linux-kernel - Re: fsnotify_mark

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Message-ID: <CAJfpegsWcTz15gKOPXhDHyUviPuv59ypF=SDy7wTW1OqVfhGTw@mail.gmail.com>
Date:   Thu, 10 Nov 2016 21:44:36 +0100
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Jan Kara <jack@...e.cz>
Cc:     Amir Goldstein <amir73il@...il.com>,
        Eric Paris <eparis@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: fsnotify_mark_srcu wtf?

On Thu, Nov 10, 2016 at 8:46 PM, Jan Kara <jack@...e.cz> wrote:
> Except it doesn't quite work. We can pin the current marks by a refcount
> but they can still be removed from the list so after we regain srcu lock,
> we are not sure their ->next pointers still point to still allocated marks
> :-| Sadly I realized this only after implementing all this.

I think the real problem is the synchronous nature of the notification
interface, that really doesn't fit the permission events model very
well.

If it were to be changed around to an async interface then all the
marks could be iterated, the permission events queued and then the
srcu lock can be released for good.

Did I miss something?

Thanks,
Miklos