Date: Sat, 17 May 2014 13:48:11 -0400 (EDT) From: Benjamin Kaduk <bjk@freebsd.org> To: freebsd-fs@freebsd.org Subject: Add an assert that v_holdcnt >= v_usecount? Message-ID: <alpine.GSO.1.10.1405171326480.25244@multics.mit.edu>
next in thread | raw e-mail | index | archive | help
jhb was helping me debug a crashy openafs build in one of my VMs, and the
symptoms seemed to indicate that a vnode had been partially destroyed
before vgone() was called from vflush(), as if some buggy filesystem code
had called vdrop() instead of vrele() or something similar. In a quick
check, it didn't look like we had any assertions that would catch such
bugs, so I tried adding something like this:
Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c (revision 266330)
+++ sys/kern/vfs_subr.c (working copy)
@@ -2343,6 +2343,8 @@
if (vp->v_holdcnt <= 0)
panic("vdrop: holdcnt %d", vp->v_holdcnt);
vp->v_holdcnt--;
+ VNASSERT(vp->v_holdcnt >= vp->v_usecount, vp,
+ ("hold count less than use count"));
if (vp->v_holdcnt > 0) {
VI_UNLOCK(vp);
return;
Does that seem like something that would be generally useful?
-Ben
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?alpine.GSO.1.10.1405171326480.25244>