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-rw-r--r--kernel/relay.c919
1 files changed, 919 insertions, 0 deletions
diff --git a/kernel/relay.c b/kernel/relay.c
new file mode 100644
index 000000000000..9358e8eb8476
--- /dev/null
+++ b/kernel/relay.c
@@ -0,0 +1,919 @@
1/*
2 * Public API and common code for kernel->userspace relay file support.
3 *
4 * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
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 *
11 * This file is released under the GPL.
12 */
13#include <linux/errno.h>
14#include <linux/stddef.h>
15#include <linux/slab.h>
16#include <linux/module.h>
17#include <linux/string.h>
18#include <linux/relay.h>
19#include <linux/vmalloc.h>
20#include <linux/mm.h>
21
22/*
23 * close() vm_op implementation for relay file mapping.
24 */
25static void relay_file_mmap_close(struct vm_area_struct *vma)
26{
27 struct rchan_buf *buf = vma->vm_private_data;
28 buf->chan->cb->buf_unmapped(buf, vma->vm_file);
29}
30
31/*
32 * nopage() vm_op implementation for relay file mapping.
33 */
34static struct page *relay_buf_nopage(struct vm_area_struct *vma,
35 unsigned long address,
36 int *type)
37{
38 struct page *page;
39 struct rchan_buf *buf = vma->vm_private_data;
40 unsigned long offset = address - vma->vm_start;
41
42 if (address > vma->vm_end)
43 return NOPAGE_SIGBUS; /* Disallow mremap */
44 if (!buf)
45 return NOPAGE_OOM;
46
47 page = vmalloc_to_page(buf->start + offset);
48 if (!page)
49 return NOPAGE_OOM;
50 get_page(page);
51
52 if (type)
53 *type = VM_FAULT_MINOR;
54
55 return page;
56}
57
58/*
59 * vm_ops for relay file mappings.
60 */
61static struct vm_operations_struct relay_file_mmap_ops = {
62 .nopage = relay_buf_nopage,
63 .close = relay_file_mmap_close,
64};
65
66/**
67 * relay_mmap_buf: - mmap channel buffer to process address space
68 * @buf: relay channel buffer
69 * @vma: vm_area_struct describing memory to be mapped
70 *
71 * Returns 0 if ok, negative on error
72 *
73 * Caller should already have grabbed mmap_sem.
74 */
75int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
76{
77 unsigned long length = vma->vm_end - vma->vm_start;
78 struct file *filp = vma->vm_file;
79
80 if (!buf)
81 return -EBADF;
82
83 if (length != (unsigned long)buf->chan->alloc_size)
84 return -EINVAL;
85
86 vma->vm_ops = &relay_file_mmap_ops;
87 vma->vm_private_data = buf;
88 buf->chan->cb->buf_mapped(buf, filp);
89
90 return 0;
91}
92
93/**
94 * relay_alloc_buf - allocate a channel buffer
95 * @buf: the buffer struct
96 * @size: total size of the buffer
97 *
98 * Returns a pointer to the resulting buffer, NULL if unsuccessful
99 */
100static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size)
101{
102 void *mem;
103 unsigned int i, j, n_pages;
104
105 size = PAGE_ALIGN(size);
106 n_pages = size >> PAGE_SHIFT;
107
108 buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
109 if (!buf->page_array)
110 return NULL;
111
112 for (i = 0; i < n_pages; i++) {
113 buf->page_array[i] = alloc_page(GFP_KERNEL);
114 if (unlikely(!buf->page_array[i]))
115 goto depopulate;
116 }
117 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
118 if (!mem)
119 goto depopulate;
120
121 memset(mem, 0, size);
122 buf->page_count = n_pages;
123 return mem;
124
125depopulate:
126 for (j = 0; j < i; j++)
127 __free_page(buf->page_array[j]);
128 kfree(buf->page_array);
129 return NULL;
130}
131
132/**
133 * relay_create_buf - allocate and initialize a channel buffer
134 * @alloc_size: size of the buffer to allocate
135 * @n_subbufs: number of sub-buffers in the channel
136 *
137 * Returns channel buffer if successful, NULL otherwise
138 */
139struct rchan_buf *relay_create_buf(struct rchan *chan)
140{
141 struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
142 if (!buf)
143 return NULL;
144
145 buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
146 if (!buf->padding)
147 goto free_buf;
148
149 buf->start = relay_alloc_buf(buf, chan->alloc_size);
150 if (!buf->start)
151 goto free_buf;
152
153 buf->chan = chan;
154 kref_get(&buf->chan->kref);
155 return buf;
156
157free_buf:
158 kfree(buf->padding);
159 kfree(buf);
160 return NULL;
161}
162
163/**
164 * relay_destroy_channel - free the channel struct
165 *
166 * Should only be called from kref_put().
