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From: John Ogness <john.ogness@linutronix.de>
To: Al Viro <viro@zeniv.linux.org.uk>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH v2] fs/namespace: use percpu_rw_semaphore for writer holding
Date: Mon, 20 Jul 2020 17:41:01 +0206	[thread overview]
Message-ID: <877duyryhm.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <20200719014954.GH2786714@ZenIV.linux.org.uk>

On 2020-07-19, Al Viro <viro@zeniv.linux.org.uk> 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...

You are reading it correctly. This patch introduces new possible
sleeping for__mnt_want_write() when writers for a superblock are being
held.

The RFCv1 [0] is a variant that does not introduce sleeping, but instead
reverts back to per-cpu spinlocks.

Sebastian and I are requesting comments on these two possible
solutions. Or perhaps you have an idea how to solve the potential live
lock situation.

John Ogness

[0] https://lkml.kernel.org/r/20200617104058.14902-2-john.ogness@linutronix.de

      reply	other threads:[~2020-07-20 15:35 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-02 15:46 Sebastian Andrzej Siewior
2020-07-19  1:49 ` Al Viro
2020-07-20 15:35   ` John Ogness [this message]

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