[NETFILTER] Fix Kconfig menu level for x_tables

[firewire-audio.git] / fs / relayfs / relay.c

/*
 * Public API and common code for RelayFS.
 *
 * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
 *
 * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
 * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
 *
 * This file is released under the GPL.
 */

#include <linux/errno.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/relayfs_fs.h>
#include "relay.h"
#include "buffers.h"

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

/*
 * High-level relayfs 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.  Creates file to represent buf.
 */
static struct dentry *create_buf_file_default_callback(const char *filename,
                                                       struct dentry *parent,
                                                       int mode,
                                                       struct rchan_buf *buf,
                                                       int *is_global)
{
        return relayfs_create_file(filename, parent, mode,
                                   &relay_file_operations, buf);
}

/*
 * remove_buf_file() default callback.  Removes file representing relay buffer.
 */
static int remove_buf_file_default_callback(struct dentry *dentry)
{
        return relayfs_remove(dentry);
}

/* 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
 *      @private: the channel buffer
 *
 *      This is the work function used to defer reader waking.  The
 *      reason waking is deferred is that calling directly from write
 *      causes problems if you're writing from say the scheduler.
 */
static void wakeup_readers(void *private)
{
        struct rchan_buf *buf = private;
        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 inline 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_WORK(&buf->wake_readers, NULL, NULL);
        } else {
                cancel_delayed_work(&buf->wake_readers);
                flush_scheduled_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);
}

/**
 *      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;
        struct rchan_buf *prev = NULL;

        if (!chan)
                return;

        for (i = 0; i < NR_CPUS; i++) {
                if (!chan->buf[i] || chan->buf[i] == prev)
                        break;
                __relay_reset(chan->buf[i], 0);
                prev = chan->buf[i];
        }
}

/**
 *      relay_open_buf - create a new channel buffer in relayfs
 *
 *      Internal - used by relay_open().
 */
static struct rchan_buf *relay_open_buf(struct rchan *chan,
                                        const char *filename,
                                        struct dentry *parent,
                                        int *is_global)
{
        struct rchan_buf *buf;
        struct dentry *dentry;

        if (*is_global)
                return chan->buf[0];

        buf = relay_create_buf(chan);
        if (!buf)
                return NULL;

        /* Create file in fs */
        dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR,
                                           buf, is_global);
        if (!dentry) {
                relay_destroy_buf(buf);
                return NULL;
        }

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

        return buf;
}

/**
 *      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 inline void relay_close_buf(struct rchan_buf *buf)
{
        buf->finalized = 1;
        buf->chan->cb = &default_channel_callbacks;
        cancel_delayed_work(&buf->wake_readers);
        flush_scheduled_work();
        kref_put(&buf->kref, relay_remove_buf);
}

static inline 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_open - create a new relayfs channel
 *      @base_filename: base name of files to create
 *      @parent: dentry of parent directory, NULL for root directory
 *      @subbuf_size: size of sub-buffers
 *      @n_subbufs: number of sub-buffers
 *      @cb: client callback functions
 *
 *      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)
{
        unsigned int i;
        struct rchan *chan;
        char *tmpname;
        int is_global = 0;

        if (!base_filename)
                return NULL;

        if (!(subbuf_size && n_subbufs))
                return NULL;

        chan = kcalloc(1, 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);
        setup_callbacks(chan, cb);
        kref_init(&chan->kref);

        tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
        if (!tmpname)
                goto free_chan;

        for_each_online_cpu(i) {
                sprintf(tmpname, "%s%d", base_filename, i);
                chan->buf[i] = relay_open_buf(chan, tmpname, parent,
                                              &is_global);
                chan->buf[i]->cpu = i;
                if (!chan->buf[i])
                        goto free_bufs;
        }

        kfree(tmpname);
        return chan;

free_bufs:
        for (i = 0; i < NR_CPUS; i++) {
                if (!chan->buf[i])
                        break;
                relay_close_buf(chan->buf[i]);
                if (is_global)
                        break;
        }
        kfree(tmpname);

free_chan:
        kref_put(&chan->kref, relay_destroy_channel);
        return NULL;
}

/**
 *      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 (waitqueue_active(&buf->read_wait)) {
                        PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
                        schedule_delayed_work(&buf->wake_readers, 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;
}

/**
 *      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])
                return;

        buf = chan->buf[cpu];
        buf->subbufs_consumed += subbufs_consumed;
        if (buf->subbufs_consumed > buf->subbufs_produced)
                buf->subbufs_consumed = buf->subbufs_produced;
}

/**
 *      relay_destroy_channel - free the channel struct
 *
 *      Should only be called from kref_put().
 */
void relay_destroy_channel(struct kref *kref)
{
        struct rchan *chan = container_of(kref, struct rchan, kref);
        kfree(chan);
}

/**
 *      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;
        struct rchan_buf *prev = NULL;

        if (!chan)
                return;

        for (i = 0; i < NR_CPUS; i++) {
                if (!chan->buf[i] || chan->buf[i] == prev)
                        break;
                relay_close_buf(chan->buf[i]);
                prev = chan->buf[i];
        }

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

        kref_put(&chan->kref, relay_destroy_channel);
}

/**
 *      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;
        struct rchan_buf *prev = NULL;

        if (!chan)
                return;

        for (i = 0; i < NR_CPUS; i++) {
                if (!chan->buf[i] || chan->buf[i] == prev)
                        break;
                relay_switch_subbuf(chan->buf[i], 0);
                prev = chan->buf[i];
        }
}

EXPORT_SYMBOL_GPL(relay_open);
EXPORT_SYMBOL_GPL(relay_close);
EXPORT_SYMBOL_GPL(relay_flush);
EXPORT_SYMBOL_GPL(relay_reset);
EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
EXPORT_SYMBOL_GPL(relay_switch_subbuf);
EXPORT_SYMBOL_GPL(relay_buf_full);