fs: use kmem_cache_zalloc instead
[pv_ops_mirror.git] / kernel / relay.c
blobad855017bc59de72ebf592fda7576edf6e245bb4
1 /*
2 * Public API and common code for kernel->userspace relay file support.
4 * See Documentation/filesystems/relay.txt for an overview.
6 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
7 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
9 * Moved to kernel/relay.c by Paul Mundt, 2006.
10 * November 2006 - CPU hotplug support by Mathieu Desnoyers
11 * (mathieu.desnoyers@polymtl.ca)
13 * This file is released under the GPL.
15 #include <linux/errno.h>
16 #include <linux/stddef.h>
17 #include <linux/slab.h>
18 #include <linux/module.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>
26 /* list of open channels, for cpu hotplug */
27 static DEFINE_MUTEX(relay_channels_mutex);
28 static LIST_HEAD(relay_channels);
31 * close() vm_op implementation for relay file mapping.
33 static void relay_file_mmap_close(struct vm_area_struct *vma)
35 struct rchan_buf *buf = vma->vm_private_data;
36 buf->chan->cb->buf_unmapped(buf, vma->vm_file);
40 * nopage() vm_op implementation for relay file mapping.
42 static struct page *relay_buf_nopage(struct vm_area_struct *vma,
43 unsigned long address,
44 int *type)
46 struct page *page;
47 struct rchan_buf *buf = vma->vm_private_data;
48 unsigned long offset = address - vma->vm_start;
50 if (address > vma->vm_end)
51 return NOPAGE_SIGBUS; /* Disallow mremap */
52 if (!buf)
53 return NOPAGE_OOM;
55 page = vmalloc_to_page(buf->start + offset);
56 if (!page)
57 return NOPAGE_OOM;
58 get_page(page);
60 if (type)
61 *type = VM_FAULT_MINOR;
63 return page;
67 * vm_ops for relay file mappings.
69 static struct vm_operations_struct relay_file_mmap_ops = {
70 .nopage = relay_buf_nopage,
71 .close = relay_file_mmap_close,
74 /**
75 * relay_mmap_buf: - mmap channel buffer to process address space
76 * @buf: relay channel buffer
77 * @vma: vm_area_struct describing memory to be mapped
79 * Returns 0 if ok, negative on error
81 * Caller should already have grabbed mmap_sem.
83 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
85 unsigned long length = vma->vm_end - vma->vm_start;
86 struct file *filp = vma->vm_file;
88 if (!buf)
89 return -EBADF;
91 if (length != (unsigned long)buf->chan->alloc_size)
92 return -EINVAL;
94 vma->vm_ops = &relay_file_mmap_ops;
95 vma->vm_private_data = buf;
96 buf->chan->cb->buf_mapped(buf, filp);
98 return 0;
102 * relay_alloc_buf - allocate a channel buffer
103 * @buf: the buffer struct
104 * @size: total size of the buffer
106 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
107 * passed in size will get page aligned, if it isn't already.
109 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
111 void *mem;
112 unsigned int i, j, n_pages;
114 *size = PAGE_ALIGN(*size);
115 n_pages = *size >> PAGE_SHIFT;
117 buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
118 if (!buf->page_array)
119 return NULL;
121 for (i = 0; i < n_pages; i++) {
122 buf->page_array[i] = alloc_page(GFP_KERNEL);
123 if (unlikely(!buf->page_array[i]))
124 goto depopulate;
125 set_page_private(buf->page_array[i], (unsigned long)buf);
127 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
128 if (!mem)
129 goto depopulate;
131 memset(mem, 0, *size);
132 buf->page_count = n_pages;
133 return mem;
135 depopulate:
136 for (j = 0; j < i; j++)
137 __free_page(buf->page_array[j]);
138 kfree(buf->page_array);
139 return NULL;
143 * relay_create_buf - allocate and initialize a channel buffer
144 * @chan: the relay channel
146 * Returns channel buffer if successful, %NULL otherwise.
