2 * Public API and common code for kernel->userspace relay file support.
4 * See Documentation/filesystems/relay.rst 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/export.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 vm_fault_t relay_buf_fault(struct vm_fault *vmf)
45 struct rchan_buf *buf = vmf->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 const 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)
73 const size_t pa_size = n_pages * sizeof(struct page *);
74 if (pa_size > PAGE_SIZE)
75 return vzalloc(pa_size);
76 return kzalloc(pa_size, GFP_KERNEL);
80 * free an array of pointers of struct page
82 static void relay_free_page_array(struct page **array)
88 * relay_mmap_buf: - mmap channel buffer to process address space
89 * @buf: relay channel buffer
90 * @vma: vm_area_struct describing memory to be mapped
92 * Returns 0 if ok, negative on error
94 * Caller should already have grabbed mmap_lock.
96 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
98 unsigned long length = vma->vm_end - vma->vm_start;
99 struct file *filp = vma->vm_file;
104 if (length != (unsigned long)buf->chan->alloc_size)
107 vma->vm_ops = &relay_file_mmap_ops;
108 vma->vm_flags |= VM_DONTEXPAND;
109 vma->vm_private_data = buf;
110 buf->chan->cb->buf_mapped(buf, filp);
116 * relay_alloc_buf - allocate a channel buffer
117 * @buf: the buffer struct
118 * @size: total size of the buffer
120 * Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
121 * passed in size will get page aligned, if it isn't already.
123 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
126 unsigned int i, j, n_pages;
128 *size = PAGE_ALIGN(*size);
129 n_pages = *size >> PAGE_SHIFT;
131 buf->page_array = relay_alloc_page_array(n_pages);
132 if (!buf->page_array)
135 for (i = 0; i < n_pages; i++) {
136 buf->page_array[i] = alloc_page(GFP_KERNEL);
137 if (unlikely(!buf->page_array[i]))
139 set_page_private(buf->page_array[i], (unsigned long)buf);
141 mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
145 memset(mem, 0, *size);
146 buf->page_count = n_pages;
150 for (j = 0; j < i; j++)
151 __free_page(buf->page_array[j]);
152 relay_free_page_array(buf->page_array);
157 * relay_create_buf - allocate and initialize a channel buffer
158 * @chan: the relay channel
160 * Returns channel buffer if successful, %NULL otherwise.
162 static struct rchan_buf *relay_create_buf(struct rchan *chan)
164 struct rchan_buf *buf;
166 if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t *))
169 buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
172 buf->padding = kmalloc_array(chan->n_subbufs, sizeof(size_t *),
177 buf->start = relay_alloc_buf(buf, &chan->alloc_size);
182 kref_get(&buf->chan->kref);
192 * relay_destroy_channel - free the channel struct
193 * @kref: target kernel reference that contains the relay channel
195 * Should only be called from kref_put().
197 static void relay_destroy_channel(struct kref *kref)
199 struct rchan *chan = container_of(kref, struct rchan, kref);
200 free_percpu(chan->buf);
205 * relay_destroy_buf - destroy an rchan_buf struct and associated buffer
206 * @buf: the buffer struct
208 static void relay_destroy_buf(struct rchan_buf *buf)
210 struct rchan *chan = buf->chan;
213 if (likely(buf->start)) {
215 for (i = 0; i < buf->page_count; i++)
216 __free_page(buf->page_array[i]);
217 relay_free_page_array(buf->page_array);
219 *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
222 kref_put(&chan->kref, relay_destroy_channel);
226 * relay_remove_buf - remove a channel buffer
227 * @kref: target kernel reference that contains the relay buffer
229 * Removes the file from the filesystem, which also frees the
230 * rchan_buf_struct and the channel buffer. Should only be called from
233 static void relay_remove_buf(struct kref *kref)
235 struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
236 relay_destroy_buf(buf);
240 * relay_buf_empty - boolean, is the channel buffer empty?
241 * @buf: channel buffer
243 * Returns 1 if the buffer is empty, 0 otherwise.
245 static int relay_buf_empty(struct rchan_buf *buf)
247 return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
251 * relay_buf_full - boolean, is the channel buffer full?
252 * @buf: channel buffer
254 * Returns 1 if the buffer is full, 0 otherwise.
