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_possible_cpu(i)
405 __relay_reset(chan->buf[i], 0);
406 mutex_unlock(&relay_channels_mutex);
408 EXPORT_SYMBOL_GPL(relay_reset);
410 static inline void relay_set_buf_dentry(struct rchan_buf *buf,
411 struct dentry *dentry)
413 buf->dentry = dentry;
414 buf->dentry->d_inode->i_size = buf->early_bytes;
417 static struct dentry *relay_create_buf_file(struct rchan *chan,
418 struct rchan_buf *buf,
421 struct dentry *dentry;
424 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
427 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
429 /* Create file in fs */
430 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
440 * relay_open_buf - create a new relay channel buffer
442 * used by relay_open() and CPU hotplug.
444 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
446 struct rchan_buf *buf = NULL;
447 struct dentry *dentry;
452 buf = relay_create_buf(chan);
456 if (chan->has_base_filename) {
457 dentry = relay_create_buf_file(chan, buf, cpu);
460 relay_set_buf_dentry(buf, dentry);
464 __relay_reset(buf, 1);
466 if(chan->is_global) {
474 relay_destroy_buf(buf);
479 * relay_close_buf - close a channel buffer
480 * @buf: channel buffer
482 * Marks the buffer finalized and restores the default callbacks.
483 * The channel buffer and channel buffer data structure are then freed
484 * automatically when the last reference is given up.
486 static void relay_close_buf(struct rchan_buf *buf)
489 del_timer_sync(&buf->timer);
490 kref_put(&buf->kref, relay_remove_buf);
493 static void setup_callbacks(struct rchan *chan,
494 struct rchan_callbacks *cb)
497 chan->cb = &default_channel_callbacks;
501 if (!cb->subbuf_start)
502 cb->subbuf_start = subbuf_start_default_callback;
504 cb->buf_mapped = buf_mapped_default_callback;
505 if (!cb->buf_unmapped)
506 cb->buf_unmapped = buf_unmapped_default_callback;
507 if (!cb->create_buf_file)
508 cb->create_buf_file = create_buf_file_default_callback;
509 if (!cb->remove_buf_file)
510 cb->remove_buf_file = remove_buf_file_default_callback;
515 * relay_hotcpu_callback - CPU hotplug callback
516 * @nb: notifier block
517 * @action: hotplug action to take
520 * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
522 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
523 unsigned long action,
526 unsigned int hotcpu = (unsigned long)hcpu;
531 case CPU_UP_PREPARE_FROZEN:
532 mutex_lock(&relay_channels_mutex);
533 list_for_each_entry(chan, &relay_channels, list) {
534 if (chan->buf[hotcpu])
536 chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
537 if(!chan->buf[hotcpu]) {
539 "relay_hotcpu_callback: cpu %d buffer "
540 "creation failed\n", hotcpu);
541 mutex_unlock(&relay_channels_mutex);
545 mutex_unlock(&relay_channels_mutex);
548 case CPU_DEAD_FROZEN:
549 /* No need to flush the cpu : will be flushed upon
550 * final relay_flush() call. */
557 * relay_open - create a new relay channel
558 * @base_filename: base name of files to create, %NULL for buffering only
559 * @parent: dentry of parent directory, %NULL for root directory or buffer
560 * @subbuf_size: size of sub-buffers
561 * @n_subbufs: number of sub-buffers
562 * @cb: client callback functions
563 * @private_data: user-defined data
565 * Returns channel pointer if successful, %NULL otherwise.
567 * Creates a channel buffer for each cpu using the sizes and
568 * attributes specified. The created channel buffer files
569 * will be named base_filename0...base_filenameN-1. File
570 * permissions will be %S_IRUSR.
