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References: <20210812214010.3197279-1-krisman@collabora.com> <20210812214010.3197279-12-krisman@collabora.com>
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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Fri, 13 Aug 2021 10:59:52 +0300
Message-ID: <CAOQ4uxiDQ+=gwFQPsa_F-A85rQ9d1wi9-fg+L6mTUv6tPZ93xg@mail.gmail.com>
Subject: Re: [PATCH v6 11/21] fanotify: Allow file handle encoding for
 unhashed events
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     Jan Kara <jack@suse.com>, Linux API <linux-api@vger.kernel.org>,
        Ext4 <linux-ext4@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Khazhismel Kumykov <khazhy@google.com>,
        David Howells <dhowells@redhat.com>,
        Dave Chinner <david@fromorbit.com>,
        Theodore Tso <tytso@mit.edu>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Matthew Bobrowski <repnop@google.com>, kernel@collabora.com,
        Jan Kara <jack@suse.cz>
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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
>