On Sun 30-03-25 14:55:36, Amir Goldstein wrote:
> The new FAN_PRE_ACCESS events are created before access to a file range,
> to provides an opportunity for the event listener to modify the content
> of the object before the user can accesss it.
>
> Those events are available for group in class FAN_CLASS_PRE_CONTENT
> They are reported with FAN_EVENT_INFO_TYPE_RANGE info record.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> man/man2/fanotify_init.2 | 4 ++--
> man/man2/fanotify_mark.2 | 14 +++++++++++++
> man/man7/fanotify.7 | 43 ++++++++++++++++++++++++++++++++++++++--
> 3 files changed, 57 insertions(+), 4 deletions(-)
>
> diff --git a/man/man2/fanotify_init.2 b/man/man2/fanotify_init.2
> index 23fbe126f..b1ef8018c 100644
> --- a/man/man2/fanotify_init.2
> +++ b/man/man2/fanotify_init.2
> @@ -57,8 +57,8 @@ Only one of the following notification classes may be specified in
> .B FAN_CLASS_PRE_CONTENT
> This value allows the receipt of events notifying that a file has been
> accessed and events for permission decisions if a file may be accessed.
> -It is intended for event listeners that need to access files before they
> -contain their final data.
> +It is intended for event listeners that may need to write data to files
> +before their final data can be accessed.
> This notification class might be used by hierarchical storage managers,
> for example.
> Use of this flag requires the
> diff --git a/man/man2/fanotify_mark.2 b/man/man2/fanotify_mark.2
> index 47cafb21c..edbcdc592 100644
> --- a/man/man2/fanotify_mark.2
> +++ b/man/man2/fanotify_mark.2
> @@ -445,6 +445,20 @@ or
> .B FAN_CLASS_CONTENT
> is required.
> .TP
> +.BR FAN_PRE_ACCESS " (since Linux 6.14)"
> +.\" commit 4f8afa33817a6420398d1c177c6e220a05081f51
> +Create an event before read or write access to a file range,
> +that provides an opportunity for the event listener
> +to modify the content of the file
> +before access to the content
> +in the specified range.
> +An additional information record of type
> +.B FAN_EVENT_INFO_TYPE_RANGE
> +is returned for each event in the read buffer.
> +An fanotify file descriptor created with
> +.B FAN_CLASS_PRE_CONTENT
> +is required.
> +.TP
> .B FAN_ONDIR
> Create events for directories\[em]for example, when
> .BR opendir (3),
> diff --git a/man/man7/fanotify.7 b/man/man7/fanotify.7
> index 7844f52f6..6f3a9496e 100644
> --- a/man/man7/fanotify.7
> +++ b/man/man7/fanotify.7
> @@ -247,6 +247,26 @@ struct fanotify_event_info_error {
> .EE
> .in
> .P
> +In case of
> +.B FAN_PRE_ACCESS
> +events,
> +an additional information record describing the access range
> +is returned alongside the generic
> +.I fanotify_event_metadata
> +structure within the read buffer.
> +This structure is defined as follows:
> +.P
> +.in +4n
> +.EX
> +struct fanotify_event_info_range {
> + struct fanotify_event_info_header hdr;
> + __u32 pad;
> + __u64 offset;
> + __u64 count;
> +};
> +.EE
> +.in
> +.P
> All information records contain a nested structure of type
> .IR fanotify_event_info_header .
> This structure holds meta-information about the information record
> @@ -509,8 +529,9 @@ The value of this field can be set to one of the following:
> .BR FAN_EVENT_INFO_TYPE_FID ,
> .BR FAN_EVENT_INFO_TYPE_DFID ,
> .BR FAN_EVENT_INFO_TYPE_DFID_NAME ,
> -or
> -.BR FAN_EVENT_INFO_TYPE_PIDFD .
> +.BR FAN_EVENT_INFO_TYPE_PIDFD ,
> +.BR FAN_EVENT_INFO_TYPE_ERROR ,
> +.BR FAN_EVENT_INFO_TYPE_RANGE .
> The value set for this field
> is dependent on the flags that have been supplied to
> .BR fanotify_init (2).
> @@ -711,6 +732,24 @@ Identifies the type of error that occurred.
> This is a counter of the number of errors suppressed
> since the last error was read.
> .P
> +The fields of the
> +.I fanotify_event_info_range
> +structure are as follows:
> +.TP
> +.I hdr
> +This is a structure of type
> +.IR fanotify_event_info_header .
> +The
> +.I info_type
> +field is set to
> +.BR FAN_EVENT_INFO_TYPE_RANGE .
> +.TP
> +.I count
> +The number of bytes being read or written to the file.
> +.TP
> +.I offset
> +The offset from which bytes are read or written to the file.
> +.P
> The following macros are provided to iterate over a buffer containing
> fanotify event metadata returned by a
> .BR read (2)
> --
> 2.34.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
