/*

* 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 ([email protected]), IBM Corp

* Copyright (C) 1999-2005 - Karim Yaghmour ([email protected])

*

* Moved to kernel/relay.c by Paul Mundt, 2006.

* November 2006 - CPU hotplug support by Mathieu Desnoyers

* ([email protected])

*

* 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);

}

/*

* fault() vm_op implementation for relay file mapping.

*/

static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

{

struct page *page;

struct rchan_buf *buf = 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;

}

/*

* 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);

}

/*

* free an array of pointers of struct page

*/

static void relay_free_page_array(struct page **array)

{

if (is_vmalloc_addr(array))

vfree(array);

else

kfree(array);

}

/**

* 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;

}

/**

* 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;

}

/**

* 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;

}

/**

* 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);

}

/**

* 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);

}

chan->buf[buf->cpu] = NULL;

kfree(buf->padding);

kfree(buf);

kref_put(&chan->kref, relay_destroy_channel);

}

/**

* relay_remove_buf - remove a channel buffer

* @kref: target kernel reference that contains the relay buffer

*

* Removes the file from the fileystem, 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);

buf->chan->cb->remove_buf_file(buf->dentry);

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.

*/

static int relay_buf_empty(struct rchan_buf *buf)

{

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,

umode_t mode,

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

* @data: contains the channel buffer

*

* This is the timer function used to defer reader waking.

*/

static void wakeup_readers(unsigned long data)

{

struct rchan_buf *buf = (struct rchan_buf *)data;

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

*

* 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);

setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);

} else

del_timer_sync(&buf->timer);

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.

*

* 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)

{

unsigned int i;

if (!chan)

return;

if (chan->is_global && chan->buf[0]) {

__relay_reset(chan->buf[0], 0);

return;

}

mutex_lock(&relay_channels_mutex);

for_each_possible_cpu(i)

if (chan->buf[i])

__relay_reset(chan->buf[i], 0);

mutex_unlock(&relay_channels_mutex);

}

EXPORT_SYMBOL_GPL(relay_reset);

static inline void relay_set_buf_dentry(struct rchan_buf *buf,

struct dentry *dentry)

{

buf->dentry = dentry;

buf->dentry->d_inode->i_size = buf->early_bytes;

}

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;

}

/*

* 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 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);

}

buf->cpu = cpu;

__relay_reset(buf, 1);

if(chan->is_global) {

chan->buf[0] = buf;

buf->cpu = 0;

}

return buf;

free_buf:

relay_destroy_buf(buf);

return NULL;

}

/**

* 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;

del_timer_sync(&buf->timer);

kref_put(&buf->kref, relay_remove_buf);

}

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;

}

/**

* relay_hotcpu_callback - CPU hotplug callback

* @nb: notifier block

* @action: hotplug action to take

* @hcpu: CPU number

*

* Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)

*/

static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,

unsigned long action,

void *hcpu)

{

unsigned int hotcpu = (unsigned long)hcpu;

struct rchan *chan;

switch(action) {

case CPU_UP_PREPARE:

case CPU_UP_PREPARE_FROZEN:

mutex_lock(&relay_channels_mutex);

list_for_each_entry(chan, &relay_channels, list) {

if (chan->buf[hotcpu])

continue;

chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);

if(!chan->buf[hotcpu]) {

printk(KERN_ERR

"relay_hotcpu_callback: cpu %d buffer "

"creation failed\n", hotcpu);

mutex_unlock(&relay_channels_mutex);

return notifier_from_errno(-ENOMEM);

}

}

mutex_unlock(&relay_channels_mutex);

break;

case CPU_DEAD:

case CPU_DEAD_FROZEN:

/* No need to flush the cpu : will be flushed upon

* final relay_flush() call. */

break;

}

return NOTIFY_OK;

}

/**

* 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.

*/

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;

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->version = RELAYFS_CHANNEL_VERSION;

chan->n_subbufs = n_subbufs;

chan->subbuf_size = subbuf_size;

chan->alloc_size = FIX_SIZE(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) {

chan->buf[i] = relay_open_buf(chan, i);

if (!chan->buf[i])

goto free_bufs;

}

list_add(&chan->list, &relay_channels);

mutex_unlock(&relay_channels_mutex);

return chan;

free_bufs:

for_each_possible_cpu(i) {

if (chan->buf[i])

relay_close_buf(chan->buf[i]);

}

kref_put(&chan->kref, relay_destroy_channel);

mutex_unlock(&relay_channels_mutex);

return NULL;

}

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);

}

/**

* 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.

* Useful to do early tracing in kernel, before VFS is up, for example.

*/

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_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;

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) {

if (unlikely(!chan->buf[i])) {

WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");

err = -EINVAL;

break;

}

dentry = relay_create_buf_file(chan, chan->buf[i], i);

if (unlikely(!dentry)) {

err = -EINVAL;

break;

}

if (curr_cpu == i) {

local_irq_save(flags);

relay_set_buf_dentry(chan->buf[i], dentry);

local_irq_restore(flags);

} else {

disp.buf = chan->buf[i];

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;

}

/**

* 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++;

if (buf->dentry)

buf->dentry->d_inode->i_size +=

buf->chan->subbuf_size -

buf->padding[old_subbuf];

else

buf->early_bytes += buf->chan->subbuf_size -

buf->padding[old_subbuf];

smp_mb();

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.

*/

mod_timer(&buf->timer, jiffies + 1);

}

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.

*

* NOTE. Kernel clients don't need to call this function if the channel

* mode is 'overwrite'.

*/

void relay_subbufs_consumed(struct rchan *chan,

unsigned int cpu,

size_t subbufs_consumed)

{

struct rchan_buf *buf;

if (!chan)

return;

if (cpu >= NR_CPUS || !chan->buf[cpu] ||

subbufs_consumed > chan->n_subbufs)

return;

buf = chan->buf[cpu];

if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)

buf->subbufs_consumed = buf->subbufs_produced;

else

buf->subbufs_consumed += subbufs_consumed;

}

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)

{

unsigned int i;

if (!chan)

return;

mutex_lock(&relay_channels_mutex);

if (chan->is_global && chan->buf[0])

relay_close_buf(chan->buf[0]);

else

for_each_possible_cpu(i)

if (chan->buf[i])

relay_close_buf(chan->buf[i]);

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);

list_del(&chan->list);

kref_put(&chan->kref, relay_destroy_channel);

mutex_unlock(&relay_channels_mutex);

}

EXPORT_SYMBOL_GPL(relay_close);

/**

* relay_flush - close the channel

* @chan: the channel

*

* Flushes all channel buffers, i.e. forces buffer switch.

*/

void relay_flush(struct rchan *chan)

{

unsigned int i;

if (!chan)

return;

if (chan->is_global && chan->buf[0]) {

relay_switch_subbuf(chan->buf[0], 0);

return;

}

mutex_lock(&relay_channels_mutex);

for_each_possible_cpu(i)

if (chan->buf[i])

relay_switch_subbuf(chan->buf[i], 0);

mutex_unlock(&relay_channels_mutex);

}

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)

{

struct rchan_buf *buf = inode->i_private;

kref_get(&buf->kref);

filp->private_data = buf;

return nonseekable_open(inode, filp);

}

/**

* relay_file_mmap - mmap file op for relay files

* @filp: the file

* @vma: the vma describing what to map

*

* Calls upon relay_mmap_buf() to map the file into user space.

*/

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;

}

/*

* 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;

if (buf->subbufs_produced == buf->subbufs_consumed &&

buf->offset == buf->bytes_consumed)

return;

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;

if (!read_pos)

read_subbuf = buf->subbufs_consumed % n_subbufs;

else

read_subbuf = read_pos / buf->chan->subbuf_size;

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;

}

}

/*

* 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;

size_t produced = buf->subbufs_produced;

size_t consumed = buf->subbufs_consumed;

relay_file_read_consume(buf, read_pos, 0);

consumed = buf->subbufs_consumed;

if (unlikely(buf->offset > subbuf_size)) {

if (produced == consumed)

return 0;

return 1;

}

if (unlikely(produced - consumed >= n_subbufs)) {

consumed = produced - n_subbufs + 1;

buf->subbufs_consumed = consumed;

buf->bytes_consumed = 0;

}

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;