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, 4 insertions, 16 deletions

diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
index e53a14c..07d0655 100644
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -245,18 +245,14 @@ vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
 {
 	vm_object_t ret;
 	struct pagerops *ops;
-	int hadvmlock;
 
-	hadvmlock = mtx_owned(&vm_mtx);
-	if (!hadvmlock)
-		mtx_lock(&vm_mtx);
+	GIANT_REQUIRED;
+
 	ops = pagertab[type];
 	if (ops)
 		ret = (*ops->pgo_alloc) (handle, size, prot, off);
 	else
 		ret = NULL;
-	if (!hadvmlock)
-		mtx_unlock(&vm_mtx);
 	return (ret);
 }
 
@@ -264,8 +260,7 @@ void
 vm_pager_deallocate(object)
 	vm_object_t object;
 {
-
-	mtx_assert(&vm_mtx, MA_OWNED);
+	GIANT_REQUIRED;
 	(*pagertab[object->type]->pgo_dealloc) (object);
 }
 
@@ -385,8 +380,6 @@ initpbuf(struct buf *bp)
  *
  *	NOTE: pfreecnt can be NULL, but this 'feature' will be removed
  *	relatively soon when the rest of the subsystems get smart about it. XXX
- *
- *	vm_mtx can be held or unheld
  */
 struct buf *
 getpbuf(pfreecnt)
@@ -394,12 +387,9 @@ getpbuf(pfreecnt)
 {
 	int s;
 	struct buf *bp;
-	int hadvmlock;
 
 	s = splvm();
-	hadvmlock = mtx_owned(&vm_mtx);
-	if (hadvmlock)
-		mtx_unlock(&vm_mtx);
+	GIANT_REQUIRED;
 	mtx_lock(&pbuf_mtx);
 
 	for (;;) {
@@ -424,8 +414,6 @@ getpbuf(pfreecnt)
 	splx(s);
 
 	initpbuf(bp);
-	if (hadvmlock)
-		mtx_lock(&vm_mtx);
 	return bp;
 }