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4b93dc9b1c
We're in the process of separating out core sysfs functionality into kernfs which will deal with sysfs_dirents directly. This patch rearranges mount path so that the kernfs and sysfs parts are separate. * As sysfs_super_info won't be visible outside kernfs proper, kernfs_super_ns() is added to allow kernfs users to access a super_block's namespace tag. * Generic mount operation is separated out into kernfs_mount_ns(). sysfs_mount() now just performs sysfs-specific permission check, acquires namespace tag, and invokes kernfs_mount_ns(). * Generic superblock release is separated out into kernfs_kill_sb() which can be used directly as file_system_type->kill_sb(). As sysfs needs to put the namespace tag, sysfs_kill_sb() wraps kernfs_kill_sb() with ns tag put. * sysfs_dir_cachep init and sysfs_inode_init() are separated out into kernfs_init(). kernfs_init() uses only small amount of memory and trying to handle and propagate kernfs_init() failure doesn't make much sense. Use SLAB_PANIC for sysfs_dir_cachep and make sysfs_inode_init() panic on failure. After this change, kernfs_init() should be called before sysfs_init(), fs/namespace.c::mnt_init() modified accordingly. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: linux-fsdevel@vger.kernel.org Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
229 lines
5.4 KiB
C
229 lines
5.4 KiB
C
/*
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* fs/sysfs/symlink.c - operations for initializing and mounting sysfs
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#define DEBUG
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/magic.h>
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#include <linux/slab.h>
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#include <linux/user_namespace.h>
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#include "sysfs.h"
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struct kmem_cache *sysfs_dir_cachep;
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static const struct super_operations sysfs_ops = {
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.statfs = simple_statfs,
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.drop_inode = generic_delete_inode,
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.evict_inode = sysfs_evict_inode,
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};
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static struct kernfs_root *sysfs_root;
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struct sysfs_dirent *sysfs_root_sd;
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static int sysfs_fill_super(struct super_block *sb)
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{
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struct sysfs_super_info *info = sysfs_info(sb);
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struct inode *inode;
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struct dentry *root;
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sb->s_blocksize = PAGE_CACHE_SIZE;
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sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
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sb->s_magic = SYSFS_MAGIC;
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sb->s_op = &sysfs_ops;
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sb->s_time_gran = 1;
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/* get root inode, initialize and unlock it */
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mutex_lock(&sysfs_mutex);
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inode = sysfs_get_inode(sb, info->root->sd);
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mutex_unlock(&sysfs_mutex);
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if (!inode) {
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pr_debug("sysfs: could not get root inode\n");
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return -ENOMEM;
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}
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/* instantiate and link root dentry */
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root = d_make_root(inode);
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if (!root) {
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pr_debug("%s: could not get root dentry!\n", __func__);
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return -ENOMEM;
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}
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kernfs_get(info->root->sd);
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root->d_fsdata = info->root->sd;
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sb->s_root = root;
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sb->s_d_op = &sysfs_dentry_ops;
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return 0;
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}
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static int sysfs_test_super(struct super_block *sb, void *data)
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{
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struct sysfs_super_info *sb_info = sysfs_info(sb);
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struct sysfs_super_info *info = data;
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return sb_info->root == info->root && sb_info->ns == info->ns;
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}
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static int sysfs_set_super(struct super_block *sb, void *data)
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{
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int error;
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error = set_anon_super(sb, data);
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if (!error)
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sb->s_fs_info = data;
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return error;
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}
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/**
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* kernfs_super_ns - determine the namespace tag of a kernfs super_block
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* @sb: super_block of interest
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*
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* Return the namespace tag associated with kernfs super_block @sb.
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*/
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const void *kernfs_super_ns(struct super_block *sb)
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{
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struct sysfs_super_info *info = sysfs_info(sb);
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return info->ns;
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}
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static struct dentry *sysfs_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data)
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{
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struct dentry *root;
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void *ns;
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if (!(flags & MS_KERNMOUNT)) {
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if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
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return ERR_PTR(-EPERM);
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if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
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return ERR_PTR(-EPERM);
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}
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ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
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root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns);
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if (IS_ERR(root))
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kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
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return root;
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}
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/**
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* kernfs_mount_ns - kernfs mount helper
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* @fs_type: file_system_type of the fs being mounted
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* @flags: mount flags specified for the mount
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* @root: kernfs_root of the hierarchy being mounted
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* @ns: optional namespace tag of the mount
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*
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* This is to be called from each kernfs user's file_system_type->mount()
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* implementation, which should pass through the specified @fs_type and
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* @flags, and specify the hierarchy and namespace tag to mount via @root
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* and @ns, respectively.
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*
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* The return value can be passed to the vfs layer verbatim.
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*/
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struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
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struct kernfs_root *root, const void *ns)
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{
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struct super_block *sb;
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struct sysfs_super_info *info;
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int error;
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info = kzalloc(sizeof(*info), GFP_KERNEL);
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if (!info)
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return ERR_PTR(-ENOMEM);
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info->root = root;
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info->ns = ns;
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sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
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if (IS_ERR(sb) || sb->s_fs_info != info)
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kfree(info);
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if (IS_ERR(sb))
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return ERR_CAST(sb);
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if (!sb->s_root) {
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error = sysfs_fill_super(sb);
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if (error) {
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deactivate_locked_super(sb);
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return ERR_PTR(error);
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}
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sb->s_flags |= MS_ACTIVE;
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}
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return dget(sb->s_root);
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}
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static void sysfs_kill_sb(struct super_block *sb)
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{
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kernfs_kill_sb(sb);
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kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)kernfs_super_ns(sb));
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}
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/**
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* kernfs_kill_sb - kill_sb for kernfs
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* @sb: super_block being killed
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*
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* This can be used directly for file_system_type->kill_sb(). If a kernfs
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* user needs extra cleanup, it can implement its own kill_sb() and call
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* this function at the end.
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*/
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void kernfs_kill_sb(struct super_block *sb)
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{
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struct sysfs_super_info *info = sysfs_info(sb);
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struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;
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/*
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* Remove the superblock from fs_supers/s_instances
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* so we can't find it, before freeing sysfs_super_info.
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*/
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kill_anon_super(sb);
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kfree(info);
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kernfs_put(root_sd);
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}
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static struct file_system_type sysfs_fs_type = {
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.name = "sysfs",
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.mount = sysfs_mount,
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.kill_sb = sysfs_kill_sb,
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.fs_flags = FS_USERNS_MOUNT,
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};
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void __init kernfs_init(void)
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{
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sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
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sizeof(struct sysfs_dirent),
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0, SLAB_PANIC, NULL);
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sysfs_inode_init();
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}
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int __init sysfs_init(void)
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{
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int err;
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sysfs_root = kernfs_create_root(NULL);
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if (IS_ERR(sysfs_root))
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return PTR_ERR(sysfs_root);
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sysfs_root_sd = sysfs_root->sd;
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err = register_filesystem(&sysfs_fs_type);
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if (err) {
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kernfs_destroy_root(sysfs_root);
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return err;
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}
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return 0;
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}
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