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Message-ID: <47760578.2090305@davidnewall.com>
Date: Sat, 29 Dec 2007 18:59:44 +1030
From: David Newall <david@...idnewall.com>
To: dean gaudet <dean@...tic.org>
CC: Mark Lord <lkml@....ca>, Al Viro <viro@....linux.org.uk>,
Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: RFC: permit link(2) to work across --bind mounts ?
dean gaudet wrote:
> On Wed, 19 Dec 2007, David Newall wrote:
>
>> Mark Lord wrote:
>>
>>> But.. pity there's no mount flag override for smaller systems,
>>> where bind mounts might be more useful with link(2) actually working.
>>>
>> I don't see it. You always can make hard link on the underlying filesystem.
>> If you need to make it on the bound mount, that is, if you can't locate the
>> underlying filesystem to make the hard link, you can use a symbolic link.
>>
>
> i run into it on a system where /home is a bind mount of /var/home ... i
> did this because:
>
> - i prefer /home to be nosuid,nodev (multi-user system)
>
Whatever security /home has, /var/home is the one that restricts because
users can still access their files that way.
> - i prefer /home to not be on same fs as /
> - the system has only one raid1 array, and i can't stand having two
> writable filesystems competing on the same set of spindles (i like to
> imagine that one fs competing for the spindles can potentially result
> in better seek patterns)
> ...
> - i didn't want to try to balance disk space between /var and /home
> - i didn't want to use a volume mgr just to handle disk space balance...
>
Pffuff. That's what volume managers are for! You do have (at least)
two independent spindles in your RAID1 array, which give you less need
to worry about head-stack contention. You probably want different mount
restrictions on /home than /var, so you really must use separate
filesystems. LVM is your friend.
But with regards to bind mounts and hard links: If you want to be able
to hard-link /home/me/log to /var/tmp/my-log, then I see nothing to
prevent hard-linking /var/home/me/log to /var/tmp/my-log.
I think it's possible to be too precious about preserving the illusion
of one file-system structure when the reality is something different.
Don't lose site of reality.
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