ia64/linux-2.6.18-xen.hg

view kernel/relay.c @ 0:831230e53067

Import 2.6.18 from kernel.org tarball.
author Ian Campbell <ian.campbell@xensource.com>
date Wed Apr 11 14:15:44 2007 +0100 (2007-04-11)
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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>
22 /*
23 * close() vm_op implementation for relay file mapping.
24 */
25 static 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 }
31 /*
32 * nopage() vm_op implementation for relay file mapping.
33 */
34 static 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;
42 if (address > vma->vm_end)
43 return NOPAGE_SIGBUS; /* Disallow mremap */
44 if (!buf)
45 return NOPAGE_OOM;
47 page = vmalloc_to_page(buf->start + offset);
48 if (!page)
49 return NOPAGE_OOM;
50 get_page(page);
52 if (type)
53 *type = VM_FAULT_MINOR;
55 return page;
56 }
58 /*
59 * vm_ops for relay file mappings.
60 */
61 static struct vm_operations_struct relay_file_mmap_ops = {
62 .nopage = relay_buf_nopage,
63 .close = relay_file_mmap_close,
64 };
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 */
75 int 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;
80 if (!buf)
81 return -EBADF;
83 if (length != (unsigned long)buf->chan->alloc_size)
84 return -EINVAL;
86 vma->vm_ops = &relay_file_mmap_ops;
87 vma->vm_private_data = buf;
88 buf->chan->cb->buf_mapped(buf, filp);
90 return 0;
91 }
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. The
99 * passed in size will get page aligned, if it isn't already.
100 */
101 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
102 {
103 void *mem;
104 unsigned int i, j, n_pages;
106 *size = PAGE_ALIGN(*size);
107 n_pages = *size >> PAGE_SHIFT;
109 buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
110 if (!buf->page_array)
111 return NULL;
113 for (i = 0; i < n_pages; i++) {
114 buf->page_array[i] = alloc_page(GFP_KERNEL);
115 if (unlikely(!buf->page_array[i]))
116 goto depopulate;
117 }
118 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
119 if (!mem)
120 goto depopulate;
122 memset(mem, 0, *size);
123 buf->page_count = n_pages;
124 return mem;
126 depopulate:
127 for (j = 0; j < i; j++)
128 __free_page(buf->page_array[j]);
129 kfree(buf->page_array);
130 return NULL;
131 }
133 /**
134 * relay_create_buf - allocate and initialize a channel buffer
135 * @alloc_size: size of the buffer to allocate
136 * @n_subbufs: number of sub-buffers in the channel
137 *
138 * Returns channel buffer if successful, NULL otherwise
139 */
140 struct rchan_buf *relay_create_buf(struct rchan *chan)
141 {
142 struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
143 if (!buf)
144 return NULL;
146 buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
147 if (!buf->padding)
148 goto free_buf;
150 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
151 if (!buf->start)
152 goto free_buf;
154 buf->chan = chan;
155 kref_get(&buf->chan->kref);
156 return buf;
158 free_buf:
159 kfree(buf->padding);
160 kfree(buf);
161 return NULL;
162 }
164 /**
165 * relay_destroy_channel - free the channel struct
166 *
167 * Should only be called from kref_put().
168 */
169 void relay_destroy_channel(struct kref *kref)
170 {
171 struct rchan *chan = container_of(kref, struct rchan, kref);
172 kfree(chan);
173 }
175 /**
176 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
177 * @buf: the buffer struct
178 */
179 void relay_destroy_buf(struct rchan_buf *buf)
180 {
181 struct rchan *chan = buf->chan;
182 unsigned int i;
184 if (likely(buf->start)) {
185 vunmap(buf->start);
186 for (i = 0; i < buf->page_count; i++)
187 __free_page(buf->page_array[i]);
188 kfree(buf->page_array);
189 }
190 kfree(buf->padding);
191 kfree(buf);
192 kref_put(&chan->kref, relay_destroy_channel);
193 }
195 /**
196 * relay_remove_buf - remove a channel buffer
197 *
198 * Removes the file from the fileystem, which also frees the
199 * rchan_buf_struct and the channel buffer. Should only be called from
200 * kref_put().
