split __lookup_mnt() in two functions

Instead of passing the direction as argument (and checking it on every
step through the hash chain), just have separate __lookup_mnt() and
__lookup_mnt_last().  And use the standard iterators...

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

4 files changed, 30 insertions, 25 deletions

diff --git a/fs/mount.h b/fs/mount.h
index 7076f25af35d..f0866076de6e 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -77,7 +77,8 @@ static inline int is_mounted(struct vfsmount *mnt)
         return !IS_ERR_OR_NULL(real_mount(mnt));
 }
 
-extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
+extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);
+extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *);
 
 static inline void get_mnt_ns(struct mnt_namespace *ns)
 {
diff --git a/fs/namei.c b/fs/namei.c
index 645268f23eb6..1f844fbfce72 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1111,7 +1111,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
                 if (!d_mountpoint(path->dentry))
                         break;
 
-                mounted = __lookup_mnt(path->mnt, path->dentry, 1);
+                mounted = __lookup_mnt(path->mnt, path->dentry);
                 if (!mounted)
                         break;
                 path->mnt = &mounted->mnt;
@@ -1132,7 +1132,7 @@ static void follow_mount_rcu(struct nameidata *nd)
 {
         while (d_mountpoint(nd->path.dentry)) {
                 struct mount *mounted;
-                mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
+                mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
                 if (!mounted)
                         break;
                 nd->path.mnt = &mounted->mnt;
diff --git a/fs/namespace.c b/fs/namespace.c
index 5cbe8cefadb5..500202ce10db 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -548,29 +548,33 @@ static void free_vfsmnt(struct mount *mnt)
 }
 
 /*
- * find the first or last mount at @dentry on vfsmount @mnt depending on
- * @dir. If @dir is set return the first mount else return the last mount.
+ * find the first mount at @dentry on vfsmount @mnt.
  * vfsmount_lock must be held for read or write.
  */
-struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
-                              int dir)
+struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
 {
         struct list_head *head = mount_hashtable + hash(mnt, dentry);
-        struct list_head *tmp = head;
-        struct mount *p, *found = NULL;
+        struct mount *p;
 
-        for (;;) {
-                tmp = dir ? tmp->next : tmp->prev;
-                p = NULL;
-                if (tmp == head)
-                        break;
-                p = list_entry(tmp, struct mount, mnt_hash);
-                if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) {
-                        found = p;
-                        break;
-                }
-        }
-        return found;
+        list_for_each_entry(p, head, mnt_hash)
+                if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
+                        return p;
+        return NULL;
+}
+
+/*
+ * find the last mount at @dentry on vfsmount @mnt.
+ * vfsmount_lock must be held for read or write.
+ */
+struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
+{
+        struct list_head *head = mount_hashtable + hash(mnt, dentry);
+        struct mount *p;
+
+        list_for_each_entry_reverse(p, head, mnt_hash)
+                if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
+                        return p;
+        return NULL;
 }
 
 /*
@@ -594,7 +598,7 @@ struct vfsmount *lookup_mnt(struct path *path)
         struct mount *child_mnt;
 
         br_read_lock(&vfsmount_lock);
-        child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
+        child_mnt = __lookup_mnt(path->mnt, path->dentry);
         if (child_mnt) {
                 mnt_add_count(child_mnt, 1);
                 br_read_unlock(&vfsmount_lock);
diff --git a/fs/pnode.c b/fs/pnode.c
index 58933fd149ad..c7221bb19801 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -310,7 +310,7 @@ int propagate_mount_busy(struct mount *mnt, int refcnt)
 
         for (m = propagation_next(parent, parent); m;
                         m = propagation_next(m, parent)) {
-                child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint, 0);
+                child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);
                 if (child && list_empty(&child->mnt_mounts) &&
                     (ret = do_refcount_check(child, 1)))
                         break;
@@ -332,8 +332,8 @@ static void __propagate_umount(struct mount *mnt)
         for (m = propagation_next(parent, parent); m;
                         m = propagation_next(m, parent)) {
 
-                struct mount *child = __lookup_mnt(&m->mnt,
-                                        mnt->mnt_mountpoint, 0);
+                struct mount *child = __lookup_mnt_last(&m->mnt,
+                                                mnt->mnt_mountpoint);
                 /*
                  * umount the child only if the child has no
                  * other children