relay.c 33.8 KB
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/*
 * Public API and common code for kernel->userspace relay file support.
 *
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 * See Documentation/filesystems/relay.txt for an overview.
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 *
 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
 *
 * Moved to kernel/relay.c by Paul Mundt, 2006.
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 * November 2006 - CPU hotplug support by Mathieu Desnoyers
 * 	(mathieu.desnoyers@polymtl.ca)
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 *
 * This file is released under the GPL.
 */
#include <linux/errno.h>
#include <linux/stddef.h>
#include <linux/slab.h>
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#include <linux/export.h>
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#include <linux/string.h>
#include <linux/relay.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
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#include <linux/cpu.h>
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#include <linux/splice.h>
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/* list of open channels, for cpu hotplug */
static DEFINE_MUTEX(relay_channels_mutex);
static LIST_HEAD(relay_channels);
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/*
 * close() vm_op implementation for relay file mapping.
 */
static void relay_file_mmap_close(struct vm_area_struct *vma)
{
	struct rchan_buf *buf = vma->vm_private_data;
	buf->chan->cb->buf_unmapped(buf, vma->vm_file);
}

/*
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 * fault() vm_op implementation for relay file mapping.
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 */
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static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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{
	struct page *page;
	struct rchan_buf *buf = vma->vm_private_data;
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	pgoff_t pgoff = vmf->pgoff;
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	if (!buf)
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		return VM_FAULT_OOM;
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	page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
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	if (!page)
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		return VM_FAULT_SIGBUS;
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	get_page(page);
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	vmf->page = page;
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	return 0;
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}

/*
 * vm_ops for relay file mappings.
 */
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static const struct vm_operations_struct relay_file_mmap_ops = {
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	.fault = relay_buf_fault,
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	.close = relay_file_mmap_close,
};

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/*
 * allocate an array of pointers of struct page
 */
static struct page **relay_alloc_page_array(unsigned int n_pages)
{
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	const size_t pa_size = n_pages * sizeof(struct page *);
	if (pa_size > PAGE_SIZE)
		return vzalloc(pa_size);
	return kzalloc(pa_size, GFP_KERNEL);
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}

/*
 * free an array of pointers of struct page
 */
static void relay_free_page_array(struct page **array)
{
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	kvfree(array);
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}

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/**
 *	relay_mmap_buf: - mmap channel buffer to process address space
 *	@buf: relay channel buffer
 *	@vma: vm_area_struct describing memory to be mapped
 *
 *	Returns 0 if ok, negative on error
 *
 *	Caller should already have grabbed mmap_sem.
 */
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static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
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{
	unsigned long length = vma->vm_end - vma->vm_start;
	struct file *filp = vma->vm_file;

	if (!buf)
		return -EBADF;

	if (length != (unsigned long)buf->chan->alloc_size)
		return -EINVAL;

	vma->vm_ops = &relay_file_mmap_ops;
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	vma->vm_flags |= VM_DONTEXPAND;
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	vma->vm_private_data = buf;
	buf->chan->cb->buf_mapped(buf, filp);

	return 0;
}

/**
 *	relay_alloc_buf - allocate a channel buffer
 *	@buf: the buffer struct
 *	@size: total size of the buffer
 *
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 *	Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
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 *	passed in size will get page aligned, if it isn't already.
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 */
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static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
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{
	void *mem;
	unsigned int i, j, n_pages;

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	*size = PAGE_ALIGN(*size);
	n_pages = *size >> PAGE_SHIFT;
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	buf->page_array = relay_alloc_page_array(n_pages);
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	if (!buf->page_array)
		return NULL;

	for (i = 0; i < n_pages; i++) {
		buf->page_array[i] = alloc_page(GFP_KERNEL);
		if (unlikely(!buf->page_array[i]))
			goto depopulate;
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		set_page_private(buf->page_array[i], (unsigned long)buf);
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	}
	mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
	if (!mem)
		goto depopulate;

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	memset(mem, 0, *size);
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	buf->page_count = n_pages;
	return mem;

depopulate:
	for (j = 0; j < i; j++)
		__free_page(buf->page_array[j]);
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	relay_free_page_array(buf->page_array);
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	return NULL;
}

/**
 *	relay_create_buf - allocate and initialize a channel buffer
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 *	@chan: the relay channel
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 *
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 *	Returns channel buffer if successful, %NULL otherwise.
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 */
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static struct rchan_buf *relay_create_buf(struct rchan *chan)
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{
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	struct rchan_buf *buf;

	if (chan->n_subbufs > UINT_MAX / sizeof(size_t *))
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		return NULL;

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	buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
	if (!buf)
		return NULL;
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	buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
	if (!buf->padding)
		goto free_buf;

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	buf->start = relay_alloc_buf(buf, &chan->alloc_size);
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	if (!buf->start)
		goto free_buf;

	buf->chan = chan;
	kref_get(&buf->chan->kref);
	return buf;

free_buf:
	kfree(buf->padding);
	kfree(buf);
	return NULL;
}

/**
 *	relay_destroy_channel - free the channel struct
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 *	@kref: target kernel reference that contains the relay channel
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 *
 *	Should only be called from kref_put().
 */
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static void relay_destroy_channel(struct kref *kref)
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{
	struct rchan *chan = container_of(kref, struct rchan, kref);
	kfree(chan);
}

/**
 *	relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 *	@buf: the buffer struct
 */
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static void relay_destroy_buf(struct rchan_buf *buf)
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{
	struct rchan *chan = buf->chan;
	unsigned int i;

	if (likely(buf->start)) {
		vunmap(buf->start);
		for (i = 0; i < buf->page_count; i++)
			__free_page(buf->page_array[i]);
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		relay_free_page_array(buf->page_array);
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	}
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	*per_cpu_ptr(chan->buf, buf->cpu) = NULL;
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	kfree(buf->padding);
	kfree(buf);
	kref_put(&chan->kref, relay_destroy_channel);
}

/**
 *	relay_remove_buf - remove a channel buffer
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 *	@kref: target kernel reference that contains the relay buffer
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 *
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 *	Removes the file from the filesystem, which also frees the
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 *	rchan_buf_struct and the channel buffer.  Should only be called from
 *	kref_put().
 */
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static void relay_remove_buf(struct kref *kref)
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{
	struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
	relay_destroy_buf(buf);
}

/**
 *	relay_buf_empty - boolean, is the channel buffer empty?
 *	@buf: channel buffer
 *
 *	Returns 1 if the buffer is empty, 0 otherwise.
 */
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static int relay_buf_empty(struct rchan_buf *buf)
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{
	return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
}

/**
 *	relay_buf_full - boolean, is the channel buffer full?
 *	@buf: channel buffer
 *
 *	Returns 1 if the buffer is full, 0 otherwise.
 */
int relay_buf_full(struct rchan_buf *buf)
{
	size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
	return (ready >= buf->chan->n_subbufs) ? 1 : 0;
}
EXPORT_SYMBOL_GPL(relay_buf_full);

/*
 * High-level relay kernel API and associated functions.
 */

/*
 * rchan_callback implementations defining default channel behavior.  Used
 * in place of corresponding NULL values in client callback struct.
 */

/*
 * subbuf_start() default callback.  Does nothing.
 */
static int subbuf_start_default_callback (struct rchan_buf *buf,
					  void *subbuf,
					  void *prev_subbuf,
					  size_t prev_padding)
{
	if (relay_buf_full(buf))
		return 0;

	return 1;
}

/*
 * buf_mapped() default callback.  Does nothing.
 */
static void buf_mapped_default_callback(struct rchan_buf *buf,
					struct file *filp)
{
}

/*
 * buf_unmapped() default callback.  Does nothing.
 */
static void buf_unmapped_default_callback(struct rchan_buf *buf,
					  struct file *filp)
{
}

/*
 * create_buf_file_create() default callback.  Does nothing.
 */
static struct dentry *create_buf_file_default_callback(const char *filename,
						       struct dentry *parent,
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						       umode_t mode,
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						       struct rchan_buf *buf,
						       int *is_global)
{
	return NULL;
}

/*
 * remove_buf_file() default callback.  Does nothing.
 */
static int remove_buf_file_default_callback(struct dentry *dentry)
{
	return -EINVAL;
}

/* relay channel default callbacks */
static struct rchan_callbacks default_channel_callbacks = {
	.subbuf_start = subbuf_start_default_callback,
	.buf_mapped = buf_mapped_default_callback,
	.buf_unmapped = buf_unmapped_default_callback,
	.create_buf_file = create_buf_file_default_callback,
	.remove_buf_file = remove_buf_file_default_callback,
};

/**
 *	wakeup_readers - wake up readers waiting on a channel
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 *	@data: contains the channel buffer
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 *
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 *	This is the timer function used to defer reader waking.
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 */
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static void wakeup_readers(unsigned long data)
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{
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	struct rchan_buf *buf = (struct rchan_buf *)data;
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	wake_up_interruptible(&buf->read_wait);
}

/**
 *	__relay_reset - reset a channel buffer
 *	@buf: the channel buffer
 *	@init: 1 if this is a first-time initialization
 *
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 *	See relay_reset() for description of effect.
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 */
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static void __relay_reset(struct rchan_buf *buf, unsigned int init)
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{
	size_t i;

	if (init) {
		init_waitqueue_head(&buf->read_wait);
		kref_init(&buf->kref);
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		setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
	} else
		del_timer_sync(&buf->timer);
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	buf->subbufs_produced = 0;
	buf->subbufs_consumed = 0;
	buf->bytes_consumed = 0;
	buf->finalized = 0;
	buf->data = buf->start;
	buf->offset = 0;

	for (i = 0; i < buf->chan->n_subbufs; i++)
		buf->padding[i] = 0;

	buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
}

/**
 *	relay_reset - reset the channel
 *	@chan: the channel
 *
 *	This has the effect of erasing all data from all channel buffers
 *	and restarting the channel in its initial state.  The buffers
 *	are not freed, so any mappings are still in effect.
 *
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 *	NOTE. Care should be taken that the channel isn't actually
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 *	being used by anything when this call is made.
 */
void relay_reset(struct rchan *chan)
{
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	struct rchan_buf *buf;
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	unsigned int i;

	if (!chan)
		return;

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	if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
		__relay_reset(buf, 0);
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		return;
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	}
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	mutex_lock(&relay_channels_mutex);
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	for_each_possible_cpu(i)
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		if ((buf = *per_cpu_ptr(chan->buf, i)))
			__relay_reset(buf, 0);
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	mutex_unlock(&relay_channels_mutex);
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}
EXPORT_SYMBOL_GPL(relay_reset);

