Date: Thu, 23 Nov 1995 13:15:11 -0800 (PST) From: Julian Elischer <julian@ref.tfs.com> To: hackers@freebsd.org Subject: VOP_RECLAIM and vnode references.. Message-ID: <199511232115.NAA11760@ref.tfs.com>
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In vclean() (the only usage of VOP_RECLAIM I have found) the following
happens:
If a vnode has no references, it's left that way..
if it DOES have a reference (v_usecount > 0) then it's artificially
incremented by one, to stop it going to 0 while the VOP_RECLAIM is active..
this is a bit stupid in my opinion...
firstly, in devfs, my sanity code that checks that a vnode is referenced
before it uses it, throws a fit when asked by devfs_reclaim to
find the devfs_node associated with the vnode..
(this is why those of you that have made devfs report seeing
"!no reference!" on the console.. secoondly, it's unknown how long
a VOP_RECLAIM might take and something else may
come in and raise and lower the reference count while it's
happenning.. (not devfs, but their might be slower fs's)
surely the v_usecount should be raised by one
regardless of whether it is already non-zero.?
the VOP_LOCK might make this un-needed, but I am loath
to take the sanity check code out of my devfs code..
I figure that if I'm doing a vntodn() (vnode-to-devfsnode)
then I should be doing it on a referenced vnode..
I don't like the fact that there is ONE exception..
"Except whenn asked to do it in a reclaim operation.."
I guess I could do a vref in devfs_reclaim before calling
vntodn() but why make a specific fix if a general one
is just as easy?
does anyone know why it's like it is?
I BELIEVE (but don't know) that this is the only time when
a vnode is passed toa filesystem without a reference..
julian
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