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431 lines
10 KiB
431 lines
10 KiB
/*
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* Public API and common code for RelayFS.
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*
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* See Documentation/filesystems/relayfs.txt for an overview of relayfs.
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*
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* Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
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* Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
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*
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* This file is released under the GPL.
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*/
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#include <linux/errno.h>
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#include <linux/stddef.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/string.h>
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#include <linux/relayfs_fs.h>
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#include "relay.h"
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#include "buffers.h"
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/**
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* relay_buf_empty - boolean, is the channel buffer empty?
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* @buf: channel buffer
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*
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* Returns 1 if the buffer is empty, 0 otherwise.
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*/
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int relay_buf_empty(struct rchan_buf *buf)
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{
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return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
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}
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/**
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* relay_buf_full - boolean, is the channel buffer full?
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* @buf: channel buffer
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*
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* Returns 1 if the buffer is full, 0 otherwise.
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*/
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int relay_buf_full(struct rchan_buf *buf)
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{
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size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
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return (ready >= buf->chan->n_subbufs) ? 1 : 0;
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}
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/*
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* High-level relayfs kernel API and associated functions.
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*/
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/*
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* rchan_callback implementations defining default channel behavior. Used
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* in place of corresponding NULL values in client callback struct.
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*/
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/*
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* subbuf_start() default callback. Does nothing.
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*/
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static int subbuf_start_default_callback (struct rchan_buf *buf,
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void *subbuf,
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void *prev_subbuf,
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size_t prev_padding)
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{
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if (relay_buf_full(buf))
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return 0;
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return 1;
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}
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/*
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* buf_mapped() default callback. Does nothing.
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*/
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static void buf_mapped_default_callback(struct rchan_buf *buf,
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struct file *filp)
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{
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}
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/*
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* buf_unmapped() default callback. Does nothing.
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*/
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static void buf_unmapped_default_callback(struct rchan_buf *buf,
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struct file *filp)
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{
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}
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/* relay channel default callbacks */
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static struct rchan_callbacks default_channel_callbacks = {
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.subbuf_start = subbuf_start_default_callback,
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.buf_mapped = buf_mapped_default_callback,
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.buf_unmapped = buf_unmapped_default_callback,
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};
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/**
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* wakeup_readers - wake up readers waiting on a channel
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* @private: the channel buffer
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*
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* This is the work function used to defer reader waking. The
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* reason waking is deferred is that calling directly from write
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* causes problems if you're writing from say the scheduler.
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*/
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static void wakeup_readers(void *private)
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{
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struct rchan_buf *buf = private;
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wake_up_interruptible(&buf->read_wait);
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}
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/**
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* __relay_reset - reset a channel buffer
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* @buf: the channel buffer
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* @init: 1 if this is a first-time initialization
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*
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* See relay_reset for description of effect.
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*/
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static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
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{
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size_t i;
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if (init) {
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init_waitqueue_head(&buf->read_wait);
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kref_init(&buf->kref);
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INIT_WORK(&buf->wake_readers, NULL, NULL);
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} else {
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cancel_delayed_work(&buf->wake_readers);
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flush_scheduled_work();
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}
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buf->subbufs_produced = 0;
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buf->subbufs_consumed = 0;
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buf->bytes_consumed = 0;
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buf->finalized = 0;
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buf->data = buf->start;
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buf->offset = 0;
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for (i = 0; i < buf->chan->n_subbufs; i++)
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buf->padding[i] = 0;
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buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
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}
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/**
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* relay_reset - reset the channel
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* @chan: the channel
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*
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* This has the effect of erasing all data from all channel buffers
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* and restarting the channel in its initial state. The buffers
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* are not freed, so any mappings are still in effect.
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*
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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.
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*/
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void relay_reset(struct rchan *chan)
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{
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unsigned int i;
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if (!chan)
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return;
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for (i = 0; i < NR_CPUS; i++) {
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if (!chan->buf[i])
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continue;
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__relay_reset(chan->buf[i], 0);
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}
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}
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/**
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* relay_open_buf - create a new channel buffer in relayfs
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*
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* Internal - used by relay_open().
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*/
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static struct rchan_buf *relay_open_buf(struct rchan *chan,
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const char *filename,
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struct dentry *parent)
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{
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struct rchan_buf *buf;
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struct dentry *dentry;
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/* Create file in fs */
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dentry = relayfs_create_file(filename, parent, S_IRUSR, chan);
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if (!dentry)
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return NULL;
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buf = RELAYFS_I(dentry->d_inode)->buf;
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buf->dentry = dentry;
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__relay_reset(buf, 1);
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return buf;
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}
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/**
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* relay_close_buf - close a channel buffer
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* @buf: channel buffer
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*
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* Marks the buffer finalized and restores the default callbacks.
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* The channel buffer and channel buffer data structure are then freed
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* automatically when the last reference is given up.
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*/
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static inline void relay_close_buf(struct rchan_buf *buf)
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{
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buf->finalized = 1;
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buf->chan->cb = &default_channel_callbacks;
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cancel_delayed_work(&buf->wake_readers);
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flush_scheduled_work();
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kref_put(&buf->kref, relay_remove_buf);
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}
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static inline void setup_callbacks(struct rchan *chan,
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struct rchan_callbacks *cb)
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{
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if (!cb) {
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chan->cb = &default_channel_callbacks;
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return;
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}
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if (!cb->subbuf_start)
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cb->subbuf_start = subbuf_start_default_callback;
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if (!cb->buf_mapped)
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cb->buf_mapped = buf_mapped_default_callback;
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if (!cb->buf_unmapped)
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cb->buf_unmapped = buf_unmapped_default_callback;
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chan->cb = cb;
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}
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/**
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* relay_open - create a new relayfs channel
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* @base_filename: base name of files to create
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* @parent: dentry of parent directory, NULL for root directory
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* @subbuf_size: size of sub-buffers
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* @n_subbufs: number of sub-buffers
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* @cb: client callback functions
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*
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* Returns channel pointer if successful, NULL otherwise.
