From owner-freebsd-fs@FreeBSD.ORG  Thu Mar 28 05:40:18 2013
Return-Path: <owner-freebsd-fs@FreeBSD.ORG>
Delivered-To: freebsd-fs@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by hub.freebsd.org (Postfix) with ESMTP id 37B5379C;
 Thu, 28 Mar 2013 05:40:18 +0000 (UTC)
 (envelope-from mdf356@gmail.com)
Received: from mail-qc0-x233.google.com (mail-qc0-x233.google.com
 [IPv6:2607:f8b0:400d:c01::233])
 by mx1.freebsd.org (Postfix) with ESMTP id E260B977;
 Thu, 28 Mar 2013 05:40:17 +0000 (UTC)
Received: by mail-qc0-f179.google.com with SMTP id b40so4068412qcq.10
 for <multiple recipients>; Wed, 27 Mar 2013 22:40:17 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:x-received:sender:in-reply-to:references:date
 :x-google-sender-auth:message-id:subject:from:to:cc:content-type;
 bh=4ffQ2MMb83OZN/KkxP4eFjkYTLMRzM7AvYSi8QxhsyA=;
 b=sovq3PEQrj0Xy/kr+XQ3HvLWs6oOsKsjXDE8A6ycE7CO44BKgckGg+mKSeSQwYCiAl
 MnRMvdPO0pMB+v9+tvVcqk0n6KQdMLaMK40+jZWGWTyjS1aFrqaG7OO9g2fekb6QZLRg
 r+T614tgfScnn7+8G+o5hw1XrwSeTQU+Znvmnpjysr3VpfdL2NR7ElcPUb3Y4KP+mgcD
 lAHLYLEkEgMHNczMCCsYk1bsD5r4T6JjdAweCNxYnaSodXhn7yxtxPFw825tvaKq0ttC
 aZ0qBCRlS0HcrQbCC5JDyEcujMgyMRlrfhVytzvbJowZKuLyOHUSdJmp3YlJqQHbpV1b
 SYpA==
MIME-Version: 1.0
X-Received: by 10.49.25.202 with SMTP id e10mr20122125qeg.49.1364449217129;
 Wed, 27 Mar 2013 22:40:17 -0700 (PDT)
Sender: mdf356@gmail.com
Received: by 10.229.253.201 with HTTP; Wed, 27 Mar 2013 22:40:16 -0700 (PDT)
In-Reply-To: <20130328053205.GF3794@kib.kiev.ua>
References: <CAMBSHm8Akz2-tUhjYm9+H3YTN31N8=OhGHX1ZpdV4-VixFQm+Q@mail.gmail.com>
 <CAMBSHm9VgD9Pcmiap3Cy1eW8GD9k06q+sCzaSJ+_wyA6ZFioTA@mail.gmail.com>
 <20130328053205.GF3794@kib.kiev.ua>
Date: Wed, 27 Mar 2013 22:40:16 -0700
X-Google-Sender-Auth: zJ7rBN1qp88H4U2Qe7csJJKC1E4
Message-ID: <CAMBSHm_Rbw=0-nA+n5JoT68L_4+KvAZM-o+S+01TqFZKacjfgQ@mail.gmail.com>
Subject: Re: [RFC] use a shared lock for VOP_GETEXTATTR
From: mdf@FreeBSD.org
To: Konstantin Belousov <kostikbel@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
 <mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 28 Mar 2013 05:40:18 -0000

On Wed, Mar 27, 2013 at 10:32 PM, Konstantin Belousov
<kostikbel@gmail.com> wrote:
> On Wed, Mar 27, 2013 at 06:37:51PM -0700, mdf@FreeBSD.org wrote:
>> VOP_GETEXTATTR is currently called with an exclusive lock, which seems
>> like overkill for what is essentially a read operation.  I had a look
>> over the various in-tree filesystems and it didn't look like any of
>> them will have a problem if a shared-mode lock is used for
>> vop_getextattr.
>>
>> Does anyone know otherwise?  Is someone using extended attributes
>> regularly who can test this?
>
> I think this change should be fine. At least it seems to for UFS.
>
> What other filesystems did you audited ?

I looked over zfs, pseudofs, unionfs, ffs/ufs.  None seemed to have
any asserts on the lock type nor anything that looked like it would
try to modify anything.  zfs, I think it was, even used VOP_ISLOCKED
to get the lock type in one path (but I think that was after a
lookup(), so it may have been on a different vnode).

Cheers,
matthew