256 int relay_buf_full(struct rchan_buf *buf)
258 size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
259 return (ready >= buf->chan->n_subbufs) ? 1 : 0;
261 EXPORT_SYMBOL_GPL(relay_buf_full);
264 * High-level relay kernel API and associated functions.
268 * rchan_callback implementations defining default channel behavior. Used
269 * in place of corresponding NULL values in client callback struct.
273 * subbuf_start() default callback. Does nothing.
275 static int subbuf_start_default_callback (struct rchan_buf *buf,
280 if (relay_buf_full(buf))
287 * buf_mapped() default callback. Does nothing.
289 static void buf_mapped_default_callback(struct rchan_buf *buf,
295 * buf_unmapped() default callback. Does nothing.
297 static void buf_unmapped_default_callback(struct rchan_buf *buf,
303 * create_buf_file_create() default callback. Does nothing.
305 static struct dentry *create_buf_file_default_callback(const char *filename,
306 struct dentry *parent,
308 struct rchan_buf *buf,
315 * remove_buf_file() default callback. Does nothing.
317 static int remove_buf_file_default_callback(struct dentry *dentry)
322 /* relay channel default callbacks */
323 static struct rchan_callbacks default_channel_callbacks = {
324 .subbuf_start = subbuf_start_default_callback,
325 .buf_mapped = buf_mapped_default_callback,
326 .buf_unmapped = buf_unmapped_default_callback,
327 .create_buf_file = create_buf_file_default_callback,
328 .remove_buf_file = remove_buf_file_default_callback,
332 * wakeup_readers - wake up readers waiting on a channel
333 * @work: contains the channel buffer
335 * This is the function used to defer reader waking
337 static void wakeup_readers(struct irq_work *work)
339 struct rchan_buf *buf;
341 buf = container_of(work, struct rchan_buf, wakeup_work);
342 wake_up_interruptible(&buf->read_wait);
346 * __relay_reset - reset a channel buffer
347 * @buf: the channel buffer
348 * @init: 1 if this is a first-time initialization
350 * See relay_reset() for description of effect.
352 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
357 init_waitqueue_head(&buf->read_wait);
358 kref_init(&buf->kref);
359 init_irq_work(&buf->wakeup_work, wakeup_readers);
361 irq_work_sync(&buf->wakeup_work);
364 buf->subbufs_produced = 0;
365 buf->subbufs_consumed = 0;
366 buf->bytes_consumed = 0;
368 buf->data = buf->start;
371 for (i = 0; i < buf->chan->n_subbufs; i++)
374 buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
378 * relay_reset - reset the channel
381 * This has the effect of erasing all data from all channel buffers
382 * and restarting the channel in its initial state. The buffers
383 * are not freed, so any mappings are still in effect.
385 * NOTE. Care should be taken that the channel isn't actually
386 * being used by anything when this call is made.
388 void relay_reset(struct rchan *chan)
390 struct rchan_buf *buf;
396 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
397 __relay_reset(buf, 0);
401 mutex_lock(&relay_channels_mutex);
402 for_each_possible_cpu(i)
403 if ((buf = *per_cpu_ptr(chan->buf, i)))
404 __relay_reset(buf, 0);
405 mutex_unlock(&relay_channels_mutex);
407 EXPORT_SYMBOL_GPL(relay_reset);
409 static inline void relay_set_buf_dentry(struct rchan_buf *buf,
410 struct dentry *dentry)
412 buf->dentry = dentry;
413 d_inode(buf->dentry)->i_size = buf->early_bytes;
416 static struct dentry *relay_create_buf_file(struct rchan *chan,
417 struct rchan_buf *buf,
420 struct dentry *dentry;
423 tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
426 snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
428 /* Create file in fs */
429 dentry = chan->cb->create_buf_file(tmpname, chan->parent,
441 * relay_open_buf - create a new relay channel buffer
443 * used by relay_open() and CPU hotplug.
