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![Al Viro](/assets/img/avatar_default.png)
* pull ACC_MODE to fs.h; we have several copies all over the place * nightmarish expression calculating f_mode by f_flags deserves a helper too (OPEN_FMODE(flags)) Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
245 lines
6.4 KiB
C
245 lines
6.4 KiB
C
/*
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* fs/anon_inodes.c
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*
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* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
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*
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* Thanks to Arnd Bergmann for code review and suggestions.
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* More changes for Thomas Gleixner suggestions.
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*
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*/
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#include <linux/cred.h>
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#include <linux/file.h>
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#include <linux/poll.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/magic.h>
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#include <linux/anon_inodes.h>
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#include <asm/uaccess.h>
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static struct vfsmount *anon_inode_mnt __read_mostly;
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static struct inode *anon_inode_inode;
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static const struct file_operations anon_inode_fops;
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static int anon_inodefs_get_sb(struct file_system_type *fs_type, int flags,
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const char *dev_name, void *data,
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struct vfsmount *mnt)
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{
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return get_sb_pseudo(fs_type, "anon_inode:", NULL, ANON_INODE_FS_MAGIC,
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mnt);
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}
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/*
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* anon_inodefs_dname() is called from d_path().
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*/
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static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
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{
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return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
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dentry->d_name.name);
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}
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static struct file_system_type anon_inode_fs_type = {
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.name = "anon_inodefs",
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.get_sb = anon_inodefs_get_sb,
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.kill_sb = kill_anon_super,
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};
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static const struct dentry_operations anon_inodefs_dentry_operations = {
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.d_dname = anon_inodefs_dname,
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};
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/*
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* nop .set_page_dirty method so that people can use .page_mkwrite on
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* anon inodes.
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*/
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static int anon_set_page_dirty(struct page *page)
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{
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return 0;
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};
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static const struct address_space_operations anon_aops = {
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.set_page_dirty = anon_set_page_dirty,
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};
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/**
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* anon_inode_getfd - creates a new file instance by hooking it up to an
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* anonymous inode, and a dentry that describe the "class"
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* of the file
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*
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* @name: [in] name of the "class" of the new file
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* @fops: [in] file operations for the new file
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* @priv: [in] private data for the new file (will be file's private_data)
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* @flags: [in] flags
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*
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* Creates a new file by hooking it on a single inode. This is useful for files
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* that do not need to have a full-fledged inode in order to operate correctly.
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* All the files created with anon_inode_getfile() will share a single inode,
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* hence saving memory and avoiding code duplication for the file/inode/dentry
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* setup. Returns the newly created file* or an error pointer.
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*/
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struct file *anon_inode_getfile(const char *name,
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const struct file_operations *fops,
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void *priv, int flags)
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{
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struct qstr this;
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struct path path;
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struct file *file;
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int error;
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if (IS_ERR(anon_inode_inode))
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return ERR_PTR(-ENODEV);
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if (fops->owner && !try_module_get(fops->owner))
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return ERR_PTR(-ENOENT);
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/*
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* Link the inode to a directory entry by creating a unique name
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* using the inode sequence number.
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*/
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error = -ENOMEM;
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this.name = name;
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this.len = strlen(name);
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this.hash = 0;
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path.dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
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if (!path.dentry)
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goto err_module;
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path.mnt = mntget(anon_inode_mnt);
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/*
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* We know the anon_inode inode count is always greater than zero,
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* so we can avoid doing an igrab() and we can use an open-coded
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* atomic_inc().
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*/
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atomic_inc(&anon_inode_inode->i_count);
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path.dentry->d_op = &anon_inodefs_dentry_operations;
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d_instantiate(path.dentry, anon_inode_inode);
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error = -ENFILE;
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file = alloc_file(&path, OPEN_FMODE(flags), fops);
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if (!file)
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goto err_dput;
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file->f_mapping = anon_inode_inode->i_mapping;
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file->f_pos = 0;
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file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
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file->f_version = 0;
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file->private_data = priv;
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return file;
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err_dput:
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path_put(&path);
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err_module:
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module_put(fops->owner);
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return ERR_PTR(error);
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}
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EXPORT_SYMBOL_GPL(anon_inode_getfile);
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/**
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* anon_inode_getfd - creates a new file instance by hooking it up to an
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* anonymous inode, and a dentry that describe the "class"
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* of the file
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*
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* @name: [in] name of the "class" of the new file
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* @fops: [in] file operations for the new file
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* @priv: [in] private data for the new file (will be file's private_data)
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* @flags: [in] flags
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*
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* Creates a new file by hooking it on a single inode. This is useful for files
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* that do not need to have a full-fledged inode in order to operate correctly.
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* All the files created with anon_inode_getfd() will share a single inode,
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* hence saving memory and avoiding code duplication for the file/inode/dentry
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* setup. Returns new descriptor or an error code.
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*/
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int anon_inode_getfd(const char *name, const struct file_operations *fops,
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void *priv, int flags)
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{
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int error, fd;
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struct file *file;
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error = get_unused_fd_flags(flags);
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if (error < 0)
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return error;
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fd = error;
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file = anon_inode_getfile(name, fops, priv, flags);
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if (IS_ERR(file)) {
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error = PTR_ERR(file);
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goto err_put_unused_fd;
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}
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fd_install(fd, file);
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return fd;
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err_put_unused_fd:
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put_unused_fd(fd);
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return error;
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}
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EXPORT_SYMBOL_GPL(anon_inode_getfd);
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/*
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* A single inode exists for all anon_inode files. Contrary to pipes,
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* anon_inode inodes have no associated per-instance data, so we need
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* only allocate one of them.
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*/
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static struct inode *anon_inode_mkinode(void)
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{
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struct inode *inode = new_inode(anon_inode_mnt->mnt_sb);
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if (!inode)
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return ERR_PTR(-ENOMEM);
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inode->i_fop = &anon_inode_fops;
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inode->i_mapping->a_ops = &anon_aops;
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/*
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* Mark the inode dirty from the very beginning,
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* that way it will never be moved to the dirty
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* list because mark_inode_dirty() will think
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* that it already _is_ on the dirty list.
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*/
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inode->i_state = I_DIRTY;
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inode->i_mode = S_IRUSR | S_IWUSR;
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inode->i_uid = current_fsuid();
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inode->i_gid = current_fsgid();
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inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
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return inode;
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}
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static int __init anon_inode_init(void)
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{
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int error;
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error = register_filesystem(&anon_inode_fs_type);
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if (error)
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goto err_exit;
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anon_inode_mnt = kern_mount(&anon_inode_fs_type);
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if (IS_ERR(anon_inode_mnt)) {
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error = PTR_ERR(anon_inode_mnt);
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goto err_unregister_filesystem;
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}
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anon_inode_inode = anon_inode_mkinode();
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if (IS_ERR(anon_inode_inode)) {
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error = PTR_ERR(anon_inode_inode);
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goto err_mntput;
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}
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return 0;
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err_mntput:
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mntput(anon_inode_mnt);
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err_unregister_filesystem:
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unregister_filesystem(&anon_inode_fs_type);
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err_exit:
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panic(KERN_ERR "anon_inode_init() failed (%d)\n", error);
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}
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fs_initcall(anon_inode_init);
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