diff options
Diffstat (limited to 'kernel/fs/configfs/symlink.c')
| -rw-r--r-- | kernel/fs/configfs/symlink.c | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/kernel/fs/configfs/symlink.c b/kernel/fs/configfs/symlink.c new file mode 100644 index 000000000..cc9f2546e --- /dev/null +++ b/kernel/fs/configfs/symlink.c @@ -0,0 +1,314 @@ +/* -*- mode: c; c-basic-offset: 8; -*- + * vim: noexpandtab sw=8 ts=8 sts=0: + * + * symlink.c - operations for configfs symlinks. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public + * License as published by the Free Software Foundation; either + * version 2 of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public + * License along with this program; if not, write to the + * Free Software Foundation, Inc., 59 Temple Place - Suite 330, + * Boston, MA 021110-1307, USA. + * + * Based on sysfs: + * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel + * + * configfs Copyright (C) 2005 Oracle. All rights reserved. + */ + +#include <linux/fs.h> +#include <linux/module.h> +#include <linux/namei.h> +#include <linux/slab.h> + +#include <linux/configfs.h> +#include "configfs_internal.h" + +/* Protects attachments of new symlinks */ +DEFINE_MUTEX(configfs_symlink_mutex); + +static int item_depth(struct config_item * item) +{ + struct config_item * p = item; + int depth = 0; + do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p)); + return depth; +} + +static int item_path_length(struct config_item * item) +{ + struct config_item * p = item; + int length = 1; + do { + length += strlen(config_item_name(p)) + 1; + p = p->ci_parent; + } while (p && !configfs_is_root(p)); + return length; +} + +static void fill_item_path(struct config_item * item, char * buffer, int length) +{ + struct config_item * p; + + --length; + for (p = item; p && !configfs_is_root(p); p = p->ci_parent) { + int cur = strlen(config_item_name(p)); + + /* back up enough to print this bus id with '/' */ + length -= cur; + strncpy(buffer + length,config_item_name(p),cur); + *(buffer + --length) = '/'; + } +} + +static int create_link(struct config_item *parent_item, + struct config_item *item, + struct dentry *dentry) +{ + struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata; + struct configfs_symlink *sl; + int ret; + + ret = -ENOENT; + if (!configfs_dirent_is_ready(target_sd)) + goto out; + ret = -ENOMEM; + sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL); + if (sl) { + sl->sl_target = config_item_get(item); + spin_lock(&configfs_dirent_lock); + if (target_sd->s_type & CONFIGFS_USET_DROPPING) { + spin_unlock(&configfs_dirent_lock); + config_item_put(item); + kfree(sl); + return -ENOENT; + } + list_add(&sl->sl_list, &target_sd->s_links); + spin_unlock(&configfs_dirent_lock); + ret = configfs_create_link(sl, parent_item->ci_dentry, + dentry); + if (ret) { + spin_lock(&configfs_dirent_lock); + list_del_init(&sl->sl_list); + spin_unlock(&configfs_dirent_lock); + config_item_put(item); + kfree(sl); + } + } + +out: + return ret; +} + + +static int get_target(const char *symname, struct path *path, + struct config_item **target, struct super_block *sb) +{ + int ret; + + ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path); + if (!ret) { + if (path->dentry->d_sb == sb) { + *target = configfs_get_config_item(path->dentry); + if (!