Re: [PATCH 2/6] Adjust watch_queue documentation to mention mount and superblock watches. [ver #5]

David Howells
2019-07-01T08:53:06Z

Randy Dunlap <rdunlap@infradead.org> wrote:

> I'm having a little trouble parsing that sentence.
> Could you clarify it or maybe rewrite/modify it?
> Thanks.

How about:

* ``info_filter`` and ``info_mask`` act as a filter on the info field of the
notification record. The notification is only written into the buffer if::

(watch.info & info_mask) == info_filter

This could be used, for example, to ignore events that are not exactly on
the watched point in a mount tree by specifying NOTIFY_MOUNT_IN_SUBTREE
must not be set, e.g.::

{
.type = WATCH_TYPE_MOUNT_NOTIFY,
.info_filter = 0,
.info_mask = NOTIFY_MOUNT_IN_SUBTREE,
.subtype_filter = ...,
}

as an event would be only permissible with this filter if::

(watch.info & NOTIFY_MOUNT_IN_SUBTREE) == 0

David