/*
 *  file.c - part of debugfs, a tiny little debug file system
 *
 *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
 *  Copyright (C) 2004 IBM Inc.
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License version
 *      2 as published by the Free Software Foundation.
 *
 *  debugfs is for people to use instead of /proc or /sys.
 *  See Documentation/DocBook/kernel-api for more details.
 *
 */

/* uncomment to get debug messages from the debug filesystem, ah the irony. */
/* #define DEBUG */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/debugfs.h>
#include <linux/fsnotify.h>
#include <linux/string.h>
#include <linux/magic.h>

static struct vfsmount *debugfs_mount;
static int debugfs_mount_count;
static bool debugfs_registered;

static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
{
        struct inode *inode = new_inode(sb);

        if (inode) {
                inode->i_mode = mode;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
                switch (mode & S_IFMT) {
                default:
                        init_special_inode(inode, mode, dev);
                        break;
                case S_IFREG:
                        inode->i_fop = &debugfs_file_operations;
                        break;
                case S_IFLNK:
                        inode->i_op = &debugfs_link_operations;
                        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) */
                        inc_nlink(inode);
                        break;
                }
        }
        return inode; 
}

/* SMP-safe */
static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
                         int mode, dev_t dev)
{
        struct inode *inode;
        int error = -EPERM;

        if (dentry->d_inode)
                return -EEXIST;

        inode = debugfs_get_inode(dir->i_sb, mode, dev);
        if (inode) {
                d_instantiate(dentry, inode);
                dget(dentry);
                error = 0;
        }
        return error;
}

static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        int res;

        mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
        res = debugfs_mknod(dir, dentry, mode, 0);
        if (!res) {
                inc_nlink(dir);
                fsnotify_mkdir(dir, dentry);
        }
        return res;
}

static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode)
{
        mode = (mode & S_IALLUGO) | S_IFLNK;
        return debugfs_mknod(dir, dentry, mode, 0);
}

static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
{
        int res;

        mode = (mode & S_IALLUGO) | S_IFREG;
        res = debugfs_mknod(dir, dentry, mode, 0);
        if (!res)
                fsnotify_create(dir, dentry);
        return res;
}

static inline int debugfs_positive(struct dentry *dentry)
{
        return dentry->d_inode && !d_unhashed(dentry);
}

static int debug_fill_super(struct super_block *sb, void *data, int silent)
{
        static struct tree_descr debug_files[] = {{""}};

        return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
}

static int debug_get_sb(struct file_system_type *fs_type,
                        int flags, const char *dev_name,
                        void *data, struct vfsmount *mnt)
{
        return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
}

static struct file_system_type debug_fs_type = {
        .owner =        THIS_MODULE,
        .name =         "debugfs",
        .get_sb =       debug_get_sb,
        .kill_sb =      kill_litter_super,
};

static int debugfs_create_by_name(const char *name, mode_t mode,
                                  struct dentry *parent,
                                  struct dentry **dentry)
{
        int error = 0;

        /* If the parent is not specified, we create it in the root.
         * We need the root dentry to do this, which is in the super 
         * block. A pointer to that is in the struct vfsmount that we
         * have around.
         */
        if (!parent) {
                if (debugfs_mount && debugfs_mount->mnt_sb) {
                        parent = debugfs_mount->mnt_sb->s_root;
                }
        }
        if (!parent) {
                pr_debug("debugfs: Ah! can not find a parent!\n");
                return -EFAULT;
        }

        *dentry = NULL;
        mutex_lock(&parent->d_inode->i_mutex);
        *dentry = lookup_one_len(name, parent, strlen(name));
        if (!IS_ERR(*dentry)) {
                switch (mode & S_IFMT) {
                case S_IFDIR:
                        error = debugfs_mkdir(parent->d_inode, *dentry, mode);
                        break;
                case S_IFLNK:
                        error = debugfs_link(parent->d_inode, *dentry, mode);
                        break;
                default:
                        error = debugfs_create(parent->d_inode, *dentry, mode);
                        break;
                }
                dput(*dentry);
        } else
                error = PTR_ERR(*dentry);
        mutex_unlock(&parent->d_inode->i_mutex);

        return error;
}

/**
 * debugfs_create_file - create a file in the debugfs filesystem
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this paramater is NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @data: a pointer to something that the caller will want to get to later
 *        on.  The inode.i_private pointer will point to this value on
 *        the open() call.
 * @fops: a pointer to a struct file_operations that should be used for
 *        this file.
 *
 * This is the basic "create a file" function for debugfs.  It allows for a
 * wide range of flexibility in createing a file, or a directory (if you
 * want to create a directory, the debugfs_create_dir() function is
 * recommended to be used instead.)
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, %NULL will be returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_file(const char *name, mode_t mode,
                                   struct dentry *parent, void *data,
                                   const struct file_operations *fops)
{
        struct dentry *dentry = NULL;
        int error;

