size of current event
716 *
717 * Returns either the length passed in or 0 if full.
718 *
719 * Performs sub-buffer-switch tasks such as invoking callbacks,
720 * updating padding counts, waking up readers, etc.
721 */
722size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
723{
724 void *old, *new;
725 size_t old_subbuf, new_subbuf;
726
727 if (unlikely(length > buf->chan->subbuf_size))
728 goto toobig;
729
730 if (buf->offset != buf->chan->subbuf_size + 1) {
731 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
732 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
733 buf->padding[old_subbuf] = buf->prev_padding;
734 buf->subbufs_produced++;
735 if (buf->dentry)
736 buf->dentry->d_inode->i_size +=
737 buf->chan->subbuf_size -
738 buf->padding[old_subbuf];
739 else
740 buf->early_bytes += buf->chan->subbuf_size -
741 buf->padding[old_subbuf];
742 smp_mb();
743 if (waitqueue_active(&buf->read_wait))
744 /*
745 * Calling wake_up_interruptible() from here
746 * will deadlock if we happen to be logging
747 * from the scheduler (trying to re-grab
748 * rq->lock), so defer it.
749 */
750 mod_timer(&buf->timer, jiffies + 1);
751 }
752
753 old = buf->data;
754 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
755 new = buf->start + new_subbuf * buf->chan->subbuf_size;
756 buf->offset = 0;
757 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
758 buf->offset = buf->chan->subbuf_size + 1;
759 return 0;
760 }
761 buf->data = new;
762 buf->padding[new_subbuf] = 0;
763
764 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
765 goto toobig;
766
767 return length;
768
769toobig:
770 buf->chan->last_toobig = length;
771 return 0;
772}
773EXPORT_SYMBOL_GPL(relay_switch_subbuf);
774
775/**
776 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
777 * @chan: the channel
778 * @cpu: the cpu associated with the channel buffer to update
779 * @subbufs_consumed: number of sub-buffers to add to current buf's count
780 *
781 * Adds to the channel buffer's consumed sub-buffer count.
782 * subbufs_consumed should be the number of sub-buffers newly consumed,
783 * not the total consumed.
784 *
785 * NOTE. Kernel clients don't need to call this function if the channel
786 * mode is 'overwrite'.
787 */
788void relay_subbufs_consumed(struct rchan *chan,
789 unsigned int cpu,
790 size_t subbufs_consumed)
791{
792 struct rchan_buf *buf;
793
794 if (!chan)
795 return;
796
797 if (cpu >= NR_CPUS || !chan->buf[cpu] ||
798 subbufs_consumed > chan->n_subbufs)
799 return;
800
801 buf = chan->buf[cpu];
802 if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
803 buf->subbufs_consumed = buf->subbufs_produced;
804 else
805 buf->subbufs_consumed += subbufs_consumed;
806}
807EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
808
809/**
810 * relay_close - close the channel
811 * @chan: the channel
812 *
813 * Closes all channel buffers and frees the channel.
814 */
815void relay_close(struct rchan *chan)
816{
817 unsigned int i;
818
819 if (!chan)
820 return;
821
822 mutex_lock(&relay_channels_mutex);
823 if (chan->is_global && chan->buf[0])
824 relay_close_buf(chan->buf[0]);
825 else
826 for_each_possible_cpu(i)
827 if (chan->buf[i])
828 relay_close_buf(chan->buf[i]);
829
830 if (chan->last_toobig)
831 printk(KERN_WARNING "relay: one or more items not logged "
832 "[item size (%Zd) > sub-buffer size (%Zd)]\n",
833 chan->last_toobig, chan->subbuf_size);
834
835 list_del(&chan->list);
836 kref_put(&chan->kref, relay_destroy_channel);
837 mutex_unlock(&relay_channels_mutex);
838}
839EXPORT_SYMBOL_GPL(relay_close);
840
841/**
842 * relay_flush - close the channel
843 * @chan: the channel
844 *
845 * Flushes all channel buffers, i.e. forces buffer switch.
