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Date: Fri, 26 Sep 1997 16:40:38 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199709260640.QAA23500@godzilla.zeta.org.au>
To: bde@zeta.org.au, kato@migmatite.eps.nagoya-u.ac.jp
Subject: Re: Daily SNAPshots at current.freebsd.org shut down for now.
Cc: current@FreeBSD.ORG
Sender: owner-freebsd-current@FreeBSD.ORG
X-Loop: FreeBSD.org
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>> clustering is 2 too many for a production system :-) (non-clustering for
>> /dev/vn must be forced independently of any mount options and sysctls,
>> except possibly for debugging).
>
>How does mount() in vfs_syscall.c know special device is /dev/vn?

It doesn't yet.  It could look at a new flag (vp->v_flag & VNOCLUSTER)
where vp is the vnode for the mount point.  The flag should be set in
vnopen().  This seems to require using bdevvp() to find the vnode.

>When mount() can know specical device is /dev/vn, then
>
>	if (special device is /dev/vn)
>		mp->mnt_flag |= MNT_NOCLUSTER;
>
>works, and doclusterread and doclusterwrite can be eliminated.

Right, except separate MNT_NOCLUSTER{READ,WRITE} flags are required to
give the same functionality.

Bruce