[src/trunk]: src/sys/miscfs/genfs When layer_node_alloc() finds another threa...

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/886303c77e1b
branches:  trunk
changeset: 326649:886303c77e1b
user:      hannken <hannken%NetBSD.org@localhost>
date:      Sun Feb 09 17:15:51 2014 +0000

description:
When layer_node_alloc() finds another thread already inserted the node
into the hashlist and discards the now unneeded node it will raise a
panic "dead but not clean".

Reorder the initialization and use ungetnewvnode() to discard the node.

diffstat:

 sys/miscfs/genfs/layer_subr.c |  35 ++++++++++++++---------------------
 1 files changed, 14 insertions(+), 21 deletions(-)

diffs (70 lines):

diff -r 5b865eb03508 -r 886303c77e1b sys/miscfs/genfs/layer_subr.c
--- a/sys/miscfs/genfs/layer_subr.c     Sun Feb 09 17:07:41 2014 +0000
+++ b/sys/miscfs/genfs/layer_subr.c     Sun Feb 09 17:15:51 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: layer_subr.c,v 1.33 2014/01/29 08:27:04 hannken Exp $  */
+/*     $NetBSD: layer_subr.c,v 1.34 2014/02/09 17:15:51 hannken Exp $  */
 
 /*
  * Copyright (c) 1999 National Aeronautics & Space Administration
@@ -69,7 +69,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.33 2014/01/29 08:27:04 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.34 2014/02/09 17:15:51 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -187,7 +187,6 @@
        struct layer_node *xp;
        struct vnode *vp, *nvp;
        int error;
-       extern int (**dead_vnodeop_p)(void *);
 
        /* Get a new vnode and share its interlock with underlying vnode. */
        error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p,
@@ -209,6 +208,18 @@
                spec_node_init(vp, lowervp->v_rdev);
        }
 
+       /*
+        * Before inserting the node into the hash, check if other thread
+        * did not race with us.  If so - return that node, destroy ours.
+        */
+       mutex_enter(&lmp->layerm_hashlock);
+       if ((nvp = layer_node_find(mp, lowervp)) != NULL) {
+               ungetnewvnode(vp);
+               kmem_free(xp, lmp->layerm_size);
+               *vpp = nvp;
+               return 0;
+       }
+
        vp->v_data = xp;
        vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) |
            (lowervp->v_vflag & VV_MPSAFE);
@@ -217,24 +228,6 @@
        xp->layer_flags = 0;
 
        /*
-        * Before inserting the node into the hash, check if other thread
-        * did not race with us.  If so - return that node, destroy ours.
-        */
-       mutex_enter(&lmp->layerm_hashlock);
-       if ((nvp = layer_node_find(mp, lowervp)) != NULL) {
-               /* Free the structures we have created. */
-               if (vp->v_type == VBLK || vp->v_type == VCHR)
-                       spec_node_destroy(vp);
-
-               vp->v_type = VBAD;              /* node is discarded */
-               vp->v_op = dead_vnodeop_p;      /* so ops will still work */
-               vrele(vp);                      /* get rid of it. */
-               kmem_free(xp, lmp->layerm_size);
-               *vpp = nvp;
-               return 0;
-       }
-
-       /*
         * Insert the new node into the hash.
         * Add a reference to the lower node.
         */