[PATCH] autofs4: avoid panic on bind mount of autofs owned directory

While this is not a solution to bind and move mounts on autofs owned
directories it is necessary to fix the trady error handling.

At least it avoids the kernel panic I observed checking out bug #4589.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index c7b2b8890188..9c09641ce907 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -185,6 +185,19 @@ int autofs4_wait(struct autofs_sb_info *,struct dentry *, enum autofs_notify);
 int autofs4_wait_release(struct autofs_sb_info *,autofs_wqt_t,int);
 void autofs4_catatonic_mode(struct autofs_sb_info *);
 
+static inline int autofs4_follow_mount(struct vfsmount **mnt, struct dentry **dentry)
+{
+        int res = 0;
+
+        while (d_mountpoint(*dentry)) {
+                int followed = follow_down(mnt, dentry);
+                if (!followed)
+                        break;
+                res = 1;
+        }
+        return res;
+}
+
 static inline int simple_positive(struct dentry *dentry)
 {
         return dentry->d_inode && !d_unhashed(dentry);