[src/trunk]: src/sys/fs/union Add reference count to union node.

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

details:   https://anonhg.NetBSD.org/src/rev/d8acac9c473b
branches:  trunk
changeset: 336183:d8acac9c473b
user:      hannken <hannken%NetBSD.org@localhost>
date:      Mon Feb 16 10:21:25 2015 +0000

description:
Add reference count to union node.

diffstat:

 sys/fs/union/union.h      |   3 +-
 sys/fs/union/union_subr.c |  73 ++++++++++++++++++++++++++++++++--------------
 2 files changed, 52 insertions(+), 24 deletions(-)

diffs (144 lines):

diff -r 0e45372bd563 -r d8acac9c473b sys/fs/union/union.h
--- a/sys/fs/union/union.h      Mon Feb 16 10:20:57 2015 +0000
+++ b/sys/fs/union/union.h      Mon Feb 16 10:21:25 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: union.h,v 1.26 2014/02/14 08:50:27 hannken Exp $       */
+/*     $NetBSD: union.h,v 1.27 2015/02/16 10:21:25 hannken Exp $       */
 
 /*
  * Copyright (c) 1994 The Regents of the University of California.
@@ -120,6 +120,7 @@
 struct union_node {
        kmutex_t                un_lock;
        LIST_ENTRY(union_node)  un_cache;       /* c: Hash chain */
+       int                     un_refs;        /* c: Reference counter */
        struct vnode            *un_vnode;      /* :: Back pointer */
        struct vnode            *un_uppervp;    /* m: overlaying object */
        struct vnode            *un_lowervp;    /* v: underlying object */
diff -r 0e45372bd563 -r d8acac9c473b sys/fs/union/union_subr.c
--- a/sys/fs/union/union_subr.c Mon Feb 16 10:20:57 2015 +0000
+++ b/sys/fs/union/union_subr.c Mon Feb 16 10:21:25 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: union_subr.c,v 1.68 2015/02/16 10:20:57 hannken Exp $  */
+/*     $NetBSD: union_subr.c,v 1.69 2015/02/16 10:21:25 hannken Exp $  */
 
 /*
  * Copyright (c) 1994
@@ -72,7 +72,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.68 2015/02/16 10:20:57 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.69 2015/02/16 10:21:25 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -105,6 +105,8 @@
 static kmutex_t uhash_lock;
 
 void union_updatevp(struct union_node *, struct vnode *, struct vnode *);
+static void union_ref(struct union_node *);
+static void union_rele(struct union_node *);
 static int union_do_lookup(struct vnode *, struct componentname *, kauth_cred_t,    const char *);
 int union_vn_close(struct vnode *, int, kauth_cred_t, struct lwp *);
 static void union_dircache_r(struct vnode *, struct vnode ***, int *);
@@ -289,6 +291,45 @@
        }
 }
 
+static void
+union_ref(struct union_node *un)
+{
+
+       KASSERT(mutex_owned(&uhash_lock));
+       un->un_refs++;
+}
+
+static void
+union_rele(struct union_node *un)
+{
+
+       mutex_enter(&uhash_lock);
+       un->un_refs--;
+       if (un->un_refs > 0) {
+               mutex_exit(&uhash_lock);
+               return;
+       }
+       if (un->un_cflags & UN_CACHED) {
+               un->un_cflags &= ~UN_CACHED;
+               LIST_REMOVE(un, un_cache);
+       }
+       mutex_exit(&uhash_lock);
+
+       if (un->un_pvp != NULLVP)
+               vrele(un->un_pvp);
+       if (un->un_uppervp != NULLVP)
+               vrele(un->un_uppervp);
+       if (un->un_lowervp != NULLVP)
+               vrele(un->un_lowervp);
+       if (un->un_dirvp != NULLVP)
+               vrele(un->un_dirvp);
+       if (un->un_path)
+               free(un->un_path, M_TEMP);
+       mutex_destroy(&un->un_lock);
+
+       free(un, M_TEMP);
+}
+
 /*
  * allocate a union_node/vnode pair.  the vnode is
  * referenced and unlocked.  the new vnode is returned
@@ -397,9 +438,12 @@
                                continue;
 
                        vp = UNIONTOV(un);
+                       union_ref(un);
                        mutex_enter(vp->v_interlock);
                        mutex_exit(&uhash_lock);
-                       if (vget(vp, 0))
+                       error = vget(vp, 0);
+                       union_rele(un);
+                       if (error)
                                goto loop;
                        goto found;
                }
@@ -517,6 +561,7 @@
 
        un = VTOUNION(*vpp);
        mutex_init(&un->un_lock, MUTEX_DEFAULT, IPL_NONE);
+       un->un_refs = 1;
        un->un_vnode = *vpp;
        un->un_uppervp = uppervp;
        un->un_lowervp = lowervp;
@@ -562,29 +607,11 @@
 {
        struct union_node *un = VTOUNION(vp);
 
-       mutex_enter(&uhash_lock);
-       if (un->un_cflags & UN_CACHED) {
-               un->un_cflags &= ~UN_CACHED;
-               LIST_REMOVE(un, un_cache);
-       }
-       mutex_exit(&uhash_lock);
+       union_rele(un);
 
-       if (un->un_pvp != NULLVP)
-               vrele(un->un_pvp);
-       if (un->un_uppervp != NULLVP)
-               vrele(un->un_uppervp);
-       if (un->un_lowervp != NULLVP)
-               vrele(un->un_lowervp);
-       if (un->un_dirvp != NULLVP)
-               vrele(un->un_dirvp);
-       if (un->un_path)
-               free(un->un_path, M_TEMP);
-       mutex_destroy(&un->un_lock);
-
-       free(vp->v_data, M_TEMP);
        vp->v_data = NULL;
 
-       return (0);
+       return 0;
 }
 
 /*