167 */
168void relay_destroy_channel(struct kref *kref)
169{
170 struct rchan *chan = container_of(kref, struct rchan, kref);
171 kfree(chan);
172}
173
174/**
175 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
176 * @buf: the buffer struct
177 */
178void relay_destroy_buf(struct rchan_buf *buf)
179{
180 struct rchan *chan = buf->chan;
181 unsigned int i;
182
183 if (likely(buf->start)) {
184 vunmap(buf->start);
185 for (i = 0; i < buf->page_count; i++)
186 __free_page(buf->page_array[i]);
187 kfree(buf->page_array);
188 }
189 kfree(buf->padding);
190 kfree(buf);
191 kref_put(&chan->kref, relay_destroy_channel);
192}
193
194/**
195 * relay_remove_buf - remove a channel buffer
196 *
197 * Removes the file from the fileystem, which also frees the
198 * rchan_buf_struct and the channel buffer. Should only be called from
199 * kref_put().
200 */
201void relay_remove_buf(struct kref *kref)
202{
203 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
204 buf->chan->cb->remove_buf_file(buf->dentry);
205 relay_destroy_buf(buf);
206}
207
208/**
209 * relay_buf_empty - boolean, is the channel buffer empty?
210 * @buf: channel buffer
211 *
212 * Returns 1 if the buffer is empty, 0 otherwise.
213 */
214int relay_buf_empty(struct rchan_buf *buf)
215{
216 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
217}
218EXPORT_SYMBOL_GPL(relay_buf_empty);
219
220/**
221 * relay_buf_full - boolean, is the channel buffer full?
222 * @buf: channel buffer
223 *
224 * Returns 1 if the buffer is full, 0 otherwise.
225 */
226int relay_buf_full(struct rchan_buf *buf)
227{
228 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
229 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
230}
231EXPORT_SYMBOL_GPL(relay_buf_full);
232
233/*
234 * High-level relay kernel API and associated functions.
235 */
236
237/*
238 * rchan_callback implementations defining default channel behavior. Used
239 * in place of corresponding NULL values in client callback struct.
240 */
241
242/*
243 * subbuf_start() default callback. Does nothing.
244 */
245static int subbuf_start_default_callback (struct rchan_buf *buf,
246 void *subbuf,
247 void *prev_subbuf,
248 size_t prev_padding)
249{
250 if (relay_buf_full(buf))
251 return 0;
252
253 return 1;
254}
255
256/*
257 * buf_mapped() default callback. Does nothing.
258 */
259static void buf_mapped_default_callback(struct rchan_buf *buf,
260 struct file *filp)
261{
262}
263
264/*
265 * buf_unmapped() default callback. Does nothing.
266 */
267static void buf_unmapped_default_callback(struct rchan_buf *buf,
268 struct file *filp)
269{
270}
271
272/*
273 * create_buf_file_create() default callback. Does nothing.