*target) { + ret = -ENOENT; + path_put(path); + } + } else { + ret = -EPERM; + path_put(path); + } + } + + return ret; +} + + +int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) +{ + int ret; + struct path path; + struct configfs_dirent *sd; + struct config_item *parent_item; + struct config_item *target_item = NULL; + struct config_item_type *type; + + sd = dentry->d_parent->d_fsdata; + /* + * Fake invisibility if dir belongs to a group/default groups hierarchy + * being attached + */ + ret = -ENOENT; + if (!configfs_dirent_is_ready(sd)) + goto out; + + parent_item = configfs_get_config_item(dentry->d_parent); + type = parent_item->ci_type; + + ret = -EPERM; + if (!type || !type->ct_item_ops || + !type->ct_item_ops->allow_link) + goto out_put; + + ret = get_target(symname, &path, &target_item, dentry->d_sb); + if (ret) + goto out_put; + + ret = type->ct_item_ops->allow_link(parent_item, target_item); + if (!ret) { + mutex_lock(&configfs_symlink_mutex); + ret = create_link(parent_item, target_item, dentry); + mutex_unlock(&configfs_symlink_mutex); + if (ret && type->ct_item_ops->drop_link) + type->ct_item_ops->drop_link(parent_item, + target_item); + } + + config_item_put(target_item); + path_put(&path); + +out_put: + config_item_put(parent_item); + +out: + return ret; +} + +int configfs_unlink(struct inode *dir, struct dentry *dentry) +{ + struct configfs_dirent *sd = dentry->d_fsdata; + struct configfs_symlink *sl; + struct config_item *parent_item; + struct config_item_type *type; + int ret; + + ret = -EPERM; /* What lack-of-symlink returns */ + if (!(sd->s_type & CONFIGFS_ITEM_LINK)) + goto out; + + sl = sd->s_element; + + parent_item = configfs_get_config_item(dentry->d_parent); + type = parent_item->ci_type; + + spin_lock(&configfs_dirent_lock); + list_del_init(&sd->s_sibling); + spin_unlock(&configfs_dirent_lock); + configfs_drop_dentry(sd, dentry->d_parent); + dput(dentry); + configfs_put(sd); + + /* + * drop_link() must be called before + * list_del_init(&sl->sl_list), so that the order of + * drop_link(this, target) and drop_item(target) is preserved. + */ + if (type && type->ct_item_ops && + type->ct_item_ops->drop_link) + type->ct_item_ops->drop_link(parent_item, + sl->sl_target); + + spin_lock(&configfs_dirent_lock); + list_del_init(&sl->sl_list); + spin_unlock(&configfs_dirent_lock); + + /* Put reference from create_link() */ + config_item_put(sl->sl_target); + kfree(sl); + + config_item_put(parent_item); + + ret = 0; + +out: + return ret; +} + +static int configfs_get_target_path(struct config_item * item, struct config_item * target, + char *path) +{ + char * s; + int depth, size; + + depth = item_depth(item); + size = item_path_length(target) + depth * 3 - 1; + if (size > PATH_MAX) + return -ENAMETOOLONG; + + pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size); + + for (s = path; depth--; s += 3) + strcpy(s,"../"); + + fill_item_path(target, path, size); + pr_debug("%s: path = '%s'\n", __func__, path); + + return 0; +} + +static int configfs_getlink(struct dentry *dentry, char * path) +{ + struct config_item *item, *target_item; + int error = 0; + + item = configfs_get_config_item(dentry->d_parent); + if (!item) + return -EINVAL; + + target_item = configfs_get_config_item(dentry); + if (!target_item) { + config_item_put(item); + return -EINVAL; + } + + down_read(&configfs_rename_sem); + error = configfs_get_target_path(item, target_item, path); + up_read(&configfs_rename_sem); + + config_item_put(item); + config_item_put(target_item); + return error; + +} + +static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd) +{ + int error = -ENOMEM; + unsigned long page = get_zeroed_page(GFP_KERNEL); + + if (page) { + error = configfs_getlink(dentry, (char *)page); + if (!error) { + nd_set_link(nd, (char *)page); + return (void *)page; + } + } + + nd_set_link(nd, ERR_PTR(error)); + return NULL; +} + +static void configfs_put_link(struct dentry *dentry, struct nameidata *nd, + void *cookie) +{ + if (cookie) { + unsigned long page = (unsigned long)cookie; + free_page(page); + } +} + +const struct inode_operations configfs_symlink_inode_operations = { + .follow_link = configfs_follow_link, + .readlink = generic_readlink, + .put_link = configfs_put_link, + .setattr = configfs_setattr, +}; + |