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![Masahiro Yamada](/assets/img/avatar_default.png)
The section "19) Editor modelines and other cruft" in Documentation/process/coding-style.rst clearly says, "Do not include any of these in source files." I recently receive a patch to explicitly add a new one. Let's do treewide cleanups, otherwise some people follow the existing code and attempt to upstream their favoriate editor setups. It is even nicer if scripts/checkpatch.pl can check it. If we like to impose coding style in an editor-independent manner, I think editorconfig (patch [1]) is a saner solution. [1] https://lore.kernel.org/lkml/20200703073143.423557-1-danny@kdrag0n.dev/ Link: https://lkml.kernel.org/r/20210324054457.1477489-1-masahiroy@kernel.org Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Reviewed-by: Miguel Ojeda <ojeda@kernel.org> [auxdisplay] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
270 lines
6.7 KiB
C
270 lines
6.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* symlink.c - operations for configfs symlinks.
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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/slab.h>
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#include <linux/configfs.h>
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#include "configfs_internal.h"
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/* Protects attachments of new symlinks */
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DEFINE_MUTEX(configfs_symlink_mutex);
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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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memcpy(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 configfs_get_target_path(struct config_item *item,
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struct config_item *target, char *path)
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{
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int depth, size;
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char *s;
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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", __func__, 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", __func__, path);
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return 0;
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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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char *body;
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int ret;
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if (!configfs_dirent_is_ready(target_sd))
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return -ENOENT;
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body = kzalloc(PAGE_SIZE, GFP_KERNEL);
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if (!body)
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return -ENOMEM;
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configfs_get(target_sd);
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spin_lock(&configfs_dirent_lock);
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if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
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spin_unlock(&configfs_dirent_lock);
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configfs_put(target_sd);
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kfree(body);
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return -ENOENT;
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}
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target_sd->s_links++;
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spin_unlock(&configfs_dirent_lock);
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ret = configfs_get_target_path(parent_item, item, body);
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if (!ret)
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ret = configfs_create_link(target_sd, parent_item->ci_dentry,
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dentry, body);
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if (ret) {
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spin_lock(&configfs_dirent_lock);
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target_sd->s_links--;
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spin_unlock(&configfs_dirent_lock);
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configfs_put(target_sd);
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kfree(body);
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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 path *path,
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struct config_item **target, struct super_block *sb)
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{
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int ret;
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ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
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if (!ret) {
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if (path->dentry->d_sb == sb) {
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*target = configfs_get_config_item(path->dentry);
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if (!*target) {
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ret = -ENOENT;
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path_put(path);
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}
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} else {
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ret = -EPERM;
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path_put(path);
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}
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}
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return ret;
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}
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int configfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
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struct dentry *dentry, const char *symname)
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{
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int ret;
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struct path path;
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struct configfs_dirent *sd;
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struct config_item *parent_item;
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struct config_item *target_item = NULL;
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const struct config_item_type *type;
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sd = dentry->d_parent->d_fsdata;
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/*
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* Fake invisibility if dir belongs to a group/default groups hierarchy
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* being attached
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*/
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if (!configfs_dirent_is_ready(sd))
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return -ENOENT;
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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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ret = -EPERM;
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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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/*
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* This is really sick. What they wanted was a hybrid of
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* link(2) and symlink(2) - they wanted the target resolved
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* at syscall time (as link(2) would've done), be a directory
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* (which link(2) would've refused to do) *AND* be a deep
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* fucking magic, making the target busy from rmdir POV.
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* symlink(2) is nothing of that sort, and the locking it
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* gets matches the normal symlink(2) semantics. Without
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* attempts to resolve the target (which might very well
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* not even exist yet) done prior to locking the parent
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* directory. This perversion, OTOH, needs to resolve
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* the target, which would lead to obvious deadlocks if
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* attempted with any directories locked.
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*
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* Unfortunately, that garbage is userland ABI and we should've
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* said "no" back in 2005. Too late now, so we get to
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* play very ugly games with locking.
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*
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* Try *ANYTHING* of that sort in new code, and you will
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* really regret it. Just ask yourself - what could a BOFH
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* do to me and do I want to find it out first-hand?
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*
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* AV, a thoroughly annoyed bastard.
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*/
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inode_unlock(dir);
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ret = get_target(symname, &path, &target_item, dentry->d_sb);
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inode_lock(dir);
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if (ret)
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goto out_put;
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if (dentry->d_inode || d_unhashed(dentry))
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ret = -EEXIST;
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else
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ret = inode_permission(&init_user_ns, dir,
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MAY_WRITE | MAY_EXEC);
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if (!ret)
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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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mutex_lock(&configfs_symlink_mutex);
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ret = create_link(parent_item, target_item, dentry);
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mutex_unlock(&configfs_symlink_mutex);
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if (ret && type->ct_item_ops->drop_link)
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type->ct_item_ops->drop_link(parent_item,
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target_item);
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}
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config_item_put(target_item);
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path_put(&path);
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out_put:
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config_item_put(parent_item);
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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, *target_sd;
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struct config_item *parent_item;
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const 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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target_sd = 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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spin_lock(&configfs_dirent_lock);
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list_del_init(&sd->s_sibling);
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spin_unlock(&configfs_dirent_lock);
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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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* decrementing target's ->s_links, 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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target_sd->s_element);
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spin_lock(&configfs_dirent_lock);
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target_sd->s_links--;
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spin_unlock(&configfs_dirent_lock);
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configfs_put(target_sd);
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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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const struct inode_operations configfs_symlink_inode_operations = {
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.get_link = simple_get_link,
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.setattr = configfs_setattr,
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};
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