mnt: Improve the umount_tree flags

- Remove the unneeded declaration from pnode.h
- Mark umount_tree static as it has no callers outside of namespace.c
- Define an enumeration of umount_tree's flags.
- Pass umount_tree's flags in by name

This removes the magic numbers 0, 1 and 2 making the code a little
clearer and makes it possible for there to be lazy unmounts that don't
propagate.  Which is what __detach_mounts actually wants for example.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 16 insertions, 15 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index e1ee57206eef..e06e36777b90 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1317,14 +1317,15 @@ static inline void namespace_lock(void)
         down_write(&namespace_sem);
 }
 
+enum umount_tree_flags {
+        UMOUNT_SYNC = 1,
+        UMOUNT_PROPAGATE = 2,
+};
 /*
  * mount_lock must be held
  * namespace_sem must be held for write
- * how = 0 => just this tree, don't propagate
- * how = 1 => propagate; we know that nobody else has reference to any victims
- * how = 2 => lazy umount
  */
-void umount_tree(struct mount *mnt, int how)
+static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 {
         HLIST_HEAD(tmp_list);
         struct mount *p;
@@ -1337,7 +1338,7 @@ void umount_tree(struct mount *mnt, int how)
         hlist_for_each_entry(p, &tmp_list, mnt_hash)
                 list_del_init(&p->mnt_child);
 
-        if (how)
+        if (how & UMOUNT_PROPAGATE)
                 propagate_umount(&tmp_list);
 
         while (!hlist_empty(&tmp_list)) {
@@ -1347,7 +1348,7 @@ void umount_tree(struct mount *mnt, int how)
                 list_del_init(&p->mnt_list);
                 __touch_mnt_namespace(p->mnt_ns);
                 p->mnt_ns = NULL;
-                if (how < 2)
+                if (how & UMOUNT_SYNC)
                         p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
 
                 pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, &unmounted);
@@ -1445,14 +1446,14 @@ static int do_umount(struct mount *mnt, int flags)
 
         if (flags & MNT_DETACH) {
                 if (!list_empty(&mnt->mnt_list))
-                        umount_tree(mnt, 2);
+                        umount_tree(mnt, UMOUNT_PROPAGATE);
                 retval = 0;
         } else {
                 shrink_submounts(mnt);
                 retval = -EBUSY;
                 if (!propagate_mount_busy(mnt, 2)) {
                         if (!list_empty(&mnt->mnt_list))
-                                umount_tree(mnt, 1);
+                                umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
                         retval = 0;
                 }
         }
@@ -1484,7 +1485,7 @@ void __detach_mounts(struct dentry *dentry)
         lock_mount_hash();
         while (!hlist_empty(&mp->m_list)) {
                 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
-                umount_tree(mnt, 2);
+                umount_tree(mnt, UMOUNT_PROPAGATE);
         }
         unlock_mount_hash();
         put_mountpoint(mp);
@@ -1646,7 +1647,7 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
 out:
         if (res) {
                 lock_mount_hash();
-                umount_tree(res, 0);
+                umount_tree(res, UMOUNT_SYNC);
                 unlock_mount_hash();
         }
         return q;
@@ -1670,7 +1671,7 @@ void drop_collected_mounts(struct vfsmount *mnt)
 {
         namespace_lock();
         lock_mount_hash();
-        umount_tree(real_mount(mnt), 0);
+        umount_tree(real_mount(mnt), UMOUNT_SYNC);
         unlock_mount_hash();
         namespace_unlock();
 }
@@ -1853,7 +1854,7 @@ static int attach_recursive_mnt(struct mount *source_mnt,
  out_cleanup_ids:
         while (!hlist_empty(&tree_list)) {
                 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
-                umount_tree(child, 0);
+                umount_tree(child, UMOUNT_SYNC);
         }
         unlock_mount_hash();
         cleanup_group_ids(source_mnt, NULL);
@@ -2033,7 +2034,7 @@ static int do_loopback(struct path *path, const char *old_name,
         err = graft_tree(mnt, parent, mp);
         if (err) {
                 lock_mount_hash();
-                umount_tree(mnt, 0);
+                umount_tree(mnt, UMOUNT_SYNC);
                 unlock_mount_hash();
         }
 out2:
@@ -2404,7 +2405,7 @@ void mark_mounts_for_expiry(struct list_head *mounts)
         while (!list_empty(&graveyard)) {
                 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
                 touch_mnt_namespace(mnt->mnt_ns);
-                umount_tree(mnt, 1);
+                umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
         }
         unlock_mount_hash();
         namespace_unlock();
@@ -2475,7 +2476,7 @@ static void shrink_submounts(struct mount *mnt)
                         m = list_first_entry(&graveyard, struct mount,
                                                 mnt_expire);
                         touch_mnt_namespace(m->mnt_ns);
-                        umount_tree(m, 1);
+                        umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
                 }
         }
 }