Introduce a global lock for the vm subsystem (vm_mtx).

vm_mtx does not recurse and is required for most low level
vm operations.

faults can not be taken without holding Giant.

Memory subsystems can now call the base page allocators safely.

Almost all atomic ops were removed as they are covered under the
vm mutex.

Alpha and ia64 now need to catch up to i386's trap handlers.

FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).

Reviewed (partially) by: jake, jhb

1 files changed, 15 insertions, 1 deletions

diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index 328a9b1..d17e934 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -535,14 +535,18 @@ 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);
+			mtx_unlock(&vm_mtx);
 		} else if (devsw(vp->v_rdev) != NULL) {
 			/*
 			 * This simply allocates the biggest object possible
 			 * 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);
+			mtx_unlock(&vm_mtx);
 		} else {
 			goto retn;
 		}
@@ -550,15 +554,23 @@ retry:
 		 * Dereference the reference we just created.  This assumes
 		 * that the object is associated with the vp.
 		 */
+		mtx_lock(&vm_mtx);
 		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);
-			tsleep(object, PVM, "vodead", 0);
+			msleep(object, VM_OBJECT_MTX(object), PVM, "vodead", 0);
+			mtx_unlock(&vm_mtx);
 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 			goto retry;
 		}
+		mtx_unlock(&vm_mtx);
 	}
 
 	KASSERT(vp->v_object != NULL, ("vfs_object_create: NULL object"));
@@ -580,6 +592,7 @@ vop_stddestroyvobject(ap)
 	if (vp->v_object == NULL)
 		return (0);
 
+	mtx_lock(&vm_mtx);
 	if (obj->ref_count == 0) {
 		/*
 		 * vclean() may be called twice. The first time
@@ -594,6 +607,7 @@ vop_stddestroyvobject(ap)
 		 */
 		vm_pager_deallocate(obj);
 	}
+	mtx_unlock(&vm_mtx);
 	return (0);
 }