148 static struct rchan_buf *relay_create_buf(struct rchan *chan)
150 struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
151 if (!buf)
152 return NULL;
154 buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
155 if (!buf->padding)
156 goto free_buf;
158 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
159 if (!buf->start)
160 goto free_buf;
162 buf->chan = chan;
163 kref_get(&buf->chan->kref);
164 return buf;
166 free_buf:
167 kfree(buf->padding);
168 kfree(buf);
169 return NULL;
173 * relay_destroy_channel - free the channel struct
174 * @kref: target kernel reference that contains the relay channel
176 * Should only be called from kref_put().
178 static void relay_destroy_channel(struct kref *kref)
180 struct rchan *chan = container_of(kref, struct rchan, kref);
181 kfree(chan);
185 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
186 * @buf: the buffer struct
188 static void relay_destroy_buf(struct rchan_buf *buf)
190 struct rchan *chan = buf->chan;
191 unsigned int i;
193 if (likely(buf->start)) {
194 vunmap(buf->start);
195 for (i = 0; i < buf->page_count; i++)
196 __free_page(buf->page_array[i]);
197 kfree(buf->page_array);
199 chan->buf[buf->cpu] = NULL;
200 kfree(buf->padding);
201 kfree(buf);
202 kref_put(&chan->kref, relay_destroy_channel);
206 * relay_remove_buf - remove a channel buffer
207 * @kref: target kernel reference that contains the relay buffer
209 * Removes the file from the fileystem, which also frees the
210 * rchan_buf_struct and the channel buffer. Should only be called from
211 * kref_put().
213 static void relay_remove_buf(struct kref *kref)
215 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
216 buf->chan->cb->remove_buf_file(buf->dentry);
217 relay_destroy_buf(buf);
221 * relay_buf_empty - boolean, is the channel buffer empty?
222 * @buf: channel buffer
224 * Returns 1 if the buffer is empty, 0 otherwise.
226 static int relay_buf_empty(struct rchan_buf *buf)
228 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
232 * relay_buf_full - boolean, is the channel buffer full?
233 * @buf: channel buffer
235 * Returns 1 if the buffer is full, 0 otherwise.
237 int relay_buf_full(struct rchan_buf *buf)
239 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
240 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
242 EXPORT_SYMBOL_GPL(relay_buf_full);
245 * High-level relay kernel API and associated functions.
249 * rchan_callback implementations defining default channel behavior. Used
250 * in place of corresponding NULL values in client callback struct.
254 * subbuf_start() default callback. Does nothing.
256 static int subbuf_start_default_callback (struct rchan_buf *buf,
257 void *subbuf,
258 void *prev_subbuf,
259 size_t prev_padding)
261 if (relay_buf_full(buf))
262 return 0;
264 return 1;
268 * buf_mapped() default callback. Does nothing.
270 static void buf_mapped_default_callback(struct rchan_buf *buf,
271 struct file *filp)
276 * buf_unmapped() default callback. Does nothing.
278 static void buf_unmapped_default_callback(struct rchan_buf *buf,
279 struct file *filp)
284 * create_buf_file_create() default callback. Does nothing.
286 static struct dentry *create_buf_file_default_callback(const char *filename,
287 struct dentry *parent,
288 int mode,
289 struct rchan_buf *buf,
290 int *is_global)
292 return NULL;
296 * remove_buf_file() default callback. Does nothing.
298 static int remove_buf_file_default_callback(struct dentry *dentry)
300 return -EINVAL;
303 /* relay channel default callbacks */
304 static struct rchan_callbacks default_channel_callbacks = {
305 .subbuf_start = subbuf_start_default_callback,
306 .buf_mapped = buf_mapped_default_callback,
307 .buf_unmapped = buf_unmapped_default_callback,
308 .create_buf_file = create_buf_file_default_callback,
309 .remove_buf_file = remove_buf_file_default_callback,
313 * wakeup_readers - wake up readers waiting on a channel
314 * @data: contains the channel buffer
316 * This is the timer function used to defer reader waking.
