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From: Karel Zak <kzak@redhat.com>
To: "Lukáš Czerner" <lczerner@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Dexuan Cui <decui@microsoft.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"'linux-ext4'" <linux-ext4@vger.kernel.org>
Subject: Re: Can one file system be R/W mounted multiple times in Linux?
Date: Mon, 12 Jan 2015 17:47:05 +0100	[thread overview]
Message-ID: <20150112164705.GP20899@x2.net.home> (raw)
In-Reply-To: <alpine.LFD.2.00.1501121514550.32312@localhost.localdomain>

On Mon, Jan 12, 2015 at 03:20:19PM +0100, Lukáš Czerner wrote:
> that's not what I meant at all. Yes, things like MMP should help.
> But what I was suggesting was not FS specific.

And what do you want to do when somebody will implement any
cluster-like or multi-root filesystem where share the same FS image
between two loop devices is expected and supported feature?

I don't think there is any such generic VFS restriction, it's about FS
driver(s).

> mount(8) could in case of '-o loop' look whether there is already a
> block device associated with the file and if so use it instead of
> creating new one.
 
mount(8) already checks if the same backing file is not mounted on the
same mountpoint

 # mount -o loop fs.img /mnt/A
 # mount -o loop fs.img /mnt/A
 mount: fs.img is already mounted

but I don't want to make decision about anything else in userspace.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com
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      reply	other threads:[~2015-01-12 16:47 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-09  3:44 Can one file system be R/W mounted multiple times in Linux? Dexuan Cui
2015-01-09  3:51 ` Al Viro
2015-01-09  4:58   ` Dexuan Cui
2015-01-09  6:04     ` Eric Sandeen
2015-01-09  6:48       ` Dexuan Cui
2015-01-09 13:25         ` Bob Peterson
2015-01-09 12:01   ` Stefan Hajnoczi
2015-01-09 14:55     ` Christoph Hellwig
2015-01-09 15:52     ` Lukáš Czerner
2015-01-09 19:31       ` Pranay Srivastava
2015-01-09 20:37         ` Al Viro
2015-01-10  3:52           ` Dexuan Cui
2015-01-12 13:00       ` Karel Zak
2015-01-12 14:20         ` Lukáš Czerner
2015-01-12 16:47           ` Karel Zak [this message]

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