274 */
275static struct dentry *create_buf_file_default_callback(const char *filename,
276 struct dentry *parent,
277 int mode,
278 struct rchan_buf *buf,
279 int *is_global)
280{
281 return NULL;
282}
283
284/*
285 * remove_buf_file() default callback. Does nothing.
286 */
287static int remove_buf_file_default_callback(struct dentry *dentry)
288{
289 return -EINVAL;
290}
291
292/* relay channel default callbacks */
293static struct rchan_callbacks default_channel_callbacks = {
294 .subbuf_start = subbuf_start_default_callback,
295 .buf_mapped = buf_mapped_default_callback,
296 .buf_unmapped = buf_unmapped_default_callback,
297 .create_buf_file = create_buf_file_default_callback,
298 .remove_buf_file = remove_buf_file_default_callback,
299};
300
301/**
302 * wakeup_readers - wake up readers waiting on a channel
303 * @private: the channel buffer
304 *
305 * This is the work function used to defer reader waking. The
306 * reason waking is deferred is that calling directly from write
307 * causes problems if you're writing from say the scheduler.
308 */
309static void wakeup_readers(void *private)
310{
311 struct rchan_buf *buf = private;
312 wake_up_interruptible(&buf->read_wait);
313}
314
315/**
316 * __relay_reset - reset a channel buffer
317 * @buf: the channel buffer
318 * @init: 1 if this is a first-time initialization
319 *
320 * See relay_reset for description of effect.
321 */
322static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
323{
324 size_t i;
325
326 if (init) {
327 init_waitqueue_head(&buf->read_wait);
328 kref_init(&buf->kref);
329 INIT_WORK(&buf->wake_readers, NULL, NULL);
330 } else {
331 cancel_delayed_work(&buf->wake_readers);
332 flush_scheduled_work();
333 }
334
335 buf->subbufs_produced = 0;
336 buf->subbufs_consumed = 0;
337 buf->bytes_consumed = 0;
338 buf->finalized = 0;
339 buf->data = buf->start;
340 buf->offset = 0;
341
342 for (i = 0; i < buf->chan->n_subbufs; i++)
343 buf->padding[i] = 0;
344
345 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
346}
347
348/**
349 * relay_reset - reset the channel
350 * @chan: the channel
351 *
352 * This has the effect of erasing all data from all channel buffers
353 * and restarting the channel in its initial state. The buffers
354 * are not freed, so any mappings are still in effect.
355 *
356 * NOTE: Care should be taken that the channel isn't actually
357 * being used by anything when this call is made.
358 */
359void relay_reset(struct rchan *chan)
360{
361 unsigned int i;
362 struct rchan_buf *prev = NULL;
363
364 if (!chan)
365 return;
366
367 for (i = 0; i < NR_CPUS; i++) {
368 if (!chan->buf[i] || chan->buf[i] == prev)
369 break;
370 __relay_reset(chan->buf[i], 0);
371 prev = chan->buf[i];
372 }
373}
374EXPORT_SYMBOL_GPL(relay_reset);
375
376/**
377 * relay_open_buf - create a new relay channel buffer
378 *
379 * Internal - used by relay_open().
380 */
381static struct rchan_buf *relay_open_buf(struct rchan *chan,
382 const char *filename,
383 struct dentry *parent,
384 int *is_global)
385{
386 struct rchan_buf *buf;
387 struct dentry *dentry;
388
389 if (*is_global)
390 return chan->buf[0];
391
392 buf = relay_create_buf(chan);
393 if (!buf)
394 return NULL;
395
396 /* Create file in fs */
397 dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
398 buf, is_global);
399 if (!dentry) {
400 relay_destroy_buf(buf);
401 return NULL;
402 }
403
404 buf->dentry = dentry;
405 __relay_reset(buf, 1);
406
407 return buf;
408}
409
410/**
411 * relay_close_buf - close a channel buffer
412 * @buf: channel buffer
413 *
414 * Marks the buffer finalized and restores the default callbacks.
415 * The channel buffer and channel buffer data structure are then freed
416 * automatically when the last reference is given up.
