autofs4 - fix autofs4_expire_indirect() traversal

The vfs-scale changes changed the traversal used in
autofs4_expire_indirect() from a list to a depth first tree traversal
which isn't right.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index c403abcc725b2df3357d791c27a7052ccb72bf37..bc482e07b925d41a92d5a562cde2b1d97c32c7c2 100644 (file)
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -86,6 +86,56 @@ done:
        return status;
 }
 
+/*
+ * Calculate and dget next entry in the subdirs list under root.
+ */
+static struct dentry *get_next_positive_subdir(struct dentry *prev,
+                                               struct dentry *root)
+{
+       struct list_head *next;
+       struct dentry *p, *q;
+
+       spin_lock(&autofs4_lock);
+
+       if (prev == NULL) {
+               spin_lock(&root->d_lock);
+               prev = dget_dlock(root);
+               next = prev->d_subdirs.next;
+               p = prev;
+               goto start;
+       }
+
+       p = prev;
+       spin_lock(&p->d_lock);
+again:
+       next = p->d_u.d_child.next;
+start:
+       if (next == &root->d_subdirs) {
+               spin_unlock(&p->d_lock);
+               spin_unlock(&autofs4_lock);
+               dput(prev);
+               return NULL;
+       }
+
+       q = list_entry(next, struct dentry, d_u.d_child);
+
+       spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
+       /* Negative dentry - try next */
+       if (!simple_positive(q)) {
+               spin_unlock(&p->d_lock);
+               p = q;
+               goto again;
+       }
+       dget_dlock(q);
+       spin_unlock(&q->d_lock);
+       spin_unlock(&p->d_lock);
+       spin_unlock(&autofs4_lock);
+
+       dput(prev);
+
+       return q;
+}
+
 /*
  * Calculate and dget next entry in top down tree traversal.
  */
@@ -333,7 +383,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
        timeout = sbi->exp_timeout;
 
        dentry = NULL;
-       while ((dentry = get_next_positive_dentry(dentry, root))) {
+       while ((dentry = get_next_positive_subdir(dentry, root))) {
                spin_lock(&sbi->fs_lock);
                ino = autofs4_dentry_ino(dentry);
                /* No point expiring a pending mount */