1 files changed, 431 insertions, 0 deletions

diff --git a/fs/relayfs/relay.c b/fs/relayfs/relay.c
new file mode 100644
index 000000000000..16446a15c96d
--- /dev/null
+++ b/fs/relayfs/relay.c
@@ -0,0 +1,431 @@
+/*
+ * 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)
+{
+}
+
+/* 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,
+};
+
+/**
+ *      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;
+
+        if (!chan)
+                return;
+
+        for (i = 0; i < NR_CPUS; i++) {
+                if (!chan->buf[i])
+                        continue;
+                __relay_reset(chan->buf[i], 0);
+        }
+}
+
+/**
+ *      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)
+{
+        struct rchan_buf *buf;
+        struct dentry *dentry;
+
+        /* Create file in fs */
+        dentry = relayfs_create_file(filename, parent, S_IRUSR, chan);
+        if (!dentry)
+                return NULL;
+
+        buf = RELAYFS_I(dentry->d_inode)->buf;
+        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;
+        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;
+
+        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);
+                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]);
+        }
+        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:
+        printk(KERN_WARNING "relayfs: event too large (%Zd)\n", length);
+        WARN_ON(1);
+        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;
+
+        if (!chan)
+                return;
+
+        for (i = 0; i < NR_CPUS; i++) {
+                if (!chan->buf[i])
+                        continue;
+                relay_close_buf(chan->buf[i]);
+        }
+
+        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;
+
+        if (!chan)
+                return;
+
+        for (i = 0; i < NR_CPUS; i++) {
+                if (!chan->buf[i])
+                        continue;
+                relay_switch_subbuf(chan->buf[i], 0);
+        }
+}
+
+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);