318 static void wakeup_readers(unsigned long data)
320 struct rchan_buf *buf = (struct rchan_buf *)data;
321 wake_up_interruptible(&buf->read_wait);
325 * __relay_reset - reset a channel buffer
326 * @buf: the channel buffer
327 * @init: 1 if this is a first-time initialization
329 * See relay_reset() for description of effect.
331 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
333 size_t i;
335 if (init) {
336 init_waitqueue_head(&buf->read_wait);
337 kref_init(&buf->kref);
338 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
339 } else
340 del_timer_sync(&buf->timer);
342 buf->subbufs_produced = 0;
343 buf->subbufs_consumed = 0;
344 buf->bytes_consumed = 0;
345 buf->finalized = 0;
346 buf->data = buf->start;
347 buf->offset = 0;
349 for (i = 0; i < buf->chan->n_subbufs; i++)
350 buf->padding[i] = 0;
352 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
356 * relay_reset - reset the channel
357 * @chan: the channel
359 * This has the effect of erasing all data from all channel buffers
360 * and restarting the channel in its initial state. The buffers
361 * are not freed, so any mappings are still in effect.
363 * NOTE. Care should be taken that the channel isn't actually
364 * being used by anything when this call is made.
366 void relay_reset(struct rchan *chan)
368 unsigned int i;
370 if (!chan)
371 return;
373 if (chan->is_global && chan->buf[0]) {
374 __relay_reset(chan->buf[0], 0);
375 return;
378 mutex_lock(&relay_channels_mutex);
379 for_each_online_cpu(i)
380 if (chan->buf[i])
381 __relay_reset(chan->buf[i], 0);
382 mutex_unlock(&relay_channels_mutex);
384 EXPORT_SYMBOL_GPL(relay_reset);
387 * relay_open_buf - create a new relay channel buffer
389 * used by relay_open() and CPU hotplug.
391 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
393 struct rchan_buf *buf = NULL;
394 struct dentry *dentry;
395 char *tmpname;
397 if (chan->is_global)
398 return chan->buf[0];
400 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
401 if (!tmpname)
402 goto end;
403 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
405 buf = relay_create_buf(chan);
406 if (!buf)
407 goto free_name;
409 buf->cpu = cpu;
410 __relay_reset(buf, 1);
412 /* Create file in fs */
413 dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
414 buf, &chan->is_global);
415 if (!dentry)
416 goto free_buf;
418 buf->dentry = dentry;
420 if(chan->is_global) {
421 chan->buf[0] = buf;
422 buf->cpu = 0;
425 goto free_name;
427 free_buf:
428 relay_destroy_buf(buf);
429 buf = NULL;
430 free_name:
431 kfree(tmpname);
432 end:
433 return buf;
437 * relay_close_buf - close a channel buffer
438 * @buf: channel buffer
440 * Marks the buffer finalized and restores the default callbacks.
441 * The channel buffer and channel buffer data structure are then freed
442 * automatically when the last reference is given up.
