From: Christoph Hellwig Subject: Re: Can one file system be R/W mounted multiple times in Linux? Date: Fri, 9 Jan 2015 06:55:46 -0800 Message-ID: <20150109145546.GA26251@infradead.org> References: <20150109035123.GG22149@ZenIV.linux.org.uk> <20150109120159.GA20300@stefanha-thinkpad.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Al Viro , Dexuan Cui , "linux-fsdevel@vger.kernel.org" , 'linux-ext4' To: Stefan Hajnoczi Return-path: Received: from bombadil.infradead.org ([198.137.202.9]:52659 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756876AbbAIOzt (ORCPT ); Fri, 9 Jan 2015 09:55:49 -0500 Content-Disposition: inline In-Reply-To: <20150109120159.GA20300@stefanha-thinkpad.redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Jan 09, 2015 at 12:01:59PM +0000, Stefan Hajnoczi wrote: > Can you explain under what conditions mounting the same file system > twice will work? > > I guess the kernel is looking up the block device and then sharing the > superblock if the file system is already mounted on this block device? Exactly. > > If I use two loop devices for the same underlying storage it does not > work: Because that's very much the same situation as two different systems trying to mount it.