Hi,
Here's the latest relayfs patch, incorporating the previous round of
suggestions. Thanks to everyone who sent comments. Here's a list of
the major changes:
- replaced remap_page_range() and reserved bits with a nopage()
handler.
- buffers are now allocated/freed as part of inode alloc/destroy.
- got rid of the automatic creation/teardown of directory hierarchies,
and exported create/remove dir functions instead.
- replaced the fileop callback with explicit map/unmap callbacks - these
were the only fileops currently being used by anything, so I got rid
of the other cases.
- relay_write() and __relay_write() no longer return a value - it
doesn't really make sense for clients to check a return value in the
fast path anyway.
- added a buf_full() callback to notify users that a buffer has become
full and therefore events might be lost.
- got rid of the 'helper' macros, which weren't helping much.
- various other bits of code and comment cleanup.
Also, there was some question as to whether or not the memcpy in
relay_write() was being inlined properly - I looked at the generated
assembly code, and it seems to be, but I'll be taking a closer look
later.
This is what the API now looks like:
API functions:
rchan *relay_open(base_filename, parent, subbuf_size, n_subbufs,
flags, callbacks);
void relay_close(chan);
dentry *relayfs_create_dir(name, parent);
int relayfs_remove_dir(dentry);
void relay_reset(chan);
void relay_write(chan, data, length);
void __relay_write(chan, data, length);
void *relay_reserve(chan, length);
void relay_subbufs_consumed(chan, subbufs_consumed, cpu);
void relay_commit(buf, subbuf_idx, count);
callbacks:
int subbuf_start(buf, subbuf, prev_subbuf_idx);
int deliver(buffer, subbuf, subbuf_idx);
void buf_mapped(buf, filp);
void buf_unmapped(buf, filp);
void buf_full(buf);
As before, I've tested this code on a single proc machine using a
hacked version of the kprobes network packet tracing module, which can
be found here:
http://prdownloads.sourceforge.net/dprobes/plog.tar.gz?download
If people are more or less happy with the current version, I'll do
some SMP testing and write some Documentation.
Thanks,
Tom
Signed-off-by: Tom Zanussi <[email protected]>
fs/Kconfig | 12
fs/Makefile | 1
fs/relayfs/Makefile | 4
fs/relayfs/buffers.c | 119 ++++++++
fs/relayfs/buffers.h | 14 +
fs/relayfs/inode.c | 447 ++++++++++++++++++++++++++++++++
fs/relayfs/relay.c | 616 +++++++++++++++++++++++++++++++++++++++++++++
fs/relayfs/relay.h | 31 ++
include/linux/relayfs_fs.h | 253 ++++++++++++++++++
9 files changed, 1497 insertions(+)
diff -urpN -X dontdiff linux-2.6.10/fs/Kconfig linux-2.6.10-cur/fs/Kconfig
--- linux-2.6.10/fs/Kconfig 2004-12-24 15:34:58.000000000 -0600
+++ linux-2.6.10-cur/fs/Kconfig 2005-01-31 21:49:27.000000000 -0600
@@ -972,6 +972,18 @@ config RAMFS
To compile this as a module, choose M here: the module will be called
ramfs.
+config RELAYFS_FS
+ tristate "Relayfs file system support"
+ ---help---
+ Relayfs is a high-speed data relay filesystem designed to provide
+ an efficient mechanism for tools and facilities to relay large
+ amounts of data from kernel space to user space.
+
+ To compile this code as a module, choose M here: the module will be
+ called relayfs.
+
+ If unsure, say N.
+
endmenu
menu "Miscellaneous filesystems"
diff -urpN -X dontdiff linux-2.6.10/fs/Makefile linux-2.6.10-cur/fs/Makefile
--- linux-2.6.10/fs/Makefile 2004-12-24 15:34:58.000000000 -0600
+++ linux-2.6.10-cur/fs/Makefile 2005-01-31 21:49:27.000000000 -0600
@@ -94,3 +94,4 @@ obj-$(CONFIG_AFS_FS) += afs/
obj-$(CONFIG_BEFS_FS) += befs/
obj-$(CONFIG_HOSTFS) += hostfs/
obj-$(CONFIG_HPPFS) += hppfs/
+obj-$(CONFIG_RELAYFS_FS) += relayfs/
diff -urpN -X dontdiff linux-2.6.10/fs/relayfs/Makefile linux-2.6.10-cur/fs/relayfs/Makefile
--- linux-2.6.10/fs/relayfs/Makefile 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/fs/relayfs/Makefile 2005-02-03 06:34:11.000000000 -0600
@@ -0,0 +1,4 @@
+obj-$(CONFIG_RELAYFS_FS) += relayfs.o
+
+relayfs-y := relay.o buffers.o inode.o
+
diff -urpN -X dontdiff linux-2.6.10/fs/relayfs/buffers.c linux-2.6.10-cur/fs/relayfs/buffers.c
--- linux-2.6.10/fs/relayfs/buffers.c 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/fs/relayfs/buffers.c 2005-02-03 08:16:39.000000000 -0600
@@ -0,0 +1,119 @@
+/*
+ * RelayFS buffer management code.
+ *
+ * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp
+ * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected])
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include "buffers.h"
+
+/**
+ * alloc_page_array - alloc array to hold pages, but not pages
+ * @size: the total size of the memory represented by the page array
+ * @page_count: the number of pages the array can hold
+ *
+ * Returns a pointer to the page array if successful, NULL otherwise.
+ */
+static inline struct page **alloc_page_array(int size, int *page_count)
+{
+ int n_pages;
+ struct page **page_array;
+
+ size = PAGE_ALIGN(size);
+ n_pages = size >> PAGE_SHIFT;
+
+ page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
+ if (!page_array)
+ return NULL;
+ *page_count = n_pages;
+
+ return page_array;
+}
+
+/**
+ * depopulate_page_array - free and unreserve all pages in the array
+ * @page_array: pointer to the page array
+ * @page_count: number of pages to free
+ */
+static void depopulate_page_array(struct page **page_array, int page_count)
+{
+ int i;
+
+ for (i = 0; i < page_count; i++)
+ __free_page(page_array[i]);
+}
+
+/**
+ * populate_page_array - allocate and reserve pages
+ * @page_array: pointer to the page array
+ * @page_count: number of pages to allocate
+ *
+ * Returns 0 if successful, negative otherwise.