846 */
847void relay_flush(struct rchan *chan)
848{
849 unsigned int i;
850
851 if (!chan)
852 return;
853
854 if (chan->is_global && chan->buf[0]) {
855 relay_switch_subbuf(chan->buf[0], 0);
856 return;
857 }
858
859 mutex_lock(&relay_channels_mutex);
860 for_each_possible_cpu(i)
861 if (chan->buf[i])
862 relay_switch_subbuf(chan->buf[i], 0);
863 mutex_unlock(&relay_channels_mutex);
864}
865EXPORT_SYMBOL_GPL(relay_flush);
866
867/**
868 * relay_file_open - open file op for relay files
869 * @inode: the inode
870 * @filp: the file
871 *
872 * Increments the channel buffer refcount.
873 */
874static int relay_file_open(struct inode *inode, struct file *filp)
875{
876 struct rchan_buf *buf = inode->i_private;
877 kref_get(&buf->kref);
878 filp->private_data = buf;
879
880 return nonseekable_open(inode, filp);
881}
882
883/**
884 * relay_file_mmap - mmap file op for relay files
885 * @filp: the file
886 * @vma: the vma describing what to map
887 *
888 * Calls upon relay_mmap_buf() to map the file into user space.
889 */
890static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
891{
892 struct rchan_buf *buf = filp->private_data;
893 return relay_mmap_buf(buf, vma);
894}
895
896/**
897 * relay_file_poll - poll file op for relay files
898 * @filp: the file
899 * @wait: poll table
900 *
901 * Poll implemention.
902 */
903static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
904{
905 unsigned int mask = 0;
906 struct rchan_buf *buf = filp->private_data;
907
908 if (buf->finalized)
909 return POLLERR;
910
911 if (filp->f_mode & FMODE_READ) {
912 poll_wait(filp, &buf->read_wait, wait);
913 if (!relay_buf_empty(buf))
914 mask |= POLLIN | POLLRDNORM;
915 }
916
917 return mask;
918}
919
920/**
921 * relay_file_release - release file op for relay files
922 * @inode: the inode
923 * @filp: the file
924 *
925 * Decrements the channel refcount, as the filesystem is
926 * no longer using it.
927 */
928static int relay_file_release(struct inode *inode, struct file *filp)
929{
930 struct rchan_buf *buf = filp->private_data;
931 kref_put(&buf->kref, relay_remove_buf);
932
933 return 0;
934}
935
936/*
937 * relay_file_read_consume - update the consumed count for the buffer
938 */
939static void relay_file_read_consume(struct rchan_buf *buf,
940 size_t read_pos,
941 size_t bytes_consumed)
942{
943 size_t subbuf_size = buf->chan->subbuf_size;
944 size_t n_subbufs = buf->chan->n_subbufs;
945 size_t read_subbuf;
946
947 if (buf->subbufs_produced == buf->subbufs_consumed &&
948 buf->offset == buf->bytes_consumed)
949 return;
950
951 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
952 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
953 buf->bytes_consumed = 0;
954 }
955
956 buf->bytes_consumed += bytes_consumed;
957 if (!read_pos)
958 read_subbuf = buf->subbufs_consumed % n_subbufs;
959 else
960 read_subbuf = read_pos / buf->chan->subbuf_size;
961 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
962 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
963 (buf->offset == subbuf_size))
964 return;
965 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
966 buf->bytes_consumed = 0;
967 }
968}
969
970/*
971 * relay_file_read_avail - boolean, are there unconsumed bytes available?
