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