Release 4.15 kernel/relay.c

/*
 * Public API and common code for kernel->userspace relay file support.
 *
 * See Documentation/filesystems/relay.txt for an overview.
 *
 * 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.
 * November 2006 - CPU hotplug support by Mathieu Desnoyers
 *      (mathieu.desnoyers@polymtl.ca)
 *
 * This file is released under the GPL.
 */
#include <linux/errno.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/string.h>
#include <linux/relay.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/splice.h>

/* list of open channels, for cpu hotplug */
static DEFINE_MUTEX(relay_channels_mutex);
static LIST_HEAD(relay_channels);

/*
 * 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.
 */


static int relay_buf_fault(struct vm_fault *vmf)
{
	struct page *page;
	struct rchan_buf *buf = vmf->vma->vm_private_data;
	pgoff_t pgoff = vmf->pgoff;

	if (!buf)
		return VM_FAULT_OOM;

	page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
	if (!page)
		return VM_FAULT_SIGBUS;
	get_page(page);
	vmf->page = page;

	return 0;
}

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57
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20
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Dave Jiang
2
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/*
 * vm_ops for relay file mappings.
 */

static const struct vm_operations_struct relay_file_mmap_ops = {
	.fault = relay_buf_fault,
	.close = relay_file_mmap_close,
};

/*
 * allocate an array of pointers of struct page
 */


static struct page **relay_alloc_page_array(unsigned int n_pages)
{
	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)
{
	kvfree(array);
}

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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.
 */


static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
{
	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;
	vma->vm_flags |= VM_DONTEXPAND;
	vma->vm_private_data = buf;
	buf->chan->cb->buf_mapped(buf, filp);

	return 0;
}

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/**
 *      relay_alloc_buf - allocate a channel buffer
 *      @buf: the buffer struct
 *      @size: total size of the buffer
 *
 *      Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
 *      passed in size will get page aligned, if it isn't already.
 */


static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
{
	void *mem;
	unsigned int i, j, n_pages;

	*size = PAGE_ALIGN(*size);
	n_pages = *size >> PAGE_SHIFT;

	buf->page_array = relay_alloc_page_array(n_pages);
	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;
		set_page_private(buf->page_array[i], (unsigned long)buf);
	}
	mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
	if (!mem)
		goto depopulate;

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

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

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16
8.04%
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Masami Hiramatsu
2
1.01%
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/**
 *      relay_create_buf - allocate and initialize a channel buffer
 *      @chan: the relay channel
 *
 *      Returns channel buffer if successful, %NULL otherwise.
 */


static struct rchan_buf *relay_create_buf(struct rchan *chan)
{
	struct rchan_buf *buf;

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

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

	buf->start = relay_alloc_buf(buf, &chan->alloc_size);
	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;
}

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Robert P. J. Day
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/**
 *      relay_destroy_channel - free the channel struct
 *      @kref: target kernel reference that contains the relay channel
 *
 *      Should only be called from kref_put().
 */


static void relay_destroy_channel(struct kref *kref)
{
	struct rchan *chan = container_of(kref, struct rchan, kref);
	kfree(chan);
}

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/**
 *      relay_destroy_buf - destroy an rchan_buf struct and associated buffer
 *      @buf: the buffer struct
 */


static void relay_destroy_buf(struct rchan_buf *buf)
{
	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]);
		relay_free_page_array(buf->page_array);
	}
	*per_cpu_ptr(chan->buf, buf->cpu) = NULL;
	kfree(buf->padding);
	kfree(buf);
	kref_put(&chan->kref, relay_destroy_channel);
}

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9
8.18%
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Akash Goel
5
4.55%
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Adrian Bunk
1
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Masami Hiramatsu
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/**
 *      relay_remove_buf - remove a channel buffer
 *      @kref: target kernel reference that contains the relay buffer
 *
 *      Removes the file from the filesystem, which also frees the
 *      rchan_buf_struct and the channel buffer.  Should only be called from
 *      kref_put().
 */


static void relay_remove_buf(struct kref *kref)
{
	struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
	relay_destroy_buf(buf);
}

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/**
 *      relay_buf_empty - boolean, is the channel buffer empty?
 *      @buf: channel buffer
 *
 *      Returns 1 if the buffer is empty, 0 otherwise.
 */


static int relay_buf_empty(struct rchan_buf *buf)
{
	return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
}

