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![Arjan van de Ven](/assets/img/avatar_default.png)
Many struct inode_operations in the kernel can be "const". Marking them const moves these to the .rodata section, which avoids false sharing with potential dirty data. In addition it'll catch accidental writes at compile time to these shared resources. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
281 lines
6.5 KiB
C
281 lines
6.5 KiB
C
/* -*- 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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BUG_ON(dentry->d_parent == configfs_sb->s_root);
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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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const 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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.setattr = configfs_setattr,
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};
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