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

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Date:   Sun, 30 Jun 2019 19:59:33 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     David Howells <dhowells@...hat.com>, viro@...iv.linux.org.uk
Cc:     Casey Schaufler <casey@...aufler-ca.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        nicolas.dichtel@...nd.com, raven@...maw.net,
        Christian Brauner <christian@...uner.io>,
        keyrings@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] Adjust watch_queue documentation to mention mount and
 superblock watches. [ver #5]

Hi David,

On 6/28/19 8:50 AM, David Howells wrote:
> Signed-off-by: David Howells <dhowells@...hat.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