[PATCH] configfs: User-driven configuration filesystem
Configfs, a file system for userspace-driven kernel object configuration. The OCFS2 stack makes extensive use of this for propagation of cluster configuration information into kernel. Signed-off-by: Joel Becker <joel.becker@oracle.com>
This commit is contained in:
Joel Becker
281
fs/configfs/symlink.c
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281
fs/configfs/symlink.c
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/* -*- mode: c; c-basic-offset: 8; -*-
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* vim: noexpandtab sw=8 ts=8 sts=0:
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*
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* symlink.c - operations for configfs symlinks.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*
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* Based on sysfs:
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* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
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*
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* configfs Copyright (C) 2005 Oracle. All rights reserved.
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*/
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#include <linux/fs.h>
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#include <linux/module.h>
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#include <linux/namei.h>
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#include <linux/configfs.h>
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#include "configfs_internal.h"
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static int item_depth(struct config_item * item)
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{
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struct config_item * p = item;
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int depth = 0;
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do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
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return depth;
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}
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static int item_path_length(struct config_item * item)
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{
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struct config_item * p = item;
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int length = 1;
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do {
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length += strlen(config_item_name(p)) + 1;
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p = p->ci_parent;
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} while (p && !configfs_is_root(p));
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return length;
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}
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static void fill_item_path(struct config_item * item, char * buffer, int length)
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{
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struct config_item * p;
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--length;
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for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
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int cur = strlen(config_item_name(p));
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/* back up enough to print this bus id with '/' */
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length -= cur;
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strncpy(buffer + length,config_item_name(p),cur);
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*(buffer + --length) = '/';
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}
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}
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static int create_link(struct config_item *parent_item,
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struct config_item *item,
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struct dentry *dentry)
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{
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struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
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struct configfs_symlink *sl;
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int ret;
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ret = -ENOMEM;
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sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
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if (sl) {
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sl->sl_target = config_item_get(item);
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/* FIXME: needs a lock, I'd bet */
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list_add(&sl->sl_list, &target_sd->s_links);
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ret = configfs_create_link(sl, parent_item->ci_dentry,
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dentry);
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if (ret) {
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list_del_init(&sl->sl_list);
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config_item_put(item);
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kfree(sl);
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}
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}
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return ret;
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}
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static int get_target(const char *symname, struct nameidata *nd,
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struct config_item **target)
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{
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int ret;
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ret = path_lookup(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, nd);
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if (!ret) {
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if (nd->dentry->d_sb == configfs_sb) {
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*target = configfs_get_config_item(nd->dentry);
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if (!*target) {
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ret = -ENOENT;
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path_release(nd);
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}
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} else
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ret = -EPERM;
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}
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return ret;
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}
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int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
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{
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int ret;
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struct nameidata nd;
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struct config_item *parent_item;
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struct config_item *target_item;
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struct config_item_type *type;
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ret = -EPERM; /* What lack-of-symlink returns */
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if (dentry->d_parent == configfs_sb->s_root)
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goto out;
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parent_item = configfs_get_config_item(dentry->d_parent);
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type = parent_item->ci_type;
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if (!type || !type->ct_item_ops ||
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!type->ct_item_ops->allow_link)
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goto out_put;
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ret = get_target(symname, &nd, &target_item);
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if (ret)
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goto out_put;
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ret = type->ct_item_ops->allow_link(parent_item, target_item);
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if (!ret)
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ret = create_link(parent_item, target_item, dentry);
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config_item_put(target_item);
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path_release(&nd);
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out_put:
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config_item_put(parent_item);
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out:
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return ret;
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}
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int configfs_unlink(struct inode *dir, struct dentry *dentry)
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{
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struct configfs_dirent *sd = dentry->d_fsdata;
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struct configfs_symlink *sl;
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struct config_item *parent_item;
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struct config_item_type *type;
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int ret;
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ret = -EPERM; /* What lack-of-symlink returns */
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if (!(sd->s_type & CONFIGFS_ITEM_LINK))
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goto out;
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if (dentry->d_parent == configfs_sb->s_root)
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BUG();
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sl = sd->s_element;
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parent_item = configfs_get_config_item(dentry->d_parent);
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type = parent_item->ci_type;
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list_del_init(&sd->s_sibling);
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configfs_drop_dentry(sd, dentry->d_parent);
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dput(dentry);
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configfs_put(sd);
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/*
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* drop_link() must be called before
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* list_del_init(&sl->sl_list), so that the order of
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* drop_link(this, target) and drop_item(target) is preserved.
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*/
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if (type && type->ct_item_ops &&
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type->ct_item_ops->drop_link)
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type->ct_item_ops->drop_link(parent_item,
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sl->sl_target);
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/* FIXME: Needs lock */
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list_del_init(&sl->sl_list);
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/* Put reference from create_link() */
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config_item_put(sl->sl_target);
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kfree(sl);
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config_item_put(parent_item);
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ret = 0;
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out:
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return ret;
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}
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static int configfs_get_target_path(struct config_item * item, struct config_item * target,
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char *path)
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{
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char * s;
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int depth, size;
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depth = item_depth(item);
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size = item_path_length(target) + depth * 3 - 1;
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if (size > PATH_MAX)
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return -ENAMETOOLONG;
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pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
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for (s = path; depth--; s += 3)
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strcpy(s,"../");
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fill_item_path(target, path, size);
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pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
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return 0;
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}
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static int configfs_getlink(struct dentry *dentry, char * path)
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{
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struct config_item *item, *target_item;
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int error = 0;
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item = configfs_get_config_item(dentry->d_parent);
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if (!item)
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return -EINVAL;
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target_item = configfs_get_config_item(dentry);
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if (!target_item) {
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config_item_put(item);
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return -EINVAL;
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}
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down_read(&configfs_rename_sem);
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error = configfs_get_target_path(item, target_item, path);
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up_read(&configfs_rename_sem);
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config_item_put(item);
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config_item_put(target_item);
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return error;
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}
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static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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int error = -ENOMEM;
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unsigned long page = get_zeroed_page(GFP_KERNEL);
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if (page) {
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error = configfs_getlink(dentry, (char *)page);
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if (!error) {
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nd_set_link(nd, (char *)page);
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return (void *)page;
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}
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}
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nd_set_link(nd, ERR_PTR(error));
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return NULL;
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}
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static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
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void *cookie)
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{
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if (cookie) {
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unsigned long page = (unsigned long)cookie;
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free_page(page);
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}
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}
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struct inode_operations configfs_symlink_inode_operations = {
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.follow_link = configfs_follow_link,
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.readlink = generic_readlink,
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.put_link = configfs_put_link,
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};
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