201 */
202 void relay_remove_buf(struct kref *kref)
203 {
204 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
205 buf->chan->cb->remove_buf_file(buf->dentry);
206 relay_destroy_buf(buf);
207 }
209 /**
210 * relay_buf_empty - boolean, is the channel buffer empty?
211 * @buf: channel buffer
212 *
213 * Returns 1 if the buffer is empty, 0 otherwise.
214 */
215 int relay_buf_empty(struct rchan_buf *buf)
216 {
217 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
218 }
219 EXPORT_SYMBOL_GPL(relay_buf_empty);
221 /**
222 * relay_buf_full - boolean, is the channel buffer full?
223 * @buf: channel buffer
224 *
225 * Returns 1 if the buffer is full, 0 otherwise.
226 */
227 int relay_buf_full(struct rchan_buf *buf)
228 {
229 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
230 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
231 }
232 EXPORT_SYMBOL_GPL(relay_buf_full);
234 /*
235 * High-level relay kernel API and associated functions.
236 */
238 /*
239 * rchan_callback implementations defining default channel behavior. Used
240 * in place of corresponding NULL values in client callback struct.
241 */
243 /*
244 * subbuf_start() default callback. Does nothing.
245 */
246 static int subbuf_start_default_callback (struct rchan_buf *buf,
247 void *subbuf,
248 void *prev_subbuf,
249 size_t prev_padding)
250 {
251 if (relay_buf_full(buf))
252 return 0;
254 return 1;
255 }
257 /*
258 * buf_mapped() default callback. Does nothing.
259 */
260 static void buf_mapped_default_callback(struct rchan_buf *buf,
261 struct file *filp)
262 {
263 }
265 /*
266 * buf_unmapped() default callback. Does nothing.
267 */
268 static void buf_unmapped_default_callback(struct rchan_buf *buf,
269 struct file *filp)
270 {
271 }
273 /*
274 * create_buf_file_create() default callback. Does nothing.
275 */
276 static struct dentry *create_buf_file_default_callback(const char *filename,
277 struct dentry *parent,
278 int mode,
279 struct rchan_buf *buf,
280 int *is_global)
281 {
282 return NULL;
283 }
285 /*
286 * remove_buf_file() default callback. Does nothing.
287 */
288 static int remove_buf_file_default_callback(struct dentry *dentry)
289 {
290 return -EINVAL;
291 }
293 /* relay channel default callbacks */
294 static struct rchan_callbacks default_channel_callbacks = {
295 .subbuf_start = subbuf_start_default_callback,
296 .buf_mapped = buf_mapped_default_callback,
297 .buf_unmapped = buf_unmapped_default_callback,
298 .create_buf_file = create_buf_file_default_callback,
299 .remove_buf_file = remove_buf_file_default_callback,
300 };
302 /**
303 * wakeup_readers - wake up readers waiting on a channel
304 * @private: the channel buffer
305 *
306 * This is the work function used to defer reader waking. The
307 * reason waking is deferred is that calling directly from write
308 * causes problems if you're writing from say the scheduler.
309 */
310 static void wakeup_readers(void *private)
311 {
312 struct rchan_buf *buf = private;
313 wake_up_interruptible(&buf->read_wait);
314 }
316 /**
317 * __relay_reset - reset a channel buffer
318 * @buf: the channel buffer
319 * @init: 1 if this is a first-time initialization
320 *
321 * See relay_reset for description of effect.
322 */
323 static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
324 {
325 size_t i;
327 if (init) {
328 init_waitqueue_head(&buf->read_wait);
329 kref_init(&buf->kref);
330 INIT_WORK(&buf->wake_readers, NULL, NULL);
331 } else {
332 cancel_delayed_work(&buf->wake_readers);
333 flush_scheduled_work();
334 }
336 buf->subbufs_produced = 0;
337 buf->subbufs_consumed = 0;
338 buf->bytes_consumed = 0;
339 buf->finalized = 0;
340 buf->data = buf->start;
341 buf->offset = 0;
343 for (i = 0; i < buf->chan->n_subbufs; i++)
344 buf->padding[i] = 0;
346 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
347 }
349 /**
350 * relay_reset - reset the channel
351 * @chan: the channel
352 *
353 * This has the effect of erasing all data from all channel buffers
354 * and restarting the channel in its initial state. The buffers
355 * are not freed, so any mappings are still in effect.
