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

Randy Dunlap
2019-07-01T02:59:44Z

Hi David,

On 6/28/19 8:50 AM, David Howells wrote:
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>
> Documentation/watch_queue.rst | 20 +++++++++++++++++++-
> drivers/misc/Kconfig | 5 +++--
> 2 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/watch_queue.rst b/Documentation/watch_queue.rst
> index 4087a8e670a8..1bec2018d549 100644
> --- a/Documentation/watch_queue.rst
> +++ b/Documentation/watch_queue.rst
> @@ -13,6 +13,10 @@ receive notifications from the kernel. This can be used in conjunction with::
>
> * USB subsystem event notifications
>
> + * Mount topology change notifications
> +
> + * Superblock event notifications
> +
>
> The notifications buffers can be enabled by:
>
> @@ -324,6 +328,19 @@ Any particular buffer can be fed from multiple sources. Sources include:
> for buses and devices. Watchpoints of this type are set on the global
> device watch list.
>
> + * WATCH_TYPE_MOUNT_NOTIFY
> +
> + Notifications of this type indicate mount tree topology changes and mount
> + attribute changes. A watch can be set on a particular file or directory
> + and notifications from the path subtree rooted at that point will be
> + intercepted.
> +
> + * WATCH_TYPE_SB_NOTIFY
> +
> + Notifications of this type indicate superblock events, such as quota limits
> + being hit, I/O errors being produced or network server loss/reconnection.
> + Watches of this type are set directly on superblocks.
> +
>
> Event Filtering
> ===============
> @@ -365,7 +382,8 @@ Where:
> (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.
> + the watched point in a mount tree by specifying NOTIFY_MOUNT_IN_SUBTREE
> + must be 0.

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

>
> * ``subtype_filter`` is a bitmask indicating the subtypes that are of
> interest. Bit 0 of subtype_filter[0] corresponds to subtype 0, bit 1 to

--
~Randy