Re: [PATCH v6 11/21] fanotify: Allow file handle encoding for unhashed events

[Amir Goldstein <amir73il@gmail.com>]

On Fri, Aug 13, 2021 at 12:41 AM Gabriel Krisman Bertazi
<krisman@collabora.com> wrote:
>
> FAN_FS_ERROR will report a file handle, but it is an unhashed event.
> Allow passing a NULL hash to fanotify_encode_fh and avoid calculating
> the hash if not needed.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> Reviewed-by: Jan Kara <jack@suse.cz>

Reviewed-by: Amir Goldstein <amir73il@gmail.com>

> ---
>  fs/notify/fanotify/fanotify.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index acf78c0ed219..50fce4fec0d6 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -403,8 +403,12 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
>         fh->type = type;
>         fh->len = fh_len;
>
> -       /* Mix fh into event merge key */
> -       *hash ^= fanotify_hash_fh(fh);
> +       /*
> +        * Mix fh into event merge key.  Hash might be NULL in case of
> +        * unhashed FID events (i.e. FAN_FS_ERROR).
> +        */
> +       if (hash)
> +               *hash ^= fanotify_hash_fh(fh);
>
>         return FANOTIFY_FH_HDR_LEN + fh_len;
>
> --
> 2.32.0
>