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Date:   Sun, 19 Jul 2020 02:49:54 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        John Ogness <john.ogness@linutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH v2] fs/namespace: use percpu_rw_semaphore for writer
 holding
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On Thu, Jul 02, 2020 at 05:46:46PM +0200, Sebastian Andrzej Siewior wrote:

> The MNT_WRITE_HOLD flag is used to manually implement a rwsem.

Could you show me where does it currently sleep?  Your version does,
unless I'm misreading it...