This abstracts the core parts needed for relay channel buffer management
out of relayfs. With relay_file_operations exported, we can trivially
support relay channels through other file systems (like sysfs and
debugfs).
While we're at it, get rid of some of the outstanding relayfs references
from the code, as there's nothing file system dependent in the new relay
abstraction.
Signed-off-by: Paul Mundt <[email protected]>
---
include/linux/relayfs_fs.h | 3
init/Kconfig | 11 +
kernel/Makefile | 1
kernel/relay.c | 919 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 934 insertions(+), 0 deletions(-)
create mode 100644 kernel/relay.c
7bf637f67e20f807d5c7ee42390a12bee64b6273
diff --git a/include/linux/relayfs_fs.h b/include/linux/relayfs_fs.h
index 7342e66..435ebb1 100644
--- a/include/linux/relayfs_fs.h
+++ b/include/linux/relayfs_fs.h
@@ -19,6 +19,9 @@
#include <linux/poll.h>
#include <linux/kref.h>
+/* Needs a _much_ better name... */
+#define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
+
/*
* Tracks changes to rchan/rchan_buf structs
*/
diff --git a/init/Kconfig b/init/Kconfig
index 38416a1..fb74fdd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -214,6 +214,17 @@ config CPUSETS
Say N if unsure.
+config RELAY
+ bool "Kernel->user space relay support (formerly relayfs)"
+ help
+ This option enables support for relay interface support in
+ certain file systems (such as sysfs, and trivially debugfs).
+ It is designed to provide an efficient mechanism for tools and
+ facilities to relay large amounts of data from kernel space to
+ user space.
+
+ If unsure, say N.
+
source "usr/Kconfig"
config UID16
diff --git a/kernel/Makefile b/kernel/Makefile
index 4ae0fbd..aebd7a7 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_RELAY) += relay.o
ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <[email protected]>, the -fno-omit-frame-pointer is
diff --git a/kernel/relay.c b/kernel/relay.c
new file mode 100644
index 0000000..7dd674b
--- /dev/null
+++ b/kernel/relay.c
@@ -0,0 +1,919 @@
+/*
+ * Public API and common code for kernel->userspace relay file support.
+ *
+ * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
+ *
+ * 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.
+ *
+ * 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 <linux/vmalloc.h>
+#include <linux/mm.h>
+
+/*
+ * 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);
+}
+
+/*
+ * nopage() vm_op implementation for relay file mapping.
+ */
+static struct page *relay_buf_nopage(struct vm_area_struct *vma,
+ unsigned long address,
+ int *type)
+{
+ struct page *page;
+ struct rchan_buf *buf = vma->vm_private_data;
+ unsigned long offset = address - vma->vm_start;
+
+ if (address > vma->vm_end)
+ return NOPAGE_SIGBUS; /* Disallow mremap */
+ if (!buf)
+ return NOPAGE_OOM;
+
+ page = vmalloc_to_page(buf->start + offset);
+ if (!page)
+ return NOPAGE_OOM;
+ get_page(page);
+
+ if (type)
+ *type = VM_FAULT_MINOR;
+
+ return page;
+}
+
+/*
+ * vm_ops for relay file mappings.
+ */
+static struct vm_operations_struct relay_file_mmap_ops = {
+ .nopage = relay_buf_nopage,
+ .close = relay_file_mmap_close,
+};
+
+/**
+ * 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.
+ */
+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_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
+ */
+static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size)
+{
+ void *mem;
+ unsigned int i, j, n_pages;
+
+ size = PAGE_ALIGN(size);
+ n_pages = size >> PAGE_SHIFT;
+
+ buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
+ 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;
+ }
+ 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]);
+ kfree(buf->page_array);
+ return NULL;
+}
+
+/**
+ * relay_create_buf - allocate and initialize a channel buffer
+ * @alloc_size: size of the buffer to allocate
+ * @n_subbufs: number of sub-buffers in the channel
+ *
+ * Returns channel buffer if successful, NULL otherwise
+ */
+struct rchan_buf *relay_create_buf(struct rchan *chan)
+{
+ struct rchan_buf *buf = kcalloc(1, 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
+ *
+ * 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_destroy_buf - destroy an rchan_buf struct and associated buffer
+ * @buf: the buffer struct
+ */
+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]);
+ kfree(buf->page_array);
+ }
+ kfree(buf->padding);
+ kfree(buf);
+ kref_put(&chan->kref, relay_destroy_channel);
+}
+
+/**
+ * relay_remove_buf - remove a channel 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().
+ */
+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.
+ */
+int relay_buf_empty(struct rchan_buf *buf)
+{
+ return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
+}
+EXPORT_SYMBOL_GPL(relay_buf_empty);
+
+/**
+ * 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. 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 NULL;
+}
+
+/*
+ * remove_buf_file() default callback. Removes file representing relay buffer.
