MFC r288281

  The conversion of kmem_alloc_attr() from operating on a vm map to a vmem
  arena in r254025 introduced a bug in the case when an allocation is only
  partially successful.  Specifically, the vm object lock was not being
  acquired before freeing the allocated pages.  To address this bug, replace
  the existing code by a call to kmem_unback().

  Change the type of a variable in kmem_alloc_attr() so that an allocation
  of two or more gigabytes won't fail.

  Replace the error handling code in kmem_back() by a call to kmem_unback().

1 files changed, 13 insertions, 28 deletions

diff --git a/sys/vm/vm_kern.c b/sys/vm/vm_kern.c
index edfcf7a..291d0dd 100644
--- a/sys/vm/vm_kern.c
+++ b/sys/vm/vm_kern.c
@@ -159,11 +159,10 @@ kmem_alloc_attr(vmem_t *vmem, vm_size_t size, int flags, vm_paddr_t low,
     vm_paddr_t high, vm_memattr_t memattr)
 {
 	vm_object_t object = vmem == kmem_arena ? kmem_object : kernel_object;
-	vm_offset_t addr;
+	vm_offset_t addr, i;
 	vm_ooffset_t offset;
 	vm_page_t m;
 	int pflags, tries;
-	int i;
 
 	size = round_page(size);
 	if (vmem_alloc(vmem, size, M_BESTFIT | flags, &addr))
@@ -184,18 +183,7 @@ retry:
 				tries++;
 				goto retry;
 			}
-			/* 
-			 * Unmap and free the pages.
-			 */
-			if (i != 0)
-				pmap_remove(kernel_pmap, addr, addr + i);
-			while (i != 0) {
-				i -= PAGE_SIZE;
-				m = vm_page_lookup(object,
-				    OFF_TO_IDX(offset + i));
-				vm_page_unwire(m, 0);
-				vm_page_free(m);
-			}
+			kmem_unback(object, addr, i);
 			vmem_free(vmem, addr, size);
 			return (0);
 		}
@@ -353,25 +341,13 @@ retry:
 		 * aren't on any queues.
 		 */
 		if (m == NULL) {
+			VM_OBJECT_WUNLOCK(object);
 			if ((flags & M_NOWAIT) == 0) {
-				VM_OBJECT_WUNLOCK(object);
 				VM_WAIT;
 				VM_OBJECT_WLOCK(object);
 				goto retry;
 			}
-			/* 
-			 * Unmap and free the pages.
-			 */
-			if (i != 0)
-				pmap_remove(kernel_pmap, addr, addr + i);
-			while (i != 0) {
-				i -= PAGE_SIZE;
-				m = vm_page_lookup(object,
-						   OFF_TO_IDX(offset + i));
-				vm_page_unwire(m, 0);
-				vm_page_free(m);
-			}
-			VM_OBJECT_WUNLOCK(object);
+			kmem_unback(object, addr, i);
 			return (KERN_NO_SPACE);
 		}
 		if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
@@ -387,6 +363,15 @@ retry:
 	return (KERN_SUCCESS);
 }
 
+/*
+ *	kmem_unback:
+ *
+ *	Unmap and free the physical pages underlying the specified virtual
+ *	address range.
+ *
+ *	A physical page must exist within the specified object at each index
+ *	that is being unmapped.
+ */
 void
 kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
 {