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>
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 * fault() vm_op implementation for relay file mapping.
42 static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
45 struct rchan_buf *buf = vma->vm_private_data;
46 pgoff_t pgoff = vmf->pgoff;
51 page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
53 return VM_FAULT_SIGBUS;
61 * vm_ops for relay file mappings.
63 static struct vm_operations_struct relay_file_mmap_ops = {
64 .fault = relay_buf_fault,
65 .close = relay_file_mmap_close,
69 * allocate an array of pointers of struct page
71 static struct page **relay_alloc_page_array(unsigned int n_pages)
74 size_t pa_size = n_pages * sizeof(struct page *);
76 if (pa_size > PAGE_SIZE) {
77 array = vmalloc(pa_size);
79 memset(array, 0, pa_size);
81 array = kzalloc(pa_size, GFP_KERNEL);
87 * free an array of pointers of struct page
89 static void relay_free_page_array(struct page **array)
91 if (is_vmalloc_addr(array))
98 * relay_mmap_buf: - mmap channel buffer to process address space
99 * @buf: relay channel buffer
100 * @vma: vm_area_struct describing memory to be mapped
102 * Returns 0 if ok, negative on error
104 * Caller should already have grabbed mmap_sem.
106 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
108 unsigned long length = vma->vm_end - vma->vm_start;
109 struct file *filp = vma->vm_file;
114 if (length != (unsigned long)buf->chan->alloc_size)
117 vma->vm_ops = &relay_file_mmap_ops;
118 vma->vm_flags |= VM_DONTEXPAND;
119 vma->vm_private_data = buf;
120 buf->chan->cb->buf_mapped(buf, filp);
126 * relay_alloc_buf - allocate a channel buffer
127 * @buf: the buffer struct
128 * @size: total size of the buffer
130 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
131 * passed in size will get page aligned, if it isn't already.
133 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
136 unsigned int i, j, n_pages;
138 *size = PAGE_ALIGN(*size);
139 n_pages = *size >> PAGE_SHIFT;
141 buf->page_array = relay_alloc_page_array(n_pages);
142 if (!buf->page_array)
145 for (i = 0; i < n_pages; i++) {
146 buf->page_array[i] = alloc_page(GFP_KERNEL);
147 if (unlikely(!buf->page_array[i]))
149 set_page_private(buf->page_array[i], (unsigned long)buf);
151 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
155 memset(mem, 0, *size);
156 buf->page_count = n_pages;
160 for (j = 0; j < i; j++)
161 __free_page(buf->page_array[j]);
162 relay_free_page_array(buf->page_array);
167 * relay_create_buf - allocate and initialize a channel buffer
168 * @chan: the relay channel
170 * Returns channel buffer if successful, %NULL otherwise.
172 static struct rchan_buf *relay_create_buf(struct rchan *chan)
174 struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
178 buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
182 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
187 kref_get(&buf->chan->kref);
197 * relay_destroy_channel - free the channel struct
198 * @kref: target kernel reference that contains the relay channel
200 * Should only be called from kref_put().
202 static void relay_destroy_channel(struct kref *kref)
204 struct rchan *chan = container_of(kref, struct rchan, kref);
209 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
210 * @buf: the buffer struct
212 static void relay_destroy_buf(struct rchan_buf *buf)
214 struct rchan *chan = buf->chan;
217 if (likely(buf->start)) {
219 for (i = 0; i < buf->page_count; i++)
220 __free_page(buf->page_array[i]);
221 relay_free_page_array(buf->page_array);
223 chan->buf[buf->cpu] = NULL;
226 kref_put(&chan->kref, relay_destroy_channel);
230 * relay_remove_buf - remove a channel buffer
231 * @kref: target kernel reference that contains the relay buffer
233 * Removes the file from the fileystem, which also frees the
234 * rchan_buf_struct and the channel buffer. Should only be called from
237 static void relay_remove_buf(struct kref *kref)
239 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
240 buf->chan->cb->remove_buf_file(buf->dentry);
241 relay_destroy_buf(buf);
245 * relay_buf_empty - boolean, is the channel buffer empty?
246 * @buf: channel buffer
248 * Returns 1 if the buffer is empty, 0 otherwise.
