[PATCH] relayfs: decouple buffer creation from inode creation

[linux-2.6/kmemtrace.git] / fs / relayfs / inode.c

/*
 * VFS-related code for RelayFS, a high-speed data relay filesystem.
 *
 * Copyright (C) 2003-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp
 * Copyright (C) 2003-2005 - Karim Yaghmour <karim@opersys.com>
 *
 * 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"
#include "buffers.h"

#define RELAYFS_MAGIC                   0xF0B4A981

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 */
        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};

static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
                                       void *data)
{
        struct inode *inode;

        inode = new_inode(sb);
        if (!inode)
                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 = data;
                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
 *      @data: user-associated data for this file
 *
 *      Returns the new dentry, NULL on failure
 *
 *      Creates a file or directory with the specifed permissions.
 */
static struct dentry *relayfs_create_entry(const char *name,
                                           struct dentry *parent,
                                           int mode,
                                           void *data)
{
        struct dentry *d;
        struct inode *inode;
        int error = 0;

        BUG_ON(!name || !(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 NULL;
        }

        if (!parent && relayfs_mount && relayfs_mount->mnt_sb)
                parent = relayfs_mount->mnt_sb->s_root;

        if (!parent) {
                simple_release_fs(&relayfs_mount, &relayfs_mount_count);
                return NULL;
        }

        parent = dget(parent);
        down(&parent->d_inode->i_sem);
        d = lookup_one_len(name, parent, strlen(name));
        if (IS_ERR(d)) {
                d = NULL;
                goto release_mount;
        }

        if (d->d_inode) {
                d = NULL;
                goto release_mount;
        }

        inode = relayfs_get_inode(parent->d_inode->i_sb, mode, data);
        if (!inode) {
                d = NULL;
                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:
        up(&parent->d_inode->i_sem);
        dput(parent);
        return d;
}

/**
 *      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
 *      @data: user-associated data for this 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, void *data)
{
        if (!mode)
                mode = S_IRUSR;
        mode = (mode & S_IALLUGO) | S_IFREG;

        return relayfs_create_entry(name, parent, mode, data);
}

/**
 *      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 mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
        return relayfs_create_entry(name, parent, mode, NULL);
}

/**
 *      relayfs_remove - remove a file or directory in the relay filesystem
 *      @dentry: file or directory dentry
 *
 *      Returns 0 if successful, negative otherwise.
 */
int relayfs_remove(struct dentry *dentry)
{
        struct dentry *parent;
        int error = 0;

        if (!dentry)
                return -EINVAL;
        parent = dentry->d_parent;
        if (!parent)
                return -EINVAL;

        parent = dget(parent);
        down(&parent->d_inode->i_sem);
        if (dentry->d_inode) {
                if (S_ISDIR(dentry->d_inode->i_mode))
                        error = simple_rmdir(parent->d_inode, dentry);
                else
                        error = simple_unlink(parent->d_inode, dentry);
                if (!error)
                        d_delete(dentry);
        }
        if (!error)
                dput(dentry);
        up(&parent->d_inode->i_sem);
        dput(parent);

        if (!error)
                simple_release_fs(&relayfs_mount, &relayfs_mount_count);

        return error;
}

/**
 *      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)
{
        return relayfs_remove(dentry);
}

/**
 *      relayfs_open - open file op for relayfs files
 *      @inode: the inode
 *      @filp: the file
 *
 *      Increments the channel buffer refcount.
 */
static 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_buf to map the file into user space.
 */
static int relayfs_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct inode *inode = filp->f_dentry->d_inode;
        return relay_mmap_buf(RELAYFS_I(inode)->buf, vma);
}

/**
 *      relayfs_poll - poll file op for relayfs files
 *      @filp: the file
 *      @wait: poll table
 *
 *      Poll implemention.
 */
static 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.
 */
static int relayfs_release(struct inode *inode, struct file *filp)
{
        struct rchan_buf *buf = RELAYFS_I(inode)->buf;
        kref_put(&buf->kref, relay_remove_buf);

        return 0;
}

/**
 *      relayfs_read_consume - update the consumed count for the buffer
 */
static void relayfs_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;
        }
}

/**
 *      relayfs_read_avail - boolean, are there unconsumed bytes available?
 */
static int relayfs_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;

        relayfs_read_consume(buf, read_pos, 0);

        return 1;
}

/**
 *      relayfs_read_subbuf_avail - return bytes available in sub-buffer
 */
static size_t relayfs_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;
}

/**
 *      relayfs_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 relayfs_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;
}

/**
 *      relayfs_read_end_pos - return the new read position
 */
static size_t relayfs_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;
}

/**
 *      relayfs_read - read file op for relayfs 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 relayfs_read(struct file *filp,
                            char __user *buffer,
                            size_t count,
                            loff_t *ppos)
{
        struct inode *inode = filp->f_dentry->d_inode;
        struct rchan_buf *buf = RELAYFS_I(inode)->buf;
        size_t read_start, avail;
        ssize_t ret = 0;
        void *from;

        down(&inode->i_sem);
        if(!relayfs_read_avail(buf, *ppos))
                goto out;

        read_start = relayfs_read_start_pos(*ppos, buf);
        avail = relayfs_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;
        }
        relayfs_read_consume(buf, read_start, count);
        *ppos = relayfs_read_end_pos(buf, read_start, count);
out:
        up(&inode->i_sem);
        return ret;
}

/**
 *      relayfs alloc_inode() implementation
 */
static struct inode *relayfs_alloc_inode(struct super_block *sb)
{
        struct relayfs_inode_info *p = 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)
{
        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,
        .read           = relayfs_read,
        .llseek         = no_llseek,
        .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_file_operations);
EXPORT_SYMBOL_GPL(relayfs_create_dir);
EXPORT_SYMBOL_GPL(relayfs_remove_dir);

MODULE_AUTHOR("Tom Zanussi <zanussi@us.ibm.com> and Karim Yaghmour <karim@opersys.com>");
MODULE_DESCRIPTION("Relay Filesystem");
MODULE_LICENSE("GPL");