356 *
357 * NOTE: Care should be taken that the channel isn't actually
358 * being used by anything when this call is made.
359 */
360 void relay_reset(struct rchan *chan)
361 {
362 unsigned int i;
363 struct rchan_buf *prev = NULL;
365 if (!chan)
366 return;
368 for (i = 0; i < NR_CPUS; i++) {
369 if (!chan->buf[i] || chan->buf[i] == prev)
370 break;
371 __relay_reset(chan->buf[i], 0);
372 prev = chan->buf[i];
373 }
374 }
375 EXPORT_SYMBOL_GPL(relay_reset);
377 /**
378 * relay_open_buf - create a new relay channel buffer
379 *
380 * Internal - used by relay_open().
381 */
382 static struct rchan_buf *relay_open_buf(struct rchan *chan,
383 const char *filename,
384 struct dentry *parent,
385 int *is_global)
386 {
387 struct rchan_buf *buf;
388 struct dentry *dentry;
390 if (*is_global)
391 return chan->buf[0];
393 buf = relay_create_buf(chan);
394 if (!buf)
395 return NULL;
397 /* Create file in fs */
398 dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
399 buf, is_global);
400 if (!dentry) {
401 relay_destroy_buf(buf);
402 return NULL;
403 }
405 buf->dentry = dentry;
406 __relay_reset(buf, 1);
408 return buf;
409 }
411 /**
412 * relay_close_buf - close a channel buffer
413 * @buf: channel buffer
414 *
415 * Marks the buffer finalized and restores the default callbacks.
416 * The channel buffer and channel buffer data structure are then freed
417 * automatically when the last reference is given up.
418 */
419 static inline void relay_close_buf(struct rchan_buf *buf)
420 {
421 buf->finalized = 1;
422 cancel_delayed_work(&buf->wake_readers);
423 flush_scheduled_work();
424 kref_put(&buf->kref, relay_remove_buf);
425 }
427 static inline void setup_callbacks(struct rchan *chan,
428 struct rchan_callbacks *cb)
429 {
430 if (!cb) {
431 chan->cb = &default_channel_callbacks;
432 return;
433 }
435 if (!cb->subbuf_start)
436 cb->subbuf_start = subbuf_start_default_callback;
437 if (!cb->buf_mapped)
438 cb->buf_mapped = buf_mapped_default_callback;
439 if (!cb->buf_unmapped)
440 cb->buf_unmapped = buf_unmapped_default_callback;
441 if (!cb->create_buf_file)
442 cb->create_buf_file = create_buf_file_default_callback;
443 if (!cb->remove_buf_file)
444 cb->remove_buf_file = remove_buf_file_default_callback;
445 chan->cb = cb;
446 }
448 /**
449 * relay_open - create a new relay channel
450 * @base_filename: base name of files to create
451 * @parent: dentry of parent directory, NULL for root directory
452 * @subbuf_size: size of sub-buffers
453 * @n_subbufs: number of sub-buffers
454 * @cb: client callback functions
455 *
456 * Returns channel pointer if successful, NULL otherwise.
457 *
458 * Creates a channel buffer for each cpu using the sizes and
459 * attributes specified. The created channel buffer files
460 * will be named base_filename0...base_filenameN-1. File
461 * permissions will be S_IRUSR.