250 static int relay_buf_empty(struct rchan_buf *buf)
252 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
256 * relay_buf_full - boolean, is the channel buffer full?
257 * @buf: channel buffer
259 * Returns 1 if the buffer is full, 0 otherwise.
261 int relay_buf_full(struct rchan_buf *buf)
263 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
264 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
266 EXPORT_SYMBOL_GPL(relay_buf_full);
269 * High-level relay kernel API and associated functions.
273 * rchan_callback implementations defining default channel behavior. Used
274 * in place of corresponding NULL values in client callback struct.
278 * subbuf_start() default callback. Does nothing.
280 static int subbuf_start_default_callback (struct rchan_buf *buf,
285 if (relay_buf_full(buf))
292 * buf_mapped() default callback. Does nothing.
294 static void buf_mapped_default_callback(struct rchan_buf *buf,
300 * buf_unmapped() default callback. Does nothing.
302 static void buf_unmapped_default_callback(struct rchan_buf *buf,
308 * create_buf_file_create() default callback. Does nothing.
310 static struct dentry *create_buf_file_default_callback(const char *filename,
311 struct dentry *parent,
313 struct rchan_buf *buf,
320 * remove_buf_file() default callback. Does nothing.
322 static int remove_buf_file_default_callback(struct dentry *dentry)
327 /* relay channel default callbacks */
328 static struct rchan_callbacks default_channel_callbacks = {
329 .subbuf_start = subbuf_start_default_callback,
330 .buf_mapped = buf_mapped_default_callback,
331 .buf_unmapped = buf_unmapped_default_callback,
332 .create_buf_file = create_buf_file_default_callback,
333 .remove_buf_file = remove_buf_file_default_callback,
337 * wakeup_readers - wake up readers waiting on a channel
338 * @data: contains the channel buffer
340 * This is the timer function used to defer reader waking.
342 static void wakeup_readers(unsigned long data)
344 struct rchan_buf *buf = (struct rchan_buf *)data;
345 wake_up_interruptible(&buf->read_wait);
349 * __relay_reset - reset a channel buffer
350 * @buf: the channel buffer
351 * @init: 1 if this is a first-time initialization
353 * See relay_reset() for description of effect.
355 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
360 init_waitqueue_head(&buf->read_wait);
361 kref_init(&buf->kref);
362 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
364 del_timer_sync(&buf->timer);
366 buf->subbufs_produced = 0;
367 buf->subbufs_consumed = 0;
368 buf->bytes_consumed = 0;
370 buf->data = buf->start;
373 for (i = 0; i < buf->chan->n_subbufs; i++)
376 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
380 * relay_reset - reset the channel
383 * This has the effect of erasing all data from all channel buffers
384 * and restarting the channel in its initial state. The buffers
385 * are not freed, so any mappings are still in effect.
387 * NOTE. Care should be taken that the channel isn't actually
388 * being used by anything when this call is made.
390 void relay_reset(struct rchan *chan)
397 if (chan->is_global && chan->buf[0]) {
398 __relay_reset(chan->buf[0], 0);
402 mutex_lock(&relay_channels_mutex);
403 for_each_online_cpu(i)
405 __relay_reset(chan->buf[i], 0);
406 mutex_unlock(&relay_channels_mutex);
408 EXPORT_SYMBOL_GPL(relay_reset);
411 * relay_open_buf - create a new relay channel buffer
413 * used by relay_open() and CPU hotplug.
415 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
417 struct rchan_buf *buf = NULL;
418 struct dentry *dentry;
424 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
427 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
429 buf = relay_create_buf(chan);
434 __relay_reset(buf, 1);
436 /* Create file in fs */
437 dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR,
438 buf, &chan->is_global);
442 buf->dentry = dentry;
444 if(chan->is_global) {
452 relay_destroy_buf(buf);
461 * relay_close_buf - close a channel buffer
462 * @buf: channel buffer
464 * Marks the buffer finalized and restores the default callbacks.
465 * The channel buffer and channel buffer data structure are then freed
466 * automatically when the last reference is given up.