        pr_debug("debugfs: creating file '%s'\n",name);

        error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
                              &debugfs_mount_count);
        if (error)
                goto exit;

        error = debugfs_create_by_name(name, mode, parent, &dentry);
        if (error) {
                dentry = NULL;
                simple_release_fs(&debugfs_mount, &debugfs_mount_count);
                goto exit;
        }

        if (dentry->d_inode) {
                if (data)
                        dentry->d_inode->i_private = data;
                if (fops)
                        dentry->d_inode->i_fop = fops;
        }
exit:
        return dentry;
}
EXPORT_SYMBOL_GPL(debugfs_create_file);

/**
 * debugfs_create_dir - create a directory in the debugfs filesystem
 * @name: a pointer to a string containing the name of the directory to
 *        create.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this paramater is NULL, then the
 *          directory will be created in the root of the debugfs filesystem.
 *
 * This function creates a directory in debugfs with the given name.
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, %NULL will be returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
{
        return debugfs_create_file(name, 
                                   S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
                                   parent, NULL, NULL);
}
EXPORT_SYMBOL_GPL(debugfs_create_dir);

/**
 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 * @name: a pointer to a string containing the name of the symbolic link to
 *        create.
 * @parent: a pointer to the parent dentry for this symbolic link.  This
 *          should be a directory dentry if set.  If this paramater is NULL,
 *          then the symbolic link will be created in the root of the debugfs
 *          filesystem.
 * @target: a pointer to a string containing the path to the target of the
 *          symbolic link.
 *
 * This function creates a symbolic link with the given name in debugfs that
 * links to the given target path.
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the symbolic
 * link is to be removed (no automatic cleanup happens if your module is
 * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 * returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
                                      const char *target)
{
        struct dentry *result;
        char *link;

        link = kstrdup(target, GFP_KERNEL);
        if (!link)
                return NULL;

        result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
                                     NULL);
        if (!result)
                kfree(link);
        return result;
}
EXPORT_SYMBOL_GPL(debugfs_create_symlink);

static void __debugfs_remove(struct dentry *dentry, struct dentry *parent)
{
        int ret = 0;

        if (debugfs_positive(dentry)) {
                if (dentry->d_inode) {
                        dget(dentry);
                        switch (dentry->d_inode->i_mode & S_IFMT) {
                        case S_IFDIR:
                                ret = simple_rmdir(parent->d_inode, dentry);
                                break;
                        case S_IFLNK:
                                kfree(dentry->d_inode->i_private);
                                /* fall through */
                        default:
                                simple_unlink(parent->d_inode, dentry);
                                break;
                        }
                        if (!ret)
                                d_delete(dentry);
                        dput(dentry);
                }
        }
}

/**
 * debugfs_remove - removes a file or directory from the debugfs filesystem
 * @dentry: a pointer to a the dentry of the file or directory to be
 *          removed.
 *
 * This function removes a file or directory in debugfs that was previously
 * created with a call to another debugfs function (like
 * debugfs_create_file() or variants thereof.)
 *
 * This function is required to be called in order for the file to be
 * removed, no automatic cleanup of files will happen when a module is
 * removed, you are responsible here.
 */
void debugfs_remove(struct dentry *dentry)
{
        struct dentry *parent;
        
        if (!dentry)
                return;

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

        mutex_lock(&parent->d_inode->i_mutex);
        __debugfs_remove(dentry, parent);
        mutex_unlock(&parent->d_inode->i_mutex);
        simple_release_fs(&debugfs_mount, &debugfs_mount_count);
}
EXPORT_SYMBOL_GPL(debugfs_remove);

/**
 * debugfs_remove_recursive - recursively removes a directory
 * @dentry: a pointer to a the dentry of the directory to be removed.
 *
 * This function recursively removes a directory tree in debugfs that
 * was previously created with a call to another debugfs function
 * (like debugfs_create_file() or variants thereof.)
 *
 * This function is required to be called in order for the file to be
 * removed, no automatic cleanup of files will happen when a module is
 * removed, you are responsible here.
 */
void debugfs_remove_recursive(struct dentry *dentry)
{
        struct dentry *child;
        struct dentry *parent;

        if (!dentry)
                return;

