VFS: allow ->d_manage() to declare -EISDIR in rcu_walk mode.
In REF-walk mode, ->d_manage can return -EISDIR to indicate
that the dentry is not really a mount trap (or even a mount point)
and that any mounts or any DCACHE_NEED_AUTOMOUNT flag should be
ignored.
RCU-walk mode doesn't currently support this, so if there is a dentry
with DCACHE_NEED_AUTOMOUNT set but which shouldn't be a mount-trap,
lookup_fast() will always drop in REF-walk mode.
With this patch, an -EISDIR from ->d_manage will always cause mounts
and automounts to be ignored, both in REF-walk and RCU-walk.
Bug-fixed-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index a1d0d7a..61d65cc 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -1053,7 +1053,8 @@
If the 'rcu_walk' parameter is true, then the caller is doing a
pathwalk in RCU-walk mode. Sleeping is not permitted in this mode,
and the caller can be asked to leave it and call again by returning
- -ECHILD.
+ -ECHILD. -EISDIR may also be returned to tell pathwalk to
+ ignore d_automount or any mounts.
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.