linux-kernel - Re: [PATCH 2/4] NFS: replace per-net client lock by mutex

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Message-ID: <4F4BA479.60907@parallels.com>
Date:	Mon, 27 Feb 2012 19:42:49 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
CC:	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	Pavel Emelianov <xemul@...allels.com>,
	"neilb@...e.de" <neilb@...e.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	James Bottomley <jbottomley@...allels.com>,
	"bfields@...ldses.org" <bfields@...ldses.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH 2/4] NFS: replace per-net client lock by mutex

27.02.2012 19:00, Myklebust, Trond пишет:
> On Mon, 2012-02-27 at 17:49 +0400, Stanislav Kinsbursky wrote:
>> Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
>> creation, which can be called on mount notification, where this per-net client
>> lock is taken on clients list walk.
>>
>> Note: I used simple mutex instead of rw semaphore because of
>> nfs_put_client->atomic_dec_and_mutex_lock() call. Probably, there is a better
>> solution here.
>>
>> Signed-off-by: Stanislav Kinsbursky<skinsbursky@...allels.com>
>>
>
> This is overkill... We end up blocking NFSv4 callbacks while the
> rpc_pipefs notifier runs through the nfs_clients creating or destroying
> idmapper dentries.
>
> Surely the rpc_pipefs_event() can take a reference to the nfs_client and
> then drop the spin_lock if it sees that it needs to create or destroy a
> dentry?
>

Sure, thanks for notice.
Looks like this logic also works to SUNRPC clients.
I'll send updated version soon.

-- 
Best regards,
Stanislav Kinsbursky
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