vfs: introduce d_instantiate_no_diralias()

...which just returns -EBUSY if a directory alias would be created.

This is to be used by fuse mkdir to make sure that a buggy or malicious
userspace filesystem doesn't do anything nasty.  Previously fuse used a
private mutex for this purpose, which can now go away.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 0 insertions, 3 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5b9e6f3b6aef..fe446c222e3f 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -374,9 +374,6 @@ struct fuse_conn {
 	/** Lock protecting accessess to  members of this structure */
 	spinlock_t lock;
 
-	/** Mutex protecting against directory alias creation */
-	struct mutex inst_mutex;
-
 	/** Refcount */
 	atomic_t count;