417 */
418static inline void relay_close_buf(struct rchan_buf *buf)
419{
420 buf->finalized = 1;
421 cancel_delayed_work(&buf->wake_readers);
422 flush_scheduled_work();
423 kref_put(&buf->kref, relay_remove_buf);
424}
425
426static inline void setup_callbacks(struct rchan *chan,
427 struct rchan_callbacks *cb)
428{
429 if (!cb) {
430 chan->cb = &default_channel_callbacks;
431 return;
432 }
433
434 if (!cb->subbuf_start)
435 cb->subbuf_start = subbuf_start_default_callback;
436 if (!cb->buf_mapped)
437 cb->buf_mapped = buf_mapped_default_callback;
438 if (!cb->buf_unmapped)
439 cb->buf_unmapped = buf_unmapped_default_callback;
440 if (!cb->create_buf_file)
441 cb->create_buf_file = create_buf_file_default_callback;
442 if (!cb->remove_buf_file)
443 cb->remove_buf_file = remove_buf_file_default_callback;
444 chan->cb = cb;
445}
446
447/**
448 * relay_open - create a new relay channel
449 * @base_filename: base name of files to create
450 * @parent: dentry of parent directory, NULL for root directory
451 * @subbuf_size: size of sub-buffers
452 * @n_subbufs: number of sub-buffers
453 * @cb: client callback functions
454 *
455 * Returns channel pointer if successful, NULL otherwise.
456 *
457 * Creates a channel buffer for each cpu using the sizes and
458 * attributes specified. The created channel buffer files
459 * will be named base_filename0...base_filenameN-1. File
460 * permissions will be S_IRUSR.
461 */
462struct rchan *relay_open(const char *base_filename,
463 struct dentry *parent,
464 size_t subbuf_size,
465 size_t n_subbufs,
466 struct rchan_callbacks *cb)
467{
468 unsigned int i;
469 struct rchan *chan;
470 char *tmpname;
471 int is_global = 0;
472
473 if (!base_filename)
474 return NULL;
475
476 if (!(subbuf_size && n_subbufs))
477 return NULL;
478
479 chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
480 if (!chan)
481 return NULL;
482
483 chan->version = RELAYFS_CHANNEL_VERSION;
484 chan->n_subbufs = n_subbufs;
485 chan->subbuf_size = subbuf_size;
486 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
487 setup_callbacks(chan, cb);
488 kref_init(&chan->kref);
489
490 tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
491 if (!tmpname)
492 goto free_chan;
493
494 for_each_online_cpu(i) {
495 sprintf(tmpname, "%s%d", base_filename, i);
496 chan->buf[i] = relay_open_buf(chan, tmpname, parent,
497 &is_global);
498 if (!chan->buf[i])
499 goto free_bufs;
500
501 chan->buf[i]->cpu = i;
502 }
503
504 kfree(tmpname);
505 return chan;
506
507free_bufs:
508 for (i = 0; i < NR_CPUS; i++) {
509 if (!chan->buf[i])
510 break;
511 relay_close_buf(chan->buf[i]);
512 if (is_global)
513 break;
514 }
515 kfree(tmpname);
516
517free_chan:
518 kref_put(&chan->kref, relay_destroy_channel);
519 return NULL;
520}
521EXPORT_SYMBOL_GPL(relay_open);
522
523/**
524 * relay_switch_subbuf - switch to a new sub-buffer
525 * @buf: channel buffer
526 * @length: size of current event
527 *
528 * Returns either the length passed in or 0 if full.
529 *
530 * Performs sub-buffer-switch tasks such as invoking callbacks,
531 * updating padding counts, waking up readers, etc.