972 */
973static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
974{
975 size_t subbuf_size = buf->chan->subbuf_size;
976 size_t n_subbufs = buf->chan->n_subbufs;
977 size_t produced = buf->subbufs_produced;
978 size_t consumed = buf->subbufs_consumed;
979
980 relay_file_read_consume(buf, read_pos, 0);
981
982 consumed = buf->subbufs_consumed;
983
984 if (unlikely(buf->offset > subbuf_size)) {
985 if (produced == consumed)
986 return 0;
987 return 1;
988 }
989
990 if (unlikely(produced - consumed >= n_subbufs)) {
991 consumed = produced - n_subbufs + 1;
992 buf->subbufs_consumed = consumed;
993 buf->bytes_consumed = 0;
994 }
995
996 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
997 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
998
999 if (consumed > produced)
1000 produced += n_subbufs * subbuf_size;
1001
1002 if (consumed == produced) {
1003 if (buf->offset == subbuf_size &&
1004 buf->subbufs_produced > buf->subbufs_consumed)
1005 return 1;
1006 return 0;
1007 }
1008
1009 return 1;
1010}
1011
1012/**
1013 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
1014 * @read_pos: file read position
1015 * @buf: relay channel buffer
1016 */
1017static size_t relay_file_read_subbuf_avail(size_t read_pos,
1018 struct rchan_buf *buf)
1019{
1020 size_t padding, avail = 0;
1021 size_t read_subbuf, read_offset, write_subbuf, write_offset;
1022 size_t subbuf_size = buf->chan->subbuf_size;
1023
1024 write_subbuf = (buf->data - buf->start) / subbuf_size;
1025 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1026 read_subbuf = read_pos / subbuf_size;
1027 read_offset = read_pos % subbuf_size;
1028 padding = buf->padding[read_subbuf];
1029
1030 if (read_subbuf == write_subbuf) {
1031 if (read_offset + padding < write_offset)
1032 avail = write_offset - (read_offset + padding);
1033 } else
1034 avail = (subbuf_size - padding) - read_offset;
1035
1036 return avail;
1037}
1038
1039/**
1040 * relay_file_read_start_pos - find the first available byte to read
1041 * @read_pos: file read position
1042 * @buf: relay channel buffer
1043 *
1044 * If the @read_pos is in the middle of padding, return the
1045 * position of the first actually available byte, otherwise
1046 * return the original value.
1047 */
1048static size_t relay_file_read_start_pos(size_t read_pos,
1049 struct rchan_buf *buf)
1050{
1051 size_t read_subbuf, padding, padding_start, padding_end;
1052 size_t subbuf_size = buf->chan->subbuf_size;
1053 size_t n_subbufs = buf->chan->n_subbufs;
1054 size_t consumed = buf->subbufs_consumed % n_subbufs;
1055
1056 if (!read_pos)
1057 read_pos = consumed * subbuf_size + buf->bytes_consumed;
1058 read_subbuf = read_pos / subbuf_size;
1059 padding = buf->padding[read_subbuf];
1060 padding_start = (read_subbuf + 1) * subbuf_size - padding;
1061 padding_end = (read_subbuf + 1) * subbuf_size;
1062 if (read_pos >= padding_start && read_pos < padding_end) {
1063 read_subbuf = (read_subbuf + 1) % n_subbufs;
1064 read_pos = read_subbuf * subbuf_size;
1065 }
1066
1067 return read_pos;
1068}
1069
1070/**
1071 * relay_file_read_end_pos - return the new read position
1072 * @read_pos: file read position
1073 * @buf: relay channel buffer
1074 * @count: number of bytes to be read
1075 */
1076static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1077 size_t read_pos,
1078 size_t count)
1079{
1080 size_t read_subbuf, padding, end_pos;
1081 size_t subbuf_size = buf->chan->subbuf_size;
1082 size_t n_subbufs = buf->chan->n_subbufs;
1083
1084 read_subbuf = read_pos / subbuf_size;
1085 padding = buf->padding[read_subbuf];
1086 if (read_pos % subbuf_size + count + padding == subbuf_size)
1087 end_pos = (read_subbuf + 1) * subbuf_size;
1088 else
1089 end_pos = read_pos + count;
1090 if (end_pos >= subbuf_size * n_subbufs)
1091 end_pos = 0;
1092
1093 return end_pos;
1094}
1095
1096/*
1097 * subbuf_read_actor - read up to one subbuf's worth of data
1098 */
1099static int subbuf_read_actor(size_t read_start,
1100 struct rchan_buf *buf,
1101 size_t avail,
1102 read_descriptor_t *desc,
1103 read_actor_t actor)
1104{
1105 void *from;
1106 int ret = 0;
1107
1108 from = buf->start + read_start;
1109 ret = avail;
