mount.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#include <linux/mount.h>
  3#include <linux/seq_file.h>
  4#include <linux/poll.h>
  5#include <linux/ns_common.h>
  6#include <linux/fs_pin.h>
  7
  8extern struct list_head notify_list;
  9
 10struct mnt_namespace {
 11	struct ns_common	ns;
 12	struct mount *	root;
 13	struct {
 14		struct rb_root	mounts;		 /* Protected by namespace_sem */
 15		struct rb_node	*mnt_last_node;	 /* last (rightmost) mount in the rbtree */
 16		struct rb_node	*mnt_first_node; /* first (leftmost) mount in the rbtree */
 17	};
 18	struct user_namespace	*user_ns;
 19	struct ucounts		*ucounts;
 20	wait_queue_head_t	poll;
 21	u64			seq_origin; /* Sequence number of origin mount namespace */
 22	u64 event;
 23#ifdef CONFIG_FSNOTIFY
 24	__u32			n_fsnotify_mask;
 25	struct fsnotify_mark_connector __rcu *n_fsnotify_marks;
 26#endif
 27	unsigned int		nr_mounts; /* # of mounts in the namespace */
 28	unsigned int		pending_mounts;
 29	refcount_t		passive; /* number references not pinning @mounts */
 30	bool			is_anon;
 31} __randomize_layout;
 32
 33struct mnt_pcp {
 34	int mnt_count;
 35	int mnt_writers;
 36};
 37
 38struct mountpoint {
 39	struct hlist_node m_hash;
 40	struct dentry *m_dentry;
 41	struct hlist_head m_list;
 42};
 43
 44struct mount {
 45	struct hlist_node mnt_hash;
 46	struct mount *mnt_parent;
 47	struct dentry *mnt_mountpoint;
 48	struct vfsmount mnt;
 49	union {
 50		struct rb_node mnt_node; /* node in the ns->mounts rbtree */
 51		struct rcu_head mnt_rcu;
 52		struct llist_node mnt_llist;
 53	};
 54#ifdef CONFIG_SMP
 55	struct mnt_pcp __percpu *mnt_pcp;
 56#else
 57	int mnt_count;
 58	int mnt_writers;
 59#endif
 60	struct list_head mnt_mounts;	/* list of children, anchored here */
 61	struct list_head mnt_child;	/* and going through their mnt_child */
 62	struct mount *mnt_next_for_sb;	/* the next two fields are hlist_node, */
 63	struct mount * __aligned(1) *mnt_pprev_for_sb;
 64					/* except that LSB of pprev is stolen */
 65#define WRITE_HOLD 1			/* ... for use by mnt_hold_writers() */
 66	const char *mnt_devname;	/* Name of device e.g. /dev/dsk/hda1 */
 67	struct list_head mnt_list;
 68	struct list_head mnt_expire;	/* link in fs-specific expiry list */
 69	struct list_head mnt_share;	/* circular list of shared mounts */
 70	struct hlist_head mnt_slave_list;/* list of slave mounts */
 71	struct hlist_node mnt_slave;	/* slave list entry */
 72	struct mount *mnt_master;	/* slave is on master->mnt_slave_list */
 73	struct mnt_namespace *mnt_ns;	/* containing namespace */
 74	struct mountpoint *mnt_mp;	/* where is it mounted */
 75	union {
 76		struct hlist_node mnt_mp_list;	/* list mounts with the same mountpoint */
 77		struct hlist_node mnt_umount;
 78	};
 79#ifdef CONFIG_FSNOTIFY
 80	struct fsnotify_mark_connector __rcu *mnt_fsnotify_marks;
 81	__u32 mnt_fsnotify_mask;
 82	struct list_head to_notify;	/* need to queue notification */
 83	struct mnt_namespace *prev_ns;	/* previous namespace (NULL if none) */
 84#endif
 85	int mnt_t_flags;		/* namespace_sem-protected flags */
 86	int mnt_id;			/* mount identifier, reused */
 87	u64 mnt_id_unique;		/* mount ID unique until reboot */
 88	int mnt_group_id;		/* peer group identifier */
 89	int mnt_expiry_mark;		/* true if marked for expiry */
 90	struct hlist_head mnt_pins;
 91	struct hlist_head mnt_stuck_children;
 92	struct mount *overmount;	/* mounted on ->mnt_root */
 93} __randomize_layout;
 94
 95enum {
 96	T_SHARED		= 1, /* mount is shared */
 97	T_UNBINDABLE		= 2, /* mount is unbindable */
 98	T_MARKED		= 4, /* internal mark for propagate_... */
 99	T_UMOUNT_CANDIDATE	= 8, /* for propagate_umount */
100
101	/*
102	 * T_SHARED_MASK is the set of flags that should be cleared when a
103	 * mount becomes shared.  Currently, this is only the flag that says a
104	 * mount cannot be bind mounted, since this is how we create a mount
105	 * that shares events with another mount.  If you add a new T_*
106	 * flag, consider how it interacts with shared mounts.
