"It should be noted that the kernel may return fields that weren't requested and may fail to return fields that were requested, depending on what the backing filesystem supports. (Fields that are given values despite being unrequested can just be ignored.) In either case, stx_mask will not be equal mask. <snip> "A filesystem may also fill in fields that the caller didn't ask for if it has values for them available and the information is available at no extra cost. If this happens, the corresponding bits will be set in stx_mask." In other words, the kernel is allowed to return information/flags that weren't requested, and userspace can ignore it. --D