572 struct rchan *relay_open(const char *base_filename,
573 struct dentry *parent,
576 struct rchan_callbacks *cb,
582 if (!(subbuf_size && n_subbufs))
585 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
589 chan->version = RELAYFS_CHANNEL_VERSION;
590 chan->n_subbufs = n_subbufs;
591 chan->subbuf_size = subbuf_size;
592 chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
593 chan->parent = parent;
594 chan->private_data = private_data;
596 chan->has_base_filename = 1;
597 strlcpy(chan->base_filename, base_filename, NAME_MAX);
599 setup_callbacks(chan, cb);
600 kref_init(&chan->kref);
602 mutex_lock(&relay_channels_mutex);
603 for_each_online_cpu(i) {
604 chan->buf[i] = relay_open_buf(chan, i);
608 list_add(&chan->list, &relay_channels);
609 mutex_unlock(&relay_channels_mutex);
614 for_each_possible_cpu(i) {
616 relay_close_buf(chan->buf[i]);
619 kref_put(&chan->kref, relay_destroy_channel);
620 mutex_unlock(&relay_channels_mutex);
623 EXPORT_SYMBOL_GPL(relay_open);
625 struct rchan_percpu_buf_dispatcher {
626 struct rchan_buf *buf;
627 struct dentry *dentry;
630 /* Called in atomic context. */
631 static void __relay_set_buf_dentry(void *info)
633 struct rchan_percpu_buf_dispatcher *p = info;
635 relay_set_buf_dentry(p->buf, p->dentry);
639 * relay_late_setup_files - triggers file creation
640 * @chan: channel to operate on
641 * @base_filename: base name of files to create
642 * @parent: dentry of parent directory, %NULL for root directory
644 * Returns 0 if successful, non-zero otherwise.
646 * Use to setup files for a previously buffer-only channel.
647 * Useful to do early tracing in kernel, before VFS is up, for example.
649 int relay_late_setup_files(struct rchan *chan,
650 const char *base_filename,
651 struct dentry *parent)
654 unsigned int i, curr_cpu;
656 struct dentry *dentry;
657 struct rchan_percpu_buf_dispatcher disp;
659 if (!chan || !base_filename)
662 strlcpy(chan->base_filename, base_filename, NAME_MAX);
664 mutex_lock(&relay_channels_mutex);
665 /* Is chan already set up? */
666 if (unlikely(chan->has_base_filename))
668 chan->has_base_filename = 1;
669 chan->parent = parent;
670 curr_cpu = get_cpu();
672 * The CPU hotplug notifier ran before us and created buffers with
673 * no files associated. So it's safe to call relay_setup_buf_file()
674 * on all currently online CPUs.
676 for_each_online_cpu(i) {
677 if (unlikely(!chan->buf[i])) {
678 printk(KERN_ERR "relay_late_setup_files: CPU %u "
679 "has no buffer, it must have!\n", i);
685 dentry = relay_create_buf_file(chan, chan->buf[i], i);
686 if (unlikely(!dentry)) {
692 local_irq_save(flags);
693 relay_set_buf_dentry(chan->buf[i], dentry);
694 local_irq_restore(flags);
696 disp.buf = chan->buf[i];
697 disp.dentry = dentry;
699 /* relay_channels_mutex must be held, so wait. */
700 err = smp_call_function_single(i,
701 __relay_set_buf_dentry,
708 mutex_unlock(&relay_channels_mutex);
714 * relay_switch_subbuf - switch to a new sub-buffer
715 * @buf: channel buffer
716 * @length: size of current event
718 * Returns either the length passed in or 0 if full.
720 * Performs sub-buffer-switch tasks such as invoking callbacks,
721 * updating padding counts, waking up readers, etc.
723 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
726 size_t old_subbuf, new_subbuf;
728 if (unlikely(length > buf->chan->subbuf_size))
731 if (buf->offset != buf->chan->subbuf_size + 1) {
732 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
733 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
734 buf->padding[old_subbuf] = buf->prev_padding;
735 buf->subbufs_produced++;
737 buf->dentry->d_inode->i_size +=
738 buf->chan->subbuf_size -
739 buf->padding[old_subbuf];
741 buf->early_bytes += buf->chan->subbuf_size -
742 buf->padding[old_subbuf];
744 if (waitqueue_active(&buf->read_wait))
746 * Calling wake_up_interruptible() from here
747 * will deadlock if we happen to be logging
748 * from the scheduler (trying to re-grab
749 * rq->lock), so defer it.
751 __mod_timer(&buf->timer, jiffies + 1);
755 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
756 new = buf->start + new_subbuf * buf->chan->subbuf_size;
758 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
759 buf->offset = buf->chan->subbuf_size + 1;
763 buf->padding[new_subbuf] = 0;
765 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
771 buf->chan->last_toobig = length;
774 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
777 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
779 * @cpu: the cpu associated with the channel buffer to update
780 * @subbufs_consumed: number of sub-buffers to add to current buf's count
782 * Adds to the channel buffer's consumed sub-buffer count.
