switch the remnants of releasing the mountpoint away from fs_pin

We used to need rather convoluted ordering trickery to guarantee
that dput() of ex-mountpoints happens before the final mntput()
of the same.  Since we don't need that anymore, there's no point
playing with fs_pin for that.

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

diff --git a/fs/fs_pin.c b/fs/fs_pin.c
index a6497cf..47ef3c7 100644 (file)
--- a/fs/fs_pin.c
+++ b/fs/fs_pin.c
@@ -19,20 +19,14 @@ void pin_remove(struct fs_pin *pin)
        spin_unlock_irq(&pin->wait.lock);
 }
 
-void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p)
+void pin_insert(struct fs_pin *pin, struct vfsmount *m)
 {
        spin_lock(&pin_lock);
-       if (p)
-               hlist_add_head(&pin->s_list, p);
+       hlist_add_head(&pin->s_list, &m->mnt_sb->s_pins);
        hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
        spin_unlock(&pin_lock);
 }
 
-void pin_insert(struct fs_pin *pin, struct vfsmount *m)
-{
-       pin_insert_group(pin, m, &m->mnt_sb->s_pins);
-}
-
 void pin_kill(struct fs_pin *p)
 {
        wait_queue_entry_t wait;

diff --git a/fs/mount.h b/fs/mount.h
index 84aa8cd..711a409 100644 (file)
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -58,7 +58,10 @@ struct mount {
        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 */
+       union {
+               struct hlist_node mnt_mp_list;  /* list mounts with the same mountpoint */
+               struct hlist_node mnt_umount;
+       };
        struct list_head mnt_umounting; /* list entry for umount propagation */
 #ifdef CONFIG_FSNOTIFY
        struct fsnotify_mark_connector __rcu *mnt_fsnotify_marks;
@@ -68,7 +71,7 @@ struct mount {
        int mnt_group_id;               /* peer group identifier */
        int mnt_expiry_mark;            /* true if marked for expiry */
        struct hlist_head mnt_pins;
-       struct fs_pin mnt_umount;
+       struct hlist_head mnt_stuck_children;
 } __randomize_layout;
 
 #define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */

diff --git a/fs/namespace.c b/fs/namespace.c
index 46316ba..54a815e 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -171,13 +171,6 @@ unsigned int mnt_get_count(struct mount *mnt)
 #endif
 }
 
-static void drop_mountpoint(struct fs_pin *p)
-{
-       struct mount *m = container_of(p, struct mount, mnt_umount);
-       pin_remove(p);
-       mntput(&m->mnt);
-}
-
 static struct mount *alloc_vfsmnt(const char *name)
 {
        struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
@@ -215,7 +208,7 @@ static struct mount *alloc_vfsmnt(const char *name)
                INIT_LIST_HEAD(&mnt->mnt_slave);
                INIT_HLIST_NODE(&mnt->mnt_mp_list);
                INIT_LIST_HEAD(&mnt->mnt_umounting);
-               init_fs_pin(&mnt->mnt_umount, drop_mountpoint);
+               INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
        }
        return mnt;
 
@@ -1087,19 +1080,22 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
 
 static void cleanup_mnt(struct mount *mnt)
 {
+       struct hlist_node *p;
+       struct mount *m;
        /*
-        * This probably indicates that somebody messed
-        * up a mnt_want/drop_write() pair.  If this
-        * happens, the filesystem was probably unable
-        * to make r/w->r/o transitions.
-        */
-       /*
+        * The warning here probably indicates that somebody messed
+        * up a mnt_want/drop_write() pair.  If this happens, the
+        * filesystem was probably unable to make r/w->r/o transitions.
         * The locking used to deal with mnt_count decrement provides barriers,
         * so mnt_get_writers() below is safe.
         */
        WARN_ON(mnt_get_writers(mnt));
        if (unlikely(mnt->mnt_pins.first))
                mnt_pin_kill(mnt);
+       hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
+               hlist_del(&m->mnt_umount);
+               mntput(&m->mnt);
+       }
        fsnotify_vfsmount_delete(&mnt->mnt);
        dput(mnt->mnt.mnt_root);
        deactivate_super(mnt->mnt.mnt_sb);
@@ -1168,6 +1164,7 @@ static void mntput_no_expire(struct mount *mnt)
                struct mount *p, *tmp;
                list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts,  mnt_child) {
                        __put_mountpoint(unhash_mnt(p), &list);
+                       hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
                }
        }
        unlock_mount_hash();
@@ -1360,6 +1357,8 @@ EXPORT_SYMBOL(may_umount);
 static void namespace_unlock(void)
 {
        struct hlist_head head;
+       struct hlist_node *p;
+       struct mount *m;
        LIST_HEAD(list);
 
        hlist_move_list(&unmounted, &head);
@@ -1374,7 +1373,10 @@ static void namespace_unlock(void)
 
        synchronize_rcu_expedited();
 
-       group_pin_kill(&head);
+       hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
+               hlist_del(&m->mnt_umount);
+               mntput(&m->mnt);
+       }
 }
 
 static inline void namespace_lock(void)
@@ -1461,8 +1463,6 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 
                disconnect = disconnect_mount(p, how);
 
-               pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
-                                disconnect ? &unmounted : NULL);
                if (mnt_has_parent(p)) {
                        mnt_add_count(p->mnt_parent, -1);
                        if (!disconnect) {
@@ -1470,6 +1470,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
                                list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
                        } else {
                                umount_mnt(p);
+                               hlist_add_head(&p->mnt_umount, &unmounted);
                        }
                }
                change_mnt_propagation(p, MS_PRIVATE);
@@ -1622,8 +1623,8 @@ void __detach_mounts(struct dentry *dentry)
        while (!hlist_empty(&mp->m_list)) {
                mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
                if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
-                       hlist_add_head(&mnt->mnt_umount.s_list, &unmounted);
                        umount_mnt(mnt);
+                       hlist_add_head(&mnt->mnt_umount, &unmounted);
                }
                else umount_tree(mnt, UMOUNT_CONNECTED);
        }

diff --git a/include/linux/fs_pin.h b/include/linux/fs_pin.h
index 7cab74d..bdd09fd 100644 (file)
--- a/include/linux/fs_pin.h
+++ b/include/linux/fs_pin.h
@@ -20,6 +20,5 @@ static inline void init_fs_pin(struct fs_pin *p, void (*kill)(struct fs_pin *))
 }
 
 void pin_remove(struct fs_pin *);
-void pin_insert_group(struct fs_pin *, struct vfsmount *, struct hlist_head *);
 void pin_insert(struct fs_pin *, struct vfsmount *);
 void pin_kill(struct fs_pin *);