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static inline void relay_set_buf_dentry(struct rchan_buf *buf,
					struct dentry *dentry)
{
	buf->dentry = dentry;
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	d_inode(buf->dentry)->i_size = buf->early_bytes;
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}

static struct dentry *relay_create_buf_file(struct rchan *chan,
					    struct rchan_buf *buf,
					    unsigned int cpu)
{
	struct dentry *dentry;
	char *tmpname;

	tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
	if (!tmpname)
		return NULL;
	snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);

	/* Create file in fs */
	dentry = chan->cb->create_buf_file(tmpname, chan->parent,
					   S_IRUSR, buf,
					   &chan->is_global);

	kfree(tmpname);

	return dentry;
}

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/*
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 *	relay_open_buf - create a new relay channel buffer
 *
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 *	used by relay_open() and CPU hotplug.
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 */
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static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
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{
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 	struct rchan_buf *buf = NULL;
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	struct dentry *dentry;

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 	if (chan->is_global)
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		return *per_cpu_ptr(chan->buf, 0);
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	buf = relay_create_buf(chan);
	if (!buf)
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		return NULL;

	if (chan->has_base_filename) {
		dentry = relay_create_buf_file(chan, buf, cpu);
		if (!dentry)
			goto free_buf;
		relay_set_buf_dentry(buf, dentry);
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	} else {
		/* Only retrieve global info, nothing more, nothing less */
		dentry = chan->cb->create_buf_file(NULL, NULL,
						   S_IRUSR, buf,
						   &chan->is_global);
		if (WARN_ON(dentry))
			goto free_buf;
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	}
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 	buf->cpu = cpu;
 	__relay_reset(buf, 1);
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 	if(chan->is_global) {
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		*per_cpu_ptr(chan->buf, 0) = buf;
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 		buf->cpu = 0;
  	}

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	return buf;
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free_buf:
 	relay_destroy_buf(buf);
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	return NULL;
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}

/**
 *	relay_close_buf - close a channel buffer
 *	@buf: channel buffer
 *
 *	Marks the buffer finalized and restores the default callbacks.
 *	The channel buffer and channel buffer data structure are then freed
 *	automatically when the last reference is given up.
 */
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static void relay_close_buf(struct rchan_buf *buf)
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{
	buf->finalized = 1;
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	del_timer_sync(&buf->timer);
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	buf->chan->cb->remove_buf_file(buf->dentry);
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	kref_put(&buf->kref, relay_remove_buf);
}

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static void setup_callbacks(struct rchan *chan,
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				   struct rchan_callbacks *cb)
{
	if (!cb) {
		chan->cb = &default_channel_callbacks;
		return;
	}

	if (!cb->subbuf_start)
		cb->subbuf_start = subbuf_start_default_callback;
	if (!cb->buf_mapped)
		cb->buf_mapped = buf_mapped_default_callback;
	if (!cb->buf_unmapped)
		cb->buf_unmapped = buf_unmapped_default_callback;
	if (!cb->create_buf_file)
		cb->create_buf_file = create_buf_file_default_callback;
	if (!cb->remove_buf_file)
		cb->remove_buf_file = remove_buf_file_default_callback;
	chan->cb = cb;
}

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/**
 * 	relay_hotcpu_callback - CPU hotplug callback
 * 	@nb: notifier block
 * 	@action: hotplug action to take
 * 	@hcpu: CPU number
 *
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 * 	Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
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 */
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static int relay_hotcpu_callback(struct notifier_block *nb,
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				unsigned long action,
				void *hcpu)
{
	unsigned int hotcpu = (unsigned long)hcpu;
	struct rchan *chan;
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	struct rchan_buf *buf;
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	switch(action) {
	case CPU_UP_PREPARE:
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	case CPU_UP_PREPARE_FROZEN:
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		mutex_lock(&relay_channels_mutex);
		list_for_each_entry(chan, &relay_channels, list) {
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			if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
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				continue;
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			buf = relay_open_buf(chan, hotcpu);
			if (!buf) {
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				printk(KERN_ERR
					"relay_hotcpu_callback: cpu %d buffer "
					"creation failed\n", hotcpu);
				mutex_unlock(&relay_channels_mutex);
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				return notifier_from_errno(-ENOMEM);
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			}
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			*per_cpu_ptr(chan->buf, hotcpu) = buf;
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		}
		mutex_unlock(&relay_channels_mutex);
		break;
	case CPU_DEAD:
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	case CPU_DEAD_FROZEN:
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		/* No need to flush the cpu : will be flushed upon
		 * final relay_flush() call. */
		break;
	}
	return NOTIFY_OK;
}

