Revert r253939:

We cannot busy a page before doing pagefaults.
Infact, it can deadlock against vnode lock, as it tries to vget().
Other functions, right now, have an opposite lock ordering, like
vm_object_sync(), which acquires the vnode lock first and then
sleeps on the busy mechanism.

Before this patch is reinserted we need to break this ordering.

Sponsored by:	EMC / Isilon storage division
Reported by:	kib

1 files changed, 9 insertions, 7 deletions

diff --git a/sys/vm/vm_glue.c b/sys/vm/vm_glue.c
index 445a24a..948e2b3 100644
--- a/sys/vm/vm_glue.c
+++ b/sys/vm/vm_glue.c
@@ -223,7 +223,7 @@ vsunlock(void *addr, size_t len)
  * Return the pinned page if successful; otherwise, return NULL.
  */
 static vm_page_t
-vm_imgact_page_iostart(vm_object_t object, vm_ooffset_t offset)
+vm_imgact_hold_page(vm_object_t object, vm_ooffset_t offset)
 {
 	vm_page_t m, ma[1];
 	vm_pindex_t pindex;
@@ -249,7 +249,9 @@ vm_imgact_page_iostart(vm_object_t object, vm_ooffset_t offset)
 		}
 		vm_page_wakeup(m);
 	}
-	vm_page_io_start(m);
+	vm_page_lock(m);
+	vm_page_hold(m);
+	vm_page_unlock(m);
 out:
 	VM_OBJECT_WUNLOCK(object);
 	return (m);
@@ -264,7 +266,7 @@ vm_imgact_map_page(vm_object_t object, vm_ooffset_t offset)
 {
 	vm_page_t m;
 
-	m = vm_imgact_page_iostart(object, offset);
+	m = vm_imgact_hold_page(object, offset);
 	if (m == NULL)
 		return (NULL);
 	sched_pin();
@@ -275,16 +277,16 @@ vm_imgact_map_page(vm_object_t object, vm_ooffset_t offset)
  * Destroy the given CPU private mapping and unpin the page that it mapped.
  */
 void
-vm_imgact_unmap_page(vm_object_t object, struct sf_buf *sf)
+vm_imgact_unmap_page(struct sf_buf *sf)
 {
 	vm_page_t m;
 
 	m = sf_buf_page(sf);
 	sf_buf_free(sf);
 	sched_unpin();
-	VM_OBJECT_WLOCK(object);
-	vm_page_io_finish(m);
-	VM_OBJECT_WUNLOCK(object);
+	vm_page_lock(m);
+	vm_page_unhold(m);
+	vm_page_unlock(m);
 }
 
 void