With Alfred's permission, remove vm_mtx in favor of a fine-grained approach

(this commit is just the first stage).  Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.

1 files changed, 5 insertions, 12 deletions

diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index dc5b9c9..1a1f55b 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -527,6 +527,8 @@ vop_stdcreatevobject(ap)
 	vm_object_t object;
 	int error = 0;
 
+	GIANT_REQUIRED;
+
 	if (!vn_isdisk(vp, NULL) && vn_canvmio(vp) == FALSE)
 		return (0);
 
@@ -535,7 +537,6 @@ retry:
 		if (vp->v_type == VREG || vp->v_type == VDIR) {
 			if ((error = VOP_GETATTR(vp, &vat, cred, p)) != 0)
 				goto retn;
-			mtx_lock(&vm_mtx);
 			object = vnode_pager_alloc(vp, vat.va_size, 0, 0);
 		} else if (devsw(vp->v_rdev) != NULL) {
 			/*
@@ -543,7 +544,6 @@ retry:
 			 * for a disk vnode.  This should be fixed, but doesn't
 			 * cause any problems (yet).
 			 */
-			mtx_lock(&vm_mtx);
 			object = vnode_pager_alloc(vp, IDX_TO_OFF(INT_MAX), 0, 0);
 		} else {
 			goto retn;
@@ -553,21 +553,14 @@ retry:
 		 * that the object is associated with the vp.
 		 */
 		object->ref_count--;
-		mtx_unlock(&vm_mtx);
 		vp->v_usecount--;
 	} else {
-		/*
-		 * XXX: safe to hold vm mutex through VOP_UNLOCK?
-		 */
-		mtx_lock(&vm_mtx);
 		if (object->flags & OBJ_DEAD) {
 			VOP_UNLOCK(vp, 0, p);
-			msleep(object, VM_OBJECT_MTX(object), PVM, "vodead", 0);
-			mtx_unlock(&vm_mtx);
+			tsleep(object, PVM, "vodead", 0);
 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 			goto retry;
 		}
-		mtx_unlock(&vm_mtx);
 	}
 
 	KASSERT(vp->v_object != NULL, ("vfs_object_create: NULL object"));
@@ -586,10 +579,11 @@ vop_stddestroyvobject(ap)
 	struct vnode *vp = ap->a_vp;
 	vm_object_t obj = vp->v_object;
 
+	GIANT_REQUIRED;
+
 	if (vp->v_object == NULL)
 		return (0);
 
-	mtx_lock(&vm_mtx);
 	if (obj->ref_count == 0) {
 		/*
 		 * vclean() may be called twice. The first time
@@ -604,7 +598,6 @@ vop_stddestroyvobject(ap)
 		 */
 		vm_pager_deallocate(obj);
 	}
-	mtx_unlock(&vm_mtx);
 	return (0);
 }