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/**
 *	relay_open - create a new relay channel
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 *	@base_filename: base name of files to create, %NULL for buffering only
 *	@parent: dentry of parent directory, %NULL for root directory or buffer
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 *	@subbuf_size: size of sub-buffers
 *	@n_subbufs: number of sub-buffers
 *	@cb: client callback functions
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 *	@private_data: user-defined data
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 *
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 *	Returns channel pointer if successful, %NULL otherwise.
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 *
 *	Creates a channel buffer for each cpu using the sizes and
 *	attributes specified.  The created channel buffer files
 *	will be named base_filename0...base_filenameN-1.  File
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 *	permissions will be %S_IRUSR.
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 *
 *	If opening a buffer (@parent = NULL) that you later wish to register
 *	in a filesystem, call relay_late_setup_files() once the @parent dentry
 *	is available.
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 */
struct rchan *relay_open(const char *base_filename,
			 struct dentry *parent,
			 size_t subbuf_size,
			 size_t n_subbufs,
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			 struct rchan_callbacks *cb,
			 void *private_data)
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{
	unsigned int i;
	struct rchan *chan;
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	struct rchan_buf *buf;
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	if (!(subbuf_size && n_subbufs))
		return NULL;
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	if (subbuf_size > UINT_MAX / n_subbufs)
		return NULL;
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	chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
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	if (!chan)
		return NULL;

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	chan->buf = alloc_percpu(struct rchan_buf *);
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	chan->version = RELAYFS_CHANNEL_VERSION;
	chan->n_subbufs = n_subbufs;
	chan->subbuf_size = subbuf_size;
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	chan->alloc_size = PAGE_ALIGN(subbuf_size * n_subbufs);
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	chan->parent = parent;
	chan->private_data = private_data;
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	if (base_filename) {
		chan->has_base_filename = 1;
		strlcpy(chan->base_filename, base_filename, NAME_MAX);
	}
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	setup_callbacks(chan, cb);
	kref_init(&chan->kref);

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	mutex_lock(&relay_channels_mutex);
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	for_each_online_cpu(i) {
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		buf = relay_open_buf(chan, i);
		if (!buf)
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			goto free_bufs;
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		*per_cpu_ptr(chan->buf, i) = buf;
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	}
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	list_add(&chan->list, &relay_channels);
	mutex_unlock(&relay_channels_mutex);
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	return chan;

free_bufs:
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	for_each_possible_cpu(i) {
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		if ((buf = *per_cpu_ptr(chan->buf, i)))
			relay_close_buf(buf);
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	}

	kref_put(&chan->kref, relay_destroy_channel);
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	mutex_unlock(&relay_channels_mutex);
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	kfree(chan);
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	return NULL;
}
EXPORT_SYMBOL_GPL(relay_open);

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struct rchan_percpu_buf_dispatcher {
	struct rchan_buf *buf;
	struct dentry *dentry;
};

/* Called in atomic context. */
static void __relay_set_buf_dentry(void *info)
{
	struct rchan_percpu_buf_dispatcher *p = info;

	relay_set_buf_dentry(p->buf, p->dentry);
}

/**
 *	relay_late_setup_files - triggers file creation
 *	@chan: channel to operate on
 *	@base_filename: base name of files to create
 *	@parent: dentry of parent directory, %NULL for root directory
 *
 *	Returns 0 if successful, non-zero otherwise.
 *
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 *	Use to setup files for a previously buffer-only channel created
 *	by relay_open() with a NULL parent dentry.
 *
 *	For example, this is useful for perfomring early tracing in kernel,
 *	before VFS is up and then exposing the early results once the dentry
 *	is available.
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 */
int relay_late_setup_files(struct rchan *chan,
			   const char *base_filename,
			   struct dentry *parent)
{
	int err = 0;
	unsigned int i, curr_cpu;
	unsigned long flags;
	struct dentry *dentry;
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	struct rchan_buf *buf;
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	struct rchan_percpu_buf_dispatcher disp;

	if (!chan || !base_filename)
		return -EINVAL;

	strlcpy(chan->base_filename, base_filename, NAME_MAX);

	mutex_lock(&relay_channels_mutex);
	/* Is chan already set up? */
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	if (unlikely(chan->has_base_filename)) {
		mutex_unlock(&relay_channels_mutex);
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		return -EEXIST;
688
	}
689 690
	chan->has_base_filename = 1;
	chan->parent = parent;
691 692 693

	if (chan->is_global) {
		err = -EINVAL;
694 695 696
		buf = *per_cpu_ptr(chan->buf, 0);
		if (!WARN_ON_ONCE(!buf)) {
			dentry = relay_create_buf_file(chan, buf, 0);
697
			if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
698
				relay_set_buf_dentry(buf, dentry);
699 700 701 702 703 704 705
				err = 0;
			}
		}
		mutex_unlock(&relay_channels_mutex);
		return err;
	}

706 707 708 709 710 711 712
	curr_cpu = get_cpu();
	/*
	 * The CPU hotplug notifier ran before us and created buffers with
	 * no files associated. So it's safe to call relay_setup_buf_file()
	 * on all currently online CPUs.
	 */
	for_each_online_cpu(i) {
713 714
		buf = *per_cpu_ptr(chan->buf, i);
		if (unlikely(!buf)) {
715
			WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
716 717 718 719
			err = -EINVAL;
			break;
		}

