[src/trunk]: src/sys/fs/union Restructure union_lock() to always lock before ...

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

details:   https://anonhg.NetBSD.org/src/rev/aecf6ff13374
branches:  trunk
changeset: 327595:aecf6ff13374
user:      hannken <hannken%NetBSD.org@localhost>
date:      Wed Mar 12 09:40:05 2014 +0000

description:
Restructure union_lock() to always lock before testing for dead node.
Add two little helpers to lock or unlock a node.  Use "vp" for the
union node and "lockvp" for the node to be locked.  Use ISSET() to
test flags, add assertions.

diffstat:

 sys/fs/union/union_vnops.c |  103 +++++++++++++++++++++++++-------------------
 1 files changed, 58 insertions(+), 45 deletions(-)

diffs (162 lines):

diff -r b865335c2abc -r aecf6ff13374 sys/fs/union/union_vnops.c
--- a/sys/fs/union/union_vnops.c        Wed Mar 12 09:39:23 2014 +0000
+++ b/sys/fs/union/union_vnops.c        Wed Mar 12 09:40:05 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: union_vnops.c,v 1.57 2014/02/27 16:51:38 hannken Exp $ */
+/*     $NetBSD: union_vnops.c,v 1.58 2014/03/12 09:40:05 hannken Exp $ */
 
 /*
  * Copyright (c) 1992, 1993, 1994, 1995
@@ -72,7 +72,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: union_vnops.c,v 1.57 2014/02/27 16:51:38 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: union_vnops.c,v 1.58 2014/03/12 09:40:05 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1590,6 +1590,31 @@
        return (0);
 }
 
+static int
+union_lock1(struct vnode *vp, struct vnode *lockvp, int flags)
+{
+       struct vop_lock_args ap;
+
+       if (lockvp == vp) {
+               ap.a_vp = vp;
+               ap.a_flags = flags;
+               return genfs_lock(&ap);
+       } else
+               return VOP_LOCK(lockvp, flags);
+}
+
+static int
+union_unlock1(struct vnode *vp, struct vnode *lockvp)
+{
+       struct vop_unlock_args ap;
+
+       if (lockvp == vp) {
+               ap.a_vp = vp;
+               return genfs_unlock(&ap);
+       } else
+               return VOP_UNLOCK(lockvp);
+}
+
 int
 union_lock(void *v)
 {
@@ -1597,66 +1622,57 @@
                struct vnode *a_vp;
                int a_flags;
        } */ *ap = v;
-       struct vnode *vp;
-       struct union_node *un = VTOUNION(ap->a_vp);
+       struct vnode *vp = ap->a_vp, *lockvp;
+       struct union_node *un = VTOUNION(vp);
        int flags = ap->a_flags;
        int error;
 
        if ((flags & LK_NOWAIT) != 0) {
                if (!mutex_tryenter(&un->un_lock))
                        return EBUSY;
-               vp = LOCKVP(ap->a_vp);
-               if (!mutex_tryenter(vp->v_interlock)) {
-                       mutex_exit(&un->un_lock);
-                       return EBUSY;
-               }
-               if ((vp->v_iflag & (VI_XLOCK | VI_CLEAN)) != 0) {
+               lockvp = LOCKVP(vp);
+               error = union_lock1(vp, lockvp, flags);
+               mutex_exit(&un->un_lock);
+               if (error)
+                       return error;
+               if (mutex_tryenter(vp->v_interlock)) {
+                       if (ISSET(vp->v_iflag, VI_XLOCK))
+                               error = EBUSY;
+                       else if (ISSET(vp->v_iflag, VI_CLEAN))
+                               error = ENOENT;
+                       else
+                               error = 0;
                        mutex_exit(vp->v_interlock);
-                       mutex_exit(&un->un_lock);
-                       return EBUSY;
-               }
-               mutex_exit(vp->v_interlock);
-               if (vp == ap->a_vp)
-                       error = genfs_lock(ap);
-               else
-                       error = VOP_LOCK(vp, flags);
-               mutex_exit(&un->un_lock);
+               } else
+                       error = EBUSY;
+               if (error)
+                       union_unlock1(vp, lockvp);
                return error;
        }
 
        mutex_enter(&un->un_lock);
        for (;;) {
-               vp = LOCKVP(ap->a_vp);
+               lockvp = LOCKVP(vp);
                mutex_exit(&un->un_lock);
-               if (vp == ap->a_vp)
-                       error = genfs_lock(ap);
-               else
-                       error = VOP_LOCK(vp, ap->a_flags);
+               error = union_lock1(vp, lockvp, flags);
                if (error != 0)
                        return error;
                mutex_enter(&un->un_lock);
-               if (vp == LOCKVP(ap->a_vp))
+               if (lockvp == LOCKVP(vp))
                        break;
-               if (vp == ap->a_vp)
-                       genfs_unlock(ap);
-               else
-                       VOP_UNLOCK(vp);
+               union_unlock1(vp, lockvp);
        }
+       mutex_exit(&un->un_lock);
+
        mutex_enter(vp->v_interlock);
-       if ((vp->v_iflag & (VI_XLOCK | VI_CLEAN)) != 0) {
-               if (vp == ap->a_vp)
-                       genfs_unlock(ap);
-               else
-                       VOP_UNLOCK(vp);
-               if ((vp->v_iflag & VI_XLOCK))
-                       vwait(vp, VI_XLOCK);
+       if (ISSET(vp->v_iflag, VI_XLOCK) || ISSET(vp->v_iflag, VI_CLEAN)) {
+               union_unlock1(vp, lockvp);
+               vwait(vp, VI_XLOCK);
+               KASSERT(ISSET(vp->v_iflag, VI_CLEAN));
                mutex_exit(vp->v_interlock);
-               mutex_exit(&un->un_lock);
                return ENOENT;
        }
        mutex_exit(vp->v_interlock);
-       mutex_exit(&un->un_lock);
-
        return 0;
 }
 
@@ -1667,13 +1683,10 @@
                struct vnode *a_vp;
                int a_flags;
        } */ *ap = v;
-       struct vnode *vp;
+       struct vnode *vp = ap->a_vp, *lockvp;
 
-       vp = LOCKVP(ap->a_vp);
-       if (vp == ap->a_vp)
-               genfs_unlock(ap);
-       else
-               VOP_UNLOCK(vp);
+       lockvp = LOCKVP(vp);
+       union_unlock1(vp, lockvp);
 
        return 0;
 }