Commit ba97a0a3 authored by Ian Kent's avatar Ian Kent Committed by Andrew Morton
Browse files

autofs: add comment about autofs_mountpoint_changed() 

The function autofs_mountpoint_changed() is unusual, add a comment about
two cases for which it is needed.

Link: https://lkml.kernel.org/r/165724459804.30914.10974834416046555127.stgit@donald.themaw.net


Signed-off-by: default avatarIan Kent <raven@themaw.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent a4a87303

fs/autofs/root.c

+20 −3
Original line number Diff line number Diff line
@@ -291,9 +291,26 @@ static struct dentry *autofs_mountpoint_changed(struct path *path) 
	struct dentry *dentry = path->dentry;

	struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);



	/*

	 * If this is an indirect mount the dentry could have gone away

	 * as a result of an expire and a new one created.

	/* If this is an indirect mount the dentry could have gone away

	 * and a new one created.

	 *

	 * This is unusual and I can't remember the case for which it

	 * was originally added now. But an example of how this can

	 * happen is an autofs indirect mount that has the "browse"

	 * option set and also has the "symlink" option in the autofs

	 * map entry. In this case the daemon will remove the browse

	 * directory and create a symlink as the mount leaving the

	 * struct path stale.

	 *

	 * Another not so obvious case is when a mount in an autofs

	 * indirect mount that uses the "nobrowse" option is being

	 * expired at the same time as a path walk. If the mount has

	 * been umounted but the mount point directory seen before

	 * becoming unhashed (during a lockless path walk) when a stat

	 * family system call is made the mount won't be re-mounted as

	 * it should. In this case the mount point that's been removed

	 * (by the daemon) will be stale and the a new mount point

	 * dentry created.

	 */

	if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) {

		struct dentry *parent = dentry->d_parent;