468 static void relay_close_buf(struct rchan_buf *buf)
471 del_timer_sync(&buf->timer);
472 kref_put(&buf->kref, relay_remove_buf);
475 static void setup_callbacks(struct rchan *chan,
476 struct rchan_callbacks *cb)
479 chan->cb = &default_channel_callbacks;
483 if (!cb->subbuf_start)
484 cb->subbuf_start = subbuf_start_default_callback;
486 cb->buf_mapped = buf_mapped_default_callback;
487 if (!cb->buf_unmapped)
488 cb->buf_unmapped = buf_unmapped_default_callback;
489 if (!cb->create_buf_file)
490 cb->create_buf_file = create_buf_file_default_callback;
491 if (!cb->remove_buf_file)
492 cb->remove_buf_file = remove_buf_file_default_callback;
497 * relay_hotcpu_callback - CPU hotplug callback
498 * @nb: notifier block
499 * @action: hotplug action to take
502 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
504 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
505 unsigned long action,
508 unsigned int hotcpu = (unsigned long)hcpu;
513 case CPU_UP_PREPARE_FROZEN:
514 mutex_lock(&relay_channels_mutex);
515 list_for_each_entry(chan, &relay_channels, list) {
516 if (chan->buf[hotcpu])
518 chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
519 if(!chan->buf[hotcpu]) {
521 "relay_hotcpu_callback: cpu %d buffer "
522 "creation failed\n", hotcpu);
523 mutex_unlock(&relay_channels_mutex);
527 mutex_unlock(&relay_channels_mutex);
530 case CPU_DEAD_FROZEN:
531 /* No need to flush the cpu : will be flushed upon
532 * final relay_flush() call. */
539 * relay_open - create a new relay channel
540 * @base_filename: base name of files to create
541 * @parent: dentry of parent directory, %NULL for root directory
542 * @subbuf_size: size of sub-buffers
543 * @n_subbufs: number of sub-buffers
544 * @cb: client callback functions
545 * @private_data: user-defined data
547 * Returns channel pointer if successful, %NULL otherwise.
549 * Creates a channel buffer for each cpu using the sizes and
550 * attributes specified. The created channel buffer files
551 * will be named base_filename0...base_filenameN-1. File
552 * permissions will be %S_IRUSR.
554 struct rchan *relay_open(const char *base_filename,
555 struct dentry *parent,
558 struct rchan_callbacks *cb,
566 if (!(subbuf_size && n_subbufs))
569 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
573 chan->version = RELAYFS_CHANNEL_VERSION;
574 chan->n_subbufs = n_subbufs;
575 chan->subbuf_size = subbuf_size;
576 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
577 chan->parent = parent;
578 chan->private_data = private_data;
579 strlcpy(chan->base_filename, base_filename, NAME_MAX);
580 setup_callbacks(chan, cb);
581 kref_init(&chan->kref);
583 mutex_lock(&relay_channels_mutex);
584 for_each_online_cpu(i) {
585 chan->buf[i] = relay_open_buf(chan, i);
589 list_add(&chan->list, &relay_channels);
590 mutex_unlock(&relay_channels_mutex);
595 for_each_online_cpu(i) {
598 relay_close_buf(chan->buf[i]);
601 kref_put(&chan->kref, relay_destroy_channel);
602 mutex_unlock(&relay_channels_mutex);
605 EXPORT_SYMBOL_GPL(relay_open);
608 * relay_switch_subbuf - switch to a new sub-buffer
609 * @buf: channel buffer
610 * @length: size of current event
612 * Returns either the length passed in or 0 if full.
614 * Performs sub-buffer-switch tasks such as invoking callbacks,
615 * updating padding counts, waking up readers, etc.
617 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
620 size_t old_subbuf, new_subbuf;
622 if (unlikely(length > buf->chan->subbuf_size))
625 if (buf->offset != buf->chan->subbuf_size + 1) {
626 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
627 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
628 buf->padding[old_subbuf] = buf->prev_padding;
629 buf->subbufs_produced++;
630 buf->dentry->d_inode->i_size += buf->chan->subbuf_size -
631 buf->padding[old_subbuf];
633 if (waitqueue_active(&buf->read_wait))
635 * Calling wake_up_interruptible() from here
636 * will deadlock if we happen to be logging
637 * from the scheduler (trying to re-grab
638 * rq->lock), so defer it.