444 static void relay_close_buf(struct rchan_buf *buf)
446 buf->finalized = 1;
447 del_timer_sync(&buf->timer);
448 kref_put(&buf->kref, relay_remove_buf);
451 static void setup_callbacks(struct rchan *chan,
452 struct rchan_callbacks *cb)
454 if (!cb) {
455 chan->cb = &default_channel_callbacks;
456 return;
459 if (!cb->subbuf_start)
460 cb->subbuf_start = subbuf_start_default_callback;
461 if (!cb->buf_mapped)
462 cb->buf_mapped = buf_mapped_default_callback;
463 if (!cb->buf_unmapped)
464 cb->buf_unmapped = buf_unmapped_default_callback;
465 if (!cb->create_buf_file)
466 cb->create_buf_file = create_buf_file_default_callback;
467 if (!cb->remove_buf_file)
468 cb->remove_buf_file = remove_buf_file_default_callback;
469 chan->cb = cb;
473 * relay_hotcpu_callback - CPU hotplug callback
474 * @nb: notifier block
475 * @action: hotplug action to take
476 * @hcpu: CPU number
478 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
480 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
481 unsigned long action,
482 void *hcpu)
484 unsigned int hotcpu = (unsigned long)hcpu;
485 struct rchan *chan;
487 switch(action) {
488 case CPU_UP_PREPARE:
489 case CPU_UP_PREPARE_FROZEN:
490 mutex_lock(&relay_channels_mutex);
491 list_for_each_entry(chan, &relay_channels, list) {
492 if (chan->buf[hotcpu])
493 continue;
494 chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
495 if(!chan->buf[hotcpu]) {
496 printk(KERN_ERR
497 "relay_hotcpu_callback: cpu %d buffer "
498 "creation failed\n", hotcpu);
499 mutex_unlock(&relay_channels_mutex);
500 return NOTIFY_BAD;
503 mutex_unlock(&relay_channels_mutex);
504 break;
505 case CPU_DEAD:
506 case CPU_DEAD_FROZEN:
507 /* No need to flush the cpu : will be flushed upon
508 * final relay_flush() call. */
509 break;
511 return NOTIFY_OK;
515 * relay_open - create a new relay channel
516 * @base_filename: base name of files to create
517 * @parent: dentry of parent directory, %NULL for root directory
518 * @subbuf_size: size of sub-buffers
519 * @n_subbufs: number of sub-buffers
520 * @cb: client callback functions
521 * @private_data: user-defined data
523 * Returns channel pointer if successful, %NULL otherwise.
525 * Creates a channel buffer for each cpu using the sizes and
526 * attributes specified. The created channel buffer files
527 * will be named base_filename0...base_filenameN-1. File
528 * permissions will be %S_IRUSR.
530 struct rchan *relay_open(const char *base_filename,
531 struct dentry *parent,
532 size_t subbuf_size,
533 size_t n_subbufs,
534 struct rchan_callbacks *cb,
535 void *private_data)
537 unsigned int i;
538 struct rchan *chan;
539 if (!base_filename)
540 return NULL;
542 if (!(subbuf_size && n_subbufs))
543 return NULL;
545 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
546 if (!chan)
547 return NULL;
549 chan->version = RELAYFS_CHANNEL_VERSION;
550 chan->n_subbufs = n_subbufs;
551 chan->subbuf_size = subbuf_size;
552 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
553 chan->parent = parent;
554 chan->private_data = private_data;
555 strlcpy(chan->base_filename, base_filename, NAME_MAX);
556 setup_callbacks(chan, cb);
557 kref_init(&chan->kref);
559 mutex_lock(&relay_channels_mutex);
560 for_each_online_cpu(i) {
561 chan->buf[i] = relay_open_buf(chan, i);
562 if (!chan->buf[i])
563 goto free_bufs;
565 list_add(&chan->list, &relay_channels);
566 mutex_unlock(&relay_channels_mutex);
568 return chan;
570 free_bufs:
571 for_each_online_cpu(i) {
572 if (!chan->buf[i])
573 break;
574 relay_close_buf(chan->buf[i]);
577 kref_put(&chan->kref, relay_destroy_channel);
578 mutex_unlock(&relay_channels_mutex);
579 return NULL;
581 EXPORT_SYMBOL_GPL(relay_open);
584 * relay_switch_subbuf - switch to a new sub-buffer
585 * @buf: channel buffer
586 * @length: size of current event
588 * Returns either the length passed in or 0 if full.
590 * Performs sub-buffer-switch tasks such as invoking callbacks,
591 * updating padding counts, waking up readers, etc.
593 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
595 void *old, *new;
596 size_t old_subbuf, new_subbuf;
598 if (unlikely(length > buf->chan->subbuf_size))
599 goto toobig;
601 if (buf->offset != buf->chan->subbuf_size + 1) {
602 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
603 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
604 buf->padding[old_subbuf] = buf->prev_padding;
605 buf->subbufs_produced++;
606 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
607 buf->padding[old_subbuf];
608 smp_mb();
609 if (waitqueue_active(&buf->read_wait))
611 * Calling wake_up_interruptible() from here
612 * will deadlock if we happen to be logging
613 * from the scheduler (trying to re-grab
614 * rq->lock), so defer it.
