On Mon, Apr 26, 2021 at 9:42 PM Gabriel Krisman Bertazi
<krisman@xxxxxxxxxxxxx> wrote:
>
> This record describes a fs error in a fs agnostic way. It will be send
> back to userspace in response to a FSNOTIFY_EVENT_ERROR for groups with
> the FAN_ERROR mark.
It's not a mark, it's an event, so:
"...for groups with the FAN_ERROR event in their mark mask"
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
> ---
> fs/notify/fanotify/fanotify.h | 16 ++++++++++++++++
> fs/notify/fanotify/fanotify_user.c | 28 ++++++++++++++++++++++++++++
> include/uapi/linux/fanotify.h | 10 ++++++++++
> 3 files changed, 54 insertions(+)
>
> diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
> index 47299e3d6efd..4cb9dd31f084 100644
> --- a/fs/notify/fanotify/fanotify.h
> +++ b/fs/notify/fanotify/fanotify.h
> @@ -179,6 +179,22 @@ FANOTIFY_NE(struct fanotify_event *event)
> return container_of(event, struct fanotify_name_event, fae);
> }
>
> +struct fanotify_error_event {
> + struct fanotify_event fae;
> + int error;
> + __kernel_fsid_t fsid;
> +
> + int fs_data_size;
> + /* Must be the last item in the structure */
> + char fs_data[0];
> +};
> +
> +static inline struct fanotify_error_event *
> +FANOTIFY_EE(struct fanotify_event *event)
> +{
> + return container_of(event, struct fanotify_error_event, fae);
> +}
> +
> static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
> {
> if (event->type == FANOTIFY_EVENT_TYPE_FID)
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 5031198bf7db..21162d347bd1 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -64,6 +64,11 @@ static int fanotify_fid_info_len(int fh_len, int name_len)
> return roundup(FANOTIFY_INFO_HDR_LEN + info_len, FANOTIFY_EVENT_ALIGN);
> }
>
> +static size_t fanotify_error_info_len(struct fanotify_error_event *fee)
> +{
> + return sizeof(struct fanotify_event_info_error);
> +}
> +
> static size_t fanotify_event_len(struct fanotify_event *event,
> unsigned int fid_mode)
> {
> @@ -232,6 +237,29 @@ static int process_access_response(struct fsnotify_group *group,
> return -ENOENT;
> }
>
> +static size_t copy_error_info_to_user(struct fanotify_error_event *fee,
> + char __user *buf, int count)
> +{
> + struct fanotify_event_info_error info;
> +
> + info.hdr.info_type = FAN_EVENT_INFO_TYPE_ERROR;
> + info.hdr.pad = 0;
> + info.hdr.len = fanotify_error_info_len(fee);
> +
> + if (WARN_ON(count < info.hdr.len))
> + return -EFAULT;
> +
> + info.version = FANOTIFY_EVENT_INFO_ERROR_VERS_1;
> + info.error = fee->error;
> + info.fsid = fee->fsid;
> +
> + if (copy_to_user(buf, &info, sizeof(info)))
> + return -EFAULT;
> +
> + return info.hdr.len;
> +
> +}
> +
> static int copy_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
> int info_type, const char *name, size_t name_len,
> char __user *buf, size_t count)
> diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
> index b283531549f1..cc9a1fa80e30 100644
> --- a/include/uapi/linux/fanotify.h
> +++ b/include/uapi/linux/fanotify.h
> @@ -124,6 +124,7 @@ struct fanotify_event_metadata {
> #define FAN_EVENT_INFO_TYPE_FID 1
> #define FAN_EVENT_INFO_TYPE_DFID_NAME 2
> #define FAN_EVENT_INFO_TYPE_DFID 3
> +#define FAN_EVENT_INFO_TYPE_ERROR 4
>
> /* Variable length info record following event metadata */
> struct fanotify_event_info_header {
> @@ -149,6 +150,15 @@ struct fanotify_event_info_fid {
> unsigned char handle[0];
> };
>
> +#define FANOTIFY_EVENT_INFO_ERROR_VERS_1 1
Honestly, this struct is too simple to have a 'version'.
The format of this simple struct is already defined by
FAN_EVENT_INFO_TYPE_ERROR and if we want to change
the reported info in the future, we can use
FAN_EVENT_INFO_TYPE_ERROR_V2.
In fact, I suggest to name the type
FAN_EVENT_INFO_TYPE_FS_ERROR
to differentiate from a future
FAN_EVENT_INFO_TYPE_WB_ERROR
> +
> +struct fanotify_event_info_error {
> + struct fanotify_event_info_header hdr;
> + int version;
> + int error;
> + __kernel_fsid_t fsid;
> +};
I suggest to put an error seq counter in this struct.
The per-sb seq counter can be provided by the filesystem
or by fsnotify.
Thanks,
Amir.