+ */
+static int populate_page_array(struct page **page_array, int page_count)
+{
+ int i;
+
+ for (i = 0; i < page_count; i++) {
+ page_array[i] = alloc_page(GFP_KERNEL);
+ if (unlikely(!page_array[i])) {
+ depopulate_page_array(page_array, i);
+ return -ENOMEM;
+ }
+ }
+ return 0;
+}
+
+/**
+ * relay_alloc_rchan_buf - allocate a channel buffer
+ * @size: total size of the buffer
+ * @page_array: receives a pointer to the buffer's page array
+ * @page_count: receives the number of pages allocated
+ *
+ * Returns a pointer to the resulting buffer, NULL if unsuccessful
+ */
+void *relay_alloc_rchan_buf(unsigned long size, struct page ***page_array,
+ int *page_count)
+{
+ void *mem;
+
+ *page_array = alloc_page_array(size, page_count);
+ if (!*page_array)
+ return NULL;
+
+ if (populate_page_array(*page_array, *page_count)) {
+ kfree(*page_array);
+ *page_array = NULL;
+ return NULL;
+ }
+
+ mem = vmap(*page_array, *page_count, GFP_KERNEL, PAGE_KERNEL);
+ if (!mem) {
+ depopulate_page_array(*page_array, *page_count);
+ kfree(*page_array);
+ *page_array = NULL;
+ return NULL;
+ }
+ memset(mem, 0, size);
+
+ return mem;
+}
+
+/**
+ * relay_free_rchan_buf - free a channel buffer
+ * @buf: pointer to the buffer to free
+ * @page_array: pointer to the buffer's page array
+ * @page_count: number of pages in page array
+ */
+void relay_free_rchan_buf(void *buf, struct page **page_array,
+ int page_count)
+{
+ vunmap(buf);
+ depopulate_page_array(page_array, page_count);
+ kfree(page_array);
+}
diff -urpN -X dontdiff linux-2.6.10/fs/relayfs/buffers.h linux-2.6.10-cur/fs/relayfs/buffers.h
--- linux-2.6.10/fs/relayfs/buffers.h 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/fs/relayfs/buffers.h 2005-01-31 21:49:27.000000000 -0600
@@ -0,0 +1,14 @@
+#ifndef _BUFFERS_H
+#define _BUFFERS_H
+
+/* This inspired by rtai/shmem */
+#define FIX_SIZE(x) (((x) - 1) & PAGE_MASK) + PAGE_SIZE
+
+extern void *relay_alloc_rchan_buf(unsigned long size,
+ struct page ***page_array,
+ int *page_count);
+extern void relay_free_rchan_buf(void *buf,
+ struct page **page_array,
+ int page_count);
+
+#endif/* _BUFFERS_H */
diff -urpN -X dontdiff linux-2.6.10/fs/relayfs/inode.c linux-2.6.10-cur/fs/relayfs/inode.c
--- linux-2.6.10/fs/relayfs/inode.c 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/fs/relayfs/inode.c 2005-02-06 00:22:18.000000000 -0600
@@ -0,0 +1,447 @@
+/*
+ * VFS-related code for RelayFS, a high-speed data relay filesystem.
+ *
+ * Copyright (C) 2003 - Tom Zanussi <[email protected]>, IBM Corp
+ * Copyright (C) 2003 - Karim Yaghmour <[email protected]>
+ *
+ * Based on ramfs, Copyright (C) 2002 - Linus Torvalds
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/backing-dev.h>
+#include <linux/namei.h>
+#include <linux/poll.h>
+#include <linux/relayfs_fs.h>
+#include "relay.h"
+
+#define RELAYFS_MAGIC 0x26F82121
+
+static struct vfsmount * relayfs_mount;
+static int relayfs_mount_count;
+static kmem_cache_t * relayfs_inode_cachep;
+
+static struct backing_dev_info relayfs_backing_dev_info = {
+ .ra_pages = 0, /* No readahead */
+ .memory_backed = 1, /* Does not contribute to dirty memory */
+};
+
+static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
+ struct rchan *chan)
+{
+ struct rchan_buf *buf = NULL;
+ struct inode *inode;
+
+ if (S_ISREG(mode)) {
+ BUG_ON(!chan);
+ buf = rchan_create_buf(chan);
+ if (!buf)
+ return NULL;
+ }
+
+ inode = new_inode(sb);
+ if (!inode) {
+ rchan_destroy_buf(buf);
+ return NULL;
+ }
+
+ inode->i_mode = mode;
+ inode->i_uid = 0;
+ inode->i_gid = 0;
+ inode->i_blksize = PAGE_CACHE_SIZE;
+ inode->i_blocks = 0;
+ inode->i_mapping->backing_dev_info = &relayfs_backing_dev_info;
+ inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ switch (mode & S_IFMT) {
+ case S_IFREG:
+ inode->i_fop = &relayfs_file_operations;
+ RELAYFS_I(inode)->buf = buf;
+ break;
+ case S_IFDIR:
+ inode->i_op = &simple_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+
+ /* directory inodes start off with i_nlink == 2 (for "." entry) */
+ inode->i_nlink++;
+ break;
+ default:
+ break;
+ }
+
+ return inode;
+}
+
+/**
+ * relayfs_create_entry - create a relayfs directory or file
+ * @name: the name of the file to create
+ * @parent: parent directory
+ * @mode: mode
+ * @chan: relay channel associated with the file
+ * @dentry: result dentry
+ *
+ * Creates a file or directory with the specifed permissions.
