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Change vnode operation lookup to return the resulting vnode *vpp unlocked.

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Change cache_lookup() to return an unlocked vnode.

Discussed on tech-kern@
This commit is contained in:
hannken 2014-02-07 15:26:42 +00:00
parent 62342f9d4d
commit f106eaceb6
1 changed files with 5 additions and 15 deletions
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20
sys/kern/vnode_if.src
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@ -1,4 +1,4 @@
# $NetBSD: vnode_if.src,v 1.65 2014/01/23 10:11:55 hannken Exp $ # $NetBSD: vnode_if.src,v 1.66 2014/02/07 15:26:42 hannken Exp $
# #
# Copyright (c) 1992, 1993 # Copyright (c) 1992, 1993
# The Regents of the University of California. All rights reserved. # The Regents of the University of California. All rights reserved.
@ -61,27 +61,17 @@ vop_bwrite {
# #
#% lookup dvp L L L #% lookup dvp L L L
#% lookup vpp - L - #% lookup vpp - U -
# #
# XXX - the lookup locking protocol defies simple description.
# Note especially that *vpp may equal dvp. # Note especially that *vpp may equal dvp.
# #
# More details: # More details:
# There are three types of lookups: ".", ".." (ISDOTDOT), and other. # All lookups find the named node (creating the vnode if needed) and
# On successful lookup of ".", a reference is added to dvp, and it # return it, referenced and unlocked, in *vpp.
# is returned in *vpp.
# To look up ISDOTDOT, dvp is unlocked, the ".." node is locked, and
# then dvp is relocked. This preserves the protocol of always
# locking nodes from root ("/") downward and prevents deadlock.
# Other lookups find the named node (creating the vnode if needed) and
# return it, locked, in *vpp.
# On failure, *vpp is NULL, and *dvp is left locked. # On failure, *vpp is NULL, and *dvp is left locked.
# #
# *vpp is always locked on return if the operation succeeds.
# Typically, if *vpp == dvp, you need to release twice, but
# unlock only once.
#
vop_lookup { vop_lookup {
VERSION 2
IN struct vnode *dvp; IN struct vnode *dvp;
OUT WILLMAKE struct vnode **vpp; OUT WILLMAKE struct vnode **vpp;
IN struct componentname *cnp; IN struct componentname *cnp;