Bug 484190

Summary:	mount: tmpfs to reject mounts of the same mountpoint
Product:	[Fedora] Fedora	Reporter:	Ondrej Valousek <ondrejv>
Component:	util-linux-ng	Assignee:	Karel Zak <kzak>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	low	Docs Contact:
Priority:	low
Version:	10	CC:	kzak
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2009-02-05 12:18:24 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Ondrej Valousek 2009-02-05 10:11:50 UTC

Description of problem:
mount should reject attempts to mount already mounted filesystem. Example: 
[root@dorado_v1 /]# mount dorado:/exports/ext1/tmp /tmp2 
[root@dorado_v1 /]# mount dorado:/exports/ext1/tmp /tmp2 
mount.nfs: /tmp2 is already mounted or busy 
-- correct behavior. However if I try the same using tmpfs, it does not reject it: 
[root@dorado_v1 /]# mount -t tmpfs none /tmp2 
[root@dorado_v1 /]# mount -t tmpfs none /tmp2 
So /tmp2 is mounted twice now. This should not be possible.

Version-Release number of selected component (if applicable):
All versions of Fedora and RHEL are affected by this bug.

How reproducible:


Steps to Reproduce:
1.
2.
3.
  
Actual results:
/tmp2 is mounted twice using tmpfs

Expected results:
Once /tmp2 is mounted, any consequential mounts to this mountpoint should be refused (as it already work for NFS, for example).

Additional info:

Comment 1 Karel Zak 2009-02-05 12:18:24 UTC

That's correct.

You cannot mount the same filesystem on the same mountpoint more than once (e.g your NFS), BUT linux supports overlaying -- it means you can mount more (different) filesystems on the same mountpoint, e.g:

  mount /dev/foo /mnt
  mount /dev/bar /mnt

and you can also mount the same device on more places, e.g:

 mount /dev/foo /mnt
 mount /dev/foo /mnt2

Note that the "tmpfs" is always unique filesystem.