720
		dentry = relay_create_buf_file(chan, buf, i);
721 722 723 724 725 726 727
		if (unlikely(!dentry)) {
			err = -EINVAL;
			break;
		}

		if (curr_cpu == i) {
			local_irq_save(flags);
728
			relay_set_buf_dentry(buf, dentry);
729 730
			local_irq_restore(flags);
		} else {
731
			disp.buf = buf;
732 733 734 735 736 737 738 739 740 741 742 743 744 745 746
			disp.dentry = dentry;
			smp_mb();
			/* relay_channels_mutex must be held, so wait. */
			err = smp_call_function_single(i,
						       __relay_set_buf_dentry,
						       &disp, 1);
		}
		if (unlikely(err))
			break;
	}
	put_cpu();
	mutex_unlock(&relay_channels_mutex);

	return err;
}
747
EXPORT_SYMBOL_GPL(relay_late_setup_files);
748

749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771
/**
 *	relay_switch_subbuf - switch to a new sub-buffer
 *	@buf: channel buffer
 *	@length: size of current event
 *
 *	Returns either the length passed in or 0 if full.
 *
 *	Performs sub-buffer-switch tasks such as invoking callbacks,
 *	updating padding counts, waking up readers, etc.
 */
size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
{
	void *old, *new;
	size_t old_subbuf, new_subbuf;

	if (unlikely(length > buf->chan->subbuf_size))
		goto toobig;

	if (buf->offset != buf->chan->subbuf_size + 1) {
		buf->prev_padding = buf->chan->subbuf_size - buf->offset;
		old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
		buf->padding[old_subbuf] = buf->prev_padding;
		buf->subbufs_produced++;
772
		if (buf->dentry)
773
			d_inode(buf->dentry)->i_size +=
774 775 776 777 778
				buf->chan->subbuf_size -
				buf->padding[old_subbuf];
		else
			buf->early_bytes += buf->chan->subbuf_size -
					    buf->padding[old_subbuf];
779
		smp_mb();
780 781 782 783 784 785 786
		if (waitqueue_active(&buf->read_wait))
			/*
			 * Calling wake_up_interruptible() from here
			 * will deadlock if we happen to be logging
			 * from the scheduler (trying to re-grab
			 * rq->lock), so defer it.
			 */
I
Ingo Molnar 已提交
787
			mod_timer(&buf->timer, jiffies + 1);
788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821
	}

	old = buf->data;
	new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
	new = buf->start + new_subbuf * buf->chan->subbuf_size;
	buf->offset = 0;
	if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
		buf->offset = buf->chan->subbuf_size + 1;
		return 0;
	}
	buf->data = new;
	buf->padding[new_subbuf] = 0;

	if (unlikely(length + buf->offset > buf->chan->subbuf_size))
		goto toobig;

	return length;

toobig:
	buf->chan->last_toobig = length;
	return 0;
}
EXPORT_SYMBOL_GPL(relay_switch_subbuf);

/**
 *	relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
 *	@chan: the channel
 *	@cpu: the cpu associated with the channel buffer to update
 *	@subbufs_consumed: number of sub-buffers to add to current buf's count
 *
 *	Adds to the channel buffer's consumed sub-buffer count.
 *	subbufs_consumed should be the number of sub-buffers newly consumed,
 *	not the total consumed.
 *
822
 *	NOTE. Kernel clients don't need to call this function if the channel
823 824 825 826 827 828 829 830 831 832 833
 *	mode is 'overwrite'.
 */
void relay_subbufs_consumed(struct rchan *chan,
			    unsigned int cpu,
			    size_t subbufs_consumed)
{
	struct rchan_buf *buf;

	if (!chan)
		return;

834 835
	buf = *per_cpu_ptr(chan->buf, cpu);
	if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
836 837
		return;

838
	if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
839
		buf->subbufs_consumed = buf->subbufs_produced;
840 841
	else
		buf->subbufs_consumed += subbufs_consumed;
842 843 844 845 846 847 848 849 850 851 852
}
EXPORT_SYMBOL_GPL(relay_subbufs_consumed);

/**
 *	relay_close - close the channel
 *	@chan: the channel
 *
 *	Closes all channel buffers and frees the channel.
 */
void relay_close(struct rchan *chan)
{
853
	struct rchan_buf *buf;
854 855 856 857 858
	unsigned int i;

	if (!chan)
		return;

859
	mutex_lock(&relay_channels_mutex);
860 861
	if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
		relay_close_buf(buf);
862 863
	else
		for_each_possible_cpu(i)
864 865
			if ((buf = *per_cpu_ptr(chan->buf, i)))
				relay_close_buf(buf);
866 867 868 869 870 871

	if (chan->last_toobig)
		printk(KERN_WARNING "relay: one or more items not logged "
		       "[item size (%Zd) > sub-buffer size (%Zd)]\n",
		       chan->last_toobig, chan->subbuf_size);

872
	list_del(&chan->list);
873
	kref_put(&chan->kref, relay_destroy_channel);
874
	mutex_unlock(&relay_channels_mutex);
875 876 877 878 879 880 881
}
EXPORT_SYMBOL_GPL(relay_close);

/**
 *	relay_flush - close the channel
 *	@chan: the channel
 *
882
 *	Flushes all channel buffers, i.e. forces buffer switch.
883 884 885
 */
void relay_flush(struct rchan *chan)
{
886
	struct rchan_buf *buf;
887 888 889 890 891
	unsigned int i;

	if (!chan)
		return;

892 893
	if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
		relay_switch_subbuf(buf, 0);
894
		return;
895
	}
896 897 898

	mutex_lock(&relay_channels_mutex);
	for_each_possible_cpu(i)
899 900
		if ((buf = *per_cpu_ptr(chan->buf, i)))
			relay_switch_subbuf(buf, 0);
901
	mutex_unlock(&relay_channels_mutex);
902 903 904 905 906 907 908 909 910 911 912 913
}
EXPORT_SYMBOL_GPL(relay_flush);

