linux/fs/mount.h
Eric W. Biederman 80b5dce8c5 vfs: Add a function to lazily unmount all mounts from any dentry.
The new function detach_mounts comes in two pieces.  The first piece
is a static inline test of d_mounpoint that returns immediately
without taking any locks if d_mounpoint is not set.  In the common
case when mountpoints are absent this allows the vfs to continue
running with it's same cacheline foot print.

The second piece of detach_mounts __detach_mounts actually does the
work and it assumes that a mountpoint is present so it is slow and
takes namespace_sem for write, and then locks the mount hash (aka
mount_lock) after a struct mountpoint has been found.

With those two locks held each entry on the list of mounts on a
mountpoint is selected and lazily unmounted until all of the mount
have been lazily unmounted.

v7: Wrote a proper change description and removed the changelog
    documenting deleted wrong turns.

Signed-off-by: Eric W. Biederman <ebiederman@twitter.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-10-09 02:38:55 -04:00

138 lines
3.4 KiB
C

#include <linux/mount.h>
#include <linux/seq_file.h>
#include <linux/poll.h>
struct mnt_namespace {
atomic_t count;
unsigned int proc_inum;
struct mount * root;
struct list_head list;
struct user_namespace *user_ns;
u64 seq; /* Sequence number to prevent loops */
wait_queue_head_t poll;
u64 event;
};
struct mnt_pcp {
int mnt_count;
int mnt_writers;
};
struct mountpoint {
struct hlist_node m_hash;
struct dentry *m_dentry;
struct hlist_head m_list;
int m_count;
};
struct mount {
struct hlist_node mnt_hash;
struct mount *mnt_parent;
struct dentry *mnt_mountpoint;
struct vfsmount mnt;
union {
struct rcu_head mnt_rcu;
struct llist_node mnt_llist;
};
#ifdef CONFIG_SMP
struct mnt_pcp __percpu *mnt_pcp;
#else
int mnt_count;
int mnt_writers;
#endif
struct list_head mnt_mounts; /* list of children, anchored here */
struct list_head mnt_child; /* and going through their mnt_child */
struct list_head mnt_instance; /* mount instance on sb->s_mounts */
const char *mnt_devname; /* Name of device e.g. /dev/dsk/hda1 */
struct list_head mnt_list;
struct list_head mnt_expire; /* link in fs-specific expiry list */
struct list_head mnt_share; /* circular list of shared mounts */
struct list_head mnt_slave_list;/* list of slave mounts */
struct list_head mnt_slave; /* slave list entry */
struct mount *mnt_master; /* slave is on master->mnt_slave_list */
struct mnt_namespace *mnt_ns; /* containing namespace */
struct mountpoint *mnt_mp; /* where is it mounted */
struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */
#ifdef CONFIG_FSNOTIFY
struct hlist_head mnt_fsnotify_marks;
__u32 mnt_fsnotify_mask;
#endif
int mnt_id; /* mount identifier */
int mnt_group_id; /* peer group identifier */
int mnt_expiry_mark; /* true if marked for expiry */
struct hlist_head mnt_pins;
struct path mnt_ex_mountpoint;
};
#define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
static inline struct mount *real_mount(struct vfsmount *mnt)
{
return container_of(mnt, struct mount, mnt);
}
static inline int mnt_has_parent(struct mount *mnt)
{
return mnt != mnt->mnt_parent;
}
static inline int is_mounted(struct vfsmount *mnt)
{
/* neither detached nor internal? */
return !IS_ERR_OR_NULL(real_mount(mnt)->mnt_ns);
}
extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);
extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *);
extern bool legitimize_mnt(struct vfsmount *, unsigned);
extern void __detach_mounts(struct dentry *dentry);
static inline void detach_mounts(struct dentry *dentry)
{
if (!d_mountpoint(dentry))
return;
__detach_mounts(dentry);
}
static inline void get_mnt_ns(struct mnt_namespace *ns)
{
atomic_inc(&ns->count);
}
extern seqlock_t mount_lock;
static inline void lock_mount_hash(void)
{
write_seqlock(&mount_lock);
}
static inline void unlock_mount_hash(void)
{
write_sequnlock(&mount_lock);
}
struct proc_mounts {
struct seq_file m;
struct mnt_namespace *ns;
struct path root;
int (*show)(struct seq_file *, struct vfsmount *);
void *cached_mount;
u64 cached_event;
loff_t cached_index;
};
#define proc_mounts(p) (container_of((p), struct proc_mounts, m))
extern const struct seq_operations mounts_op;
extern bool __is_local_mountpoint(struct dentry *dentry);
static inline bool is_local_mountpoint(struct dentry *dentry)
{
if (!d_mountpoint(dentry))
return false;
return __is_local_mountpoint(dentry);
}