Author: rmacklem
Date: Tue Sep 14 01:28:05 2010
New Revision: 212590
URL: http://svn.freebsd.org/changeset/base/212590
Log:
MFC: r212043
Add a null_remove() function to nullfs, so that the v_usecount
of the lower level vnode is incremented to greater than 1 when
the upper level vnode's v_usecount is greater than one. This
is necessary for the NFS clients, so that they will do a silly
rename of the file instead of actually removing it when the
file is still in use. It is "racy", since the v_usecount is
incremented in many places in the kernel with
minimal synchronization, but an extraneous silly rename is
preferred to not doing a silly rename when it is required.
The only other file systems that currently check the value
of v_usecount in their VOP_REMOVE() functions are nwfs and
smbfs. These file systems choose to fail a remove when the
v_usecount is greater than 1 and I believe will function
more correctly with this patch, as well.
Modified:
stable/8/sys/fs/nullfs/null_vnops.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
stable/8/sys/dev/xen/xenpci/ (props changed)
Modified: stable/8/sys/fs/nullfs/null_vnops.c
==============================================================================
--- stable/8/sys/fs/nullfs/null_vnops.c Tue Sep 14 01:27:53 2010
(r212589)
+++ stable/8/sys/fs/nullfs/null_vnops.c Tue Sep 14 01:28:05 2010
(r212590)
@@ -499,6 +499,32 @@ null_accessx(struct vop_accessx_args *ap
}
/*
+ * Increasing refcount of lower vnode is needed at least for the case
+ * when lower FS is NFS to do sillyrename if the file is in use.
+ * Unfortunately v_usecount is incremented in many places in
+ * the kernel and, as such, there may be races that result in
+ * the NFS client doing an extraneous silly rename, but that seems
+ * preferable to not doing a silly rename when it is needed.
+ */
+static int
+null_remove(struct vop_remove_args *ap)
+{
+ int retval, vreleit;
+ struct vnode *lvp;
+
+ if (vrefcnt(ap->a_vp) > 1) {
+ lvp = NULLVPTOLOWERVP(ap->a_vp);
+ VREF(lvp);
+ vreleit = 1;
+ } else
+ vreleit = 0;
+ retval = null_bypass(&ap->a_gen);
+ if (vreleit != 0)
+ vrele(lvp);
+ return (retval);
+}
+
+/*
* We handle this to eliminate null FS to lower FS
* file moving. Don't know why we don't allow this,
* possibly we should.
@@ -808,6 +834,7 @@ struct vop_vector null_vnodeops = {
.vop_open = null_open,
.vop_print = null_print,
.vop_reclaim = null_reclaim,
+ .vop_remove = null_remove,
.vop_rename = null_rename,
.vop_setattr = null_setattr,
.vop_strategy = VOP_EOPNOTSUPP,
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