+ */
+static int relayfs_create_entry(const char *name, struct dentry *parent,
+ int mode, struct rchan *chan,
+ struct dentry **dentry)
+{
+ struct qstr qname;
+ struct dentry *d;
+ struct inode *inode;
+ int error = 0;
+
+ BUG_ON(!(S_ISREG(mode) || S_ISDIR(mode)));
+
+ error = simple_pin_fs("relayfs", &relayfs_mount, &relayfs_mount_count);
+ if (error) {
+ printk(KERN_ERR "Couldn't mount relayfs: errcode %d\n", error);
+ return error;
+ }
+
+ qname.name = name;
+ qname.len = strlen(name);
+ qname.hash = full_name_hash(name, qname.len);
+
+ if (!parent)
+ if (relayfs_mount && relayfs_mount->mnt_sb)
+ parent = relayfs_mount->mnt_sb->s_root;
+
+ if (!parent) {
+ simple_release_fs(&relayfs_mount, &relayfs_mount_count);
+ return -EINVAL;
+ }
+
+ parent = dget(parent);
+ down(&parent->d_inode->i_sem);
+ d = lookup_hash(&qname, parent);
+ if (IS_ERR(d)) {
+ error = PTR_ERR(d);
+ goto release_mount;
+ }
+
+ if (d->d_inode) {
+ error = -EEXIST;
+ goto release_mount;
+ }
+
+ inode = relayfs_get_inode(parent->d_inode->i_sb, mode, chan);
+ if (!inode) {
+ error = -ENOSPC;
+ goto release_mount;
+ }
+
+ d_instantiate(d, inode);
+ dget(d); /* Extra count - pin the dentry in core */
+
+ if (S_ISDIR(mode))
+ parent->d_inode->i_nlink++;
+
+ goto exit;
+
+release_mount:
+ simple_release_fs(&relayfs_mount, &relayfs_mount_count);
+
+exit:
+ *dentry = d;
+ up(&parent->d_inode->i_sem);
+ dput(parent);
+
+ return error;
+}
+
+/**
+ * relayfs_create_file - create a file in the relay filesystem
+ * @name: the name of the file to create
+ * @parent: parent directory
+ * @mode: mode, if not specied the default perms are used
+ * @chan: channel associated with the file
+ *
+ * Returns file dentry if successful, NULL otherwise.
+ *
+ * The file will be created user r on behalf of current user.
+ */
+struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
+ int mode, struct rchan *chan)
+{
+ struct dentry *dentry;
+ int error;
+
+ if (!mode)
+ mode = S_IRUSR;
+ mode = (mode & S_IALLUGO) | S_IFREG;
+
+ error = relayfs_create_entry(name, parent, mode, chan, &dentry);
+ if (error)
+ return NULL;
+
+ return dentry;
+}
+
+/**
+ * relayfs_create_dir - create a directory in the relay filesystem
+ * @name: the name of the directory to create
+ * @parent: parent directory, NULL if parent should be fs root
+ *
+ * Returns directory dentry if successful, NULL otherwise.
+ *
+ * The directory will be created world rwx on behalf of current user.
+ */
+struct dentry *relayfs_create_dir(const char *name, struct dentry *parent)
+{
+ int error;
+ struct dentry *dentry = NULL;
+ int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+
+ if (!name)
+ return NULL;
+
+ error = relayfs_create_entry(name, parent, mode, NULL, &dentry);
+ if (error)
+ return NULL;
+
+ return dentry;
+}
+
+/**
+ * relayfs_remove - remove a file or directory in the relay filesystem
+ * @dentry: file or directory dentry
+ */
+int relayfs_remove(struct dentry *dentry)
+{
+ struct dentry *parent = dentry->d_parent;
+
+ if (!parent)
+ return -EINVAL;
+
+ parent = dget(parent);
+ down(&parent->d_inode->i_sem);
+ if (dentry->d_inode) {
+ simple_unlink(parent->d_inode, dentry);
+ d_delete(dentry);
+ }
+ dput(dentry);
+ up(&parent->d_inode->i_sem);
+ dput(parent);
+
+ simple_release_fs(&relayfs_mount, &relayfs_mount_count);
+
+ return 0;
+}
+
+/**
+ * relayfs_remove_dir - remove a directory in the relay filesystem
+ * @dentry: directory dentry
+ *
+ * Returns 0 if successful, negative otherwise.
+ */
+int relayfs_remove_dir(struct dentry *dentry)
+{
+ if (!dentry)
+ return -EINVAL;
+
+ return relayfs_remove(dentry);
+}
+
+/**
+ * relayfs_open - open file op for relayfs files
+ * @inode: the inode
+ * @filp: the file
+ *
+ * Associates the channel buffer with the file, and increments the
+ * channel buffer refcount.
+ */
+int relayfs_open(struct inode *inode, struct file *filp)
+{
+ struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+ kref_get(&buf->kref);
+
+ return 0;
+}
+
+/**
+ * relayfs_mmap - mmap file op for relayfs files
+ * @filp: the file
+ * @vma: the vma describing what to map
+ *
+ * Calls upon relay_mmap_buffer to map the file into user space.
+ */
+int relayfs_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+ struct inode *inode = filp->f_dentry->d_inode;
+ struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+
+ return relay_mmap_buffer(buf, vma);
+}
+
+/**
+ * relayfs_poll - poll file op for relayfs files
+ * @filp: the file
+ * @wait: poll table
+ *
+ * Poll implemention.
+ */
+unsigned int relayfs_poll(struct file *filp, poll_table *wait)
+{
+ unsigned int mask = 0;
+ struct inode *inode = filp->f_dentry->d_inode;
+ struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+
+ 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;
+}
+
+/**
+ * relayfs_release - release file op for relayfs files
+ * @inode: the inode
+ * @filp: the file
+ *
+ * Decrements the channel refcount, as the filesystem is
+ * no longer using it.