445 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
447 struct rchan_buf *buf = NULL;
448 struct dentry *dentry;
451 return *per_cpu_ptr(chan->buf, 0);
453 buf = relay_create_buf(chan);
457 if (chan->has_base_filename) {
458 dentry = relay_create_buf_file(chan, buf, cpu);
461 relay_set_buf_dentry(buf, dentry);
463 /* Only retrieve global info, nothing more, nothing less */
464 dentry = chan->cb->create_buf_file(NULL, NULL,
467 if (IS_ERR_OR_NULL(dentry))
472 __relay_reset(buf, 1);
474 if(chan->is_global) {
475 *per_cpu_ptr(chan->buf, 0) = buf;
482 relay_destroy_buf(buf);
487 * relay_close_buf - close a channel buffer
488 * @buf: channel buffer
490 * Marks the buffer finalized and restores the default callbacks.
491 * The channel buffer and channel buffer data structure are then freed
492 * automatically when the last reference is given up.
494 static void relay_close_buf(struct rchan_buf *buf)
497 irq_work_sync(&buf->wakeup_work);
498 buf->chan->cb->remove_buf_file(buf->dentry);
499 kref_put(&buf->kref, relay_remove_buf);
502 static void setup_callbacks(struct rchan *chan,
503 struct rchan_callbacks *cb)
506 chan->cb = &default_channel_callbacks;
510 if (!cb->subbuf_start)
511 cb->subbuf_start = subbuf_start_default_callback;
513 cb->buf_mapped = buf_mapped_default_callback;
514 if (!cb->buf_unmapped)
515 cb->buf_unmapped = buf_unmapped_default_callback;
516 if (!cb->create_buf_file)
517 cb->create_buf_file = create_buf_file_default_callback;
518 if (!cb->remove_buf_file)
519 cb->remove_buf_file = remove_buf_file_default_callback;
523 int relay_prepare_cpu(unsigned int cpu)
526 struct rchan_buf *buf;
528 mutex_lock(&relay_channels_mutex);
529 list_for_each_entry(chan, &relay_channels, list) {
530 if ((buf = *per_cpu_ptr(chan->buf, cpu)))
532 buf = relay_open_buf(chan, cpu);
534 pr_err("relay: cpu %d buffer creation failed\n", cpu);
535 mutex_unlock(&relay_channels_mutex);
538 *per_cpu_ptr(chan->buf, cpu) = buf;
540 mutex_unlock(&relay_channels_mutex);
545 * relay_open - create a new relay channel
546 * @base_filename: base name of files to create, %NULL for buffering only
547 * @parent: dentry of parent directory, %NULL for root directory or buffer
548 * @subbuf_size: size of sub-buffers
549 * @n_subbufs: number of sub-buffers
550 * @cb: client callback functions
551 * @private_data: user-defined data
553 * Returns channel pointer if successful, %NULL otherwise.
555 * Creates a channel buffer for each cpu using the sizes and
556 * attributes specified. The created channel buffer files
557 * will be named base_filename0...base_filenameN-1. File
558 * permissions will be %S_IRUSR.
560 * If opening a buffer (@parent = NULL) that you later wish to register
561 * in a filesystem, call relay_late_setup_files() once the @parent dentry
564 struct rchan *relay_open(const char *base_filename,
565 struct dentry *parent,
568 struct rchan_callbacks *cb,
573 struct rchan_buf *buf;
575 if (!(subbuf_size && n_subbufs))
577 if (subbuf_size > UINT_MAX / n_subbufs)
580 chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
584 chan->buf = alloc_percpu(struct rchan_buf *);
590 chan->version = RELAYFS_CHANNEL_VERSION;
591 chan->n_subbufs = n_subbufs;
592 chan->subbuf_size = subbuf_size;
593 chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
594 chan->parent = parent;
595 chan->private_data = private_data;
597 chan->has_base_filename = 1;
598 strlcpy(chan->base_filename, base_filename, NAME_MAX);
600 setup_callbacks(chan, cb);
601 kref_init(&chan->kref);
603 mutex_lock(&relay_channels_mutex);
604 for_each_online_cpu(i) {
605 buf = relay_open_buf(chan, i);
608 *per_cpu_ptr(chan->buf, i) = buf;
610 list_add(&chan->list, &relay_channels);
611 mutex_unlock(&relay_channels_mutex);
616 for_each_possible_cpu(i) {
617 if ((buf = *per_cpu_ptr(chan->buf, i)))
618 relay_close_buf(buf);
621 kref_put(&chan->kref, relay_destroy_channel);
622 mutex_unlock(&relay_channels_mutex);
625 EXPORT_SYMBOL_GPL(relay_open);
627 struct rchan_percpu_buf_dispatcher {
628 struct rchan_buf *buf;
629 struct dentry *dentry;
632 /* Called in atomic context. */
633 static void __relay_set_buf_dentry(void *info)
635 struct rchan_percpu_buf_dispatcher *p = info;
637 relay_set_buf_dentry(p->buf, p->dentry);
641 * relay_late_setup_files - triggers file creation
642 * @chan: channel to operate on
643 * @base_filename: base name of files to create
644 * @parent: dentry of parent directory, %NULL for root directory
646 * Returns 0 if successful, non-zero otherwise.
