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Date:   Wed, 15 Jan 2020 00:09:05 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Amir Goldstein <amir73il@gmail.com>
Cc:     Jan Kara <jack@suse.cz>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: dcache: abstract take_name_snapshot() interface
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On Wed, Jan 15, 2020 at 02:03:35AM +0200, Amir Goldstein wrote:

> Only problem I forgot about is that I need to propagate name_snapshot
> into fsnotify_move() instead of qstr (in order to snapshot it).
> That means I will need to snapshot also new_dentry in vfs_rename(), so
> I have a name_snapshot to pass into the RENAME_EXCHANGE
> fsnotify_move() hook.
> 
> My current patch passes the cute &old_dentry->d_name_snap abstract
> to fsnotify_move().
> 
> What shall I do about that?
> 
>         take_dentry_name_snapshot(&new_name, new_dentry);
> ???

Wait a sec...  How long is that thing going to be using the snapshot?
And I bloody well hope that this is _not_ going to be unconditional -
having each rename() pay for *notify is a bad idea, for obvious
reasons.  Details, please...