+ */
+int relayfs_release(struct inode *inode, struct file *filp)
+{
+ struct rchan_buf *buf = RELAYFS_I(inode)->buf;
+
+ kref_put(&buf->kref, relay_destroy_buf);
+
+ return 0;
+}
+
+/**
+ * relayfs alloc_inode() implementation
+ */
+static struct inode *relayfs_alloc_inode(struct super_block *sb)
+{
+ struct relayfs_inode_info *p;
+ p = (struct relayfs_inode_info *)kmem_cache_alloc(relayfs_inode_cachep,
+ SLAB_KERNEL);
+ if (!p)
+ return NULL;
+ p->buf = NULL;
+
+ return &p->vfs_inode;
+}
+
+/**
+ * relayfs destroy_inode() implementation
+ */
+static void relayfs_destroy_inode(struct inode *inode)
+{
+ if (RELAYFS_I(inode)->buf)
+ rchan_destroy_buf(RELAYFS_I(inode)->buf);
+
+ kmem_cache_free(relayfs_inode_cachep, RELAYFS_I(inode));
+}
+
+static void init_once(void *p, kmem_cache_t *cachep, unsigned long flags)
+{
+ struct relayfs_inode_info *i = p;
+ if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == SLAB_CTOR_CONSTRUCTOR)
+ inode_init_once(&i->vfs_inode);
+}
+
+struct file_operations relayfs_file_operations = {
+ .open = relayfs_open,
+ .poll = relayfs_poll,
+ .mmap = relayfs_mmap,
+ .release = relayfs_release,
+};
+
+static struct super_operations relayfs_ops = {
+ .statfs = simple_statfs,
+ .drop_inode = generic_delete_inode,
+ .alloc_inode = relayfs_alloc_inode,
+ .destroy_inode = relayfs_destroy_inode,
+};
+
+static int relayfs_fill_super(struct super_block * sb, void * data, int silent)
+{
+ struct inode *inode;
+ struct dentry *root;
+ int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+
+ sb->s_blocksize = PAGE_CACHE_SIZE;
+ sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+ sb->s_magic = RELAYFS_MAGIC;
+ sb->s_op = &relayfs_ops;
+ inode = relayfs_get_inode(sb, mode, NULL);
+
+ if (!inode)
+ return -ENOMEM;
+
+ root = d_alloc_root(inode);
+ if (!root) {
+ iput(inode);
+ return -ENOMEM;
+ }
+ sb->s_root = root;
+
+ return 0;
+}
+
+static struct super_block * relayfs_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name,
+ void *data)
+{
+ return get_sb_single(fs_type, flags, data, relayfs_fill_super);
+}
+
+static struct file_system_type relayfs_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "relayfs",
+ .get_sb = relayfs_get_sb,
+ .kill_sb = kill_litter_super,
+};
+
+static int __init init_relayfs_fs(void)
+{
+ int err;
+
+ relayfs_inode_cachep = kmem_cache_create("relayfs_inode_cache",
+ sizeof(struct relayfs_inode_info), 0,
+ 0, init_once, NULL);
+ if (!relayfs_inode_cachep)
+ return -ENOMEM;
+
+ err = register_filesystem(&relayfs_fs_type);
+ if (err)
+ kmem_cache_destroy(relayfs_inode_cachep);
+
+ return err;
+}
+
+static void __exit exit_relayfs_fs(void)
+{
+ unregister_filesystem(&relayfs_fs_type);
+ kmem_cache_destroy(relayfs_inode_cachep);
+}
+
+module_init(init_relayfs_fs)
+module_exit(exit_relayfs_fs)
+
+EXPORT_SYMBOL_GPL(relayfs_open);
+EXPORT_SYMBOL_GPL(relayfs_poll);
+EXPORT_SYMBOL_GPL(relayfs_mmap);
+EXPORT_SYMBOL_GPL(relayfs_release);
+EXPORT_SYMBOL_GPL(relayfs_file_operations);
+EXPORT_SYMBOL_GPL(relayfs_create_dir);
+EXPORT_SYMBOL_GPL(relayfs_remove_dir);
+
+MODULE_AUTHOR("Tom Zanussi <[email protected]> and Karim Yaghmour <[email protected]>");
+MODULE_DESCRIPTION("Relay Filesystem");
+MODULE_LICENSE("GPL");
+
diff -urpN -X dontdiff linux-2.6.10/fs/relayfs/relay.c linux-2.6.10-cur/fs/relayfs/relay.c
--- linux-2.6.10/fs/relayfs/relay.c 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/fs/relayfs/relay.c 2005-02-06 00:22:32.000000000 -0600
@@ -0,0 +1,616 @@
+/*
+ * Public API and common code for RelayFS.
+ *
+ * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp
+ * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected])
+ *
+ * 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/mm.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)
+{
+ int produced = atomic_read(&buf->subbufs_produced);
+ int consumed = atomic_read(&buf->subbufs_consumed);
+
+ return (produced - consumed) ? 0 : 1;
+}
+
+/**
+ * relay_buf_full - boolean, is the channel buffer full?
+ * @buf: channel buffer
+ *
+ * Returns 1 if the buffer is full, 0 otherwise.
+ */
+static inline int relay_buf_full(struct rchan_buf *buf)
+{
+ int produced, consumed;
+
+ if (relay_mode_continuous(buf->chan))
+ return 0;
+
+ produced = atomic_read(&buf->subbufs_produced);
+ consumed = atomic_read(&buf->subbufs_consumed);
+
+ return (produced - consumed > buf->chan->n_subbufs - 1) ? 1 : 0;
+}
+
+/*
+ * close() vm_op implementation for relayfs 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 relayfs 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_buffer: - mmap 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_buffer(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;
+}
+
+/*
+ * 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,
+ unsigned prev_subbuf_idx)
+{
+ return 0;
+}
+
+/*
+ * deliver() default callback. Does nothing.
+ */
+static void deliver_default_callback (struct rchan_buf *buf,
+ void *subbuf,
+ unsigned subbuf_idx)
+{
+}
+
+/*
+ * 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)
+{
+}
+
+/*
+ * buf_full() default callback. Does nothing.
+ */
+static void buf_full_default_callback(struct rchan_buf *buf)
+{
+}
+
+/* relay channel default callbacks */
+static struct rchan_callbacks default_channel_callbacks = {
+ .subbuf_start = subbuf_start_default_callback,
+ .deliver = deliver_default_callback,
+ .buf_mapped = buf_mapped_default_callback,
+ .buf_unmapped = buf_unmapped_default_callback,
+ .buf_full = buf_full_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);
+}
+
+/**
+ * get_next_subbuf - return next sub-buffer within channel buffer
+ * @buf: channel buffer
+ */
+static inline void *get_next_subbuf(struct rchan_buf *buf)
+{
+ void *next = buf->data + buf->chan->subbuf_size;
+
+ if (next >= buf->start + buf->chan->subbuf_size * buf->chan->n_subbufs)
+ next = buf->start;
+
+ return next;
+}
+
+/**
+ * rchan_destroy_buf - destroy an rchan_buf struct and associated buffer
+ * @buf: the buffer struct
+ */
+void rchan_destroy_buf(struct rchan_buf *buf)
+{
+ if (likely(buf->start))
+ relay_free_rchan_buf(buf->start, buf->page_array, buf->page_count);
+ kfree(buf->padding);
+ kfree(buf->commit);
+ kfree(buf);
+}
+
+/**
+ * relay_destroy_buf - destroy a channel buffer
+ *
+ * Removes the file from the relayfs fileystem, which also frees the
+ * rchan_buf_struct and the channel buffer. Should only be called from
+ * kref_put().