648 * Use to setup files for a previously buffer-only channel created
649 * by relay_open() with a NULL parent dentry.
651 * For example, this is useful for perfomring early tracing in kernel,
652 * before VFS is up and then exposing the early results once the dentry
655 int relay_late_setup_files(struct rchan *chan,
656 const char *base_filename,
657 struct dentry *parent)
660 unsigned int i, curr_cpu;
662 struct dentry *dentry;
663 struct rchan_buf *buf;
664 struct rchan_percpu_buf_dispatcher disp;
666 if (!chan || !base_filename)
669 strlcpy(chan->base_filename, base_filename, NAME_MAX);
671 mutex_lock(&relay_channels_mutex);
672 /* Is chan already set up? */
673 if (unlikely(chan->has_base_filename)) {
674 mutex_unlock(&relay_channels_mutex);
677 chan->has_base_filename = 1;
678 chan->parent = parent;
680 if (chan->is_global) {
682 buf = *per_cpu_ptr(chan->buf, 0);
683 if (!WARN_ON_ONCE(!buf)) {
684 dentry = relay_create_buf_file(chan, buf, 0);
685 if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
686 relay_set_buf_dentry(buf, dentry);
690 mutex_unlock(&relay_channels_mutex);
694 curr_cpu = get_cpu();
696 * The CPU hotplug notifier ran before us and created buffers with
697 * no files associated. So it's safe to call relay_setup_buf_file()
698 * on all currently online CPUs.
700 for_each_online_cpu(i) {
701 buf = *per_cpu_ptr(chan->buf, i);
702 if (unlikely(!buf)) {
703 WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
708 dentry = relay_create_buf_file(chan, buf, i);
709 if (unlikely(!dentry)) {
715 local_irq_save(flags);
716 relay_set_buf_dentry(buf, dentry);
717 local_irq_restore(flags);
720 disp.dentry = dentry;
722 /* relay_channels_mutex must be held, so wait. */
723 err = smp_call_function_single(i,
724 __relay_set_buf_dentry,
731 mutex_unlock(&relay_channels_mutex);
735 EXPORT_SYMBOL_GPL(relay_late_setup_files);
738 * relay_switch_subbuf - switch to a new sub-buffer
739 * @buf: channel buffer
740 * @length: size of current event
742 * Returns either the length passed in or 0 if full.
744 * Performs sub-buffer-switch tasks such as invoking callbacks,
745 * updating padding counts, waking up readers, etc.
747 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
750 size_t old_subbuf, new_subbuf;
752 if (unlikely(length > buf->chan->subbuf_size))
755 if (buf->offset != buf->chan->subbuf_size + 1) {
756 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
757 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
758 buf->padding[old_subbuf] = buf->prev_padding;
759 buf->subbufs_produced++;
761 d_inode(buf->dentry)->i_size +=
762 buf->chan->subbuf_size -
763 buf->padding[old_subbuf];
765 buf->early_bytes += buf->chan->subbuf_size -
766 buf->padding[old_subbuf];
768 if (waitqueue_active(&buf->read_wait)) {
770 * Calling wake_up_interruptible() from here
771 * will deadlock if we happen to be logging
772 * from the scheduler (trying to re-grab
773 * rq->lock), so defer it.
775 irq_work_queue(&buf->wakeup_work);
780 new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
781 new = buf->start + new_subbuf * buf->chan->subbuf_size;
783 if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
784 buf->offset = buf->chan->subbuf_size + 1;
788 buf->padding[new_subbuf] = 0;
790 if (unlikely(length + buf->offset > buf->chan->subbuf_size))
796 buf->chan->last_toobig = length;
799 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
802 * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
804 * @cpu: the cpu associated with the channel buffer to update
805 * @subbufs_consumed: number of sub-buffers to add to current buf's count
807 * Adds to the channel buffer's consumed sub-buffer count.