532 */
533size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
534{
535 void *old, *new;
536 size_t old_subbuf, new_subbuf;
537
538 if (unlikely(length > buf->chan->subbuf_size))
539 goto toobig;
540
541 if (buf->offset != buf->chan->subbuf_size + 1) {
542 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
543 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
544 buf->padding[old_subbuf] = buf->prev_padding;
545 buf->subbufs_produced++;
546 if (waitqueue_active(&buf->read_wait)) {
547 PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
548 schedule_delayed_work(&buf->wake_readers, 1);
549 }
550 }
551
552 old = buf->data;
553 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
554 new = buf->start + new_subbuf * buf->chan->subbuf_size;
555 buf->offset = 0;
556 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
557 buf->offset = buf->chan->subbuf_size + 1;
558 return 0;
559 }
560 buf->data = new;
561 buf->padding[new_subbuf] = 0;
562
563 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
564 goto toobig;
565
566 return length;
567
568toobig:
569 buf->chan->last_toobig = length;
570 return 0;
571}
572EXPORT_SYMBOL_GPL(relay_switch_subbuf);
573
574/**
575 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
576 * @chan: the channel
577 * @cpu: the cpu associated with the channel buffer to update
578 * @subbufs_consumed: number of sub-buffers to add to current buf's count
579 *
580 * Adds to the channel buffer's consumed sub-buffer count.
581 * subbufs_consumed should be the number of sub-buffers newly consumed,
582 * not the total consumed.
583 *
584 * NOTE: kernel clients don't need to call this function if the channel
585 * mode is 'overwrite'.
586 */
587void relay_subbufs_consumed(struct rchan *chan,
588 unsigned int cpu,
589 size_t subbufs_consumed)
590{
591 struct rchan_buf *buf;
592
593 if (!chan)
594 return;
595
596 if (cpu >= NR_CPUS || !chan->buf[cpu])
597 return;
598
599 buf = chan->buf[cpu];
600 buf->subbufs_consumed += subbufs_consumed;
601 if (buf->subbufs_consumed > buf->subbufs_produced)
602 buf->subbufs_consumed = buf->subbufs_produced;
603}
604EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
605
606/**
607 * relay_close - close the channel
608 * @chan: the channel
609 *
610 * Closes all channel buffers and frees the channel.
611 */
612void relay_close(struct rchan *chan)
613{
614 unsigned int i;
615 struct rchan_buf *prev = NULL;
616
617 if (!chan)
618 return;
619
620 for (i = 0; i < NR_CPUS; i++) {
621 if (!chan->buf[i] || chan->buf[i] == prev)
622 break;
623 relay_close_buf(chan->buf[i]);
624 prev = chan->buf[i];
625 }
626
627 if (chan->last_toobig)
628 printk(KERN_WARNING "relay: one or more items not logged "
629 "[item size (%Zd) > sub-buffer size (%Zd)]\n",
630 chan->last_toobig, chan->subbuf_size);
631
632 kref_put(&chan->kref, relay_destroy_channel);
633}
634EXPORT_SYMBOL_GPL(relay_close);
635
636/**
637 * relay_flush - close the channel
638 * @chan: the channel
639 *
640 * Flushes all channel buffers i.e. forces buffer switch.
641 */
642void relay_flush(struct rchan *chan)
643{
644 unsigned int i;
645 struct rchan_buf *prev = NULL;
646
647 if (!chan)
648 return;
649
650 for (i = 0; i < NR_CPUS; i++) {
651 if (!chan->buf[i] || chan->buf[i] == prev)
652 break;
653 relay_switch_subbuf(chan->buf[i], 0);
654 prev = chan->buf[i];
655 }
656}
657EXPORT_SYMBOL_GPL(relay_flush);
658
659/**
660 * relay_file_open - open file op for relay files
661 * @inode: the inode
662 * @filp: the file
663 *
664 * Increments the channel buffer refcount.
665 */
666static int relay_file_open(struct inode *inode, struct file *filp)
667{
668 struct rchan_buf *buf = inode->u.generic_ip;
669 kref_get(&buf->kref);
670 filp->private_data = buf;
671
672 return 0;
673}
674
675/**
676 * relay_file_mmap - mmap file op for relay files
677 * @filp: the file
678 * @vma: the vma describing what to map
679 *
680 * Calls upon relay_mmap_buf to map the file into user space.