+ */
+void relay_destroy_buf(struct kref *kref)
+{
+ struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
+ relayfs_remove(buf->dentry);
+}
+
+/**
+ * __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, int init)
+{
+ int i;
+
+ if (init) {
+ init_waitqueue_head(&buf->read_wait);
+ kref_init(&buf->kref);
+ }
+
+ atomic_set(&buf->subbufs_produced, 0);
+ atomic_set(&buf->subbufs_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->commit[i] = 0;
+ }
+
+ INIT_WORK(&buf->wake_readers, NULL, NULL);
+}
+
+/**
+ * relay_reset - reset the channel
+ * @chan: the channel
+ *
+ * Returns 0 if successful, negative if not.
+ *
+ * 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)
+{
+ int i;
+
+ for (i = 0; i < NR_CPUS; i++)
+ if (chan->buf[i] != NULL)
+ __relay_reset(chan->buf[i], 0);
+}
+
+/**
+ * check_attribute_flags - check sanity of channel attributes
+ * @attibute_flags: channel attributes
+ *
+ * Returns 0 if successful, negative otherwise.
+ */
+static inline int check_attribute_flags(u32 attribute_flags)
+{
+ if ((attribute_flags & RELAY_MODE_CONTINUOUS) &&
+ (attribute_flags & RELAY_MODE_NO_OVERWRITE))
+ return -EINVAL; /* Can't have it both ways */
+
+ if (!(attribute_flags & RELAY_MODE_CONTINUOUS) &&
+ !(attribute_flags & RELAY_MODE_NO_OVERWRITE))
+ return -EINVAL; /* Gotta have it one way */
+
+ return 0;
+}
+
+/**
+ * rchan_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 *rchan_create_buf(struct rchan *chan)
+{
+ struct page **page_array;
+ int page_count;
+ struct rchan_buf *buf;
+
+ buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL);
+ if (!buf)
+ return NULL;
+
+ buf->padding = kmalloc(chan->n_subbufs * sizeof(unsigned *), GFP_KERNEL);
+ if (!buf->padding)
+ goto free_buf;
+
+ buf->commit = kmalloc(chan->n_subbufs * sizeof(unsigned *), GFP_KERNEL);
+ if (!buf->commit)
+ goto free_padding;
+
+ buf->start = relay_alloc_rchan_buf(chan->alloc_size, &page_array, &page_count);
+ if (!buf->start)
+ goto free_commit;
+
+ buf->page_array = page_array;
+ buf->page_count = page_count;
+ buf->chan = chan;
+ return buf;
+
+free_commit:
+ kfree(buf->commit);
+
+free_padding:
+ kfree(buf->padding);
+
+free_buf:
+ kfree(buf);
+ return NULL;
+}
+
+/**
+ * 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;
+}
+
+static void relay_close_buf(struct rchan_buf *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->deliver)
+ cb->deliver = deliver_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->buf_full)
+ cb->buf_full = buf_full_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
+ * @attribute_flags: channel attributes
+ * @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,
+ unsigned subbuf_size,
+ unsigned n_subbufs,
+ u32 attribute_flags,
+ struct rchan_callbacks *cb)
+{
+ int i;
+ struct rchan *chan;
+ char *tmpname;
+
+ if (!base_filename)
+ return NULL;
+
+ if (check_attribute_flags(attribute_flags))
+ return NULL;
+
+ chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
+ if (!chan)
+ return NULL;
+
+ chan->version = RELAYFS_CHANNEL_VERSION;
+ chan->flags = attribute_flags;
+ chan->n_subbufs = n_subbufs;
+ chan->subbuf_size = subbuf_size;
+ chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
+ setup_callbacks(chan, cb);
+
+ 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);
+ if (!chan->buf[i])
+ goto free_bufs;
+ }
+
+ kfree(tmpname);
+ return chan;
+
+free_bufs:
+ for (i = 0; i < NR_CPUS; i++)
+ if (chan->buf[i])
+ relay_close_buf(chan->buf[i]);
+ kfree(tmpname);
+
+free_chan:
+ kfree(chan);
+ return NULL;
+}
+
+/**
+ * deliver_check - deliver a guaranteed full sub-buffer if applicable
+ */
+static inline void deliver_check(struct rchan_buf *buf,
+ unsigned subbuf_idx)
+{
+ unsigned full;
+ void *subbuf;
+
+ full = buf->chan->subbuf_size - buf->padding[subbuf_idx];
+
+ if (buf->commit[subbuf_idx] == full) {
+ subbuf = buf->start + subbuf_idx * buf->chan->subbuf_size;
+ buf->chan->cb->deliver(buf, subbuf, subbuf_idx);
+ }
+}
+
+/**
+ * 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.
+ */
+unsigned relay_switch_subbuf(struct rchan_buf *buf, unsigned length)
+{
+ int cur_subbuf, prev_subbuf, subbufs_produced;
+ unsigned start = 0, padding = buf->chan->subbuf_size - buf->offset;
+
+ if (unlikely(relay_buf_full(buf)))
+ return 0;
+
+ subbufs_produced = atomic_read(&buf->subbufs_produced);
+ cur_subbuf = prev_subbuf = subbufs_produced % buf->chan->n_subbufs;
+ buf->padding[cur_subbuf] = padding;
+
+ atomic_inc(&buf->subbufs_produced);
+
+ if (waitqueue_active(&buf->read_wait)) {
+ PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
+ schedule_delayed_work(&buf->wake_readers, 1);
+ }
+
+ if (unlikely(relay_buf_full(buf))) {
+ return 0;
+ buf->chan->cb->buf_full(buf);
+ }
+
+ buf->data = get_next_subbuf(buf);
+ cur_subbuf = (subbufs_produced + 1) % buf->chan->n_subbufs;
+ buf->padding[cur_subbuf] = buf->commit[cur_subbuf] = 0;
+ start = buf->chan->cb->subbuf_start(buf, buf->data, prev_subbuf);
+ deliver_check(buf, prev_subbuf);
+
+ buf->offset = start;
+
+ return length;
+}
+
+/**
+ * relay_commit - add count bytes to a sub-buffer's commit count
+ * @buf: channel buffer
+ * @subbuf_idx: sub-buffer index to add to
+ * @count: number of bytes committed
+ *
+ * Invokes deliver() callback if sub-buffer is completely written
+ */
+void relay_commit(struct rchan_buf *buf,
+ unsigned subbuf_idx,
+ unsigned count)
+{
+ if (subbuf_idx >= buf->chan->n_subbufs)
+ return;
+
+ buf->commit[subbuf_idx] += count;
+
+ deliver_check(buf, subbuf_idx);
+}
+
+/**
+ * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
+ * @chan: the channel
+ * @subbufs_consumed: number of sub-buffers to add to current buf's count
+ * @cpu: the cpu associated with the channel buffer to update
+ *
+ * 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
+ * is MODE_CONTINUOUS.