808 * subbufs_consumed should be the number of sub-buffers newly consumed,
809 * not the total consumed.
811 * NOTE. Kernel clients don't need to call this function if the channel
812 * mode is 'overwrite'.
814 void relay_subbufs_consumed(struct rchan *chan,
816 size_t subbufs_consumed)
818 struct rchan_buf *buf;
820 if (!chan || cpu >= NR_CPUS)
823 buf = *per_cpu_ptr(chan->buf, cpu);
824 if (!buf || subbufs_consumed > chan->n_subbufs)
827 if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
828 buf->subbufs_consumed = buf->subbufs_produced;
830 buf->subbufs_consumed += subbufs_consumed;
832 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
835 * relay_close - close the channel
838 * Closes all channel buffers and frees the channel.
840 void relay_close(struct rchan *chan)
842 struct rchan_buf *buf;
848 mutex_lock(&relay_channels_mutex);
849 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
850 relay_close_buf(buf);
852 for_each_possible_cpu(i)
853 if ((buf = *per_cpu_ptr(chan->buf, i)))
854 relay_close_buf(buf);
856 if (chan->last_toobig)
857 printk(KERN_WARNING "relay: one or more items not logged "
858 "[item size (%zd) > sub-buffer size (%zd)]\n",
859 chan->last_toobig, chan->subbuf_size);
861 list_del(&chan->list);
862 kref_put(&chan->kref, relay_destroy_channel);
863 mutex_unlock(&relay_channels_mutex);
865 EXPORT_SYMBOL_GPL(relay_close);
868 * relay_flush - close the channel
871 * Flushes all channel buffers, i.e. forces buffer switch.
873 void relay_flush(struct rchan *chan)
875 struct rchan_buf *buf;
881 if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
882 relay_switch_subbuf(buf, 0);
886 mutex_lock(&relay_channels_mutex);
887 for_each_possible_cpu(i)
888 if ((buf = *per_cpu_ptr(chan->buf, i)))
889 relay_switch_subbuf(buf, 0);
890 mutex_unlock(&relay_channels_mutex);
892 EXPORT_SYMBOL_GPL(relay_flush);
895 * relay_file_open - open file op for relay files
899 * Increments the channel buffer refcount.
901 static int relay_file_open(struct inode *inode, struct file *filp)
903 struct rchan_buf *buf = inode->i_private;
904 kref_get(&buf->kref);
905 filp->private_data = buf;
907 return nonseekable_open(inode, filp);
911 * relay_file_mmap - mmap file op for relay files
913 * @vma: the vma describing what to map
915 * Calls upon relay_mmap_buf() to map the file into user space.
917 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
919 struct rchan_buf *buf = filp->private_data;
920 return relay_mmap_buf(buf, vma);
924 * relay_file_poll - poll file op for relay files
930 static __poll_t relay_file_poll(struct file *filp, poll_table *wait)
933 struct rchan_buf *buf = filp->private_data;
938 if (filp->f_mode & FMODE_READ) {
939 poll_wait(filp, &buf->read_wait, wait);
940 if (!relay_buf_empty(buf))
941 mask |= EPOLLIN | EPOLLRDNORM;
948 * relay_file_release - release file op for relay files
952 * Decrements the channel refcount, as the filesystem is
953 * no longer using it.
955 static int relay_file_release(struct inode *inode, struct file *filp)
957 struct rchan_buf *buf = filp->private_data;
958 kref_put(&buf->kref, relay_remove_buf);
964 * relay_file_read_consume - update the consumed count for the buffer
966 static void relay_file_read_consume(struct rchan_buf *buf,
968 size_t bytes_consumed)
970 size_t subbuf_size = buf->chan->subbuf_size;
971 size_t n_subbufs = buf->chan->n_subbufs;
974 if (buf->subbufs_produced == buf->subbufs_consumed &&
975 buf->offset == buf->bytes_consumed)
978 if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
979 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
980 buf->bytes_consumed = 0;
983 buf->bytes_consumed += bytes_consumed;
985 read_subbuf = buf->subbufs_consumed % n_subbufs;
987 read_subbuf = read_pos / buf->chan->subbuf_size;
988 if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
989 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
990 (buf->offset == subbuf_size))
992 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
993 buf->bytes_consumed = 0;
998 * relay_file_read_avail - boolean, are there unconsumed bytes available?