681 */
682static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
683{
684 struct rchan_buf *buf = filp->private_data;
685 return relay_mmap_buf(buf, vma);
686}
687
688/**
689 * relay_file_poll - poll file op for relay files
690 * @filp: the file
691 * @wait: poll table
692 *
693 * Poll implemention.
694 */
695static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
696{
697 unsigned int mask = 0;
698 struct rchan_buf *buf = filp->private_data;
699
700 if (buf->finalized)
701 return POLLERR;
702
703 if (filp->f_mode & FMODE_READ) {
704 poll_wait(filp, &buf->read_wait, wait);
705 if (!relay_buf_empty(buf))
706 mask |= POLLIN | POLLRDNORM;
707 }
708
709 return mask;
710}
711
712/**
713 * relay_file_release - release file op for relay files
714 * @inode: the inode
715 * @filp: the file
716 *
717 * Decrements the channel refcount, as the filesystem is
718 * no longer using it.
719 */
720static int relay_file_release(struct inode *inode, struct file *filp)
721{
722 struct rchan_buf *buf = filp->private_data;
723 kref_put(&buf->kref, relay_remove_buf);
724
725 return 0;
726}
727
728/**
729 * relay_file_read_consume - update the consumed count for the buffer
730 */
731static void relay_file_read_consume(struct rchan_buf *buf,
732 size_t read_pos,
733 size_t bytes_consumed)
734{
735 size_t subbuf_size = buf->chan->subbuf_size;
736 size_t n_subbufs = buf->chan->n_subbufs;
737 size_t read_subbuf;
738
739 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
740 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
741 buf->bytes_consumed = 0;
742 }
743
744 buf->bytes_consumed += bytes_consumed;
745 read_subbuf = read_pos / buf->chan->subbuf_size;
746 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
747 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
748 (buf->offset == subbuf_size))
749 return;
750 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
751 buf->bytes_consumed = 0;
752 }
753}
754
755/**
756 * relay_file_read_avail - boolean, are there unconsumed bytes available?
757 */
758static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
759{
760 size_t bytes_produced, bytes_consumed, write_offset;
761 size_t subbuf_size = buf->chan->subbuf_size;
762 size_t n_subbufs = buf->chan->n_subbufs;
763 size_t produced = buf->subbufs_produced % n_subbufs;
764 size_t consumed = buf->subbufs_consumed % n_subbufs;
765
766 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
767
768 if (consumed > produced) {
769 if ((produced > n_subbufs) &&
770 (produced + n_subbufs - consumed <= n_subbufs))
771 produced += n_subbufs;
772 } else if (consumed == produced) {
773 if (buf->offset > subbuf_size) {
774 produced += n_subbufs;
775 if (buf->subbufs_produced == buf->subbufs_consumed)
776 consumed += n_subbufs;
777 }
778 }
779
780 if (buf->offset > subbuf_size)
781 bytes_produced = (produced - 1) * subbuf_size + write_offset;
782 else
783 bytes_produced = produced * subbuf_size + write_offset;
784 bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;
785
786 if (bytes_produced == bytes_consumed)
787 return 0;
788
789 relay_file_read_consume(buf, read_pos, 0);
790
791 return 1;
792}
793
794/**
795 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
796 */
797static size_t relay_file_read_subbuf_avail(size_t read_pos,
798 struct rchan_buf *buf)
799{
800 size_t padding, avail = 0;
801 size_t read_subbuf, read_offset, write_subbuf, write_offset;
802 size_t subbuf_size = buf->chan->subbuf_size;
803
804 write_subbuf = (buf->data - buf->start) / subbuf_size;
805 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
806 read_subbuf = read_pos / subbuf_size;
807 read_offset = read_pos % subbuf_size;
808 padding = buf->padding[read_subbuf];
809
810 if (read_subbuf == write_subbuf) {
811 if (read_offset + padding < write_offset)
812 avail = write_offset - (read_offset + padding);
813 } else
814 avail = (subbuf_size - padding) - read_offset;
815
816 return avail;
817}
818
819/**
820 * relay_file_read_start_pos - find the first available byte to read
821 *
822 * If the read_pos is in the middle of padding, return the
823 * position of the first actually available byte, otherwise
824 * return the original value.
