Re: [RFC PATCH 1/1] fanotify.7, fanotify_init.2, fanotify_mark.2: Document FAN_REPORT_FID and directory modification events

[Jan Kara <jack@suse.cz>]

Thanks for the manpage updates! Some small comments below.

On Tue 12-03-19 13:48:29, Matthew Bobrowski wrote:
> +.TP
> +.B FAN_MOVED_FROM
> +Create an event when a marked file or directory is moved from the current
> +location.
> +.TP
> +.B FAN_MOVED_TO
> +Create an event when a marked file or directory is moved to a new
> +location.

For these two events (like other directory events), marked thing is
actually again the parent directory - i.e., these events trigger is
something is moved to / from marked directory. So I think it would be
clearer and use the same language like e.g. for FAN_CREATE and speak about
marked parent directory.

>  Without this flag, only events for files are created.
> +The
> +.BR FAN_ONDIR
> +flag is reported in an event mask only if the
> +.I fanotify_fd
> +file descriptor has been initialized with the flag
> +.BR FAN_REPORT_FID .
> +In the context of directory entry events, such as
> +.BR FAN_CREATE ,
> +.BR FAN_DELETE
> +and
> +.BR FAN_MOVE

Maybe too early to speak about FAN_MOVE here as it's not defined yet? I'd
rather explicitely use FAN_MOVE_FROM and FAN_MOVE_TO here.

> diff --git a/man7/fanotify.7 b/man7/fanotify.7
> index 74246063e..039764d30 100644
> --- a/man7/fanotify.7
> +++ b/man7/fanotify.7
...
> +.B FAN_ATTRIB
> +A file or directory metadata was changed.
> +.TP
> +.B FAN_CREATE
> +A child file or directory was created in a watched parent.
> +.TP
> +.B FAN_DELETE
> +A child file or directory was deleted in a watched parent.
> +.TP
> +.B FAN_DELETE_SELF
> +A watched file or directory was deleted.
> +.TP
> +.B FAN_MOVED_FROM
> +A watched file or directory was moved from the current location.
> +.TP
> +.B FAN_MOVED_TO
> +A watched file or directory was moved to a new location.

The same comment here about parent directory being actually marked.

> +.TP
> +.I hdr
> +This is a structure of type
> +.IR fanotify_event_info_header .
> +It is a generic header that contains information used to describe the type
> +of event.

"type of event" seems a bit unfortunate wording here since I'd expect that
to be FAN_CREATE or whatever. I'd rather choose something like "used to
describe additional information attached to the event".

> +For example, when an fanotify file descriptor is created using
> +.B FAN_REPORT_FID
> +the
> +.I info_type
> +field of this header is set to
> +.BR FAN_EVENT_INFO_TYPE_FID .
> +Event listeners can use this field to check that events of the correct
> +type are being received.

I think here you should also speak about the 'len' field in the header
which can be used to skip additional information that is not understood /
uninteresting for the receiver of the event.

> +.TP
> +.I fsid
> +This is a unique identifier of the filesystem containing the object
> +associated with the event.
> +It is a structure of type
> +.I __kernel_fsid_t
> +and contains the same value as
> +.I f_fsid
> +when calling
> +.BR statfs (2).
> +.TP
> +.I file_handle
> +This is a variable length structure of type
> +.IR file_handle .
> +It is an opaque handle that corresponds to a specified object on a
> +filesystem as returned by
> +.BR name_at_handle_at (2) .

name_to_handle_at (2)

> +.PP
> +The second example program output was captured from fanotify_fid.
> +There are two discrete invocations to this program with each invocation
> +accommodating a different action performed on a watched object.
> +This first session shows a mark being placed on
> +.IR /home/user .
> +This is followed by a subsequent regular file
> +.IR /home/user/testfile.txt
> +being created.
> +This results in a
> +.B FAN_CREATE
> +event being created and reported against the files parent watched
						^^^ file's ?

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR