get rid of ->mnt_longterm

it's enough to set ->mnt_ns of internal vfsmounts to something
distinct from all struct mnt_namespace out there; then we can
just use the check for ->mnt_ns != NULL in the fast path of
mntput_no_expire()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 7 insertions, 46 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 1e4a5fe3d7b7..a524ea4dbd80 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -621,21 +621,6 @@ static void attach_mnt(struct mount *mnt, struct path *path)
         list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
 }
 
-static inline void __mnt_make_longterm(struct mount *mnt)
-{
-#ifdef CONFIG_SMP
-        atomic_inc(&mnt->mnt_longterm);
-#endif
-}
-
-/* needs vfsmount lock for write */
-static inline void __mnt_make_shortterm(struct mount *mnt)
-{
-#ifdef CONFIG_SMP
-        atomic_dec(&mnt->mnt_longterm);
-#endif
-}
-
 /*
  * vfsmount lock must be held for write
  */
@@ -649,10 +634,8 @@ static void commit_tree(struct mount *mnt)
         BUG_ON(parent == mnt);
 
         list_add_tail(&head, &mnt->mnt_list);
-        list_for_each_entry(m, &head, mnt_list) {
+        list_for_each_entry(m, &head, mnt_list)
                 m->mnt_ns = n;
-                __mnt_make_longterm(m);
-        }
 
         list_splice(&head, n->list.prev);
 
@@ -804,7 +787,8 @@ static void mntput_no_expire(struct mount *mnt)
 put_again:
 #ifdef CONFIG_SMP
         br_read_lock(&vfsmount_lock);
-        if (likely(atomic_read(&mnt->mnt_longterm))) {
+        if (likely(mnt->mnt_ns)) {
+                /* shouldn't be the last one */
                 mnt_add_count(mnt, -1);
                 br_read_unlock(&vfsmount_lock);
                 return;
@@ -1074,8 +1058,6 @@ void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
                 list_del_init(&p->mnt_expire);
                 list_del_init(&p->mnt_list);
                 __touch_mnt_namespace(p->mnt_ns);
-                if (p->mnt_ns)
-                        __mnt_make_shortterm(p);
                 p->mnt_ns = NULL;
                 list_del_init(&p->mnt_child);
                 if (mnt_has_parent(p)) {
@@ -2209,23 +2191,6 @@ static struct mnt_namespace *alloc_mnt_ns(void)
         return new_ns;
 }
 
-void mnt_make_longterm(struct vfsmount *mnt)
-{
-        __mnt_make_longterm(real_mount(mnt));
-}
-
-void mnt_make_shortterm(struct vfsmount *m)
-{
-#ifdef CONFIG_SMP
-        struct mount *mnt = real_mount(m);
-        if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
-                return;
-        br_write_lock(&vfsmount_lock);
-        atomic_dec(&mnt->mnt_longterm);
-        br_write_unlock(&vfsmount_lock);
-#endif
-}
-
 /*
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
@@ -2265,18 +2230,13 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
         q = new;
         while (p) {
                 q->mnt_ns = new_ns;
-                __mnt_make_longterm(q);
                 if (fs) {
                         if (&p->mnt == fs->root.mnt) {
                                 fs->root.mnt = mntget(&q->mnt);
-                                __mnt_make_longterm(q);
-                                mnt_make_shortterm(&p->mnt);
                                 rootmnt = &p->mnt;
                         }
                         if (&p->mnt == fs->pwd.mnt) {
                                 fs->pwd.mnt = mntget(&q->mnt);
-                                __mnt_make_longterm(q);
-                                mnt_make_shortterm(&p->mnt);
                                 pwdmnt = &p->mnt;
                         }
                 }
@@ -2320,7 +2280,6 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
         if (!IS_ERR(new_ns)) {
                 struct mount *mnt = real_mount(m);
                 mnt->mnt_ns = new_ns;
-                __mnt_make_longterm(mnt);
                 new_ns->root = mnt;
                 list_add(&new_ns->list, &mnt->mnt_list);
         } else {
@@ -2615,7 +2574,7 @@ struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
                  * it is a longterm mount, don't release mnt until
                  * we unmount before file sys is unregistered
                 */
-                mnt_make_longterm(mnt);
+                real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
         }
         return mnt;
 }
@@ -2625,7 +2584,9 @@ void kern_unmount(struct vfsmount *mnt)
 {
         /* release long term mount so mount point can be released */
         if (!IS_ERR_OR_NULL(mnt)) {
-                mnt_make_shortterm(mnt);
+                br_write_lock(&vfsmount_lock);
+                real_mount(mnt)->mnt_ns = NULL;
+                br_write_unlock(&vfsmount_lock);
                 mntput(mnt);
         }
 }