107	 */
108	T_SHARED_MASK	= T_UNBINDABLE,
109};
110
111#define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
112
113static inline struct mount *real_mount(struct vfsmount *mnt)
114{
115	return container_of(mnt, struct mount, mnt);
116}
117
118static inline int mnt_has_parent(const struct mount *mnt)
119{
120	return mnt != mnt->mnt_parent;
121}
122
123static inline int is_mounted(struct vfsmount *mnt)
124{
125	/* neither detached nor internal? */
126	return !IS_ERR_OR_NULL(real_mount(mnt)->mnt_ns);
127}
128
129extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);
130
131extern int __legitimize_mnt(struct vfsmount *, unsigned);
132
133static inline bool __path_is_mountpoint(const struct path *path)
134{
135	struct mount *m = __lookup_mnt(path->mnt, path->dentry);
136	return m && likely(!(m->mnt.mnt_flags & MNT_SYNC_UMOUNT));
137}
138
139extern void __detach_mounts(struct dentry *dentry);
140
141static inline void detach_mounts(struct dentry *dentry)
142{
143	if (!d_mountpoint(dentry))
144		return;
145	__detach_mounts(dentry);
146}
147
148static inline void get_mnt_ns(struct mnt_namespace *ns)
149{
150	ns_ref_inc(ns);
151}
152
153extern seqlock_t mount_lock;
154
155DEFINE_LOCK_GUARD_0(mount_writer, write_seqlock(&mount_lock),
156		    write_sequnlock(&mount_lock))
157DEFINE_LOCK_GUARD_0(mount_locked_reader, read_seqlock_excl(&mount_lock),
158		    read_sequnlock_excl(&mount_lock))
159
160struct proc_mounts {
161	struct mnt_namespace *ns;
162	struct path root;
163	int (*show)(struct seq_file *, struct vfsmount *);
164};
165
166extern const struct seq_operations mounts_op;
167
168extern bool __is_local_mountpoint(const struct dentry *dentry);
169static inline bool is_local_mountpoint(const struct dentry *dentry)
170{
171	if (!d_mountpoint(dentry))
172		return false;
173
174	return __is_local_mountpoint(dentry);
175}
176
177static inline bool is_anon_ns(struct mnt_namespace *ns)
178{
179	return ns->is_anon;
180}
181
182static inline bool anon_ns_root(const struct mount *m)
183{
184	struct mnt_namespace *ns = READ_ONCE(m->mnt_ns);
185
186	return !IS_ERR_OR_NULL(ns) && is_anon_ns(ns) && m == ns->root;
187}
188
189static inline bool mnt_ns_attached(const struct mount *mnt)
190{
191	return !RB_EMPTY_NODE(&mnt->mnt_node);
192}
193
194static inline bool mnt_ns_empty(const struct mnt_namespace *ns)
195{
196	return RB_EMPTY_ROOT(&ns->mounts);
197}
198
199static inline void move_from_ns(struct mount *mnt)
200{
201	struct mnt_namespace *ns = mnt->mnt_ns;
202	WARN_ON(!mnt_ns_attached(mnt));
203	if (ns->mnt_last_node == &mnt->mnt_node)
204		ns->mnt_last_node = rb_prev(&mnt->mnt_node);
205	if (ns->mnt_first_node == &mnt->mnt_node)
206		ns->mnt_first_node = rb_next(&mnt->mnt_node);
207	rb_erase(&mnt->mnt_node, &ns->mounts);
208	RB_CLEAR_NODE(&mnt->mnt_node);
209}
210
211bool has_locked_children(struct mount *mnt, struct dentry *dentry);
212struct mnt_namespace *get_sequential_mnt_ns(struct mnt_namespace *mnt_ns,
213					    bool previous);
214
215static inline struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
216{
217	return container_of(ns, struct mnt_namespace, ns);
218}
219
220#ifdef CONFIG_FSNOTIFY
221static inline void mnt_notify_add(struct mount *m)
222{
223	/* Optimize the case where there are no watches */
224	if ((m->mnt_ns && m->mnt_ns->n_fsnotify_marks) ||
225	    (m->prev_ns && m->prev_ns->n_fsnotify_marks))
226		list_add_tail(&m->to_notify, &notify_list);
227	else
228		m->prev_ns = m->mnt_ns;
229}
230#else
231static inline void mnt_notify_add(struct mount *m)
232{
233}
234#endif
235
236static inline struct mount *topmost_overmount(struct mount *m)
237{
238	while (m->overmount)
239		m = m->overmount;
240	return m;
241}
242
243static inline bool __test_write_hold(struct mount * __aligned(1) *val)
244{
245	return (unsigned long)val & WRITE_HOLD;
246}
247
248static inline bool test_write_hold(const struct mount *m)
249{
250	return __test_write_hold(m->mnt_pprev_for_sb);
251}
252
253static inline void set_write_hold(struct mount *m)
254{
255	m->mnt_pprev_for_sb = (void *)((unsigned long)m->mnt_pprev_for_sb
256				       | WRITE_HOLD);
257}
258
259static inline void clear_write_hold(struct mount *m)
260{
261	m->mnt_pprev_for_sb = (void *)((unsigned long)m->mnt_pprev_for_sb
262				       & ~WRITE_HOLD);
263}
264
265struct mnt_namespace *mnt_ns_from_dentry(struct dentry *dentry);