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/**
 *      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;
}
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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;
}

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/*
 * buf_mapped() default callback.  Does nothing.
 */


static void buf_mapped_default_callback(struct rchan_buf *buf,
					struct file *filp)
{
}

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/*
 * buf_unmapped() default callback.  Does nothing.
 */


static void buf_unmapped_default_callback(struct rchan_buf *buf,
					  struct file *filp)
{
}

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/*
 * create_buf_file_create() default callback.  Does nothing.
 */


static struct dentry *create_buf_file_default_callback(const char *filename,
						       struct dentry *parent,
						       umode_t mode,
						       struct rchan_buf *buf,
						       int *is_global)
{
	return NULL;
}

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/*
 * remove_buf_file() default callback.  Does nothing.
 */


static int remove_buf_file_default_callback(struct dentry *dentry)
{
	return -EINVAL;
}

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/* 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
 *      @work: contains the channel buffer
 *
 *      This is the function used to defer reader waking
 */


static void wakeup_readers(struct irq_work *work)
{
	struct rchan_buf *buf;

	buf = container_of(work, struct rchan_buf, wakeup_work);
	wake_up_interruptible(&buf->read_wait);
}

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David Howells
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5.56%
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/**
 *      __relay_reset - reset a channel buffer
 *      @buf: the channel buffer
 *      @init: 1 if this is a first-time initialization
 *
 *      See relay_reset() for description of effect.
 */


static void __relay_reset(struct rchan_buf *buf, unsigned int init)
{
	size_t i;

	if (init) {
		init_waitqueue_head(&buf->read_wait);
		kref_init(&buf->kref);
		init_irq_work(&buf->wakeup_work, wakeup_readers);
	} else {
		irq_work_sync(&buf->wakeup_work);
	}

	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);
}

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Tom Zanussi
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/**
 *      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.
 *
 *      NOTE. Care should be taken that the channel isn't actually
 *      being used by anything when this call is made.
 */


void relay_reset(struct rchan *chan)
{
	struct rchan_buf *buf;
	unsigned int i;

	if (!chan)
		return;

	if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
		__relay_reset(buf, 0);
		return;
	}

	mutex_lock(&relay_channels_mutex);
	for_each_possible_cpu(i)
		if ((buf = *per_cpu_ptr(chan->buf, i)))
			__relay_reset(buf, 0);
	mutex_unlock(&relay_channels_mutex);
}
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31.91%
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Akash Goel
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EXPORT_SYMBOL_GPL(relay_reset);



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

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29
80.56%
1
33.33%
Jens Axboe
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11.11%
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David Howells
3
8.33%
1
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36
100.00%
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100.00%



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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43
43.88%
1
33.33%
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33
33.67%
1
33.33%
Eduard - Gabriel Munteanu
22
22.45%
1
33.33%
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98
100.00%
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100.00%

/*
 *      relay_open_buf - create a new relay channel buffer
 *
 *      used by relay_open() and CPU hotplug.
 */


static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
{
 	struct rchan_buf *buf = NULL;
	struct dentry *dentry;

 	if (chan->is_global)
		return *per_cpu_ptr(chan->buf, 0);

	buf = relay_create_buf(chan);
	if (!buf)
		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);
	} 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;
	}

 	buf->cpu = cpu;
 	__relay_reset(buf, 1);

 	if(chan->is_global) {
		*per_cpu_ptr(chan->buf, 0) = buf;
 		buf->cpu = 0;
  	}

	return buf;

free_buf:
 	relay_destroy_buf(buf);
	return NULL;
}

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46
25.14%
2
40.00%
Mathieu Desnoyers
24
13.11%
1
20.00%
Jens Axboe
19
10.38%
1
20.00%
Total
183
100.00%
5
100.00%

/**
 *      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.
 */


static void relay_close_buf(struct rchan_buf *buf)
{
	buf->finalized = 1;
	irq_work_sync(&buf->wakeup_work);
	buf->chan->cb->remove_buf_file(buf->dentry);
	kref_put(&buf->kref, relay_remove_buf);
}

