From: Al Viro <viro@ZenIV.linux.org.uk>
To: Pranay Srivastava <pranjas@gmail.com>
Cc: "Lukáš Czerner" <lczerner@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
kzak@redhat.com, "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: Fri, 9 Jan 2015 20:37:11 +0000 [thread overview]
Message-ID: <20150109203711.GJ22149@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+aCy1Esm-2NGvJFG4_22rNaXiOqx1f2beCPpSCcovrXFf07+A@mail.gmail.com>
On Sat, Jan 10, 2015 at 01:01:19AM +0530, Pranay Srivastava wrote:
> It's not the mount. If you see mount_bdev it checks for this and uses
> the existing super block from the first mount
> for all subsequent mounts of that block device.
>
> When block devices differ, as in with 2 loop devices they have
> different bdev and that's why it doesn't work with 2
> loop devices.
What Lukas is suggesting is for mount(8) to spot an existing loop device with
the desired backing store and reuse it, rather than try and set the new one
up. That's where -o loop is handled - it's gone before mount(2) might see
it. The problem is in races...
next prev parent reply other threads:[~2015-01-09 20:37 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 [this message]
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
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