640 __mod_timer(&buf->timer, jiffies + 1);
644 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
645 new = buf->start + new_subbuf * buf->chan->subbuf_size;
647 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
648 buf->offset = buf->chan->subbuf_size + 1;
652 buf->padding[new_subbuf] = 0;
654 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
660 buf->chan->last_toobig = length;
663 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
666 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
668 * @cpu: the cpu associated with the channel buffer to update
669 * @subbufs_consumed: number of sub-buffers to add to current buf's count
671 * Adds to the channel buffer's consumed sub-buffer count.
672 * subbufs_consumed should be the number of sub-buffers newly consumed,
673 * not the total consumed.
675 * NOTE. Kernel clients don't need to call this function if the channel
676 * mode is 'overwrite'.
678 void relay_subbufs_consumed(struct rchan *chan,
680 size_t subbufs_consumed)
682 struct rchan_buf *buf;
687 if (cpu >= NR_CPUS || !chan->buf[cpu])
690 buf = chan->buf[cpu];
691 buf->subbufs_consumed += subbufs_consumed;
692 if (buf->subbufs_consumed > buf->subbufs_produced)
693 buf->subbufs_consumed = buf->subbufs_produced;
695 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
698 * relay_close - close the channel
701 * Closes all channel buffers and frees the channel.
703 void relay_close(struct rchan *chan)
710 mutex_lock(&relay_channels_mutex);
711 if (chan->is_global && chan->buf[0])
712 relay_close_buf(chan->buf[0]);
714 for_each_possible_cpu(i)
716 relay_close_buf(chan->buf[i]);
718 if (chan->last_toobig)
719 printk(KERN_WARNING "relay: one or more items not logged "
720 "[item size (%Zd) > sub-buffer size (%Zd)]\n",
721 chan->last_toobig, chan->subbuf_size);
723 list_del(&chan->list);
724 kref_put(&chan->kref, relay_destroy_channel);
725 mutex_unlock(&relay_channels_mutex);
727 EXPORT_SYMBOL_GPL(relay_close);
730 * relay_flush - close the channel
733 * Flushes all channel buffers, i.e. forces buffer switch.
735 void relay_flush(struct rchan *chan)
742 if (chan->is_global && chan->buf[0]) {
743 relay_switch_subbuf(chan->buf[0], 0);
747 mutex_lock(&relay_channels_mutex);
748 for_each_possible_cpu(i)
750 relay_switch_subbuf(chan->buf[i], 0);
751 mutex_unlock(&relay_channels_mutex);
753 EXPORT_SYMBOL_GPL(relay_flush);
756 * relay_file_open - open file op for relay files
760 * Increments the channel buffer refcount.
762 static int relay_file_open(struct inode *inode, struct file *filp)
764 struct rchan_buf *buf = inode->i_private;
765 kref_get(&buf->kref);
766 filp->private_data = buf;
768 return nonseekable_open(inode, filp);
772 * relay_file_mmap - mmap file op for relay files
774 * @vma: the vma describing what to map
776 * Calls upon relay_mmap_buf() to map the file into user space.
778 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
780 struct rchan_buf *buf = filp->private_data;
781 return relay_mmap_buf(buf, vma);
785 * relay_file_poll - poll file op for relay files
791 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
793 unsigned int mask = 0;
794 struct rchan_buf *buf = filp->private_data;
799 if (filp->f_mode & FMODE_READ) {
800 poll_wait(filp, &buf->read_wait, wait);
801 if (!relay_buf_empty(buf))
802 mask |= POLLIN | POLLRDNORM;
809 * relay_file_release - release file op for relay files
813 * Decrements the channel refcount, as the filesystem is
814 * no longer using it.
816 static int relay_file_release(struct inode *inode, struct file *filp)
818 struct rchan_buf *buf = filp->private_data;
819 kref_put(&buf->kref, relay_remove_buf);
825 * relay_file_read_consume - update the consumed count for the buffer
827 static void relay_file_read_consume(struct rchan_buf *buf,
829 size_t bytes_consumed)
831 size_t subbuf_size = buf->chan->subbuf_size;
832 size_t n_subbufs = buf->chan->n_subbufs;
835 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
836 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
837 buf->bytes_consumed = 0;
840 buf->bytes_consumed += bytes_consumed;
842 read_subbuf = buf->subbufs_consumed % n_subbufs;
844 read_subbuf = read_pos / buf->chan->subbuf_size;
845 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
846 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
847 (buf->offset == subbuf_size))
849 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
850 buf->bytes_consumed = 0;
855 * relay_file_read_avail - boolean, are there unconsumed bytes available?