783 * subbufs_consumed should be the number of sub-buffers newly consumed,
784 * not the total consumed.
786 * NOTE. Kernel clients don't need to call this function if the channel
787 * mode is 'overwrite'.
789 void relay_subbufs_consumed(struct rchan *chan,
791 size_t subbufs_consumed)
793 struct rchan_buf *buf;
798 if (cpu >= NR_CPUS || !chan->buf[cpu])
801 buf = chan->buf[cpu];
802 buf->subbufs_consumed += subbufs_consumed;
803 if (buf->subbufs_consumed > buf->subbufs_produced)
804 buf->subbufs_consumed = buf->subbufs_produced;
806 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
809 * relay_close - close the channel
812 * Closes all channel buffers and frees the channel.
814 void relay_close(struct rchan *chan)
821 mutex_lock(&relay_channels_mutex);
822 if (chan->is_global && chan->buf[0])
823 relay_close_buf(chan->buf[0]);
825 for_each_possible_cpu(i)
827 relay_close_buf(chan->buf[i]);
829 if (chan->last_toobig)
830 printk(KERN_WARNING "relay: one or more items not logged "
831 "[item size (%Zd) > sub-buffer size (%Zd)]\n",
832 chan->last_toobig, chan->subbuf_size);
834 list_del(&chan->list);
835 kref_put(&chan->kref, relay_destroy_channel);
836 mutex_unlock(&relay_channels_mutex);
838 EXPORT_SYMBOL_GPL(relay_close);
841 * relay_flush - close the channel
844 * Flushes all channel buffers, i.e. forces buffer switch.
846 void relay_flush(struct rchan *chan)
853 if (chan->is_global && chan->buf[0]) {
854 relay_switch_subbuf(chan->buf[0], 0);
858 mutex_lock(&relay_channels_mutex);
859 for_each_possible_cpu(i)
861 relay_switch_subbuf(chan->buf[i], 0);
862 mutex_unlock(&relay_channels_mutex);
864 EXPORT_SYMBOL_GPL(relay_flush);
867 * relay_file_open - open file op for relay files
871 * Increments the channel buffer refcount.
873 static int relay_file_open(struct inode *inode, struct file *filp)
875 struct rchan_buf *buf = inode->i_private;
876 kref_get(&buf->kref);
877 filp->private_data = buf;
879 return nonseekable_open(inode, filp);
883 * relay_file_mmap - mmap file op for relay files
885 * @vma: the vma describing what to map
887 * Calls upon relay_mmap_buf() to map the file into user space.
889 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
891 struct rchan_buf *buf = filp->private_data;
892 return relay_mmap_buf(buf, vma);
896 * relay_file_poll - poll file op for relay files
902 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
904 unsigned int mask = 0;
905 struct rchan_buf *buf = filp->private_data;
910 if (filp->f_mode & FMODE_READ) {
911 poll_wait(filp, &buf->read_wait, wait);
912 if (!relay_buf_empty(buf))
913 mask |= POLLIN | POLLRDNORM;
920 * relay_file_release - release file op for relay files
924 * Decrements the channel refcount, as the filesystem is
925 * no longer using it.
927 static int relay_file_release(struct inode *inode, struct file *filp)
929 struct rchan_buf *buf = filp->private_data;
930 kref_put(&buf->kref, relay_remove_buf);
936 * relay_file_read_consume - update the consumed count for the buffer
938 static void relay_file_read_consume(struct rchan_buf *buf,
940 size_t bytes_consumed)
942 size_t subbuf_size = buf->chan->subbuf_size;
943 size_t n_subbufs = buf->chan->n_subbufs;
946 if (buf->subbufs_produced == buf->subbufs_consumed &&
947 buf->offset == buf->bytes_consumed)
950 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
951 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
952 buf->bytes_consumed = 0;
955 buf->bytes_consumed += bytes_consumed;
957 read_subbuf = buf->subbufs_consumed % n_subbufs;
959 read_subbuf = read_pos / buf->chan->subbuf_size;
960 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
961 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
962 (buf->offset == subbuf_size))
964 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
965 buf->bytes_consumed = 0;
970 * relay_file_read_avail - boolean, are there unconsumed bytes available?