616 __mod_timer(&buf->timer, jiffies + 1);
619 old = buf->data;
620 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
621 new = buf->start + new_subbuf * buf->chan->subbuf_size;
622 buf->offset = 0;
623 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
624 buf->offset = buf->chan->subbuf_size + 1;
625 return 0;
627 buf->data = new;
628 buf->padding[new_subbuf] = 0;
630 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
631 goto toobig;
633 return length;
635 toobig:
636 buf->chan->last_toobig = length;
637 return 0;
639 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
642 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
643 * @chan: the channel
644 * @cpu: the cpu associated with the channel buffer to update
645 * @subbufs_consumed: number of sub-buffers to add to current buf's count
647 * Adds to the channel buffer's consumed sub-buffer count.
648 * subbufs_consumed should be the number of sub-buffers newly consumed,
649 * not the total consumed.
651 * NOTE. Kernel clients don't need to call this function if the channel
652 * mode is 'overwrite'.
654 void relay_subbufs_consumed(struct rchan *chan,
655 unsigned int cpu,
656 size_t subbufs_consumed)
658 struct rchan_buf *buf;
660 if (!chan)
661 return;
663 if (cpu >= NR_CPUS || !chan->buf[cpu])
664 return;
666 buf = chan->buf[cpu];
667 buf->subbufs_consumed += subbufs_consumed;
668 if (buf->subbufs_consumed > buf->subbufs_produced)
669 buf->subbufs_consumed = buf->subbufs_produced;
671 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
674 * relay_close - close the channel
675 * @chan: the channel
677 * Closes all channel buffers and frees the channel.
679 void relay_close(struct rchan *chan)
681 unsigned int i;
683 if (!chan)
684 return;
686 mutex_lock(&relay_channels_mutex);
687 if (chan->is_global && chan->buf[0])
688 relay_close_buf(chan->buf[0]);
689 else
690 for_each_possible_cpu(i)
691 if (chan->buf[i])
692 relay_close_buf(chan->buf[i]);
694 if (chan->last_toobig)
695 printk(KERN_WARNING "relay: one or more items not logged "
696 "[item size (%Zd) > sub-buffer size (%Zd)]\n",
697 chan->last_toobig, chan->subbuf_size);
699 list_del(&chan->list);
700 kref_put(&chan->kref, relay_destroy_channel);
701 mutex_unlock(&relay_channels_mutex);
703 EXPORT_SYMBOL_GPL(relay_close);
706 * relay_flush - close the channel
707 * @chan: the channel
709 * Flushes all channel buffers, i.e. forces buffer switch.
711 void relay_flush(struct rchan *chan)
713 unsigned int i;
715 if (!chan)
716 return;
718 if (chan->is_global && chan->buf[0]) {
719 relay_switch_subbuf(chan->buf[0], 0);
720 return;
723 mutex_lock(&relay_channels_mutex);
724 for_each_possible_cpu(i)
725 if (chan->buf[i])
726 relay_switch_subbuf(chan->buf[i], 0);
727 mutex_unlock(&relay_channels_mutex);
729 EXPORT_SYMBOL_GPL(relay_flush);
732 * relay_file_open - open file op for relay files
733 * @inode: the inode
734 * @filp: the file
736 * Increments the channel buffer refcount.
738 static int relay_file_open(struct inode *inode, struct file *filp)
740 struct rchan_buf *buf = inode->i_private;
741 kref_get(&buf->kref);
742 filp->private_data = buf;
744 return 0;
748 * relay_file_mmap - mmap file op for relay files
749 * @filp: the file
750 * @vma: the vma describing what to map
752 * Calls upon relay_mmap_buf() to map the file into user space.
754 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
756 struct rchan_buf *buf = filp->private_data;
757 return relay_mmap_buf(buf, vma);
761 * relay_file_poll - poll file op for relay files
762 * @filp: the file
763 * @wait: poll table
765 * Poll implemention.