462 */
463 struct rchan *relay_open(const char *base_filename,
464 struct dentry *parent,
465 size_t subbuf_size,
466 size_t n_subbufs,
467 struct rchan_callbacks *cb)
468 {
469 unsigned int i;
470 struct rchan *chan;
471 char *tmpname;
472 int is_global = 0;
474 if (!base_filename)
475 return NULL;
477 if (!(subbuf_size && n_subbufs))
478 return NULL;
480 chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
481 if (!chan)
482 return NULL;
484 chan->version = RELAYFS_CHANNEL_VERSION;
485 chan->n_subbufs = n_subbufs;
486 chan->subbuf_size = subbuf_size;
487 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
488 setup_callbacks(chan, cb);
489 kref_init(&chan->kref);
491 tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
492 if (!tmpname)
493 goto free_chan;
495 for_each_online_cpu(i) {
496 sprintf(tmpname, "%s%d", base_filename, i);
497 chan->buf[i] = relay_open_buf(chan, tmpname, parent,
498 &is_global);
499 if (!chan->buf[i])
500 goto free_bufs;
502 chan->buf[i]->cpu = i;
503 }
505 kfree(tmpname);
506 return chan;
508 free_bufs:
509 for (i = 0; i < NR_CPUS; i++) {
510 if (!chan->buf[i])
511 break;
512 relay_close_buf(chan->buf[i]);
513 if (is_global)
514 break;
515 }
516 kfree(tmpname);
518 free_chan:
519 kref_put(&chan->kref, relay_destroy_channel);
520 return NULL;
521 }
522 EXPORT_SYMBOL_GPL(relay_open);
524 /**
525 * relay_switch_subbuf - switch to a new sub-buffer
526 * @buf: channel buffer
527 * @length: size of current event
528 *
529 * Returns either the length passed in or 0 if full.
530 *
531 * Performs sub-buffer-switch tasks such as invoking callbacks,
532 * updating padding counts, waking up readers, etc.
533 */
534 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
535 {
536 void *old, *new;
537 size_t old_subbuf, new_subbuf;
539 if (unlikely(length > buf->chan->subbuf_size))
540 goto toobig;
542 if (buf->offset != buf->chan->subbuf_size + 1) {
543 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
544 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
545 buf->padding[old_subbuf] = buf->prev_padding;
546 buf->subbufs_produced++;
547 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
548 buf->padding[old_subbuf];
549 smp_mb();
550 if (waitqueue_active(&buf->read_wait)) {
551 PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
552 schedule_delayed_work(&buf->wake_readers, 1);
553 }
554 }
556 old = buf->data;
557 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
558 new = buf->start + new_subbuf * buf->chan->subbuf_size;
559 buf->offset = 0;
560 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
561 buf->offset = buf->chan->subbuf_size + 1;
562 return 0;
563 }
564 buf->data = new;
565 buf->padding[new_subbuf] = 0;
567 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
568 goto toobig;
570 return length;
572 toobig:
573 buf->chan->last_toobig = length;
574 return 0;
575 }
576 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
578 /**
579 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
580 * @chan: the channel
581 * @cpu: the cpu associated with the channel buffer to update
582 * @subbufs_consumed: number of sub-buffers to add to current buf's count
583 *
584 * Adds to the channel buffer's consumed sub-buffer count.
585 * subbufs_consumed should be the number of sub-buffers newly consumed,
586 * not the total consumed.
587 *
588 * NOTE: kernel clients don't need to call this function if the channel
589 * mode is 'overwrite'.
590 */
591 void relay_subbufs_consumed(struct rchan *chan,
592 unsigned int cpu,
593 size_t subbufs_consumed)
594 {
595 struct rchan_buf *buf;
597 if (!chan)
598 return;
600 if (cpu >= NR_CPUS || !chan->buf[cpu])
601 return;
603 buf = chan->buf[cpu];
604 buf->subbufs_consumed += subbufs_consumed;
605 if (buf->subbufs_consumed > buf->subbufs_produced)
606 buf->subbufs_consumed = buf->subbufs_produced;
607 }
608 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
610 /**
611 * relay_close - close the channel
612 * @chan: the channel
613 *
614 * Closes all channel buffers and frees the channel.
615 */
616 void relay_close(struct rchan *chan)
617 {
618 unsigned int i;
619 struct rchan_buf *prev = NULL;
621 if (!chan)
622 return;
624 for (i = 0; i < NR_CPUS; i++) {
625 if (!chan->buf[i] || chan->buf[i] == prev)
626 break;
627 relay_close_buf(chan->buf[i]);
628 prev = chan->buf[i];
629 }
631 if (chan->last_toobig)
632 printk(KERN_WARNING "relay: one or more items not logged "
633 "[item size (%Zd) > sub-buffer size (%Zd)]\n",
634 chan->last_toobig, chan->subbuf_size);
636 kref_put(&chan->kref, relay_destroy_channel);
637 }
638 EXPORT_SYMBOL_GPL(relay_close);
640 /**
641 * relay_flush - close the channel
642 * @chan: the channel
643 *
644 * Flushes all channel buffers i.e. forces buffer switch.
