root/fs/fuse/control.c

DEFINITIONS

1. fuse_ctl_file_conn_get
2. fuse_conn_abort_write
3. fuse_conn_waiting_read
4. fuse_ctl_add_dentry
5. fuse_ctl_add_conn
6. fuse_ctl_remove_conn
7. fuse_ctl_fill_super
8. fuse_ctl_get_sb
9. fuse_ctl_kill_sb
10. fuse_ctl_init
11. fuse_ctl_cleanup

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2006  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#include "fuse_i.h"

#include <linux/init.h>
#include <linux/module.h>

#define FUSE_CTL_SUPER_MAGIC 0x65735543

/*
 * This is non-NULL when the single instance of the control filesystem
 * exists.  Protected by fuse_mutex
 */
static struct super_block *fuse_control_sb;

static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
{
        struct fuse_conn *fc;
        mutex_lock(&fuse_mutex);
        fc = file->f_path.dentry->d_inode->i_private;
        if (fc)
                fc = fuse_conn_get(fc);
        mutex_unlock(&fuse_mutex);
        return fc;
}

static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
                                     size_t count, loff_t *ppos)
{
        struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
        if (fc) {
                fuse_abort_conn(fc);
                fuse_conn_put(fc);
        }
        return count;
}

static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
                                      size_t len, loff_t *ppos)
{
        char tmp[32];
        size_t size;

        if (!*ppos) {
                struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
                if (!fc)
                        return 0;

                file->private_data=(void *)(long)atomic_read(&fc->num_waiting);
                fuse_conn_put(fc);
        }
        size = sprintf(tmp, "%ld\n", (long)file->private_data);
        return simple_read_from_buffer(buf, len, ppos, tmp, size);
}

static const struct file_operations fuse_ctl_abort_ops = {
        .open = nonseekable_open,
        .write = fuse_conn_abort_write,
};

static const struct file_operations fuse_ctl_waiting_ops = {
        .open = nonseekable_open,
        .read = fuse_conn_waiting_read,
};

static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
                                          struct fuse_conn *fc,
                                          const char *name,
                                          int mode, int nlink,
                                          const struct inode_operations *iop,
                                          const struct file_operations *fop)
{
        struct dentry *dentry;
        struct inode *inode;

        BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
        dentry = d_alloc_name(parent, name);
        if (!dentry)
                return NULL;

        fc->ctl_dentry[fc->ctl_ndents++] = dentry;
        inode = new_inode(fuse_control_sb);
        if (!inode)
                return NULL;

        inode->i_mode = mode;
        inode->i_uid = fc->user_id;
        inode->i_gid = fc->group_id;
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        /* setting ->i_op to NULL is not allowed */
        if (iop)
                inode->i_op = iop;
        inode->i_fop = fop;
        inode->i_nlink = nlink;
        inode->i_private = fc;
        d_add(dentry, inode);
        return dentry;
}

/*
 * Add a connection to the control filesystem (if it exists).  Caller
 * must hold fuse_mutex
 */
int fuse_ctl_add_conn(struct fuse_conn *fc)
{
        struct dentry *parent;
        char name[32];

        if (!fuse_control_sb)
                return 0;

        parent = fuse_control_sb->s_root;
        inc_nlink(parent->d_inode);
        sprintf(name, "%u", fc->dev);
        parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
                                     &simple_dir_inode_operations,
                                     &simple_dir_operations);
        if (!parent)
                goto err;

        if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
                                NULL, &fuse_ctl_waiting_ops) ||
            !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
                                 NULL, &fuse_ctl_abort_ops))
                goto err;

        return 0;

 err:
        fuse_ctl_remove_conn(fc);
        return -ENOMEM;
}

/*
 * Remove a connection from the control filesystem (if it exists).
 * Caller must hold fuse_mutex
 */
void fuse_ctl_remove_conn(struct fuse_conn *fc)
{
        int i;

        if (!fuse_control_sb)
                return;

        for (i = fc->ctl_ndents - 1; i >= 0; i--) {
                struct dentry *dentry = fc->ctl_dentry[i];
                dentry->d_inode->i_private = NULL;
                d_drop(dentry);
                dput(dentry);
        }
        fuse_control_sb->s_root->d_inode->i_nlink--;
}

static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
{
        struct tree_descr empty_descr = {""};
        struct fuse_conn *fc;
        int err;

        err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
        if (err)
                return err;

        mutex_lock(&fuse_mutex);
        BUG_ON(fuse_control_sb);
        fuse_control_sb = sb;
        list_for_each_entry(fc, &fuse_conn_list, entry) {
                err = fuse_ctl_add_conn(fc);
                if (err) {
                        fuse_control_sb = NULL;
                        mutex_unlock(&fuse_mutex);
                        return err;
                }
        }
        mutex_unlock(&fuse_mutex);

        return 0;
}

static int fuse_ctl_get_sb(struct file_system_type *fs_type, int flags,
                        const char *dev_name, void *raw_data,
                        struct vfsmount *mnt)
{
        return get_sb_single(fs_type, flags, raw_data,
                                fuse_ctl_fill_super, mnt);
}

static void fuse_ctl_kill_sb(struct super_block *sb)
{
        struct fuse_conn *fc;

        mutex_lock(&fuse_mutex);
        fuse_control_sb = NULL;
        list_for_each_entry(fc, &fuse_conn_list, entry)
                fc->ctl_ndents = 0;
        mutex_unlock(&fuse_mutex);

        kill_litter_super(sb);
}

static struct file_system_type fuse_ctl_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "fusectl",
        .get_sb         = fuse_ctl_get_sb,
        .kill_sb        = fuse_ctl_kill_sb,
};

int __init fuse_ctl_init(void)
{
        return register_filesystem(&fuse_ctl_fs_type);
}

void fuse_ctl_cleanup(void)
{
        unregister_filesystem(&fuse_ctl_fs_type);
}