767 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
769 unsigned int mask = 0;
770 struct rchan_buf *buf = filp->private_data;
772 if (buf->finalized)
773 return POLLERR;
775 if (filp->f_mode & FMODE_READ) {
776 poll_wait(filp, &buf->read_wait, wait);
777 if (!relay_buf_empty(buf))
778 mask |= POLLIN | POLLRDNORM;
781 return mask;
785 * relay_file_release - release file op for relay files
786 * @inode: the inode
787 * @filp: the file
789 * Decrements the channel refcount, as the filesystem is
790 * no longer using it.
792 static int relay_file_release(struct inode *inode, struct file *filp)
794 struct rchan_buf *buf = filp->private_data;
795 kref_put(&buf->kref, relay_remove_buf);
797 return 0;
801 * relay_file_read_consume - update the consumed count for the buffer
803 static void relay_file_read_consume(struct rchan_buf *buf,
804 size_t read_pos,
805 size_t bytes_consumed)
807 size_t subbuf_size = buf->chan->subbuf_size;
808 size_t n_subbufs = buf->chan->n_subbufs;
809 size_t read_subbuf;
811 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
812 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
813 buf->bytes_consumed = 0;
816 buf->bytes_consumed += bytes_consumed;
817 if (!read_pos)
818 read_subbuf = buf->subbufs_consumed % n_subbufs;
819 else
820 read_subbuf = read_pos / buf->chan->subbuf_size;
821 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
822 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
823 (buf->offset == subbuf_size))
824 return;
825 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
826 buf->bytes_consumed = 0;
831 * relay_file_read_avail - boolean, are there unconsumed bytes available?
833 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
835 size_t subbuf_size = buf->chan->subbuf_size;
836 size_t n_subbufs = buf->chan->n_subbufs;
837 size_t produced = buf->subbufs_produced;
838 size_t consumed = buf->subbufs_consumed;
840 relay_file_read_consume(buf, read_pos, 0);
842 if (unlikely(buf->offset > subbuf_size)) {
843 if (produced == consumed)
844 return 0;
845 return 1;
848 if (unlikely(produced - consumed >= n_subbufs)) {
849 consumed = produced - n_subbufs + 1;
850 buf->subbufs_consumed = consumed;
851 buf->bytes_consumed = 0;
854 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
855 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
857 if (consumed > produced)
858 produced += n_subbufs * subbuf_size;
860 if (consumed == produced)
861 return 0;
863 return 1;
867 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
868 * @read_pos: file read position
869 * @buf: relay channel buffer
871 static size_t relay_file_read_subbuf_avail(size_t read_pos,
872 struct rchan_buf *buf)
874 size_t padding, avail = 0;
875 size_t read_subbuf, read_offset, write_subbuf, write_offset;
876 size_t subbuf_size = buf->chan->subbuf_size;
878 write_subbuf = (buf->data - buf->start) / subbuf_size;
879 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
880 read_subbuf = read_pos / subbuf_size;
881 read_offset = read_pos % subbuf_size;
882 padding = buf->padding[read_subbuf];
884 if (read_subbuf == write_subbuf) {
885 if (read_offset + padding < write_offset)
886 avail = write_offset - (read_offset + padding);
887 } else
888 avail = (subbuf_size - padding) - read_offset;
890 return avail;
894 * relay_file_read_start_pos - find the first available byte to read
895 * @read_pos: file read position
896 * @buf: relay channel buffer
898 * If the @read_pos is in the middle of padding, return the
899 * position of the first actually available byte, otherwise
900 * return the original value.