645 */
646 void relay_flush(struct rchan *chan)
647 {
648 unsigned int i;
649 struct rchan_buf *prev = NULL;
651 if (!chan)
652 return;
654 for (i = 0; i < NR_CPUS; i++) {
655 if (!chan->buf[i] || chan->buf[i] == prev)
656 break;
657 relay_switch_subbuf(chan->buf[i], 0);
658 prev = chan->buf[i];
659 }
660 }
661 EXPORT_SYMBOL_GPL(relay_flush);
663 /**
664 * relay_file_open - open file op for relay files
665 * @inode: the inode
666 * @filp: the file
667 *
668 * Increments the channel buffer refcount.
669 */
670 static int relay_file_open(struct inode *inode, struct file *filp)
671 {
672 struct rchan_buf *buf = inode->u.generic_ip;
673 kref_get(&buf->kref);
674 filp->private_data = buf;
676 return 0;
677 }
679 /**
680 * relay_file_mmap - mmap file op for relay files
681 * @filp: the file
682 * @vma: the vma describing what to map
683 *
684 * Calls upon relay_mmap_buf to map the file into user space.
685 */
686 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
687 {
688 struct rchan_buf *buf = filp->private_data;
689 return relay_mmap_buf(buf, vma);
690 }
692 /**
693 * relay_file_poll - poll file op for relay files
694 * @filp: the file
695 * @wait: poll table
696 *
697 * Poll implemention.
698 */
699 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
700 {
701 unsigned int mask = 0;
702 struct rchan_buf *buf = filp->private_data;
704 if (buf->finalized)
705 return POLLERR;
707 if (filp->f_mode & FMODE_READ) {
708 poll_wait(filp, &buf->read_wait, wait);
709 if (!relay_buf_empty(buf))
710 mask |= POLLIN | POLLRDNORM;
711 }
713 return mask;
714 }
716 /**
717 * relay_file_release - release file op for relay files
718 * @inode: the inode
719 * @filp: the file
720 *
721 * Decrements the channel refcount, as the filesystem is
722 * no longer using it.
723 */
724 static int relay_file_release(struct inode *inode, struct file *filp)
725 {
726 struct rchan_buf *buf = filp->private_data;
727 kref_put(&buf->kref, relay_remove_buf);
729 return 0;
730 }
732 /**
733 * relay_file_read_consume - update the consumed count for the buffer
734 */
735 static void relay_file_read_consume(struct rchan_buf *buf,
736 size_t read_pos,
737 size_t bytes_consumed)
738 {
739 size_t subbuf_size = buf->chan->subbuf_size;
740 size_t n_subbufs = buf->chan->n_subbufs;
741 size_t read_subbuf;
743 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
744 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
745 buf->bytes_consumed = 0;
746 }
748 buf->bytes_consumed += bytes_consumed;
749 read_subbuf = read_pos / buf->chan->subbuf_size;
750 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
751 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
752 (buf->offset == subbuf_size))
753 return;
754 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
755 buf->bytes_consumed = 0;
756 }
757 }
759 /**
760 * relay_file_read_avail - boolean, are there unconsumed bytes available?
