linux/fs/kernfs/kernfs-internal.h
Tejun Heo 81c173cb5e kernfs: remove KERNFS_REMOVED
KERNFS_REMOVED is used to mark half-initialized and dying nodes so
that they don't show up in lookups and deny adding new nodes under or
renaming it; however, its role overlaps that of deactivation.

It's necessary to deny addition of new children while removal is in
progress; however, this role considerably intersects with deactivation
- KERNFS_REMOVED prevents new children while deactivation prevents new
file operations.  There's no reason to have them separate making
things more complex than necessary.

This patch removes KERNFS_REMOVED.

* Instead of KERNFS_REMOVED, each node now starts its life
  deactivated.  This means that we now use both atomic_add() and
  atomic_sub() on KN_DEACTIVATED_BIAS, which is INT_MIN.  The compiler
  generates an overflow warnings when negating INT_MIN as the negation
  can't be represented as a positive number.  Nothing is actually
  broken but let's bump BIAS by one to avoid the warnings for archs
  which negates the subtrahend..

* A new helper kernfs_active() which tests whether kn->active >= 0 is
  added for convenience and lockdep annotation.  All KERNFS_REMOVED
  tests are replaced with negated kernfs_active() tests.

* __kernfs_remove() is updated to deactivate, but not drain, all nodes
  in the subtree instead of setting KERNFS_REMOVED.  This removes
  deactivation from kernfs_deactivate(), which is now renamed to
  kernfs_drain().

* Sanity check on KERNFS_REMOVED in kernfs_put() is replaced with
  checks on the active ref.

* Some comment style updates in the affected area.

v2: Reordered before removal path restructuring.  kernfs_active()
    dropped and kernfs_get/put_active() used instead.  RB_EMPTY_NODE()
    used in the lookup paths.

v3: Reverted most of v2 except for creating a new node with
    KN_DEACTIVATED_BIAS.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-02-07 15:42:41 -08:00

115 lines
3.1 KiB
C

/*
* fs/kernfs/kernfs-internal.h - kernfs internal header file
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <teheo@suse.de>
*
* This file is released under the GPLv2.
*/
#ifndef __KERNFS_INTERNAL_H
#define __KERNFS_INTERNAL_H
#include <linux/lockdep.h>
#include <linux/fs.h>
#include <linux/mutex.h>
#include <linux/xattr.h>
#include <linux/kernfs.h>
struct kernfs_iattrs {
struct iattr ia_iattr;
void *ia_secdata;
u32 ia_secdata_len;
struct simple_xattrs xattrs;
};
/* +1 to avoid triggering overflow warning when negating it */
#define KN_DEACTIVATED_BIAS (INT_MIN + 1)
/* KERNFS_TYPE_MASK and types are defined in include/linux/kernfs.h */
/**
* kernfs_root - find out the kernfs_root a kernfs_node belongs to
* @kn: kernfs_node of interest
*
* Return the kernfs_root @kn belongs to.
*/
static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
{
/* if parent exists, it's always a dir; otherwise, @sd is a dir */
if (kn->parent)
kn = kn->parent;
return kn->dir.root;
}
/*
* mount.c
*/
struct kernfs_super_info {
/*
* The root associated with this super_block. Each super_block is
* identified by the root and ns it's associated with.
*/
struct kernfs_root *root;
/*
* Each sb is associated with one namespace tag, currently the
* network namespace of the task which mounted this kernfs
* instance. If multiple tags become necessary, make the following
* an array and compare kernfs_node tag against every entry.
*/
const void *ns;
};
#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
extern struct kmem_cache *kernfs_node_cache;
/*
* inode.c
*/
struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
void kernfs_evict_inode(struct inode *inode);
int kernfs_iop_permission(struct inode *inode, int mask);
int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr);
int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat);
int kernfs_iop_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags);
int kernfs_iop_removexattr(struct dentry *dentry, const char *name);
ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
size_t size);
ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size);
void kernfs_inode_init(void);
/*
* dir.c
*/
extern struct mutex kernfs_mutex;
extern const struct dentry_operations kernfs_dops;
extern const struct file_operations kernfs_dir_fops;
extern const struct inode_operations kernfs_dir_iops;
struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
void kernfs_put_active(struct kernfs_node *kn);
int kernfs_add_one(struct kernfs_node *kn);
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
const char *name, umode_t mode,
unsigned flags);
/*
* file.c
*/
extern const struct file_operations kernfs_file_fops;
void kernfs_unmap_bin_file(struct kernfs_node *kn);
/*
* symlink.c
*/
extern const struct inode_operations kernfs_symlink_iops;
#endif /* __KERNFS_INTERNAL_H */