Commit dd89f90d authored by Ian Kent's avatar Ian Kent Committed by Al Viro
Browse files

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: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 9e3fea16

fs/autofs4/root.c

+58 −0
Original line number Diff line number Diff line
@@ -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);