972 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
974 size_t subbuf_size = buf->chan->subbuf_size;
975 size_t n_subbufs = buf->chan->n_subbufs;
976 size_t produced = buf->subbufs_produced;
977 size_t consumed = buf->subbufs_consumed;
979 relay_file_read_consume(buf, read_pos, 0);
981 consumed = buf->subbufs_consumed;
983 if (unlikely(buf->offset > subbuf_size)) {
984 if (produced == consumed)
989 if (unlikely(produced - consumed >= n_subbufs)) {
990 consumed = produced - n_subbufs + 1;
991 buf->subbufs_consumed = consumed;
992 buf->bytes_consumed = 0;
995 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
996 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
998 if (consumed > produced)
999 produced += n_subbufs * subbuf_size;
1001 if (consumed == produced) {
1002 if (buf->offset == subbuf_size &&
1003 buf->subbufs_produced > buf->subbufs_consumed)
1012 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
1013 * @read_pos: file read position
1014 * @buf: relay channel buffer
1016 static size_t relay_file_read_subbuf_avail(size_t read_pos,
1017 struct rchan_buf *buf)
1019 size_t padding, avail = 0;
1020 size_t read_subbuf, read_offset, write_subbuf, write_offset;
1021 size_t subbuf_size = buf->chan->subbuf_size;
1023 write_subbuf = (buf->data - buf->start) / subbuf_size;
1024 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1025 read_subbuf = read_pos / subbuf_size;
1026 read_offset = read_pos % subbuf_size;
1027 padding = buf->padding[read_subbuf];
1029 if (read_subbuf == write_subbuf) {
1030 if (read_offset + padding < write_offset)
1031 avail = write_offset - (read_offset + padding);
1033 avail = (subbuf_size - padding) - read_offset;
1039 * relay_file_read_start_pos - find the first available byte to read
1040 * @read_pos: file read position
1041 * @buf: relay channel buffer
1043 * If the @read_pos is in the middle of padding, return the
1044 * position of the first actually available byte, otherwise
1045 * return the original value.
1047 static size_t relay_file_read_start_pos(size_t read_pos,
1048 struct rchan_buf *buf)
1050 size_t read_subbuf, padding, padding_start, padding_end;
1051 size_t subbuf_size = buf->chan->subbuf_size;
1052 size_t n_subbufs = buf->chan->n_subbufs;
1053 size_t consumed = buf->subbufs_consumed % n_subbufs;
1056 read_pos = consumed * subbuf_size + buf->bytes_consumed;
1057 read_subbuf = read_pos / subbuf_size;
1058 padding = buf->padding[read_subbuf];
1059 padding_start = (read_subbuf + 1) * subbuf_size - padding;
1060 padding_end = (read_subbuf + 1) * subbuf_size;
1061 if (read_pos >= padding_start && read_pos < padding_end) {
1062 read_subbuf = (read_subbuf + 1) % n_subbufs;
1063 read_pos = read_subbuf * subbuf_size;
1070 * relay_file_read_end_pos - return the new read position
1071 * @read_pos: file read position
1072 * @buf: relay channel buffer
1073 * @count: number of bytes to be read
1075 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1079 size_t read_subbuf, padding, end_pos;
1080 size_t subbuf_size = buf->chan->subbuf_size;
1081 size_t n_subbufs = buf->chan->n_subbufs;
1083 read_subbuf = read_pos / subbuf_size;
1084 padding = buf->padding[read_subbuf];
1085 if (read_pos % subbuf_size + count + padding == subbuf_size)
1086 end_pos = (read_subbuf + 1) * subbuf_size;
1088 end_pos = read_pos + count;
1089 if (end_pos >= subbuf_size * n_subbufs)
1096 * subbuf_read_actor - read up to one subbuf's worth of data
1098 static int subbuf_read_actor(size_t read_start,
1099 struct rchan_buf *buf,
1101 read_descriptor_t *desc,
1107 from = buf->start + read_start;
1109 if (copy_to_user(desc->arg.buf, from, avail)) {
1110 desc->error = -EFAULT;
1113 desc->arg.data += ret;
1114 desc->written += ret;
1120 typedef int (*subbuf_actor_t) (size_t read_start,
1121 struct rchan_buf *buf,
1123 read_descriptor_t *desc,
1124 read_actor_t actor);
1127 * relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
1129 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
1130 subbuf_actor_t subbuf_actor,
1132 read_descriptor_t *desc)
1134 struct rchan_buf *buf = filp->private_data;
1135 size_t read_start, avail;
1141 mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
1143 if (!relay_file_read_avail(buf, *ppos))
1146 read_start = relay_file_read_start_pos(*ppos, buf);