1000 static int relay_file_read_avail(struct rchan_buf *buf)
1002 size_t subbuf_size = buf->chan->subbuf_size;
1003 size_t n_subbufs = buf->chan->n_subbufs;
1004 size_t produced = buf->subbufs_produced;
1007 relay_file_read_consume(buf, 0, 0);
1009 consumed = buf->subbufs_consumed;
1011 if (unlikely(buf->offset > subbuf_size)) {
1012 if (produced == consumed)
1017 if (unlikely(produced - consumed >= n_subbufs)) {
1018 consumed = produced - n_subbufs + 1;
1019 buf->subbufs_consumed = consumed;
1020 buf->bytes_consumed = 0;
1023 produced = (produced % n_subbufs) * subbuf_size + buf->offset;
1024 consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
1026 if (consumed > produced)
1027 produced += n_subbufs * subbuf_size;
1029 if (consumed == produced) {
1030 if (buf->offset == subbuf_size &&
1031 buf->subbufs_produced > buf->subbufs_consumed)
1040 * relay_file_read_subbuf_avail - return bytes available in sub-buffer
1041 * @read_pos: file read position
1042 * @buf: relay channel buffer
1044 static size_t relay_file_read_subbuf_avail(size_t read_pos,
1045 struct rchan_buf *buf)
1047 size_t padding, avail = 0;
1048 size_t read_subbuf, read_offset, write_subbuf, write_offset;
1049 size_t subbuf_size = buf->chan->subbuf_size;
1051 write_subbuf = (buf->data - buf->start) / subbuf_size;
1052 write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
1053 read_subbuf = read_pos / subbuf_size;
1054 read_offset = read_pos % subbuf_size;
1055 padding = buf->padding[read_subbuf];
1057 if (read_subbuf == write_subbuf) {
1058 if (read_offset + padding < write_offset)
1059 avail = write_offset - (read_offset + padding);
1061 avail = (subbuf_size - padding) - read_offset;
1067 * relay_file_read_start_pos - find the first available byte to read
1068 * @buf: relay channel buffer
1070 * If the read_pos is in the middle of padding, return the
1071 * position of the first actually available byte, otherwise
1072 * return the original value.
1074 static size_t relay_file_read_start_pos(struct rchan_buf *buf)
1076 size_t read_subbuf, padding, padding_start, padding_end;
1077 size_t subbuf_size = buf->chan->subbuf_size;
1078 size_t n_subbufs = buf->chan->n_subbufs;
1079 size_t consumed = buf->subbufs_consumed % n_subbufs;
1080 size_t read_pos = consumed * subbuf_size + buf->bytes_consumed;
1082 read_subbuf = read_pos / subbuf_size;
1083 padding = buf->padding[read_subbuf];
1084 padding_start = (read_subbuf + 1) * subbuf_size - padding;
1085 padding_end = (read_subbuf + 1) * subbuf_size;
1086 if (read_pos >= padding_start && read_pos < padding_end) {
1087 read_subbuf = (read_subbuf + 1) % n_subbufs;
1088 read_pos = read_subbuf * subbuf_size;
1095 * relay_file_read_end_pos - return the new read position
1096 * @read_pos: file read position
1097 * @buf: relay channel buffer
1098 * @count: number of bytes to be read
1100 static size_t relay_file_read_end_pos(struct rchan_buf *buf,
1104 size_t read_subbuf, padding, end_pos;
1105 size_t subbuf_size = buf->chan->subbuf_size;
1106 size_t n_subbufs = buf->chan->n_subbufs;
1108 read_subbuf = read_pos / subbuf_size;
1109 padding = buf->padding[read_subbuf];
1110 if (read_pos % subbuf_size + count + padding == subbuf_size)
1111 end_pos = (read_subbuf + 1) * subbuf_size;
1113 end_pos = read_pos + count;
1114 if (end_pos >= subbuf_size * n_subbufs)
1120 static ssize_t relay_file_read(struct file *filp,
1121 char __user *buffer,
1125 struct rchan_buf *buf = filp->private_data;
1126 size_t read_start, avail;
1133 inode_lock(file_inode(filp));
1137 if (!relay_file_read_avail(buf))
1140 read_start = relay_file_read_start_pos(buf);
1141 avail = relay_file_read_subbuf_avail(read_start, buf);
1145 avail = min(count, avail);
1146 from = buf->start + read_start;
