/* 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 simple_xattrs    xattrs;
        atomic_t                nr_user_xattrs;
        atomic_t                user_xattr_size;
};

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;
};

/* +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 void              *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;
#endif  /* __KERNFS_INTERNAL_H */