s3: Fix trans2 path to use case-insensitive stat optimization

Often times before creating a file, a client will first query to see
if it already exists.  Since some systems have a case-insensitive stat
that is called from unix_convert, we can definitively return
STATUS_NO_SUCH_FILE to the client without scanning the whole
directory.

This code path is taken from trans2querypathinfo, but trans2findfirst
still does a full directory scan even though the get_real_filename
(the case-insensitive stat vfs call) can prevent this.

This patch adds the get_real_filename call to the trans2find* path,
and also changes the vfs_default behavior for
SMB_VFS_GET_REAL_FILENAME.  Previously, in the absence of a
get_real_filename implementation, we would fallback to the full
directory scan.  The default behavior now returns -1 and sets errno to
EOPNOTSUPP.  This allows SMB_VFS_GET_REALFILENAME to be called from
trans2* and unix_convert.

1 files changed, 6 insertions, 2 deletions

diff --git a/source3/modules/vfs_default.c b/source3/modules/vfs_default.c
index bb01f985881..6c1946a99d0 100644
--- a/source3/modules/vfs_default.c
+++ b/source3/modules/vfs_default.c
@@ -1120,8 +1120,12 @@ static int vfswrap_get_real_filename(struct vfs_handle_struct *handle,
 				     TALLOC_CTX *mem_ctx,
 				     char **found_name)
 {
-	return get_real_filename(handle->conn, path, name, mem_ctx,
-				 found_name);
+	/*
+	 * Don't fall back to get_real_filename so callers can differentiate
+	 * between a full directory scan and an actual case-insensitive stat.
+	 */
+	errno = EOPNOTSUPP;
+	return -1;
 }
 
 static NTSTATUS vfswrap_brl_lock_windows(struct vfs_handle_struct *handle,