autofs4: Add v4 pseudo direct mount support

Version 4 of autofs provides a pseudo direct mount implementation
that relies on directories at the leaves of a directory tree under
an indirect mount to trigger mounts.

This patch adds support for that functionality.

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

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 8315565ed7d4db4e3d29505bcf91260deedb25d7..9194e274f849b65b570be6efd621e5974750fdac 100644 (file)
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -630,6 +630,58 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
        return 0;
 }
 
+/*
+ * Version 4 of autofs provides a pseudo direct mount implementation
+ * that relies on directories at the leaves of a directory tree under
+ * an indirect mount to trigger mounts. To allow for this we need to
+ * set the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags on the leaves
+ * of the directory tree. There is no need to clear the automount flag
+ * following a mount or restore it after an expire because these mounts
+ * are always covered. However, it is neccessary to ensure that these
+ * flags are clear on non-empty directories to avoid unnecessary calls
+ * during path walks.
+ */
+static void autofs_set_leaf_automount_flags(struct dentry *dentry)
+{
+       struct dentry *parent;
+
+       /* root and dentrys in the root are already handled */
+       if (IS_ROOT(dentry->d_parent))
+               return;
+
+       managed_dentry_set_managed(dentry);
+
+       parent = dentry->d_parent;
+       /* only consider parents below dentrys in the root */
+       if (IS_ROOT(parent->d_parent))
+               return;
+       managed_dentry_clear_managed(parent);
+       return;
+}
+
+static void autofs_clear_leaf_automount_flags(struct dentry *dentry)
+{
+       struct list_head *d_child;
+       struct dentry *parent;
+
+       /* flags for dentrys in the root are handled elsewhere */
+       if (IS_ROOT(dentry->d_parent))
+               return;
+
+       managed_dentry_clear_managed(dentry);
+
+       parent = dentry->d_parent;
+       /* only consider parents below dentrys in the root */
+       if (IS_ROOT(parent->d_parent))
+               return;
+       d_child = &dentry->d_u.d_child;
+       /* Set parent managed if it's becoming empty */
+       if (d_child->next == &parent->d_subdirs &&
+           d_child->prev == &parent->d_subdirs)
+               managed_dentry_set_managed(parent);
+       return;
+}
+
 static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 {
        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
@@ -657,6 +709,9 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
        spin_unlock(&dentry->d_lock);
        spin_unlock(&autofs4_lock);
 
+       if (sbi->version < 5)
+               autofs_clear_leaf_automount_flags(dentry);
+
        if (atomic_dec_and_test(&ino->count)) {
                p_ino = autofs4_dentry_ino(dentry->d_parent);
                if (p_ino && dentry->d_parent != dentry)
@@ -699,6 +754,9 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
        }
        d_add(dentry, inode);
 
+       if (sbi->version < 5)
+               autofs_set_leaf_automount_flags(dentry);
+
        dentry->d_fsdata = ino;
        ino->dentry = dget(dentry);
        atomic_inc(&ino->count);