+ */
+void relay_subbufs_consumed(struct rchan *chan, int subbufs_consumed, int cpu)
+{
+ int produced, consumed;
+ struct rchan_buf *buf = chan->buf[cpu];
+
+ atomic_add(subbufs_consumed, &buf->subbufs_consumed);
+ produced = atomic_read(&buf->subbufs_produced);
+ consumed = atomic_read(&buf->subbufs_consumed);
+ if (consumed > produced)
+ atomic_set(&buf->subbufs_consumed, produced);
+}
+
+/**
+ * relay_close_buf - close a channel buffer
+ * @buf: channel buffer
+ *
+ * Finalizes the last sub-buffer and marks the buffer as finalized.
+ * 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)
+{
+ relay_switch_subbuf(buf, 0);
+
+ buf->finalized = 1;
+ buf->chan->cb = &default_channel_callbacks;
+
+ kref_put(&buf->kref, relay_destroy_buf);
+}
+
+/**
+ * relay_close - close the channel
+ * @chan: the channel
+ *
+ * Closes all channel buffers and frees the channel.
+ */
+void relay_close(struct rchan *chan)
+{
+ int i;
+
+ for (i = 0; i < NR_CPUS; i++)
+ if (chan->buf[i])
+ relay_close_buf(chan->buf[i]);
+ kfree(chan);
+}
+
+EXPORT_SYMBOL_GPL(relay_open);
+EXPORT_SYMBOL_GPL(relay_close);
+EXPORT_SYMBOL_GPL(relay_reset);
+EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
+EXPORT_SYMBOL_GPL(relay_switch_subbuf);
+EXPORT_SYMBOL_GPL(relay_commit);
diff -urpN -X dontdiff linux-2.6.10/fs/relayfs/relay.h linux-2.6.10-cur/fs/relayfs/relay.h
--- linux-2.6.10/fs/relayfs/relay.h 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/fs/relayfs/relay.h 2005-02-05 23:00:10.000000000 -0600
@@ -0,0 +1,31 @@
+/*
+ * fs/relayfs/relay.h
+ *
+ * Copyright (C) 1999-2005 - Karim Yaghmour ([email protected]), Opersys inc.
+ * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp
+ *
+ * RelayFS internal definitions and declarations
+ */
+
+#ifndef _RELAY_H
+#define _RELAY_H
+
+/*
+ * Internal relayfs kernel API, fs/relayfs/relay.c
+ */
+
+#define relay_mode_continuous(chan) (((chan)->flags & RELAY_MODE_CONTINUOUS) ? 1 : 0)
+
+struct dentry *relayfs_create_file(const char *name,
+ struct dentry *parent,
+ int mode,
+ struct rchan *chan);
+extern int relayfs_remove(struct dentry *dentry);
+extern int relay_mmap_buffer(struct rchan_buf *buf,
+ struct vm_area_struct *vma);
+extern struct rchan_buf *rchan_create_buf(struct rchan *chan);
+extern void rchan_destroy_buf(struct rchan_buf *buf);
+extern void relay_destroy_buf(struct kref *kref);
+extern int relay_buf_empty(struct rchan_buf *buf);
+
+#endif /* _RELAY_H */
diff -urpN -X dontdiff linux-2.6.10/include/linux/relayfs_fs.h linux-2.6.10-cur/include/linux/relayfs_fs.h
--- linux-2.6.10/include/linux/relayfs_fs.h 1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.10-cur/include/linux/relayfs_fs.h 2005-02-06 00:21:44.000000000 -0600
@@ -0,0 +1,253 @@
+/*
+ * linux/include/linux/relayfs_fs.h
+ *
+ * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp
+ * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected])
+ *
+ * RelayFS definitions and declarations
+ */
+
+#ifndef _LINUX_RELAYFS_FS_H
+#define _LINUX_RELAYFS_FS_H
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/kref.h>
+
+/*
+ * Tracks changes to rchan_buf struct
+ */
+#define RELAYFS_CHANNEL_VERSION 3
+
+/*
+ * Relay attribute flags
+ */
+#define RELAY_MODE_CONTINUOUS 0x1
+#define RELAY_MODE_NO_OVERWRITE 0x2
+
+/*
+ * Per-cpu relay channel buffer
+ */
+struct rchan_buf
+{
+ void *start; /* start of channel buffer */
+ void *data; /* start of current sub-buffer */
+ unsigned offset; /* current offset into sub-buffer */
+ atomic_t subbufs_produced; /* count of sub-buffers produced */
+ atomic_t subbufs_consumed; /* count of sub-buffers consumed */
+ struct rchan *chan; /* associated channel */
+ wait_queue_head_t read_wait; /* reader wait queue */
+ struct work_struct wake_readers; /* reader wake-up work struct */
+ struct dentry *dentry; /* channel file dentry */
+ struct kref kref; /* channel refcount */
+ struct page **page_array; /* array of current buffer pages */
+ int page_count; /* number of current buffer pages */
+ unsigned *padding; /* padding counts per sub-buffer */
+ unsigned *commit; /* commit counts per sub-buffer */
+ int finalized; /* buffer has been finalized */
+} ____cacheline_aligned;
+
+/*
+ * Relay channel data structure
+ */
+struct rchan
+{
+ u32 version; /* the version of this struct */
+ unsigned subbuf_size; /* sub-buffer size */
+ unsigned n_subbufs; /* number of sub-buffers per buffer */
+ unsigned alloc_size; /* total buffer size allocated */
+ u32 flags; /* relay channel attributes */
+ struct rchan_callbacks *cb; /* client callbacks */
+ struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+};
+
+/*
+ * Relayfs inode
+ */
+struct relayfs_inode_info
+{
+ struct inode vfs_inode;
+ struct rchan_buf *buf;
+};
+
+static inline struct relayfs_inode_info *RELAYFS_I(struct inode *inode)
+{
+ return container_of(inode, struct relayfs_inode_info, vfs_inode);
+}
+
+/*
+ * Relay channel client callbacks
+ */
+struct rchan_callbacks
+{
+ /*
+ * subbuf_start - called on buffer-switch to a new sub-buffer