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*
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* Creates a channel buffer for each cpu using the sizes and
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* attributes specified. The created channel buffer files
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* will be named base_filename0...base_filenameN-1. File
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* permissions will be S_IRUSR.
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*/
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struct rchan *relay_open(const char *base_filename,
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struct dentry *parent,
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size_t subbuf_size,
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size_t n_subbufs,
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struct rchan_callbacks *cb)
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{
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unsigned int i;
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struct rchan *chan;
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char *tmpname;
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if (!base_filename)
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return NULL;
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if (!(subbuf_size && n_subbufs))
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return NULL;
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chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
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if (!chan)
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return NULL;
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chan->version = RELAYFS_CHANNEL_VERSION;
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chan->n_subbufs = n_subbufs;
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chan->subbuf_size = subbuf_size;
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chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
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setup_callbacks(chan, cb);
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kref_init(&chan->kref);
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tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
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if (!tmpname)
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goto free_chan;
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for_each_online_cpu(i) {
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sprintf(tmpname, "%s%d", base_filename, i);
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chan->buf[i] = relay_open_buf(chan, tmpname, parent);
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chan->buf[i]->cpu = i;
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if (!chan->buf[i])
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goto free_bufs;
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}
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kfree(tmpname);
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return chan;
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free_bufs:
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for (i = 0; i < NR_CPUS; i++) {
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if (!chan->buf[i])
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break;
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relay_close_buf(chan->buf[i]);
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}
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kfree(tmpname);
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free_chan:
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kref_put(&chan->kref, relay_destroy_channel);
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return NULL;
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}
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/**
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* relay_switch_subbuf - switch to a new sub-buffer
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* @buf: channel buffer
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* @length: size of current event
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*
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* Returns either the length passed in or 0 if full.
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* Performs sub-buffer-switch tasks such as invoking callbacks,
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* updating padding counts, waking up readers, etc.
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*/
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size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
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{
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void *old, *new;
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size_t old_subbuf, new_subbuf;
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if (unlikely(length > buf->chan->subbuf_size))
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goto toobig;
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if (buf->offset != buf->chan->subbuf_size + 1) {
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buf->prev_padding = buf->chan->subbuf_size - buf->offset;
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old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
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buf->padding[old_subbuf] = buf->prev_padding;
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buf->subbufs_produced++;
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if (waitqueue_active(&buf->read_wait)) {
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PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
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schedule_delayed_work(&buf->wake_readers, 1);
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}
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}
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old = buf->data;
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new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
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new = buf->start + new_subbuf * buf->chan->subbuf_size;
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buf->offset = 0;
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if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
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buf->offset = buf->chan->subbuf_size + 1;
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return 0;
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}
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buf->data = new;
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buf->padding[new_subbuf] = 0;
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if (unlikely(length + buf->offset > buf->chan->subbuf_size))
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goto toobig;
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return length;
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toobig:
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printk(KERN_WARNING "relayfs: event too large (%Zd)\n", length);
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WARN_ON(1);
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return 0;
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}
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/**
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* relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
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* @chan: the channel
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* @cpu: the cpu associated with the channel buffer to update
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* @subbufs_consumed: number of sub-buffers to add to current buf's count
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*
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* Adds to the channel buffer's consumed sub-buffer count.
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* subbufs_consumed should be the number of sub-buffers newly consumed,
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* not the total consumed.
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*
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* NOTE: kernel clients don't need to call this function if the channel
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* mode is 'overwrite'.
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*/
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void relay_subbufs_consumed(struct rchan *chan,
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unsigned int cpu,
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size_t subbufs_consumed)
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{
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struct rchan_buf *buf;
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if (!chan)
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return;
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if (cpu >= NR_CPUS || !chan->buf[cpu])
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return;
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buf = chan->buf[cpu];
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buf->subbufs_consumed += subbufs_consumed;
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if (buf->subbufs_consumed > buf->subbufs_produced)
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buf->subbufs_consumed = buf->subbufs_produced;
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}
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/**
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* relay_destroy_channel - free the channel struct
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*
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* Should only be called from kref_put().
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*/
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void relay_destroy_channel(struct kref *kref)
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{
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struct rchan *chan = container_of(kref, struct rchan, kref);
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kfree(chan);
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}
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/**
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* relay_close - close the channel
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* @chan: the channel
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*
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* Closes all channel buffers and frees the channel.
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*/
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void relay_close(struct rchan *chan)
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{
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unsigned int i;
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if (!chan)
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return;
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for (i = 0; i < NR_CPUS; i++) {
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if (!chan->buf[i])
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continue;
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relay_close_buf(chan->buf[i]);
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}
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kref_put(&chan->kref, relay_destroy_channel);
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}
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/**
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* relay_flush - close the channel
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* @chan: the channel
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*
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* Flushes all channel buffers i.e. forces buffer switch.
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*/
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void relay_flush(struct rchan *chan)
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{
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unsigned int i;
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if (!chan)
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return;
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for (i = 0; i < NR_CPUS; i++) {
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if (!chan->buf[i])
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continue;
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relay_switch_subbuf(chan->buf[i], 0);
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}
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}
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EXPORT_SYMBOL_GPL(relay_open);
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EXPORT_SYMBOL_GPL(relay_close);
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EXPORT_SYMBOL_GPL(relay_flush);
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EXPORT_SYMBOL_GPL(relay_reset);
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EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
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EXPORT_SYMBOL_GPL(relay_switch_subbuf);
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EXPORT_SYMBOL_GPL(relay_buf_full);
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