On all the architectures, avoid to preallocate the physical memory

for nodes used in vm_radix.
On architectures supporting direct mapping, also avoid to pre-allocate
the KVA for such nodes.

In order to do so make the operations derived from vm_radix_insert()
to fail and handle all the deriving failure of those.

vm_radix-wise introduce a new function called vm_radix_replace(),
which can replace a leaf node, already present, with a new one,
and take into account the possibility, during vm_radix_insert()
allocation, that the operations on the radix trie can recurse.
This means that if operations in vm_radix_insert() recursed
vm_radix_insert() will start from scratch again.

Sponsored by:	EMC / Isilon storage division
Reviewed by:	alc (older version)
Reviewed by:	jeff
Tested by:	pho, scottl

1 files changed, 2 insertions, 1 deletions

diff --git a/sys/vm/device_pager.c b/sys/vm/device_pager.c
index fd20664..ba193e9 100644
--- a/sys/vm/device_pager.c
+++ b/sys/vm/device_pager.c
@@ -348,11 +348,12 @@ old_dev_pager_fault(vm_object_t object, vm_ooffset_t offset, int prot,
 		 */
 		page = vm_page_getfake(paddr, memattr);
 		VM_OBJECT_WLOCK(object);
+		if (vm_page_replace(page, object, (*mres)->pindex) != *mres)
+			panic("old_dev_pager_fault: invalid page replacement");
 		vm_page_lock(*mres);
 		vm_page_free(*mres);
 		vm_page_unlock(*mres);
 		*mres = page;
-		vm_page_insert(page, object, pidx);
 	}
 	page->valid = VM_PAGE_BITS_ALL;
 	return (VM_PAGER_OK);