761 */
762 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
763 {
764 size_t subbuf_size = buf->chan->subbuf_size;
765 size_t n_subbufs = buf->chan->n_subbufs;
766 size_t produced = buf->subbufs_produced;
767 size_t consumed = buf->subbufs_consumed;
769 relay_file_read_consume(buf, read_pos, 0);
771 if (unlikely(buf->offset > subbuf_size)) {
772 if (produced == consumed)
773 return 0;
774 return 1;
775 }
777 if (unlikely(produced - consumed >= n_subbufs)) {
778 consumed = (produced / n_subbufs) * n_subbufs;
779 buf->subbufs_consumed = consumed;
780 }
782 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
783 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
785 if (consumed > produced)
786 produced += n_subbufs * subbuf_size;
788 if (consumed == produced)
789 return 0;
791 return 1;
792 }
794 /**
795 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
796 */
797 static 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;
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];
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;
816 return avail;
817 }
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 */
826 static 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;
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 }
842 return read_pos;
843 }
845 /**
846 * relay_file_read_end_pos - return the new read position
847 */
848 static 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;
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;
865 return end_pos;
866 }
868 /**
869 * subbuf_read_actor - read up to one subbuf's worth of data
870 */
871 static int subbuf_read_actor(size_t read_start,
872 struct rchan_buf *buf,
873 size_t avail,
874 read_descriptor_t *desc,
875 read_actor_t actor)
876 {
877 void *from;
878 int ret = 0;
880 from = buf->start + read_start;
881 ret = avail;
882 if (copy_to_user(desc->arg.data, from, avail)) {
883 desc->error = -EFAULT;
884 ret = 0;
885 }
886 desc->arg.data += ret;
887 desc->written += ret;
888 desc->count -= ret;
890 return ret;
891 }
893 /**
894 * subbuf_send_actor - send up to one subbuf's worth of data
895 */
896 static int subbuf_send_actor(size_t read_start,
897 struct rchan_buf *buf,
898 size_t avail,
899 read_descriptor_t *desc,
900 read_actor_t actor)
901 {
902 unsigned long pidx, poff;
903 unsigned int subbuf_pages;
904 int ret = 0;
906 subbuf_pages = buf->chan->alloc_size >> PAGE_SHIFT;
907 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
908 poff = read_start & ~PAGE_MASK;
909 while (avail) {
910 struct page *p = buf->page_array[pidx];
911 unsigned int len;
913 len = PAGE_SIZE - poff;
914 if (len > avail)
915 len = avail;
917 len = actor(desc, p, poff, len);
918 if (desc->error)
919 break;
921 avail -= len;
922 ret += len;
923 poff = 0;
924 pidx = (pidx + 1) % subbuf_pages;
925 }
927 return ret;
928 }
930 typedef int (*subbuf_actor_t) (size_t read_start,
931 struct rchan_buf *buf,
932 size_t avail,
933 read_descriptor_t *desc,
934 read_actor_t actor);
936 /**
937 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
938 */
939 static inline ssize_t relay_file_read_subbufs(struct file *filp,
940 loff_t *ppos,
941 size_t count,
942 subbuf_actor_t subbuf_actor,
943 read_actor_t actor,
944 void *target)
945 {
946 struct rchan_buf *buf = filp->private_data;
947 size_t read_start, avail;
948 read_descriptor_t desc;
949 int ret;
951 if (!count)
952 return 0;
954 desc.written = 0;
955 desc.count = count;
956 desc.arg.data = target;
957 desc.error = 0;
959 mutex_lock(&filp->f_dentry->d_inode->i_mutex);
960 do {
961 if (!relay_file_read_avail(buf, *ppos))
962 break;
964 read_start = relay_file_read_start_pos(*ppos, buf);
965 avail = relay_file_read_subbuf_avail(read_start, buf);
966 if (!avail)
967 break;
969 avail = min(desc.count, avail);
970 ret = subbuf_actor(read_start, buf, avail, &desc, actor);
971 if (desc.error < 0)
972 break;
974 if (ret) {
975 relay_file_read_consume(buf, read_start, ret);
976 *ppos = relay_file_read_end_pos(buf, read_start, ret);
977 }
978 } while (desc.count && ret);
979 mutex_unlock(&filp->f_dentry->d_inode->i_mutex);
981 return desc.written;
982 }
984 static ssize_t relay_file_read(struct file *filp,
985 char __user *buffer,
986 size_t count,
987 loff_t *ppos)
988 {
989 return relay_file_read_subbufs(filp, ppos, count, subbuf_read_actor,
990 NULL, buffer);
991 }
993 static ssize_t relay_file_sendfile(struct file *filp,
994 loff_t *ppos,
995 size_t count,
996 read_actor_t actor,
997 void *target)
998 {
999 return relay_file_read_subbufs(filp, ppos, count, subbuf_send_actor,
1000 actor, target);
1003 struct file_operations relay_file_operations = {
1004 .open = relay_file_open,
1005 .poll = relay_file_poll,
1006 .mmap = relay_file_mmap,
1007 .read = relay_file_read,
1008 .llseek = no_llseek,
1009 .release = relay_file_release,
1010 .sendfile = relay_file_sendfile,
1011 };
1012 EXPORT_SYMBOL_GPL(relay_file_operations);