include/linux/mount.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 *
 * Definitions for mount interface. This describes the in the kernel build 
 * linkedlist with mounted filesystems.
 *
 * Author:  Marco van Wieringen <mvw@planets.elm.net>
 *
 */
#ifndef _LINUX_MOUNT_H
#define _LINUX_MOUNT_H

#include <linux/types.h>
#include <linux/list.h>
#include <linux/nodemask.h>
#include <linux/spinlock.h>
#include <linux/seqlock.h>
#include <linux/atomic.h>

struct super_block;
struct vfsmount;
struct dentry;
struct mnt_namespace;
struct fs_context;

#define MNT_NOSUID	0x01
#define MNT_NODEV	0x02
#define MNT_NOEXEC	0x04
#define MNT_NOATIME	0x08
#define MNT_NODIRATIME	0x10
#define MNT_RELATIME	0x20
#define MNT_READONLY	0x40	/* does the user want this to be r/o? */
#define MNT_NOSYMFOLLOW	0x80

#define MNT_SHRINKABLE	0x100
#define MNT_WRITE_HOLD	0x200

#define MNT_SHARED	0x1000	/* if the vfsmount is a shared mount */
#define MNT_UNBINDABLE	0x2000	/* if the vfsmount is a unbindable mount */
/*
 * MNT_SHARED_MASK is the set of flags that should be cleared when a
 * mount becomes shared.  Currently, this is only the flag that says a
 * mount cannot be bind mounted, since this is how we create a mount
 * that shares events with another mount.  If you add a new MNT_*
 * flag, consider how it interacts with shared mounts.
 */
#define MNT_SHARED_MASK	(MNT_UNBINDABLE)
#define MNT_USER_SETTABLE_MASK  (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \
				 | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \
				 | MNT_READONLY | MNT_NOSYMFOLLOW)
#define MNT_ATIME_MASK (MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME )

#define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
			    MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED | \
			    MNT_CURSOR)

#define MNT_INTERNAL	0x4000

#define MNT_LOCK_ATIME		0x040000
#define MNT_LOCK_NOEXEC		0x080000
#define MNT_LOCK_NOSUID		0x100000
#define MNT_LOCK_NODEV		0x200000
#define MNT_LOCK_READONLY	0x400000
#define MNT_LOCKED		0x800000
#define MNT_DOOMED		0x1000000
#define MNT_SYNC_UMOUNT		0x2000000
#define MNT_MARKED		0x4000000
#define MNT_UMOUNT		0x8000000
#define MNT_CURSOR		0x10000000

struct vfsmount {
	struct dentry *mnt_root;	/* root of the mounted tree */
	struct super_block *mnt_sb;	/* pointer to superblock */
	int mnt_flags;
	struct user_namespace *mnt_userns;
} __randomize_layout;

static inline struct user_namespace *mnt_user_ns(const struct vfsmount *mnt)
{
	/* Pairs with smp_store_release() in do_idmap_mount(). */
	return smp_load_acquire(&mnt->mnt_userns);
}

struct file; /* forward dec */
struct path;

extern int mnt_want_write(struct vfsmount *mnt);
extern int mnt_want_write_file(struct file *file);
extern void mnt_drop_write(struct vfsmount *mnt);
extern void mnt_drop_write_file(struct file *file);
extern void mntput(struct vfsmount *mnt);
extern struct vfsmount *mntget(struct vfsmount *mnt);
extern struct vfsmount *mnt_clone_internal(const struct path *path);
extern bool __mnt_is_readonly(struct vfsmount *mnt);
extern bool mnt_may_suid(struct vfsmount *mnt);

struct path;
extern struct vfsmount *clone_private_mount(const struct path *path);
extern int __mnt_want_write(struct vfsmount *);
extern void __mnt_drop_write(struct vfsmount *);

struct file_system_type;
extern struct vfsmount *fc_mount(struct fs_context *fc);
extern struct vfsmount *vfs_create_mount(struct fs_context *fc);
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
				      int flags, const char *name,
				      void *data);
extern struct vfsmount *vfs_submount(const struct dentry *mountpoint,
				     struct file_system_type *type,
				     const char *name, void *data);

extern void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list);
extern void mark_mounts_for_expiry(struct list_head *mounts);

extern dev_t name_to_dev_t(const char *name);
extern bool path_is_mountpoint(const struct path *path);

extern void kern_unmount_array(struct vfsmount *mnt[], unsigned int num);

#endif /* _LINUX_MOUNT_H */