902 static size_t relay_file_read_start_pos(size_t read_pos,
903 struct rchan_buf *buf)
905 size_t read_subbuf, padding, padding_start, padding_end;
906 size_t subbuf_size = buf->chan->subbuf_size;
907 size_t n_subbufs = buf->chan->n_subbufs;
908 size_t consumed = buf->subbufs_consumed % n_subbufs;
910 if (!read_pos)
911 read_pos = consumed * subbuf_size + buf->bytes_consumed;
912 read_subbuf = read_pos / subbuf_size;
913 padding = buf->padding[read_subbuf];
914 padding_start = (read_subbuf + 1) * subbuf_size - padding;
915 padding_end = (read_subbuf + 1) * subbuf_size;
916 if (read_pos >= padding_start && read_pos < padding_end) {
917 read_subbuf = (read_subbuf + 1) % n_subbufs;
918 read_pos = read_subbuf * subbuf_size;
921 return read_pos;
925 * relay_file_read_end_pos - return the new read position
926 * @read_pos: file read position
927 * @buf: relay channel buffer
928 * @count: number of bytes to be read
930 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
931 size_t read_pos,
932 size_t count)
934 size_t read_subbuf, padding, end_pos;
935 size_t subbuf_size = buf->chan->subbuf_size;
936 size_t n_subbufs = buf->chan->n_subbufs;
938 read_subbuf = read_pos / subbuf_size;
939 padding = buf->padding[read_subbuf];
940 if (read_pos % subbuf_size + count + padding == subbuf_size)
941 end_pos = (read_subbuf + 1) * subbuf_size;
942 else
943 end_pos = read_pos + count;
944 if (end_pos >= subbuf_size * n_subbufs)
945 end_pos = 0;
947 return end_pos;
951 * subbuf_read_actor - read up to one subbuf's worth of data
953 static int subbuf_read_actor(size_t read_start,
954 struct rchan_buf *buf,
955 size_t avail,
956 read_descriptor_t *desc,
957 read_actor_t actor)
959 void *from;
960 int ret = 0;
962 from = buf->start + read_start;
963 ret = avail;
964 if (copy_to_user(desc->arg.buf, from, avail)) {
965 desc->error = -EFAULT;
966 ret = 0;
968 desc->arg.data += ret;
969 desc->written += ret;
970 desc->count -= ret;
972 return ret;
975 typedef int (*subbuf_actor_t) (size_t read_start,
976 struct rchan_buf *buf,
977 size_t avail,
978 read_descriptor_t *desc,
979 read_actor_t actor);
982 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
984 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
985 subbuf_actor_t subbuf_actor,
986 read_actor_t actor,
987 read_descriptor_t *desc)
989 struct rchan_buf *buf = filp->private_data;
990 size_t read_start, avail;
991 int ret;
993 if (!desc->count)
994 return 0;
996 mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
997 do {
998 if (!relay_file_read_avail(buf, *ppos))
999 break;
1001 read_start = relay_file_read_start_pos(*ppos, buf);
1002 avail = relay_file_read_subbuf_avail(read_start, buf);
1003 if (!avail)
1004 break;
1006 avail = min(desc->count, avail);
1007 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1008 if (desc->error < 0)
1009 break;
1011 if (ret) {
1012 relay_file_read_consume(buf, read_start, ret);
1013 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1015 } while (desc->count && ret);
1016 mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1018 return desc->written;
1021 static ssize_t relay_file_read(struct file *filp,
1022 char __user *buffer,
1023 size_t count,
1024 loff_t *ppos)
1026 read_descriptor_t desc;
1027 desc.written = 0;
1028 desc.count = count;
1029 desc.arg.buf = buffer;
1030 desc.error = 0;
1031 return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1032 NULL, &desc);
1035 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1037 rbuf->bytes_consumed += bytes_consumed;
1039 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1040 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1041 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1045 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1046 struct pipe_buffer *buf)
1048 struct rchan_buf *rbuf;
1050 rbuf = (struct rchan_buf *)page_private(buf->page);