/**
 *	relay_file_open - open file op for relay files
 *	@inode: the inode
 *	@filp: the file
 *
 *	Increments the channel buffer refcount.
 */
static int relay_file_open(struct inode *inode, struct file *filp)
{
914
	struct rchan_buf *buf = inode->i_private;
915 916 917
	kref_get(&buf->kref);
	filp->private_data = buf;

918
	return nonseekable_open(inode, filp);
919 920 921 922 923 924 925
}

/**
 *	relay_file_mmap - mmap file op for relay files
 *	@filp: the file
 *	@vma: the vma describing what to map
 *
926
 *	Calls upon relay_mmap_buf() to map the file into user space.
927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973
 */
static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
{
	struct rchan_buf *buf = filp->private_data;
	return relay_mmap_buf(buf, vma);
}

/**
 *	relay_file_poll - poll file op for relay files
 *	@filp: the file
 *	@wait: poll table
 *
 *	Poll implemention.
 */
static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
{
	unsigned int mask = 0;
	struct rchan_buf *buf = filp->private_data;

	if (buf->finalized)
		return POLLERR;

	if (filp->f_mode & FMODE_READ) {
		poll_wait(filp, &buf->read_wait, wait);
		if (!relay_buf_empty(buf))
			mask |= POLLIN | POLLRDNORM;
	}

	return mask;
}

/**
 *	relay_file_release - release file op for relay files
 *	@inode: the inode
 *	@filp: the file
 *
 *	Decrements the channel refcount, as the filesystem is
 *	no longer using it.
 */
static int relay_file_release(struct inode *inode, struct file *filp)
{
	struct rchan_buf *buf = filp->private_data;
	kref_put(&buf->kref, relay_remove_buf);

	return 0;
}

974
/*
975 976 977 978 979 980 981 982 983 984
 *	relay_file_read_consume - update the consumed count for the buffer
 */
static void relay_file_read_consume(struct rchan_buf *buf,
				    size_t read_pos,
				    size_t bytes_consumed)
{
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;
	size_t read_subbuf;

985 986 987 988
	if (buf->subbufs_produced == buf->subbufs_consumed &&
	    buf->offset == buf->bytes_consumed)
		return;

989 990 991 992 993 994
	if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
		buf->bytes_consumed = 0;
	}

	buf->bytes_consumed += bytes_consumed;
M
Masami Hiramatsu 已提交
995 996 997 998
	if (!read_pos)
		read_subbuf = buf->subbufs_consumed % n_subbufs;
	else
		read_subbuf = read_pos / buf->chan->subbuf_size;
999 1000 1001 1002 1003 1004 1005 1006 1007
	if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
		if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
		    (buf->offset == subbuf_size))
			return;
		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
		buf->bytes_consumed = 0;
	}
}

1008
/*
1009 1010 1011 1012 1013 1014
 *	relay_file_read_avail - boolean, are there unconsumed bytes available?
 */
static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
{
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;
1015 1016
	size_t produced = buf->subbufs_produced;
	size_t consumed = buf->subbufs_consumed;
1017

1018
	relay_file_read_consume(buf, read_pos, 0);
1019

1020 1021
	consumed = buf->subbufs_consumed;

1022 1023 1024 1025
	if (unlikely(buf->offset > subbuf_size)) {
		if (produced == consumed)
			return 0;
		return 1;
1026 1027
	}

1028
	if (unlikely(produced - consumed >= n_subbufs)) {
M
Masami Hiramatsu 已提交
1029
		consumed = produced - n_subbufs + 1;
1030
		buf->subbufs_consumed = consumed;
M
Masami Hiramatsu 已提交
1031
		buf->bytes_consumed = 0;
1032
	}
D
Daniel Walker 已提交
1033

1034 1035 1036 1037 1038
	produced = (produced % n_subbufs) * subbuf_size + buf->offset;
	consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;

	if (consumed > produced)
		produced += n_subbufs * subbuf_size;
D
Daniel Walker 已提交
1039

1040 1041 1042 1043
	if (consumed == produced) {
		if (buf->offset == subbuf_size &&
		    buf->subbufs_produced > buf->subbufs_consumed)
			return 1;
1044
		return 0;
1045
	}
1046 1047 1048 1049 1050 1051

	return 1;
}

/**
 *	relay_file_read_subbuf_avail - return bytes available in sub-buffer
1052 1053
 *	@read_pos: file read position
 *	@buf: relay channel buffer
1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078
 */
static size_t relay_file_read_subbuf_avail(size_t read_pos,
					   struct rchan_buf *buf)
{
	size_t padding, avail = 0;
	size_t read_subbuf, read_offset, write_subbuf, write_offset;
	size_t subbuf_size = buf->chan->subbuf_size;

	write_subbuf = (buf->data - buf->start) / subbuf_size;
	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
	read_subbuf = read_pos / subbuf_size;
	read_offset = read_pos % subbuf_size;
	padding = buf->padding[read_subbuf];

	if (read_subbuf == write_subbuf) {
		if (read_offset + padding < write_offset)
			avail = write_offset - (read_offset + padding);
	} else
		avail = (subbuf_size - padding) - read_offset;

	return avail;
}

/**
 *	relay_file_read_start_pos - find the first available byte to read
1079 1080
 *	@read_pos: file read position
 *	@buf: relay channel buffer
1081
 *
1082
 *	If the @read_pos is in the middle of padding, return the
1083 1084 1085 1086 1087 1088 1089 1090 1091
 *	position of the first actually available byte, otherwise
 *	return the original value.
 */
static size_t relay_file_read_start_pos(size_t read_pos,
					struct rchan_buf *buf)
{
	size_t read_subbuf, padding, padding_start, padding_end;
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;
D
David Wilder 已提交
1092
	size_t consumed = buf->subbufs_consumed % n_subbufs;
1093

