linux-kernel - Re: [PATCH v8 01/10] kernfs: Remove reference counting for kernfs_open

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Message-ID: <YmhSYkXp0KBXOyFc@zeniv-ca.linux.org.uk>
Date:   Tue, 26 Apr 2022 20:13:22 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Tejun Heo <tj@...nel.org>
Cc:     Imran Khan <imran.f.khan@...cle.com>, gregkh@...uxfoundation.org,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 01/10] kernfs: Remove reference counting for
 kernfs_open_node.

On Tue, Apr 26, 2022 at 08:29:21AM -1000, Tejun Heo wrote:

> The code is just wrong. You can end up:
> 
>         on = kn->attr.open;
>         if (!on)
>                 return;
> 
>         // we get preempted here and someone else puts @on and then
>         // recreates it

Can't happen - the caller has guaranteed that no new openers will be
coming.  Look at the call chain of kernfs_drain_open_files()...


Al, back to life and staring at the pile of mail to sift through...