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

        parent = dentry;
        mutex_lock(&parent->d_inode->i_mutex);

        while (1) {
                /*
                 * When all dentries under "parent" has been removed,
                 * walk up the tree until we reach our starting point.
                 */
                if (list_empty(&parent->d_subdirs)) {
                        mutex_unlock(&parent->d_inode->i_mutex);
                        if (parent == dentry)
                                break;
                        parent = parent->d_parent;
                        mutex_lock(&parent->d_inode->i_mutex);
                }
                child = list_entry(parent->d_subdirs.next, struct dentry,
                                d_u.d_child);
 next_sibling:

                /*
                 * If "child" isn't empty, walk down the tree and
                 * remove all its descendants first.
                 */
                if (!list_empty(&child->d_subdirs)) {
                        mutex_unlock(&parent->d_inode->i_mutex);
                        parent = child;
                        mutex_lock(&parent->d_inode->i_mutex);
                        continue;
                }
                __debugfs_remove(child, parent);
                if (parent->d_subdirs.next == &child->d_u.d_child) {
                        /*
                         * Try the next sibling.
                         */
                        if (child->d_u.d_child.next != &parent->d_subdirs) {
                                child = list_entry(child->d_u.d_child.next,
                                                   struct dentry,
                                                   d_u.d_child);
                                goto next_sibling;
                        }

                        /*
                         * Avoid infinite loop if we fail to remove
                         * one dentry.
                         */
                        mutex_unlock(&parent->d_inode->i_mutex);
                        break;
                }
                simple_release_fs(&debugfs_mount, &debugfs_mount_count);
        }

        parent = dentry->d_parent;
        mutex_lock(&parent->d_inode->i_mutex);
        __debugfs_remove(dentry, parent);
        mutex_unlock(&parent->d_inode->i_mutex);
        simple_release_fs(&debugfs_mount, &debugfs_mount_count);
}
EXPORT_SYMBOL_GPL(debugfs_remove_recursive);

/**
 * debugfs_rename - rename a file/directory in the debugfs filesystem
 * @old_dir: a pointer to the parent dentry for the renamed object. This
 *          should be a directory dentry.
 * @old_dentry: dentry of an object to be renamed.
 * @new_dir: a pointer to the parent dentry where the object should be
 *          moved. This should be a directory dentry.
 * @new_name: a pointer to a string containing the target name.
 *
 * This function renames a file/directory in debugfs.  The target must not
 * exist for rename to succeed.
 *
 * This function will return a pointer to old_dentry (which is updated to
 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 * returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
                struct dentry *new_dir, const char *new_name)
{
        int error;
        struct dentry *dentry = NULL, *trap;
        const char *old_name;

        trap = lock_rename(new_dir, old_dir);
        /* Source or destination directories don't exist? */
        if (!old_dir->d_inode || !new_dir->d_inode)
                goto exit;
        /* Source does not exist, cyclic rename, or mountpoint? */
        if (!old_dentry->d_inode || old_dentry == trap ||
            d_mountpoint(old_dentry))
                goto exit;
        dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
        /* Lookup failed, cyclic rename or target exists? */
        if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
                goto exit;

        old_name = fsnotify_oldname_init(old_dentry->d_name.name);

        error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
                dentry);
        if (error) {
                fsnotify_oldname_free(old_name);
                goto exit;
        }
        d_move(old_dentry, dentry);
        fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
                old_dentry->d_name.name, S_ISDIR(old_dentry->d_inode->i_mode),
                NULL, old_dentry);
        fsnotify_oldname_free(old_name);
        unlock_rename(new_dir, old_dir);
        dput(dentry);
        return old_dentry;
exit:
        if (dentry && !IS_ERR(dentry))
                dput(dentry);
        unlock_rename(new_dir, old_dir);
        return NULL;
}
EXPORT_SYMBOL_GPL(debugfs_rename);

/**
 * debugfs_initialized - Tells whether debugfs has been registered
 */
bool debugfs_initialized(void)
{
        return debugfs_registered;
}
EXPORT_SYMBOL_GPL(debugfs_initialized);


static struct kobject *debug_kobj;

static int __init debugfs_init(void)
{
        int retval;

        debug_kobj = kobject_create_and_add("debug", kernel_kobj);
        if (!debug_kobj)
                return -EINVAL;

        retval = register_filesystem(&debug_fs_type);
        if (retval)
                kobject_put(debug_kobj);
        else
                debugfs_registered = true;

        return retval;
}

static void __exit debugfs_exit(void)
{
        debugfs_registered = false;

        simple_release_fs(&debugfs_mount, &debugfs_mount_count);
        unregister_filesystem(&debug_fs_type);
        kobject_put(debug_kobj);
}

core_initcall(debugfs_init);
module_exit(debugfs_exit);
MODULE_LICENSE("GPL");