1051 relay_consume_bytes(rbuf, buf->private);
1054 static struct pipe_buf_operations relay_pipe_buf_ops = {
1055 .can_merge = 0,
1056 .map = generic_pipe_buf_map,
1057 .unmap = generic_pipe_buf_unmap,
1058 .confirm = generic_pipe_buf_confirm,
1059 .release = relay_pipe_buf_release,
1060 .steal = generic_pipe_buf_steal,
1061 .get = generic_pipe_buf_get,
1065 * subbuf_splice_actor - splice up to one subbuf's worth of data
1067 static int subbuf_splice_actor(struct file *in,
1068 loff_t *ppos,
1069 struct pipe_inode_info *pipe,
1070 size_t len,
1071 unsigned int flags,
1072 int *nonpad_ret)
1074 unsigned int pidx, poff, total_len, subbuf_pages, ret;
1075 struct rchan_buf *rbuf = in->private_data;
1076 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1077 uint64_t pos = (uint64_t) *ppos;
1078 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1079 size_t read_start = (size_t) do_div(pos, alloc_size);
1080 size_t read_subbuf = read_start / subbuf_size;
1081 size_t padding = rbuf->padding[read_subbuf];
1082 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1083 struct page *pages[PIPE_BUFFERS];
1084 struct partial_page partial[PIPE_BUFFERS];
1085 struct splice_pipe_desc spd = {
1086 .pages = pages,
1087 .nr_pages = 0,
1088 .partial = partial,
1089 .flags = flags,
1090 .ops = &relay_pipe_buf_ops,
1093 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1094 return 0;
1097 * Adjust read len, if longer than what is available
1099 if (len > (subbuf_size - read_start % subbuf_size))
1100 len = subbuf_size - read_start % subbuf_size;
1102 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1103 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1104 poff = read_start & ~PAGE_MASK;
1106 for (total_len = 0; spd.nr_pages < subbuf_pages; spd.nr_pages++) {
1107 unsigned int this_len, this_end, private;
1108 unsigned int cur_pos = read_start + total_len;
1110 if (!len)
1111 break;
1113 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1114 private = this_len;
1116 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1117 spd.partial[spd.nr_pages].offset = poff;
1119 this_end = cur_pos + this_len;
1120 if (this_end >= nonpad_end) {
1121 this_len = nonpad_end - cur_pos;
1122 private = this_len + padding;
1124 spd.partial[spd.nr_pages].len = this_len;
1125 spd.partial[spd.nr_pages].private = private;
1127 len -= this_len;
1128 total_len += this_len;
1129 poff = 0;
1130 pidx = (pidx + 1) % subbuf_pages;
1132 if (this_end >= nonpad_end) {
1133 spd.nr_pages++;
1134 break;
1138 if (!spd.nr_pages)
1139 return 0;
1141 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1142 if (ret < 0 || ret < total_len)
1143 return ret;
1145 if (read_start + ret == nonpad_end)
1146 ret += padding;
1148 return ret;
1151 static ssize_t relay_file_splice_read(struct file *in,
1152 loff_t *ppos,
1153 struct pipe_inode_info *pipe,
1154 size_t len,
1155 unsigned int flags)
1157 ssize_t spliced;
1158 int ret;
1159 int nonpad_ret = 0;
1161 ret = 0;
1162 spliced = 0;
1164 while (len) {
1165 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1166 if (ret < 0)
1167 break;
1168 else if (!ret) {
1169 if (spliced)
1170 break;
1171 if (flags & SPLICE_F_NONBLOCK) {
1172 ret = -EAGAIN;
1173 break;
1177 *ppos += ret;
1178 if (ret > len)
1179 len = 0;
1180 else
1181 len -= ret;
1182 spliced += nonpad_ret;
1183 nonpad_ret = 0;
1186 if (spliced)
1187 return spliced;
1189 return ret;
1192 const struct file_operations relay_file_operations = {
1193 .open = relay_file_open,
1194 .poll = relay_file_poll,
1195 .mmap = relay_file_mmap,
1196 .read = relay_file_read,
1197 .llseek = no_llseek,
1198 .release = relay_file_release,
1199 .splice_read = relay_file_splice_read,
1201 EXPORT_SYMBOL_GPL(relay_file_operations);
1203 static __init int relay_init(void)
1206 hotcpu_notifier(relay_hotcpu_callback, 0);
1207 return 0;
1210 module_init(relay_init);