825 */
826static size_t relay_file_read_start_pos(size_t read_pos,
827 struct rchan_buf *buf)
828{
829 size_t read_subbuf, padding, padding_start, padding_end;
830 size_t subbuf_size = buf->chan->subbuf_size;
831 size_t n_subbufs = buf->chan->n_subbufs;
832
833 read_subbuf = read_pos / subbuf_size;
834 padding = buf->padding[read_subbuf];
835 padding_start = (read_subbuf + 1) * subbuf_size - padding;
836 padding_end = (read_subbuf + 1) * subbuf_size;
837 if (read_pos >= padding_start && read_pos < padding_end) {
838 read_subbuf = (read_subbuf + 1) % n_subbufs;
839 read_pos = read_subbuf * subbuf_size;
840 }
841
842 return read_pos;
843}
844
845/**
846 * relay_file_read_end_pos - return the new read position
847 */
848static size_t relay_file_read_end_pos(struct rchan_buf *buf,
849 size_t read_pos,
850 size_t count)
851{
852 size_t read_subbuf, padding, end_pos;
853 size_t subbuf_size = buf->chan->subbuf_size;
854 size_t n_subbufs = buf->chan->n_subbufs;
855
856 read_subbuf = read_pos / subbuf_size;
857 padding = buf->padding[read_subbuf];
858 if (read_pos % subbuf_size + count + padding == subbuf_size)
859 end_pos = (read_subbuf + 1) * subbuf_size;
860 else
861 end_pos = read_pos + count;
862 if (end_pos >= subbuf_size * n_subbufs)
863 end_pos = 0;
864
865 return end_pos;
866}
867
868/**
869 * relay_file_read - read file op for relay files
870 * @filp: the file
871 * @buffer: the userspace buffer
872 * @count: number of bytes to read
873 * @ppos: position to read from
874 *
875 * Reads count bytes or the number of bytes available in the
876 * current sub-buffer being read, whichever is smaller.
877 */
878static ssize_t relay_file_read(struct file *filp,
879 char __user *buffer,
880 size_t count,
881 loff_t *ppos)
882{
883 struct rchan_buf *buf = filp->private_data;
884 struct inode *inode = filp->f_dentry->d_inode;
885 size_t read_start, avail;
886 ssize_t ret = 0;
887 void *from;
888
889 mutex_lock(&inode->i_mutex);
890 if(!relay_file_read_avail(buf, *ppos))
891 goto out;
892
893 read_start = relay_file_read_start_pos(*ppos, buf);
894 avail = relay_file_read_subbuf_avail(read_start, buf);
895 if (!avail)
896 goto out;
897
898 from = buf->start + read_start;
899 ret = count = min(count, avail);
900 if (copy_to_user(buffer, from, count)) {
901 ret = -EFAULT;
902 goto out;
903 }
904 relay_file_read_consume(buf, read_start, count);
905 *ppos = relay_file_read_end_pos(buf, read_start, count);
906out:
907 mutex_unlock(&inode->i_mutex);
908 return ret;
909}
910
911struct file_operations relay_file_operations = {
912 .open = relay_file_open,
913 .poll = relay_file_poll,
914 .mmap = relay_file_mmap,
915 .read = relay_file_read,
916 .llseek = no_llseek,
917 .release = relay_file_release,
918};
919EXPORT_SYMBOL_GPL(relay_file_operations);
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-24 07:51:13 -0500