From owner-freebsd-current@FreeBSD.ORG Thu Apr 21 07:20:12 2011 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A9CF81065670 for ; Thu, 21 Apr 2011 07:20:12 +0000 (UTC) (envelope-from aavzz@yandex.ru) Received: from forward12.mail.yandex.net (forward12.mail.yandex.net [95.108.130.94]) by mx1.freebsd.org (Postfix) with ESMTP id 5BDAF8FC17 for ; Thu, 21 Apr 2011 07:20:12 +0000 (UTC) Received: from smtp12.mail.yandex.net (smtp12.mail.yandex.net [95.108.131.191]) by forward12.mail.yandex.net (Yandex) with ESMTP id 8B093C20F48; Thu, 21 Apr 2011 11:03:29 +0400 (MSD) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1303369409; bh=ukgUjXVdbWfnADgxUzgp3IpHXl5nB7KAM0usWPjEYZQ=; h=Subject:From:To:Cc:In-Reply-To:References:Content-Type:Date: Message-ID:Mime-Version:Content-Transfer-Encoding; b=P0p7dA9mf++Vab9BOySekbg7BSEx53OkC4ditEiVdAYQXft0PgkpbF2/aBLAEosas MtfV3Zo4NRtjqCZlosQvtR6I/EqrhNBEZdMcnOk+i6S6TJLLV5xbdUp3zVTKLKeZzz foaD0AKakfX92Vacl1rFgcrEiLySZC/1+WPzvWjs= Received: from [10.88.1.200] (unknown [91.210.24.47]) by smtp12.mail.yandex.net (Yandex) with ESMTPA id 330A1572803F; Thu, 21 Apr 2011 11:03:29 +0400 (MSD) From: Alex Zimnitsky To: Daichi GOTO In-Reply-To: <20110421144947.b887081e.daichi@freebsd.org> References: <20110421144947.b887081e.daichi@freebsd.org> Content-Type: text/plain; charset="UTF-8" Date: Thu, 21 Apr 2011 11:03:30 +0400 Message-ID: <1303369410.2152.21.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 (2.32.2-1.fc14) Content-Transfer-Encoding: 7bit X-Yandex-Spam: 1 X-Mailman-Approved-At: Thu, 21 Apr 2011 10:55:00 +0000 Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org Subject: Re: RFC: unionfs multiple mounts, cross mounts and recursive mounts limits and manegement feature X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 21 Apr 2011 07:20:12 -0000 On Thu, 2011-04-21 at 14:49 +0900, Daichi GOTO wrote: > It is adjustable with sysctl value 'vfs.unionfs.recursive_limit' as > multiple mounts limits. The default value is 1 and it means two-layered ok. > Max value of 'vfs.unionfs.recursive_limit' is 8, it is heuristic value. > I couldn't get a system panic unless 'vfs.unionfs.recursive_limit' is over 8. > Hmm, 8 is not enough for me, i need more :) On the other hand, why do we need recursion in unionfs_statfs at all? IMHO recursion in kernel is evil because it has a potencial of resource exhaustion. This recursion in unionfs_statfs is used to gather statistic (some of which is faked according to comments in the procedure) why not replace recursion with cycle? (I'm not skilled enough do do that :) and a feature request: it would be great if it was possible to umount one of multiple unionfs: mount -t unionfs /var/ftpdata1 /var/ftp mount -t unionfs /var/ftpdata2 /var/ftp how to unmount /var/ftpdata1 only?