1148 if (copy_to_user(buffer, from, avail))
1155 relay_file_read_consume(buf, read_start, ret);
1156 *ppos = relay_file_read_end_pos(buf, read_start, ret);
1158 inode_unlock(file_inode(filp));
1163 static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
1165 rbuf->bytes_consumed += bytes_consumed;
1167 if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
1168 relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
1169 rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
1173 static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
1174 struct pipe_buffer *buf)
1176 struct rchan_buf *rbuf;
1178 rbuf = (struct rchan_buf *)page_private(buf->page);
1179 relay_consume_bytes(rbuf, buf->private);
1182 static const struct pipe_buf_operations relay_pipe_buf_ops = {
1183 .release = relay_pipe_buf_release,
1184 .try_steal = generic_pipe_buf_try_steal,
1185 .get = generic_pipe_buf_get,
1188 static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
1193 * subbuf_splice_actor - splice up to one subbuf's worth of data
1195 static ssize_t subbuf_splice_actor(struct file *in,
1197 struct pipe_inode_info *pipe,
1202 unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
1203 struct rchan_buf *rbuf = in->private_data;
1204 unsigned int subbuf_size = rbuf->chan->subbuf_size;
1205 uint64_t pos = (uint64_t) *ppos;
1206 uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
1207 size_t read_start = (size_t) do_div(pos, alloc_size);
1208 size_t read_subbuf = read_start / subbuf_size;
1209 size_t padding = rbuf->padding[read_subbuf];
1210 size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1211 struct page *pages[PIPE_DEF_BUFFERS];
1212 struct partial_page partial[PIPE_DEF_BUFFERS];
1213 struct splice_pipe_desc spd = {
1216 .nr_pages_max = PIPE_DEF_BUFFERS,
1218 .ops = &relay_pipe_buf_ops,
1219 .spd_release = relay_page_release,
1223 if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
1225 if (splice_grow_spd(pipe, &spd))
1229 * Adjust read len, if longer than what is available
1231 if (len > (subbuf_size - read_start % subbuf_size))
1232 len = subbuf_size - read_start % subbuf_size;
1234 subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
1235 pidx = (read_start / PAGE_SIZE) % subbuf_pages;
1236 poff = read_start & ~PAGE_MASK;
1237 nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
1239 for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1240 unsigned int this_len, this_end, private;
1241 unsigned int cur_pos = read_start + total_len;
1246 this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
1249 spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
1250 spd.partial[spd.nr_pages].offset = poff;
1252 this_end = cur_pos + this_len;
1253 if (this_end >= nonpad_end) {
1254 this_len = nonpad_end - cur_pos;
1255 private = this_len + padding;
1257 spd.partial[spd.nr_pages].len = this_len;
1258 spd.partial[spd.nr_pages].private = private;
1261 total_len += this_len;
1263 pidx = (pidx + 1) % subbuf_pages;
1265 if (this_end >= nonpad_end) {
1275 ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
1276 if (ret < 0 || ret < total_len)
1279 if (read_start + ret == nonpad_end)
1283 splice_shrink_spd(&spd);
1287 static ssize_t relay_file_splice_read(struct file *in,
1289 struct pipe_inode_info *pipe,
1300 while (len && !spliced) {
1301 ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
1305 if (flags & SPLICE_F_NONBLOCK)
1315 spliced += nonpad_ret;
1325 const struct file_operations relay_file_operations = {
1326 .open = relay_file_open,
1327 .poll = relay_file_poll,
1328 .mmap = relay_file_mmap,
1329 .read = relay_file_read,
1330 .llseek = no_llseek,
1331 .release = relay_file_release,
1332 .splice_read = relay_file_splice_read,
1334 EXPORT_SYMBOL_GPL(relay_file_operations);