[src/trunk]: src/sys/kern Fix processing of vm.bufmem_lowater and vm.bufmem_h...

[dsl <dsl%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/82a566dccc7e
branches:  trunk
changeset: 779568:82a566dccc7e
user:      dsl <dsl%NetBSD.org@localhost>
date:      Sun Jun 03 11:37:44 2012 +0000

description:
Fix processing of vm.bufmem_lowater and vm.bufmem_hiwater on 64bit systems.
The values are 'u_long' so copying them into an 'int' temporary
(to avoid writing an out of range value into the actual variable)
doesn't work too well at all.
Shows up on amd64 now that the sysctl values are marked as 64bit.
sparc64 must have been badly broken for ages.

diffstat:

 sys/kern/vfs_bio.c |  30 ++++++++++++++++--------------
 1 files changed, 16 insertions(+), 14 deletions(-)

diffs (72 lines):

diff -r 8384617f9ec2 -r 82a566dccc7e sys/kern/vfs_bio.c
--- a/sys/kern/vfs_bio.c        Sun Jun 03 10:59:44 2012 +0000
+++ b/sys/kern/vfs_bio.c        Sun Jun 03 11:37:44 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_bio.c,v 1.237 2012/06/02 21:36:46 dsl Exp $        */
+/*     $NetBSD: vfs_bio.c,v 1.238 2012/06/03 11:37:44 dsl Exp $        */
 
 /*-
  * Copyright (c) 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -123,7 +123,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.237 2012/06/02 21:36:46 dsl Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.238 2012/06/03 11:37:44 dsl Exp $");
 
 #include "opt_bufcache.h"
 
@@ -1730,39 +1730,41 @@
 static int
 sysctl_bufvm_update(SYSCTLFN_ARGS)
 {
-       int t, error, rv;
+       int error, rv;
        struct sysctlnode node;
+       union u_int_long { unsigned int i; unsigned long l; } t;
 
+       /* Take a copy of the supplied node and its data */
        node = *rnode;
        node.sysctl_data = &t;
-       t = *(int *)rnode->sysctl_data;
+       t = *(union u_int_long *)rnode->sysctl_data;
+
+       /* Update the copy */
        error = sysctl_lookup(SYSCTLFN_CALL(&node));
        if (error || newp == NULL)
                return (error);
 
-       if (t < 0)
-               return EINVAL;
        if (rnode->sysctl_data == &bufcache) {
-               if (t > 100)
+               if (t.i > 100)
                        return (EINVAL);
-               bufcache = t;
+               bufcache = t.i;
                buf_setwm();
        } else if (rnode->sysctl_data == &bufmem_lowater) {
-               if (bufmem_hiwater - t < 16)
+               if (bufmem_hiwater - t.l < 16)
                        return (EINVAL);
-               bufmem_lowater = t;
+               bufmem_lowater = t.l;
        } else if (rnode->sysctl_data == &bufmem_hiwater) {
-               if (t - bufmem_lowater < 16)
+               if (t.l - bufmem_lowater < 16)
                        return (EINVAL);
-               bufmem_hiwater = t;
+               bufmem_hiwater = t.l;
        } else
                return (EINVAL);
 
        /* Drain until below new high water mark */
        sysctl_unlock();
        mutex_enter(&bufcache_lock);
-       while ((t = bufmem - bufmem_hiwater) >= 0) {
-               rv = buf_drain(t / (2 * 1024));
+       while (bufmem > bufmem_hiwater) {
+               rv = buf_drain((bufmem - bufmem_hiwater) / (2 * 1024));
                if (rv <= 0)
                        break;
        }