1110 if (copy_to_user(desc->arg.buf, from, avail)) {
1111 desc->error = -EFAULT;
1112 ret = 0;
1113 }
1114 desc->arg.data += ret;
1115 desc->written += ret;
1116 desc->count -= ret;
1117
1118 return ret;
1119}
1120
1121typedef int (*subbuf_actor_t) (size_t read_start,
1122 struct rchan_buf *buf,
1123 size_t avail,
1124 read_descriptor_t *desc,
1125 read_actor_t actor);
1126
1127/*
1128 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1129 */
1130static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1131 subbuf_actor_t subbuf_actor,
1132 read_actor_t actor,
1133 read_descriptor_t *desc)
1134{
1135 struct rchan_buf *buf = filp->private_data;
1136 size_t read_start, avail;
1137 int ret;
1138
1139 if (!desc->count)
1140 return 0;
1141
1142 mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1143 do {
1144 if (!relay_file_read_avail(buf, *ppos))
1145 break;
1146
1147 read_start = relay_file_read_start_pos(*ppos, buf);
1148 avail = relay_file_read_subbuf_avail(read_start, buf);
1149 if (!avail)
1150 break;
1151
1152 avail = min(desc->count, avail);
1153 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1154 if (desc->error < 0)
1155 break;
1156
1157 if (ret) {
1158 relay_file_read_consume(buf, read_start, ret);
1159 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1160 }
1161 } while (desc->count && ret);
1162 mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1163
1164 return desc->written;
1165}
1166
1167static ssize_t relay_file_read(struct file *filp,
1168 char __user *buffer,
1169 size_t count,
1170 loff_t *ppos)
1171{
1172 read_descriptor_t desc;
1173 desc.written = 0;
1174 desc.count = count;
1175 desc.arg.buf = buffer;
1176 desc.error = 0;
1177 return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1178 NULL, &desc);
1179}
1180
1181static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1182{
1183 rbuf->bytes_consumed += bytes_consumed;
1184
1185 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1186 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1187 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1188 }
1189}
1190
1191static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1192 struct pipe_buffer *buf)
1193{
1194 struct rchan_buf *rbuf;
1195
1196 rbuf = (struct rchan_buf *)page_private(buf->page);
1197 relay_consume_bytes(rbuf, buf->private);
1198}
1199
1200static const struct pipe_buf_operations relay_pipe_buf_ops = {
1201 .can_merge = 0,
1202 .map = generic_pipe_buf_map,
1203 .unmap = generic_pipe_buf_unmap,
1204 .confirm = generic_pipe_buf_confirm,
1205 .release = relay_pipe_buf_release,
1206 .steal = generic_pipe_buf_steal,
1207 .get = generic_pipe_buf_get,
1208};
1209
1210static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1211{
1212}
1213
1214/*
1215 * subbuf_splice_actor - splice up to one subbuf's worth of data
1216 */
1217static ssize_t subbuf_splice_actor(struct file *in,
1218 loff_t *ppos,
1219 struct pipe_inode_info *pipe,
1220 size_t len,
1221 unsigned int flags,
1222 int *nonpad_ret)
1223{
1224 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1225 struct rchan_buf *rbuf = in->private_data;
1226 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1227 uint64_t pos = (uint64_t) *ppos;
1228 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1229 size_t read_start = (size_t) do_div(pos, alloc_size);
1230 size_t read_subbuf = read_start / subbuf_size;
1231 size_t padding = rbuf->padding[read_subbuf];
1232 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1233 struct page *pages[PIPE_DEF_BUFFERS];
1234 struct partial_page partial[PIPE_DEF_BUFFERS];
1235 struct splice_pipe_desc spd = {
1236 .pages = pages,
1237 .nr_pages = 0,
1238 .nr_pages_max = PIPE_DEF_BUFFERS,
1239 .partial = partial,
1240 .flags = flags,
1241 .ops = &relay_pipe_buf_ops,
1242 .spd_release = relay_page_release,
1243 };
1244 ssize_t ret;
1245
1246 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1247 return 0;
1248 if (splice_grow_spd(pipe, &spd))
1249 return -ENOMEM;
1250
1251 /*
1252 * Adjust read len, if longer than what is available
1253 */
1254 if (len > (subbuf_size - read_start % subbuf_size))
1255 len = subbuf_size - read_start % subbuf_size;
1256