D
David Wilder 已提交
1094 1095
	if (!read_pos)
		read_pos = consumed * subbuf_size + buf->bytes_consumed;
1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109
	read_subbuf = read_pos / subbuf_size;
	padding = buf->padding[read_subbuf];
	padding_start = (read_subbuf + 1) * subbuf_size - padding;
	padding_end = (read_subbuf + 1) * subbuf_size;
	if (read_pos >= padding_start && read_pos < padding_end) {
		read_subbuf = (read_subbuf + 1) % n_subbufs;
		read_pos = read_subbuf * subbuf_size;
	}

	return read_pos;
}

/**
 *	relay_file_read_end_pos - return the new read position
1110 1111 1112
 *	@read_pos: file read position
 *	@buf: relay channel buffer
 *	@count: number of bytes to be read
1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133
 */
static size_t relay_file_read_end_pos(struct rchan_buf *buf,
				      size_t read_pos,
				      size_t count)
{
	size_t read_subbuf, padding, end_pos;
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;

	read_subbuf = read_pos / subbuf_size;
	padding = buf->padding[read_subbuf];
	if (read_pos % subbuf_size + count + padding == subbuf_size)
		end_pos = (read_subbuf + 1) * subbuf_size;
	else
		end_pos = read_pos + count;
	if (end_pos >= subbuf_size * n_subbufs)
		end_pos = 0;

	return end_pos;
}

1134
/*
1135
 *	subbuf_read_actor - read up to one subbuf's worth of data
1136
 */
1137 1138 1139
static int subbuf_read_actor(size_t read_start,
			     struct rchan_buf *buf,
			     size_t avail,
1140
			     read_descriptor_t *desc)
1141 1142
{
	void *from;
1143
	int ret = 0;
1144 1145

	from = buf->start + read_start;
1146
	ret = avail;
A
Al Viro 已提交
1147
	if (copy_to_user(desc->arg.buf, from, avail)) {
1148 1149
		desc->error = -EFAULT;
		ret = 0;
1150
	}
1151 1152 1153 1154
	desc->arg.data += ret;
	desc->written += ret;
	desc->count -= ret;

1155 1156 1157
	return ret;
}

1158 1159 1160
typedef int (*subbuf_actor_t) (size_t read_start,
			       struct rchan_buf *buf,
			       size_t avail,
1161
			       read_descriptor_t *desc);
1162

1163
/*
1164 1165
 *	relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
 */
A
Andrew Morton 已提交
1166 1167 1168
static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
					subbuf_actor_t subbuf_actor,
					read_descriptor_t *desc)
1169
{
1170 1171 1172
	struct rchan_buf *buf = filp->private_data;
	size_t read_start, avail;
	int ret;
1173

A
Al Viro 已提交
1174
	if (!desc->count)
1175 1176
		return 0;

A
Al Viro 已提交
1177
	inode_lock(file_inode(filp));
1178
	do {
1179 1180 1181 1182 1183 1184
		if (!relay_file_read_avail(buf, *ppos))
			break;

		read_start = relay_file_read_start_pos(*ppos, buf);
		avail = relay_file_read_subbuf_avail(read_start, buf);
		if (!avail)
1185 1186
			break;

A
Al Viro 已提交
1187
		avail = min(desc->count, avail);
1188
		ret = subbuf_actor(read_start, buf, avail, desc);
A
Al Viro 已提交
1189
		if (desc->error < 0)
1190 1191 1192 1193 1194 1195
			break;

		if (ret) {
			relay_file_read_consume(buf, read_start, ret);
			*ppos = relay_file_read_end_pos(buf, read_start, ret);
		}
A
Al Viro 已提交
1196
	} while (desc->count && ret);
A
Al Viro 已提交
1197
	inode_unlock(file_inode(filp));
1198

A
Al Viro 已提交
1199
	return desc->written;
1200 1201 1202 1203 1204 1205 1206
}

static ssize_t relay_file_read(struct file *filp,
			       char __user *buffer,
			       size_t count,
			       loff_t *ppos)
{
A
Al Viro 已提交
1207 1208 1209 1210 1211
	read_descriptor_t desc;
	desc.written = 0;
	desc.count = count;
	desc.arg.buf = buffer;
	desc.error = 0;
1212
	return relay_file_read_subbufs(filp, ppos, subbuf_read_actor, &desc);
1213 1214
}

1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
{
	rbuf->bytes_consumed += bytes_consumed;

	if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
		relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
		rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
	}
}

T
Tom Zanussi 已提交
1225 1226
static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
				   struct pipe_buffer *buf)
1227
{
T
Tom Zanussi 已提交
1228 1229 1230
	struct rchan_buf *rbuf;

	rbuf = (struct rchan_buf *)page_private(buf->page);
1231
	relay_consume_bytes(rbuf, buf->private);
T
Tom Zanussi 已提交
1232 1233
}