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33
68.75%
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33.33%
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13
27.08%
1
33.33%
Peter Zijlstra
2
4.17%
1
33.33%
Total
48
100.00%
3
100.00%



static void setup_callbacks(struct rchan *chan,
				   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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int relay_prepare_cpu(unsigned int cpu)
{
	struct rchan *chan;
	struct rchan_buf *buf;

	mutex_lock(&relay_channels_mutex);
	list_for_each_entry(chan, &relay_channels, list) {
		if ((buf = *per_cpu_ptr(chan->buf, cpu)))
			continue;
		buf = relay_open_buf(chan, cpu);
		if (!buf) {
			pr_err("relay: cpu %d buffer creation failed\n", cpu);
			mutex_unlock(&relay_channels_mutex);
			return -ENOMEM;
		}
		*per_cpu_ptr(chan->buf, cpu) = buf;
	}
	mutex_unlock(&relay_channels_mutex);
	return 0;
}

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69
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25
23.58%
1
25.00%
Richard Weinberger
10
9.43%
1
25.00%
Akinobu Mita
2
1.89%
1
25.00%
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106
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4
100.00%

/**
 *      relay_open - create a new relay channel
 *      @base_filename: base name of files to create, %NULL for buffering only
 *      @parent: dentry of parent directory, %NULL for root directory or buffer
 *      @subbuf_size: size of sub-buffers
 *      @n_subbufs: number of sub-buffers
 *      @cb: client callback functions
 *      @private_data: user-defined data
 *
 *      Returns channel pointer if successful, %NULL otherwise.
 *
 *      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
 *      permissions will be %S_IRUSR.
 *
 *      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.
 */


struct rchan *relay_open(const char *base_filename,
			 struct dentry *parent,
			 size_t subbuf_size,
			 size_t n_subbufs,
			 struct rchan_callbacks *cb,
			 void *private_data)
{
	unsigned int i;
	struct rchan *chan;
	struct rchan_buf *buf;

	if (!(subbuf_size && n_subbufs))
		return NULL;
	if (subbuf_size > UINT_MAX / n_subbufs)
		return NULL;

	chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
	if (!chan)
		return NULL;

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

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

	return chan;

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

	kref_put(&chan->kref, relay_destroy_channel);
	mutex_unlock(&relay_channels_mutex);
	kfree(chan);
	return NULL;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Jens Axboe
168
57.14%
1
11.11%
Mathieu Desnoyers
58
19.73%
1
11.11%
Akash Goel
37
12.59%
1
11.11%
Eduard - Gabriel Munteanu
12
4.08%
1
11.11%
Dan Carpenter
11
3.74%
1
11.11%
Zhouyi Zhou
5
1.70%
1
11.11%
Lai Jiangshan
1
0.34%
1
11.11%
Jovi Zhangwei
1
0.34%
1
11.11%
Robert P. J. Day
1
0.34%
1
11.11%
Total
294
100.00%
9
100.00%


EXPORT_SYMBOL_GPL(relay_open);


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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Eduard - Gabriel Munteanu
28
100.00%
1
100.00%
Total
28
100.00%
1
100.00%

/**
 *      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.
 *
 *      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.
 */


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;
	struct rchan_buf *buf;
	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? */
	if (unlikely(chan->has_base_filename)) {
		mutex_unlock(&relay_channels_mutex);
		return -EEXIST;
	}
	chan->has_base_filename = 1;
	chan->parent = parent;

	if (chan->is_global) {
		err = -EINVAL;
		buf = *per_cpu_ptr(chan->buf, 0);
		if (!WARN_ON_ONCE(!buf)) {
			dentry = relay_create_buf_file(chan, buf, 0);
			if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
				relay_set_buf_dentry(buf, dentry);
				err = 0;
			}
		}
		mutex_unlock(&relay_channels_mutex);
		return err;
	}

	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) {
		buf = *per_cpu_ptr(chan->buf, i);
		if (unlikely(!buf)) {
			WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
			err = -EINVAL;
			break;
		}

		dentry = relay_create_buf_file(chan, buf, i);
		if (unlikely(!dentry)) {
			err = -EINVAL;
			break;
		}

		if (curr_cpu == i) {
			local_irq_save(flags);
			relay_set_buf_dentry(buf, dentry);
			local_irq_restore(flags);
		} else {
			disp.buf = buf;
			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;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Eduard - Gabriel Munteanu
236
68.01%
1
20.00%
Akash Goel
99
28.53%
2
40.00%
Jiri Slaby
8
2.31%
1
20.00%
Ingo Molnar
4
1.15%
1
20.00%
Total
347
100.00%
5
100.00%


EXPORT_SYMBOL_GPL(relay_late_setup_files);

/**
 *      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->