svn commit: r249745 - head/sys/vm

[Alan Cox]

Author: alc
Date: Mon Apr 22 01:26:13 2013
New Revision: 249745
URL: http://svnweb.freebsd.org/changeset/base/249745

Log:
  Simplify vm_radix_{add,dec}lev().
  
  Sponsored by: EMC / Isilon Storage Division

Modified:
  head/sys/vm/vm_radix.c

Modified: head/sys/vm/vm_radix.c
==============================================================================
--- head/sys/vm/vm_radix.c      Sun Apr 21 22:47:24 2013        (r249744)
+++ head/sys/vm/vm_radix.c      Mon Apr 22 01:26:13 2013        (r249745)
@@ -265,16 +265,19 @@ vm_radix_keybarr(struct vm_radix_node *r
 static __inline int
 vm_radix_addlev(vm_pindex_t *idx, boolean_t *levels, uint16_t ilev)
 {
-       vm_pindex_t wrapidx;
 
        for (; levels[ilev] == FALSE ||
            vm_radix_slot(*idx, ilev) == (VM_RADIX_COUNT - 1); ilev--)
                if (ilev == 0)
                        return (1);
-       wrapidx = *idx;
+
+       /*
+        * The following computation cannot overflow because *idx's slot at
+        * ilev is less than VM_RADIX_COUNT - 1.
+        */
        *idx = vm_radix_trimkey(*idx, ilev);
        *idx += VM_RADIX_UNITLEVEL(ilev);
-       return (*idx < wrapidx);
+       return (0);
 }
 
 /*
@@ -286,17 +289,19 @@ vm_radix_addlev(vm_pindex_t *idx, boolea
 static __inline int
 vm_radix_declev(vm_pindex_t *idx, boolean_t *levels, uint16_t ilev)
 {
-       vm_pindex_t wrapidx;
 
        for (; levels[ilev] == FALSE ||
            vm_radix_slot(*idx, ilev) == 0; ilev--)
                if (ilev == 0)
                        return (1);
-       wrapidx = *idx;
+
+       /*
+        * The following computation cannot overflow because *idx's slot at
+        * ilev is greater than 0.
+        */
        *idx = vm_radix_trimkey(*idx, ilev);
-       *idx |= VM_RADIX_UNITLEVEL(ilev) - 1;
-       *idx -= VM_RADIX_UNITLEVEL(ilev);
-       return (*idx > wrapidx);
+       *idx -= 1;
+       return (0);
 }
 
 /*
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