+ * @buf: the channel buffer containing the new sub-buffer
+ * @subbuf: the start of the new sub-buffer
+ * @prev_subbuf_idx: the previous sub-buffer's index
+ *
+ */
+ int (*subbuf_start) (struct rchan_buf *buf,
+ void *subbuf,
+ unsigned prev_subbuf_idx);
+
+ /*
+ * deliver - deliver a guaranteed full sub-buffer to client
+ * @buf: the channel buffer containing the sub-buffer
+ * @subbuf: the start of the new sub-buffer
+ * @subbuf_idx: the sub-buffer's index
+ *
+ * Only works if relay_commit is also used
+ */
+ void (*deliver) (struct rchan_buf *buf,
+ void *subbuf,
+ unsigned subbuf_idx);
+
+ /*
+ * buf_mapped - relayfs buffer mmap notification
+ * @buf: the channel buffer
+ * @filp: relayfs file pointer
+ *
+ * Called when a relayfs file is successfully mmapped
+ */
+ void (*buf_mapped)(struct rchan_buf *buf,
+ struct file *filp);
+
+ /*
+ * buf_unmapped - relayfs buffer unmap notification
+ * @buf: the channel buffer
+ * @filp: relayfs file pointer
+ *
+ * Called when a relayfs file is successfully unmapped
+ */
+ void (*buf_unmapped)(struct rchan_buf *buf,
+ struct file *filp);
+
+ /*
+ * buf_full - relayfs buffer full notification
+ * @buf: the channel channel buffer
+ *
+ * Called when a relayfs buffer becomes full
+ */
+ void (*buf_full)(struct rchan_buf *buf);
+};
+
+/*
+ * relayfs kernel API, fs/relayfs/relay.c
+ */
+
+struct rchan *relay_open(const char *base_filename,
+ struct dentry *parent,
+ unsigned subbuf_size,
+ unsigned n_subbufs,
+ u32 flags,
+ struct rchan_callbacks *cb);
+extern void relay_close(struct rchan *chan);
+extern void relay_subbufs_consumed(struct rchan *chan,
+ int subbufs_consumed,
+ int cpu);
+extern void relay_reset(struct rchan *chan);
+extern unsigned relay_switch_subbuf(struct rchan_buf *buf,
+ unsigned length);
+extern void relay_commit(struct rchan_buf *buf,
+ unsigned subbuf_idx,
+ unsigned count);
+extern struct dentry *relayfs_create_dir(const char *name,
+ struct dentry *parent);
+extern int relayfs_remove_dir(struct dentry *dentry);
+
+/**
+ * relay_write - write data into the channel
+ * @chan: relay channel
+ * @data: data to be written
+ * @length: number of bytes to write
+ *
+ * Writes data into the current cpu's channel buffer.
+ *
+ * Can be called in any context. Try __relay_write() if you know
+ * you won't be logging in interrupt context.
+ */
+static inline void relay_write(struct rchan *chan,
+ const void *data,
+ unsigned length)
+{
+ unsigned long flags;
+ struct rchan_buf *buf;
+
+ local_irq_save(flags);
+ buf = chan->buf[smp_processor_id()];
+ if (unlikely(buf->offset + length > chan->subbuf_size))
+ length = relay_switch_subbuf(buf, length);
+ memcpy(buf->data + buf->offset, data, length);
+ buf->offset += length;
+ local_irq_restore(flags);
+}
+
+/**
+ * __relay_write - write data into the channel
+ * @chan: relay channel
+ * @data: data to be written
+ * @length: number of bytes to write
+ *
+ * Writes data into the current cpu's channel buffer.
+ *
+ * Preempt-safe but not irq-safe. Use relay_write() if you might
+ * be logging in interrupt context.
+ */
+static inline void __relay_write(struct rchan *chan,
+ const void *data,
+ unsigned length)
+{
+ struct rchan_buf *buf;
+
+ buf = chan->buf[get_cpu()];
+ if (unlikely(buf->offset + length > buf->chan->subbuf_size))
+ length = relay_switch_subbuf(buf, length);
+ memcpy(buf->data + buf->offset, data, length);
+ buf->offset += length;
+ put_cpu();
+}
+
+/**
+ * relay_reserve - reserve slot in channel buffer
+ * @chan: relay channel
+ * @length: number of bytes to reserve
+ *
+ * Returns pointer to reserved slot, NULL if full.
+ *
+ * Reserves slot in the current cpu's channel buffer.
+ * Not irq- or preempt-safe - caller must provide synchronization.
+ */
+static inline void *relay_reserve(struct rchan *chan, unsigned length)
+{
+ void *reserved;
+ struct rchan_buf *buf = chan->buf[smp_processor_id()];
+
+ if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
+ length = relay_switch_subbuf(buf, length);
+ if (!length)
+ return NULL;
+ }
+ reserved = buf->data + buf->offset;
+ buf->offset += length;
+
+ return reserved;
+}
+
+/*
+ * exported relayfs file operations, fs/relayfs/inode.c
+ */
+
+extern struct file_operations relayfs_file_operations;
+extern int relayfs_open(struct inode *inode, struct file *filp);
+extern unsigned int relayfs_poll(struct file *filp, poll_table *wait);
+extern int relayfs_mmap(struct file *filp, struct vm_area_struct *vma);
+extern int relayfs_release(struct inode *inode, struct file *filp);
+
+#endif /* _LINUX_RELAYFS_FS_H */
+
On Wed, Feb 09, 2005 at 08:49:36PM -0600, Tom Zanussi wrote:
[..]
> + */
> +struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
> + int mode, struct rchan *chan)
> +{
> + struct dentry *dentry;
> + int error;
> +
> + if (!mode)
> + mode = S_IRUSR;
> + mode = (mode & S_IALLUGO) | S_IFREG;
> +
> + error = relayfs_create_entry(name, parent, mode, chan, &dentry);
^^^^
I think you missed GregKH's suggesstion to have relayfs_create_entry()
return pointer to struct dentry, and reduce one parameter.