857 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
859 size_t subbuf_size = buf->chan->subbuf_size;
860 size_t n_subbufs = buf->chan->n_subbufs;
861 size_t produced = buf->subbufs_produced;
862 size_t consumed = buf->subbufs_consumed;
864 relay_file_read_consume(buf, read_pos, 0);
866 if (unlikely(buf->offset > subbuf_size)) {
867 if (produced == consumed)
872 if (unlikely(produced - consumed >= n_subbufs)) {
873 consumed = produced - n_subbufs + 1;
874 buf->subbufs_consumed = consumed;
875 buf->bytes_consumed = 0;
878 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
879 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
881 if (consumed > produced)
882 produced += n_subbufs * subbuf_size;
884 if (consumed == produced)
891 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
892 * @read_pos: file read position
893 * @buf: relay channel buffer
895 static size_t relay_file_read_subbuf_avail(size_t read_pos,
896 struct rchan_buf *buf)
898 size_t padding, avail = 0;
899 size_t read_subbuf, read_offset, write_subbuf, write_offset;
900 size_t subbuf_size = buf->chan->subbuf_size;
902 write_subbuf = (buf->data - buf->start) / subbuf_size;
903 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
904 read_subbuf = read_pos / subbuf_size;
905 read_offset = read_pos % subbuf_size;
906 padding = buf->padding[read_subbuf];
908 if (read_subbuf == write_subbuf) {
909 if (read_offset + padding < write_offset)
910 avail = write_offset - (read_offset + padding);
912 avail = (subbuf_size - padding) - read_offset;
918 * relay_file_read_start_pos - find the first available byte to read
919 * @read_pos: file read position
920 * @buf: relay channel buffer
922 * If the @read_pos is in the middle of padding, return the
923 * position of the first actually available byte, otherwise
924 * return the original value.
926 static size_t relay_file_read_start_pos(size_t read_pos,
927 struct rchan_buf *buf)
929 size_t read_subbuf, padding, padding_start, padding_end;
930 size_t subbuf_size = buf->chan->subbuf_size;
931 size_t n_subbufs = buf->chan->n_subbufs;
932 size_t consumed = buf->subbufs_consumed % n_subbufs;
935 read_pos = consumed * subbuf_size + buf->bytes_consumed;
936 read_subbuf = read_pos / subbuf_size;
937 padding = buf->padding[read_subbuf];
938 padding_start = (read_subbuf + 1) * subbuf_size - padding;
939 padding_end = (read_subbuf + 1) * subbuf_size;
940 if (read_pos >= padding_start && read_pos < padding_end) {
941 read_subbuf = (read_subbuf + 1) % n_subbufs;
942 read_pos = read_subbuf * subbuf_size;
949 * relay_file_read_end_pos - return the new read position
950 * @read_pos: file read position
951 * @buf: relay channel buffer
952 * @count: number of bytes to be read
954 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
958 size_t read_subbuf, padding, end_pos;
959 size_t subbuf_size = buf->chan->subbuf_size;
960 size_t n_subbufs = buf->chan->n_subbufs;
962 read_subbuf = read_pos / subbuf_size;
963 padding = buf->padding[read_subbuf];
964 if (read_pos % subbuf_size + count + padding == subbuf_size)
965 end_pos = (read_subbuf + 1) * subbuf_size;
967 end_pos = read_pos + count;
968 if (end_pos >= subbuf_size * n_subbufs)
975 * subbuf_read_actor - read up to one subbuf's worth of data
977 static int subbuf_read_actor(size_t read_start,
978 struct rchan_buf *buf,
980 read_descriptor_t *desc,
986 from = buf->start + read_start;
988 if (copy_to_user(desc->arg.buf, from, avail)) {
989 desc->error = -EFAULT;
992 desc->arg.data += ret;
993 desc->written += ret;
999 typedef int (*subbuf_actor_t) (size_t read_start,
1000 struct rchan_buf *buf,
1002 read_descriptor_t *desc,
1003 read_actor_t actor);
1006 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1008 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1009 subbuf_actor_t subbuf_actor,
1011 read_descriptor_t *desc)
1013 struct rchan_buf *buf = filp->private_data;
1014 size_t read_start, avail;
1020 mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1022 if (!relay_file_read_avail(buf, *ppos))
1025 read_start = relay_file_read_start_pos(*ppos, buf);
1026 avail = relay_file_read_subbuf_avail(read_start, buf);