1234
static const struct pipe_buf_operations relay_pipe_buf_ops = {
T
Tom Zanussi 已提交
1235
	.can_merge = 0,
1236
	.confirm = generic_pipe_buf_confirm,
T
Tom Zanussi 已提交
1237 1238 1239 1240 1241
	.release = relay_pipe_buf_release,
	.steal = generic_pipe_buf_steal,
	.get = generic_pipe_buf_get,
};

1242 1243 1244 1245
static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
{
}

T
Tom Zanussi 已提交
1246
/*
T
Tom Zanussi 已提交
1247 1248
 *	subbuf_splice_actor - splice up to one subbuf's worth of data
 */
1249
static ssize_t subbuf_splice_actor(struct file *in,
T
Tom Zanussi 已提交
1250 1251 1252 1253 1254 1255
			       loff_t *ppos,
			       struct pipe_inode_info *pipe,
			       size_t len,
			       unsigned int flags,
			       int *nonpad_ret)
{
1256
	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
T
Tom Zanussi 已提交
1257 1258
	struct rchan_buf *rbuf = in->private_data;
	unsigned int subbuf_size = rbuf->chan->subbuf_size;
1259 1260 1261
	uint64_t pos = (uint64_t) *ppos;
	uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
	size_t read_start = (size_t) do_div(pos, alloc_size);
T
Tom Zanussi 已提交
1262 1263 1264
	size_t read_subbuf = read_start / subbuf_size;
	size_t padding = rbuf->padding[read_subbuf];
	size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
1265 1266
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
1267 1268 1269
	struct splice_pipe_desc spd = {
		.pages = pages,
		.nr_pages = 0,
1270
		.nr_pages_max = PIPE_DEF_BUFFERS,
1271 1272 1273
		.partial = partial,
		.flags = flags,
		.ops = &relay_pipe_buf_ops,
1274
		.spd_release = relay_page_release,
1275
	};
1276
	ssize_t ret;
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1277 1278 1279

	if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
		return 0;
1280 1281
	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;
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1282

1283 1284 1285 1286 1287
	/*
	 * Adjust read len, if longer than what is available
	 */
	if (len > (subbuf_size - read_start % subbuf_size))
		len = subbuf_size - read_start % subbuf_size;
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	subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
	pidx = (read_start / PAGE_SIZE) % subbuf_pages;
	poff = read_start & ~PAGE_MASK;
1292
	nr_pages = min_t(unsigned int, subbuf_pages, spd.nr_pages_max);
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1293

1294
	for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
1295 1296
		unsigned int this_len, this_end, private;
		unsigned int cur_pos = read_start + total_len;
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1297

1298
		if (!len)
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1299 1300
			break;

1301 1302
		this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
		private = this_len;
T
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1303

1304 1305
		spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
		spd.partial[spd.nr_pages].offset = poff;
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1307 1308 1309 1310
		this_end = cur_pos + this_len;
		if (this_end >= nonpad_end) {
			this_len = nonpad_end - cur_pos;
			private = this_len + padding;
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1311
		}
1312 1313
		spd.partial[spd.nr_pages].len = this_len;
		spd.partial[spd.nr_pages].private = private;
T
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1314

1315 1316 1317 1318
		len -= this_len;
		total_len += this_len;
		poff = 0;
		pidx = (pidx + 1) % subbuf_pages;
T
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1319

1320 1321
		if (this_end >= nonpad_end) {
			spd.nr_pages++;
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1322 1323 1324 1325
			break;
		}
	}

1326
	ret = 0;
1327
	if (!spd.nr_pages)
1328
		goto out;
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1329

1330 1331
	ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
	if (ret < 0 || ret < total_len)
1332
		goto out;
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1333

1334 1335 1336
        if (read_start + ret == nonpad_end)
                ret += padding;

1337
out:
1338 1339
	splice_shrink_spd(&spd);
	return ret;
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1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354
}

static ssize_t relay_file_splice_read(struct file *in,
				      loff_t *ppos,
				      struct pipe_inode_info *pipe,
				      size_t len,
				      unsigned int flags)
{
	ssize_t spliced;
	int ret;
	int nonpad_ret = 0;

	ret = 0;
	spliced = 0;

1355
	while (len && !spliced) {
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1356 1357 1358 1359
		ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
		if (ret < 0)
			break;
		else if (!ret) {
1360
			if (flags & SPLICE_F_NONBLOCK)
T
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1361
				ret = -EAGAIN;
1362
			break;
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1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377
		}

		*ppos += ret;
		if (ret > len)
			len = 0;
		else
			len -= ret;
		spliced += nonpad_ret;
		nonpad_ret = 0;
	}

	if (spliced)
		return spliced;

	return ret;
1378 1379
}

1380
const struct file_operations relay_file_operations = {
1381 1382 1383 1384 1385 1386
	.open		= relay_file_open,
	.poll		= relay_file_poll,
	.mmap		= relay_file_mmap,
	.read		= relay_file_read,
	.llseek		= no_llseek,
	.release	= relay_file_release,
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1387
	.splice_read	= relay_file_splice_read,
1388 1389
};
EXPORT_SYMBOL_GPL(relay_file_operations);
1390 1391 1392 1393 1394 1395 1396 1397

static __init int relay_init(void)
{

	hotcpu_notifier(relay_hotcpu_callback, 0);
	return 0;
}

1398
early_initcall(relay_init);