linux/fs/kernfs/kernfs-internal.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * 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>
 */

#ifndef __KERNFS_INTERNAL_H
#define __KERNFS_INTERNAL_H

#include <linux/lockdep.h>
#include <linux/fs.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/xattr.h>

#include <linux/kernfs.h>
#include <linux/fs_context.h>

struct kernfs_iattrs {
	kuid_t			ia_uid;
	kgid_t			ia_gid;
	struct timespec64	ia_atime;
	struct timespec64	ia_mtime;
	struct timespec64	ia_ctime;

	struct list_head	xattrs;
	struct simple_xattr_limits xattr_limits;
};

struct kernfs_root {
	/* published fields */
	struct kernfs_node	*kn;
	unsigned int		flags;	/* KERNFS_ROOT_* flags */

	/* private fields, do not use outside kernfs proper */
	struct idr		ino_idr;
	spinlock_t		kernfs_idr_lock;	/* root->ino_idr */
	u32			last_id_lowbits;
	u32			id_highbits;
	struct kernfs_syscall_ops *syscall_ops;

	/* list of kernfs_super_info of this root, protected by kernfs_rwsem */
	struct list_head	supers;

	wait_queue_head_t	deactivate_waitq;
	struct rw_semaphore	kernfs_rwsem;
	struct rw_semaphore	kernfs_iattr_rwsem;
	struct rw_semaphore	kernfs_supers_rwsem;

	/* kn->parent and kn->name */
	rwlock_t		kernfs_rename_lock;

	struct rcu_head		rcu;

	struct simple_xattr_cache xa_cache;
};

/* +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(const struct kernfs_node *kn)
{
	const struct kernfs_node *knp;
	/* if parent exists, it's always a dir; otherwise, @sd is a dir */
	guard(rcu)();
	knp = rcu_dereference(kn->__parent);
	if (knp)
		kn = knp;
	return kn->dir.root;
}

/*
 * mount.c
 */
struct kernfs_super_info {
	struct super_block	*sb;

	/*
	 * 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 struct ns_common	*ns;

	/* anchored at kernfs_root->supers, protected by kernfs_rwsem */
	struct list_head	node;
};
#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))

static inline bool kernfs_root_is_locked(const struct kernfs_node *kn)
{
	return lockdep_is_held(&kernfs_root(kn)->kernfs_rwsem);
}

static inline bool kernfs_rename_is_locked(const struct kernfs_node *kn)
{
	return lockdep_is_held(&kernfs_root(kn)->kernfs_rename_lock);
}

static inline const char *kernfs_rcu_name(const struct kernfs_node *kn)
{
	return rcu_dereference_check(kn->name, kernfs_root_is_locked(kn));
}

static inline struct kernfs_node *kernfs_parent(const struct kernfs_node *kn)
{
	/*
	 * The kernfs_node::__parent remains valid within a RCU section. The kn
	 * can be reparented (and renamed) which changes the entry. This can be
	 * avoided by locking kernfs_root::kernfs_rwsem or
	 * kernfs_root::kernfs_rename_lock.
	 * Both locks can be used to obtain a reference on __parent. Once the
	 * reference count reaches 0 then the node is about to be freed
	 * and can not be renamed (or become a different parent) anymore.
	 */
	return rcu_dereference_check(kn->__parent,
				     kernfs_root_is_locked(kn) ||
				     kernfs_rename_is_locked(kn) ||
				     !atomic_read(&kn->count));
}

static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
{
	if (d_really_is_negative(dentry))
		return NULL;
	return d_inode(dentry)->i_private;
}

static inline void kernfs_set_rev(struct kernfs_node *parent,
				  struct dentry *dentry)
{
	dentry->d_time = parent->dir.rev;
}

static inline void kernfs_inc_rev(struct kernfs_node *parent)
{
	parent->dir.rev++;
}

static inline bool kernfs_dir_changed(struct kernfs_node *parent,
				      struct dentry *dentry)
{
	if (parent->dir.rev != dentry->d_time)
		return true;
	return false;
}

extern const struct super_operations kernfs_sops;
extern struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;

/*
 * inode.c
 */
extern const struct xattr_handler * const kernfs_xattr_handlers[];
void kernfs_evict_inode(struct inode *inode);
int kernfs_iop_permission(struct mnt_idmap *idmap,
			  struct inode *inode, int mask);
int kernfs_iop_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
		       struct iattr *iattr);
int kernfs_iop_getattr(struct mnt_idmap *idmap,
		       const struct path *path, struct kstat *stat,
		       u32 request_mask, unsigned int query_flags);
ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size);
int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);

/*
 * dir.c
 */
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,
				    kuid_t uid, kgid_t gid,
				    unsigned flags);

/*
 * file.c
 */
extern const struct file_operations kernfs_file_fops;

bool kernfs_should_drain_open_files(struct kernfs_node *kn);
void kernfs_drain_open_files(struct kernfs_node *kn);

/*
 * symlink.c
 */
extern const struct inode_operations kernfs_symlink_iops;

/*
 * kernfs locks
 */
extern struct kernfs_global_locks *kernfs_locks;

/* Hashed mutex helpers - protect per-node data structures */
static inline struct mutex *kernfs_node_lock_ptr(struct kernfs_node *kn)
{
	int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS);

	return &kernfs_locks->node_mutex[idx];
}

static inline struct mutex *kernfs_node_lock(struct kernfs_node *kn)
{
	struct mutex *lock = kernfs_node_lock_ptr(kn);

	mutex_lock(lock);
	return lock;
}

DEFINE_CLASS(kernfs_node_lock, struct mutex *,
	     mutex_unlock(_T), kernfs_node_lock(kn), struct kernfs_node *kn)

#endif	/* __KERNFS_INTERNAL_H */