1030 avail = min(desc->count, avail);
1031 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1032 if (desc->error < 0)
1036 relay_file_read_consume(buf, read_start, ret);
1037 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1039 } while (desc->count && ret);
1040 mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1042 return desc->written;
1045 static ssize_t relay_file_read(struct file *filp,
1046 char __user *buffer,
1050 read_descriptor_t desc;
1053 desc.arg.buf = buffer;
1055 return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1059 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1061 rbuf->bytes_consumed += bytes_consumed;
1063 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1064 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1065 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1069 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1070 struct pipe_buffer *buf)
1072 struct rchan_buf *rbuf;
1074 rbuf = (struct rchan_buf *)page_private(buf->page);
1075 relay_consume_bytes(rbuf, buf->private);
1078 static struct pipe_buf_operations relay_pipe_buf_ops = {
1080 .map = generic_pipe_buf_map,
1081 .unmap = generic_pipe_buf_unmap,
1082 .confirm = generic_pipe_buf_confirm,
1083 .release = relay_pipe_buf_release,
1084 .steal = generic_pipe_buf_steal,
1085 .get = generic_pipe_buf_get,
1088 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1093 * subbuf_splice_actor - splice up to one subbuf's worth of data
1095 static int subbuf_splice_actor(struct file *in,
1097 struct pipe_inode_info *pipe,
1102 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
1103 struct rchan_buf *rbuf = in->private_data;
1104 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1105 uint64_t pos = (uint64_t) *ppos;
1106 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1107 size_t read_start = (size_t) do_div(pos, alloc_size);
1108 size_t read_subbuf = read_start / subbuf_size;
1109 size_t padding = rbuf->padding[read_subbuf];
1110 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1111 struct page *pages[PIPE_BUFFERS];
1112 struct partial_page partial[PIPE_BUFFERS];
1113 struct splice_pipe_desc spd = {
1118 .ops = &relay_pipe_buf_ops,
1119 .spd_release = relay_page_release,
1122 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1126 * Adjust read len, if longer than what is available
1128 if (len > (subbuf_size - read_start % subbuf_size))
1129 len = subbuf_size - read_start % subbuf_size;
1131 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1132 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1133 poff = read_start & ~PAGE_MASK;
1134 nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS);
1136 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1137 unsigned int this_len, this_end, private;
1138 unsigned int cur_pos = read_start + total_len;
1143 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1146 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1147 spd.partial[spd.nr_pages].offset = poff;
1149 this_end = cur_pos + this_len;
1150 if (this_end >= nonpad_end) {
1151 this_len = nonpad_end - cur_pos;
1152 private = this_len + padding;
1154 spd.partial[spd.nr_pages].len = this_len;
1155 spd.partial[spd.nr_pages].private = private;
1158 total_len += this_len;
1160 pidx = (pidx + 1) % subbuf_pages;
1162 if (this_end >= nonpad_end) {
1171 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1172 if (ret < 0 || ret < total_len)
1175 if (read_start + ret == nonpad_end)
1181 static ssize_t relay_file_splice_read(struct file *in,
1183 struct pipe_inode_info *pipe,
1194 while (len && !spliced) {
1195 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1201 if (flags & SPLICE_F_NONBLOCK) {
1212 spliced += nonpad_ret;
1222 const struct file_operations relay_file_operations = {
1223 .open = relay_file_open,
1224 .poll = relay_file_poll,
1225 .mmap = relay_file_mmap,
1226 .read = relay_file_read,
1227 .llseek = no_llseek,
1228 .release = relay_file_release,
1229 .splice_read = relay_file_splice_read,
1231 EXPORT_SYMBOL_GPL(relay_file_operations);
1233 static __init int relay_init(void)
1236 hotcpu_notifier(relay_hotcpu_callback, 0);
1240 module_init(relay_init);