Index: smbd/trans2.c
===================================================================
--- smbd/trans2.c	(revision 23844)
+++ smbd/trans2.c	(working copy)
@@ -4845,18 +4845,21 @@
 		allocation_size = smb_roundup(conn, allocation_size);
 	}
 
-	if(allocation_size == get_file_size(*psbuf)) {
-		return NT_STATUS_OK;
-	}
- 
 	DEBUG(10,("smb_set_file_allocation_info: file %s : setting new allocation size to %.0f\n",
 			fname, (double)allocation_size ));
- 
+
 	if (fsp && fsp->fh->fd != -1) {
 		/* Open file handle. */
 		if (vfs_allocate_file_space(fsp, allocation_size) == -1) {
 			return map_nt_error_from_unix(errno);
 		}
+		/* Changing the allocation size should set the last mod time. */
+		fsp_set_pending_modtime(fsp, timespec_current());
+
+		/*
+		 * This is equivalent to a write. Ensure it's seen immediately.
+		 */
+		set_filetime(fsp->conn, fsp->fsp_name, fsp->pending_modtime);
 		return NT_STATUS_OK;
 	}
 
@@ -4875,6 +4878,11 @@
 		/* NB. We check for open_was_deferred in the caller. */
 		return status;
 	}
+
+	/* Changing the allocation size should set the last mod time. */
+	fsp_set_pending_modtime(new_fsp, timespec_current());
+	/* Don't need to call set_filetime as this will be flushed on
+	 * close. */
 	if (vfs_allocate_file_space(new_fsp, allocation_size) == -1) {
 		status = map_nt_error_from_unix(errno);
 		close_file(new_fsp,NORMAL_CLOSE);