Date: Sun, 18 Jul 2010 22:40:16 -0400 (EDT) From: Rick Macklem <rmacklem@uoguelph.ca> To: freebsd-fs@freebsd.org Subject: fix for remove for NFS through nullfs Message-ID: <Pine.GSO.4.63.1007182231590.21767@muncher.cs.uoguelph.ca>
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Mikolaj Golub submitted the attached patch that fixes a problem w.r.t.
a nullfs mounted NFS mount point for remove. The problem is that,
without this patch, NFS does not see that a file is still open
(v_usecount > 1) when removed and removes it instead of silly renaming
it. This patch increments the v_usecount of the lower level vnode
during the remove call, so that silly rename works. kib@ has noted
that this may be "racy" and result in silly rename happening when it
isn't required but, imho, that is less of a problem than it never
working. (I have tested it a bit for NFS and UFS and it seems to
work for those file systems under a nullfs mount.)
Why I am posting is that I am wondering if anyone knows of a file
system type where this extra v_usecount on the vnode at the time of remove
will/might cause problems?
Thanks in advance for looking at this, rick
--- submitted patch for nullfs ---
--- fs/nullfs/null_vnops.c.sav 2010-07-18 19:33:00.000000000 -0400
+++ fs/nullfs/null_vnops.c 2010-07-18 19:35:25.000000000 -0400
@@ -499,6 +499,29 @@
}
/*
+ * 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.
+ */
+static int
+null_remove(struct vop_remove_args *ap)
+{
+ int retval;
+ struct vnode *lvp;
+ boolean_t vreleit;
+
+ if (ap->a_vp->v_usecount > 1) {
+ lvp = NULLVPTOLOWERVP(ap->a_vp);
+ VREF(lvp);
+ vreleit = TRUE;
+ } else
+ vreleit = FALSE;
+ retval = null_bypass(&ap->a_gen);
+ if (vreleit)
+ 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.
@@ -809,6 +832,7 @@
.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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