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, 17 insertions, 0 deletions

diff --git a/source3/smbd/dir.c b/source3/smbd/dir.c
index b4a8f942c2..e7902871d3 100644
--- a/source3/smbd/dir.c
+++ b/source3/smbd/dir.c
@@ -576,6 +576,9 @@ const char *dptr_ReadDirName(TALLOC_CTX *ctx,
 {
 	char *name = NULL;
 	char *pathreal = NULL;
+	char *found_name = NULL;
+	int ret;
+
 	SET_STAT_INVALID(*pst);
 
 	if (dptr->has_wild || dptr->did_stat) {
@@ -640,6 +643,20 @@ const char *dptr_ReadDirName(TALLOC_CTX *ctx,
 		goto clean;
 	}
 
+	/*
+	 * Try case-insensitive stat if the fs has the ability. This avoids
+	 * scanning the whole directory.
+	 */
+	ret = SMB_VFS_GET_REAL_FILENAME(dptr->conn, dptr->path, dptr->wcard,
+					ctx, &found_name);
+	if (ret == 0) {
+		name = found_name;
+		goto clean;
+	} else if (errno == ENOENT) {
+		/* The case-insensitive lookup was authoritative. */
+		goto clean;
+	}
+
 	TALLOC_FREE(pathreal);
 
 	return dptr_normal_ReadDirName(dptr, poffset, pst);