1147 avail = relay_file_read_subbuf_avail(read_start, buf);
1151 avail = min(desc->count, avail);
1152 ret = subbuf_actor(read_start, buf, avail, desc, actor);
1153 if (desc->error < 0)
1157 relay_file_read_consume(buf, read_start, ret);
1158 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1160 } while (desc->count && ret);
1161 mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
1163 return desc->written;
1166 static ssize_t relay_file_read(struct file *filp,
1167 char __user *buffer,
1171 read_descriptor_t desc;
1174 desc.arg.buf = buffer;
1176 return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
1180 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1182 rbuf->bytes_consumed += bytes_consumed;
1184 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1185 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1186 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1190 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1191 struct pipe_buffer *buf)
1193 struct rchan_buf *rbuf;
1195 rbuf = (struct rchan_buf *)page_private(buf->page);
1196 relay_consume_bytes(rbuf, buf->private);
1199 static struct pipe_buf_operations relay_pipe_buf_ops = {
1201 .map = generic_pipe_buf_map,
1202 .unmap = generic_pipe_buf_unmap,
1203 .confirm = generic_pipe_buf_confirm,
1204 .release = relay_pipe_buf_release,
1205 .steal = generic_pipe_buf_steal,
1206 .get = generic_pipe_buf_get,
1209 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1214 * subbuf_splice_actor - splice up to one subbuf's worth of data
1216 static int subbuf_splice_actor(struct file *in,
1218 struct pipe_inode_info *pipe,
1223 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
1224 struct rchan_buf *rbuf = in->private_data;
1225 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1226 uint64_t pos = (uint64_t) *ppos;
1227 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1228 size_t read_start = (size_t) do_div(pos, alloc_size);
1229 size_t read_subbuf = read_start / subbuf_size;
1230 size_t padding = rbuf->padding[read_subbuf];
1231 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1232 struct page *pages[PIPE_BUFFERS];
1233 struct partial_page partial[PIPE_BUFFERS];
1234 struct splice_pipe_desc spd = {
1239 .ops = &relay_pipe_buf_ops,
1240 .spd_release = relay_page_release,
1243 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1247 * Adjust read len, if longer than what is available
1249 if (len > (subbuf_size - read_start % subbuf_size))
1250 len = subbuf_size - read_start % subbuf_size;
1252 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1253 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1254 poff = read_start & ~PAGE_MASK;
1255 nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS);
1257 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1258 unsigned int this_len, this_end, private;
1259 unsigned int cur_pos = read_start + total_len;
1264 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1267 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1268 spd.partial[spd.nr_pages].offset = poff;
1270 this_end = cur_pos + this_len;
1271 if (this_end >= nonpad_end) {
1272 this_len = nonpad_end - cur_pos;
1273 private = this_len + padding;
1275 spd.partial[spd.nr_pages].len = this_len;
1276 spd.partial[spd.nr_pages].private = private;
1279 total_len += this_len;
1281 pidx = (pidx + 1) % subbuf_pages;
1283 if (this_end >= nonpad_end) {
1292 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1293 if (ret < 0 || ret < total_len)
1296 if (read_start + ret == nonpad_end)
1302 static ssize_t relay_file_splice_read(struct file *in,
1304 struct pipe_inode_info *pipe,
1315 while (len && !spliced) {
1316 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1322 if (flags & SPLICE_F_NONBLOCK) {
1333 spliced += nonpad_ret;
1343 const struct file_operations relay_file_operations = {
1344 .open = relay_file_open,
1345 .poll = relay_file_poll,
1346 .mmap = relay_file_mmap,
1347 .read = relay_file_read,
1348 .llseek = no_llseek,
1349 .release = relay_file_release,
1350 .splice_read = relay_file_splice_read,
1352 EXPORT_SYMBOL_GPL(relay_file_operations);
1354 static __init int relay_init(void)
1357 hotcpu_notifier(relay_hotcpu_callback, 0);
1361 early_initcall(relay_init);