fs/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
   8 struct mnt_namespace {
   9         struct ns_common        ns;
  10         struct mount *  root;
  11         /*
  12          * Traversal and modification of .list is protected by either
  13          * - taking namespace_sem for write, OR
  14          * - taking namespace_sem for read AND taking .ns_lock.
  15          */
  16         struct list_head        list;
  17         spinlock_t              ns_lock;
  18         struct user_namespace   *user_ns;
  19         struct ucounts          *ucounts;
  20         u64                     seq;    /* Sequence number to prevent loops */
  21         wait_queue_head_t poll;
  22         u64 event;
  23         unsigned int            mounts; /* # of mounts in the namespace */
  24         unsigned int            pending_mounts;
  25 } __randomize_layout;
  26
  27 struct mnt_pcp {
  28         int mnt_count;
  29         int mnt_writers;
  30 };
  31
  32 struct mountpoint {
  33         struct hlist_node m_hash;
  34         struct dentry *m_dentry;
  35         struct hlist_head m_list;
  36         int m_count;
  37 };
  38
  39 struct mount {
  40         struct hlist_node mnt_hash;
  41         struct mount *mnt_parent;
  42         struct dentry *mnt_mountpoint;
  43         struct vfsmount mnt;
  44         union {
  45                 struct rcu_head mnt_rcu;
  46                 struct llist_node mnt_llist;
  47         };
  48 #ifdef CONFIG_SMP
  49         struct mnt_pcp __percpu *mnt_pcp;
  50 #else
  51         int mnt_count;
  52         int mnt_writers;
  53 #endif
  54         struct list_head mnt_mounts;    /* list of children, anchored here */
  55         struct list_head mnt_child;     /* and going through their mnt_child */
  56         struct list_head mnt_instance;  /* mount instance on sb->s_mounts */
  57         const char *mnt_devname;        /* Name of device e.g. /dev/dsk/hda1 */
  58         struct list_head mnt_list;
  59         struct list_head mnt_expire;    /* link in fs-specific expiry list */
  60         struct list_head mnt_share;     /* circular list of shared mounts */
  61         struct list_head mnt_slave_list;/* list of slave mounts */
  62         struct list_head mnt_slave;     /* slave list entry */
  63         struct mount *mnt_master;       /* slave is on master->mnt_slave_list */
  64         struct mnt_namespace *mnt_ns;   /* containing namespace */
  65         struct mountpoint *mnt_mp;      /* where is it mounted */
  66         union {
  67                 struct hlist_node mnt_mp_list;  /* list mounts with the same mountpoint */
  68                 struct hlist_node mnt_umount;
  69         };
  70         struct list_head mnt_umounting; /* list entry for umount propagation */
  71 #ifdef CONFIG_FSNOTIFY
  72         struct fsnotify_mark_connector __rcu *mnt_fsnotify_marks;
  73         __u32 mnt_fsnotify_mask;
  74 #endif
  75         int mnt_id;                     /* mount identifier */
  76         int mnt_group_id;               /* peer group identifier */
  77         int mnt_expiry_mark;            /* true if marked for expiry */
  78         struct hlist_head mnt_pins;
  79         struct hlist_head mnt_stuck_children;
  80 } __randomize_layout;
  81
  82 #define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
  83
  84 static inline struct mount *real_mount(struct vfsmount *mnt)
  85 {
  86         return container_of(mnt, struct mount, mnt);
  87 }
  88
  89 static inline int mnt_has_parent(struct mount *mnt)
  90 {
  91         return mnt != mnt->mnt_parent;
  92 }
  93
  94 static inline int is_mounted(struct vfsmount *mnt)
  95 {
  96         /* neither detached nor internal? */
  97         return !IS_ERR_OR_NULL(real_mount(mnt)->mnt_ns);
  98 }
  99
 100 extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);
 101
 102 extern int __legitimize_mnt(struct vfsmount *, unsigned);
 103 extern bool legitimize_mnt(struct vfsmount *, unsigned);
 104
 105 static inline bool __path_is_mountpoint(const struct path *path)
 106 {
 107         struct mount *m = __lookup_mnt(path->mnt, path->dentry);
 108         return m && likely(!(m->mnt.mnt_flags & MNT_SYNC_UMOUNT));
 109 }
 110
 111 extern void __detach_mounts(struct dentry *dentry);
 112
 113 static inline void detach_mounts(struct dentry *dentry)
 114 {
 115         if (!d_mountpoint(dentry))
 116                 return;
 117         __detach_mounts(dentry);
 118 }
 119
 120 static inline void get_mnt_ns(struct mnt_namespace *ns)
 121 {
 122         refcount_inc(&ns->ns.count);
 123 }
 124
 125 extern seqlock_t mount_lock;
 126
 127 static inline void lock_mount_hash(void)
 128 {
 129         write_seqlock(&mount_lock);
 130 }
 131
 132 static inline void unlock_mount_hash(void)
 133 {
 134         write_sequnlock(&mount_lock);
 135 }
 136
 137 struct proc_mounts {
 138         struct mnt_namespace *ns;
 139         struct path root;
 140         int (*show)(struct seq_file *, struct vfsmount *);
 141         struct mount cursor;
 142 };
 143
 144 extern const struct seq_operations mounts_op;
 145
 146 extern bool __is_local_mountpoint(struct dentry *dentry);
 147 static inline bool is_local_mountpoint(struct dentry *dentry)
 148 {
 149         if (!d_mountpoint(dentry))
 150                 return false;
 151
 152         return __is_local_mountpoint(dentry);
 153 }
 154
 155 static inline bool is_anon_ns(struct mnt_namespace *ns)
 156 {
 157         return ns->seq == 0;
 158 }
 159
 160 extern void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor);