VFS: Fix automount for negative autofs dentries

commit 5a30d8a2b8ddd5102c440c7e5a7c8e1fd729c818 upstream.
[ backport for 3.0.x: LOOKUP_PARENT => LOOKUP_CONTINUE by Chuck Ebbert
<cebbert@redhat.com> ]

Autofs may set the DCACHE_NEED_AUTOMOUNT flag on negative dentries.  These
need attention from the automounter daemon regardless of the LOOKUP_FOLLOW flag.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/namei.c b/fs/namei.c
index 7bab4add8a102477170a7b964acad12b5fd063af..80e239d685c663ab47fdadd121fd300581fe3ab7 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -781,19 +781,25 @@ static int follow_automount(struct path *path, unsigned flags,
        if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
                return -EISDIR; /* we actually want to stop here */
 
-       /* We want to mount if someone is trying to open/create a file of any
-        * type under the mountpoint, wants to traverse through the mountpoint
-        * or wants to open the mounted directory.
-        *
+       /*
         * We don't want to mount if someone's just doing a stat and they've
         * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
         * appended a '/' to the name.
         */
-       if (!(flags & LOOKUP_FOLLOW) &&
-           !(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
-                      LOOKUP_OPEN | LOOKUP_CREATE)))
-               return -EISDIR;
-
+       if (!(flags & LOOKUP_FOLLOW)) {
+               /* We do, however, want to mount if someone wants to open or
+                * create a file of any type under the mountpoint, wants to
+                * traverse through the mountpoint or wants to open the mounted
+                * directory.
+                * Also, autofs may mark negative dentries as being automount
+                * points.  These will need the attentions of the daemon to
+                * instantiate them before they can be used.
+                */
+               if (!(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
+                            LOOKUP_OPEN | LOOKUP_CREATE)) &&
+                   path->dentry->d_inode)
+                       return -EISDIR;
+       }
        current->total_link_count++;
        if (current->total_link_count >= 40)
                return -ELOOP;