+ */
+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
+ * @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];
+ }
+}
+EXPORT_SYMBOL_GPL(relay_reset);
+
+/**
+ * relay_open_buf - create a new relay channel buffer
+ *
+ * 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 relay 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;
+}
+EXPORT_SYMBOL_GPL(relay_open);
+
+/**
+ * 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;
+}
+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])
+ return;
+
+ buf = chan->buf[cpu];
+ buf->subbufs_consumed += subbufs_consumed;
+ if (buf->subbufs_consumed > buf->subbufs_produced)
+ buf->subbufs_consumed = buf->subbufs_produced;
+}
+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;
+ 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 "relay: 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);
+}
+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;
+ 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_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->u.generic_ip;
+ kref_get(&buf->kref);
+ filp->private_data = buf;
+
+ return 0;
+}
+
+/**
+ * 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->bytes_consumed + bytes_consumed > subbuf_size) {
+ relay_subbufs_consumed(buf->chan, buf->cpu, 1);
+ buf->bytes_consumed = 0;
+ }
+
+ buf->bytes_consumed += bytes_consumed;
+ 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 bytes_produced, bytes_consumed, write_offset;
+ size_t subbuf_size = buf->chan->subbuf_size;
+ size_t n_subbufs = buf->chan->n_subbufs;
+ size_t produced = buf->subbufs_produced % n_subbufs;
+ size_t consumed = buf->subbufs_consumed % n_subbufs;
+
+ write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+
+ if (consumed > produced) {
+ if ((produced > n_subbufs) &&
+ (produced + n_subbufs - consumed <= n_subbufs))
+ produced += n_subbufs;
+ } else if (consumed == produced) {
+ if (buf->offset > subbuf_size) {
+ produced += n_subbufs;
+ if (buf->subbufs_produced == buf->subbufs_consumed)
+ consumed += n_subbufs;
+ }
+ }
+
+ if (buf->offset > subbuf_size)
+ bytes_produced = (produced - 1) * subbuf_size + write_offset;
+ else
+ bytes_produced = produced * subbuf_size + write_offset;
+ bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;
+
+ if (bytes_produced == bytes_consumed)
+ return 0;
+
+ relay_file_read_consume(buf, read_pos, 0);
+
+ return 1;
+}
+
+/**
+ * relay_file_read_subbuf_avail - return bytes available in sub-buffer
+ */
+static size_t relay_file_read_subbuf_avail(size_t read_pos,
+ struct rchan_buf *buf)
+{
+ size_t padding, avail = 0;
+ size_t read_subbuf, read_offset, write_subbuf, write_offset;
+ size_t subbuf_size = buf->chan->subbuf_size;
+
+ write_subbuf = (buf->data - buf->start) / subbuf_size;
+ write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+ read_subbuf = read_pos / subbuf_size;
+ read_offset = read_pos % subbuf_size;
+ padding = buf->padding[read_subbuf];
+
+ if (read_subbuf == write_subbuf) {
+ if (read_offset + padding < write_offset)
+ avail = write_offset - (read_offset + padding);
+ } else
+ avail = (subbuf_size - padding) - read_offset;
+
+ return avail;
+}
+
+/**
+ * relay_file_read_start_pos - find the first available byte to read
+ *
+ * If the read_pos is in the middle of padding, return the
+ * position of the first actually available byte, otherwise
+ * return the original value.
+ */
+static size_t relay_file_read_start_pos(size_t read_pos,
+ struct rchan_buf *buf)
+{
+ size_t read_subbuf, padding, padding_start, padding_end;
+ size_t subbuf_size = buf->chan->subbuf_size;
+ size_t n_subbufs = buf->chan->n_subbufs;
+
+ read_subbuf = read_pos / subbuf_size;
+ padding = buf->padding[read_subbuf];
+ padding_start = (read_subbuf + 1) * subbuf_size - padding;
+ padding_end = (read_subbuf + 1) * subbuf_size;
+ if (read_pos >= padding_start && read_pos < padding_end) {
+ read_subbuf = (read_subbuf + 1) % n_subbufs;
+ read_pos = read_subbuf * subbuf_size;
+ }
+
+ return read_pos;
+}
+
+/**
+ * relay_file_read_end_pos - return the new read position
+ */
+static size_t relay_file_read_end_pos(struct rchan_buf *buf,
+ size_t read_pos,
+ size_t count)
+{
+ size_t read_subbuf, padding, end_pos;
+ size_t subbuf_size = buf->chan->subbuf_size;
+ size_t n_subbufs = buf->chan->n_subbufs;
+
+ read_subbuf = read_pos / subbuf_size;
+ padding = buf->padding[read_subbuf];
+ if (read_pos % subbuf_size + count + padding == subbuf_size)
+ end_pos = (read_subbuf + 1) * subbuf_size;
+ else
+ end_pos = read_pos + count;
+ if (end_pos >= subbuf_size * n_subbufs)
+ end_pos = 0;
+
+ return end_pos;
+}
+
+/**
+ * relay_file_read - read file op for relay files
+ * @filp: the file
+ * @buffer: the userspace buffer
+ * @count: number of bytes to read
+ * @ppos: position to read from
+ *
+ * Reads count bytes or the number of bytes available in the
+ * current sub-buffer being read, whichever is smaller.
+ */
+static ssize_t relay_file_read(struct file *filp,
+ char __user *buffer,
+ size_t count,
+ loff_t *ppos)
+{
+ struct rchan_buf *buf = filp->private_data;
+ struct inode *inode = filp->f_dentry->d_inode;
+ size_t read_start, avail;
+ ssize_t ret = 0;
+ void *from;
+
+ mutex_lock(&inode->i_mutex);
+ if(!relay_file_read_avail(buf, *ppos))
+ goto out;
+
+ read_start = relay_file_read_start_pos(*ppos, buf);
+ avail = relay_file_read_subbuf_avail(read_start, buf);
+ if (!avail)
+ goto out;
+
+ from = buf->start + read_start;
+ ret = count = min(count, avail);
+ if (copy_to_user(buffer, from, count)) {
+ ret = -EFAULT;
+ goto out;
+ }
+ relay_file_read_consume(buf, read_start, count);
+ *ppos = relay_file_read_end_pos(buf, read_start, count);
+out:
+ mutex_unlock(&inode->i_mutex);
+ return ret;
+}
+
+struct file_operations relay_file_operations = {
+ .open = relay_file_open,
+ .poll = relay_file_poll,
+ .mmap = relay_file_mmap,
+ .read = relay_file_read,
+ .llseek = no_llseek,
+ .release = relay_file_release,
+};
+EXPORT_SYMBOL_GPL(relay_file_operations);
--
1.2.0.geb68
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