Date: Mon, 13 Sep 1999 14:16:25 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Tony Finch <fanf@demon.net> Cc: hackers@FreeBSD.ORG Subject: Re: mounting a partition more than once Message-ID: <199909132116.OAA25920@apollo.backplane.com> References: <E11QZ03-000DDr-00@fanf.noc.demon.net>
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:Tony Finch <fanf@demon.net> wrote:
:
:Well, in the absence of any comments I hacked around a bit and ended
:up with the following patch (against 3.3-RC), which permits the same
:block device to be mounted read-only more than once. The motivation
:for this is to permit multiple chrooted environments to share the same
:/usr partition.
:
:Some things I wonder about this change is whether the mounts will share
:the same pages in the buffer cache, and whether the resource
:accounting is still right. I've subtly funted the meaning of
:v_specmountpoint when multiple mounts happen; does this matter?
:
:Tony.
:--
:f.a.n.finch dot@dotat.at fanf@demon.net e pluribus unix
Hmm... well, there is a problem here. I believe this will allow
you to open the underlying block device read-only as well as mount
the filesystem read-only. This will confuse the buffer cache badly.
Also, this may not be the best place to put the code. It make sense
to be able to mount a block device multiple times in a read-only
fashion, but the code should be in the open for the block device
rather then in UFS/FFS, so it can be used with other filesystems
and for other purposes.
-Matt
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