linux-ext4 - Re: [PATCH v5 10/23] fsnotify: Allow events reported with an empty inode

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Date:   Thu, 5 Aug 2021 17:55:28 +0200
From:   Jan Kara <jack@...e.cz>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Jan Kara <jack@...e.cz>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Jan Kara <jack@...e.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Theodore Tso <tytso@....edu>,
        Dave Chinner <david@...morbit.com>,
        David Howells <dhowells@...hat.com>,
        Khazhismel Kumykov <khazhy@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>, kernel@...labora.com
Subject: Re: [PATCH v5 10/23] fsnotify: Allow events reported with an empty
 inode

On Thu 05-08-21 17:14:26, Amir Goldstein wrote:
> > 2) AFAICS 'inode' can be always derived from 'data' as well. So maybe we
> > can drop it Amir?
> 
> If only we could. The reason that we pass the allegedly redundant inode
> argument is because there are two different distinguished inode
> arguments:
> 
> 1. The inode event happened on, which can be referenced from data
> 2. Inode that may be marked, which is passed in the inode argument
> 
> Particularly, dirent events carry the inode of the child as data, but
> intentionally pass NULL inode arguments, because mark on inode
> itself should not be getting e.g. FAN_DELETE event, but
> audit_mark_handle_event() uses the child inode data.

I see, thanks for explanation. I forgot that NULL 'inode' argument from
fsnotify_name() is actually needed for this to work.

> If we wanted to, we could pass report_mask arg to fsnotify()
> instead of inode arg and then fsnotify() will build iter_info
> accordingly, but that sounds very complicated and doesn't gain
> much.

Yeah. I'll think a bit more if we could simplify this but now I don't see
anything obvious.

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