> +unsigned relay_switch_subbuf(struct rchan_buf *buf, unsigned length)
> +{
> + int cur_subbuf, prev_subbuf, subbufs_produced;
> + unsigned start = 0, padding = buf->chan->subbuf_size - buf->offset;
> +
> + if (unlikely(relay_buf_full(buf)))
> + return 0;
> +
> + subbufs_produced = atomic_read(&buf->subbufs_produced);
> + cur_subbuf = prev_subbuf = subbufs_produced % buf->chan->n_subbufs;
> + buf->padding[cur_subbuf] = padding;
> +
> + atomic_inc(&buf->subbufs_produced);
> +
> + if (waitqueue_active(&buf->read_wait)) {
> + PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
> + schedule_delayed_work(&buf->wake_readers, 1);
> + }
> +
> + if (unlikely(relay_buf_full(buf))) {
> + return 0;
> + buf->chan->cb->buf_full(buf);
^^^^^^^^
Typo? statement after return !
Thanks
Maneesh
--
Maneesh Soni
Linux Technology Center,
IBM India Software Labs,
Bangalore, India
email: [email protected]
Phone: 91-80-25044990
Maneesh Soni writes:
> On Wed, Feb 09, 2005 at 08:49:36PM -0600, Tom Zanussi wrote:
> [..]
> > + */
> > +struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
> > + int mode, struct rchan *chan)
> > +{
> > + struct dentry *dentry;
> > + int error;
> > +
> > + if (!mode)
> > + mode = S_IRUSR;
> > + mode = (mode & S_IALLUGO) | S_IFREG;
> > +
> > + error = relayfs_create_entry(name, parent, mode, chan, &dentry);
>
> ^^^^
> I think you missed GregKH's suggesstion to have relayfs_create_entry()
> return pointer to struct dentry, and reduce one parameter.
Yes, you're right - somehow I missed that one.
> > +
> > + if (unlikely(relay_buf_full(buf))) {
> > + return 0;
> > + buf->chan->cb->buf_full(buf);
>
> ^^^^^^^^
> Typo? statement after return !
Yikes! Obviously I haven't tested the buffer full condition yet ;-)
Thanks for pointing these out.
Tom
Hi Tom,
On Wed, 9 Feb 2005 20:49:36 -0600, Tom Zanussi <[email protected]> wrote:
> +static inline struct page **alloc_page_array(int size, int *page_count)
> +{
> + int n_pages;
> + struct page **page_array;
> +
> + size = PAGE_ALIGN(size);
> + n_pages = size >> PAGE_SHIFT;
> +
> + page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
> + if (!page_array)
> + return NULL;
> + *page_count = n_pages;
> +
> + return page_array;
> +}
[snip]
> +static int populate_page_array(struct page **page_array, int page_count)
> +{
> + int i;
> +
> + for (i = 0; i < page_count; i++) {
> + page_array[i] = alloc_page(GFP_KERNEL);
> + if (unlikely(!page_array[i])) {
> + depopulate_page_array(page_array, i);
> + return -ENOMEM;
> + }
> + }
> + return 0;
> +}
> +
> +/**
> + * relay_alloc_rchan_buf - allocate a channel buffer
> + * @size: total size of the buffer
> + * @page_array: receives a pointer to the buffer's page array
> + * @page_count: receives the number of pages allocated
> + *
> + * Returns a pointer to the resulting buffer, NULL if unsuccessful
> + */
> +void *relay_alloc_rchan_buf(unsigned long size, struct page ***page_array,
> + int *page_count)
> +{
> + void *mem;
> +
> + *page_array = alloc_page_array(size, page_count);
> + if (!*page_array)
> + return NULL;
> +
> + if (populate_page_array(*page_array, *page_count)) {
> + kfree(*page_array);
> + *page_array = NULL;
> + return NULL;
> + }
[snip]
Please consider inlining alloc_page_array() and populate_page_array()
into relay_alloc_rchan_buf() as they're only used once. You'd get rid
of passing page_count as a pointer this way. If inlining is
unacceptable, please at least move the n_pages calculation to
relay_alloc_rchan_buf() to make the API more sane.
I think relay_alloc_rchan_buf also would benefit from goto-styled
error handling.
Pekka
On Wed, 9 Feb 2005 20:49:36 -0600, Tom Zanussi <[email protected]> wrote:
> +static int relayfs_create_entry(const char *name, struct dentry *parent,
> + int mode, struct rchan *chan,
> + struct dentry **dentry)
> +{
> + struct qstr qname;
> + struct dentry *d;
> + struct inode *inode;
> + int error = 0;
> +
> + BUG_ON(!(S_ISREG(mode) || S_ISDIR(mode)));
> +
> + error = simple_pin_fs("relayfs", &relayfs_mount, &relayfs_mount_count);
> + if (error) {
> + printk(KERN_ERR "Couldn't mount relayfs: errcode %d\n", error);
> + return error;
> + }
> +
> + qname.name = name;
> + qname.len = strlen(name);
> + qname.hash = full_name_hash(name, qname.len);
> +
> + if (!parent)
> + if (relayfs_mount && relayfs_mount->mnt_sb)
> + parent = relayfs_mount->mnt_sb->s_root;
Please move the nested if statement to the parent expression. The
!parent part is always evaluated first.
> +static struct inode *relayfs_alloc_inode(struct super_block *sb)
> +{
> + struct relayfs_inode_info *p;
> + p = (struct relayfs_inode_info *)kmem_cache_alloc(relayfs_inode_cachep,
> + SLAB_KERNEL);
Please drop the spurious cast from void *.
Pekka
>
> Please consider inlining alloc_page_array() and populate_page_array()
> into relay_alloc_rchan_buf() as they're only used once. You'd get rid
> of passing page_count as a pointer this way. If inlining is
> unacceptable, please at least move the n_pages calculation to
> relay_alloc_rchan_buf() to make the API more sane.
Modern gcc (3.3-hammer with unit-at-a-time or 3.4) will do that anyways on
its own.
-Andi
I wrote:
>> Please consider inlining alloc_page_array() and populate_page_array()
>> into relay_alloc_rchan_buf() as they're only used once. You'd get rid
>> of passing page_count as a pointer this way. If inlining is
>> unacceptable, please at least move the n_pages calculation to
>> relay_alloc_rchan_buf() to make the API more sane.
Andi Kleen writes:
> Modern gcc (3.3-hammer with unit-at-a-time or 3.4) will do that anyways on
> its own.
I know that but I am commenting on readability. The pointer passing is due
to silly interface (alloc_page_array() calculating number of pages on its
own).
Pekka