1257 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1258 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1259 poff = read_start & ~PAGE_MASK;
1260 nr_pages = min_t(unsigned int, subbuf_pages, pipe->buffers);
1261
1262 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1263 unsigned int this_len, this_end, private;
1264 unsigned int cur_pos = read_start + total_len;
1265
1266 if (!len)
1267 break;
1268
1269 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1270 private = this_len;
1271
1272 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1273 spd.partial[spd.nr_pages].offset = poff;
1274
1275 this_end = cur_pos + this_len;
1276 if (this_end >= nonpad_end) {
1277 this_len = nonpad_end - cur_pos;
1278 private = this_len + padding;
1279 }
1280 spd.partial[spd.nr_pages].len = this_len;
1281 spd.partial[spd.nr_pages].private = private;
1282
1283 len -= this_len;
1284 total_len += this_len;
1285 poff = 0;
1286 pidx = (pidx + 1) % subbuf_pages;
1287
1288 if (this_end >= nonpad_end) {
1289 spd.nr_pages++;
1290 break;
1291 }
1292 }
1293
1294 ret = 0;
1295 if (!spd.nr_pages)
1296 goto out;
1297
1298 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1299 if (ret < 0 || ret < total_len)
1300 goto out;
1301
1302 if (read_start + ret == nonpad_end)
1303 ret += padding;
1304
1305out:
1306 splice_shrink_spd(&spd);
1307 return ret;
1308}
1309
1310static ssize_t relay_file_splice_read(struct file *in,
1311 loff_t *ppos,
1312 struct pipe_inode_info *pipe,
1313 size_t len,
1314 unsigned int flags)
1315{
1316 ssize_t spliced;
1317 int ret;
1318 int nonpad_ret = 0;
1319
1320 ret = 0;
1321 spliced = 0;
1322
1323 while (len && !spliced) {
1324 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1325 if (ret < 0)
1326 break;
1327 else if (!ret) {
1328 if (flags & SPLICE_F_NONBLOCK)
1329 ret = -EAGAIN;
1330 break;
1331 }
1332
1333 *ppos += ret;
1334 if (ret > len)
1335 len = 0;
1336 else
1337 len -= ret;
1338 spliced += nonpad_ret;
1339 nonpad_ret = 0;
1340 }
1341
1342 if (spliced)
1343 return spliced;
1344
1345 return ret;
1346}
1347
1348const struct file_operations relay_file_operations = {
1349 .open = relay_file_open,
1350 .poll = relay_file_poll,
1351 .mmap = relay_file_mmap,
1352 .read = relay_file_read,
1353 .llseek = no_llseek,
1354 .release = relay_file_release,
1355 .splice_read = relay_file_splice_read,
1356};
1357EXPORT_SYMBOL_GPL(relay_file_operations);
1358
1359static __init int relay_init(void)
1360{
1361
1362 hotcpu_notifier(relay_hotcpu_callback, 0);
1363 return 0;
1364}
1365
1366early_initcall(relay_init);
1/*
2 * Public API and common code for kernel->userspace relay file support.
3 *
4 * See Documentation/filesystems/relay.rst for an overview.
5 *
6 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
7 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
8 *
9 * Moved to kernel/relay.c by Paul Mundt, 2006.
10 * November 2006 - CPU hotplug support by Mathieu Desnoyers
11 * (mathieu.desnoyers@polymtl.ca)
12 *
13 * This file is released under the GPL.
14 */
15#include <linux/errno.h>
16#include <linux/stddef.h>
17#include <linux/slab.h>
18#include <linux/export.h>
19#include <linux/string.h>
20#include <linux/relay.h>
21#include <linux/vmalloc.h>
22#include <linux/mm.h>
23#include <linux/cpu.h>
24#include <linux/splice.h>
25
26/* list of open channels, for cpu hotplug */
27static DEFINE_MUTEX(relay_channels_mutex);
28static LIST_HEAD(relay_channels);
29
30/*
31 * fault() vm_op implementation for relay file mapping.
32 */
33static vm_fault_t relay_buf_fault(struct vm_fault *vmf)
34{
35 struct page *page;
36 struct rchan_buf *buf = vmf->vma->vm_private_data;
37 pgoff_t pgoff = vmf->pgoff;
38
39 if (!buf)
40 return VM_FAULT_OOM;
41
42 page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
43 if (!page)
44 return VM_FAULT_SIGBUS;
45 get_page(page);
46 vmf->page = page;
47
48 return 0;
49}
50
51/*
52 * vm_ops for relay file mappings.
53 */
54static const struct vm_operations_struct relay_file_mmap_ops = {
55 .fault = relay_buf_fault,
56};
57
58/*
59 * allocate an array of pointers of struct page
60 */
61static struct page **relay_alloc_page_array(unsigned int n_pages)
62{
63 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);