int/long confusion with maxbcache and maxswzone (fixes 6.0 on >12GB machines)

A few weeks ago I reported that bufinit() on sparc64 machines with
>12GB of RAM goes into an infinite loop because of a 32-bit integer
counter overflowing.  On 5.x it was possible to work around this with
the kern.maxbcache tunable, but this didn't work on 6.0 or above.

It turns out the problem began here:

----
Revision 1.67 / (download) - annotate - [select for diffs], Mon Nov 8 18:20:02 2004 UTC (11 months ago) by des
Branch: MAIN
Changes since 1.66: +17 -17 lines
Diff to previous 1.66 (colored)

#include <vm/vm_param.h> instead of <machine/vmparam.h> (the former
includes the latter, but also declares variables which are defined
in kern/subr_param.c).

Change som VM parameters from quad_t to unsigned long.  They refer to
quantities (size limits for text, heap and stack segments) which must
necessarily be smaller than the size of the address space, so long is
adequate on all platforms.

MFC after:	1 week
----

which contained:

-int	maxswzone;			/* max swmeta KVA storage */
-int	maxbcache;			/* max buffer cache KVA storage */
+long	maxswzone;			/* max swmeta KVA storage */
+long	maxbcache;			/* max buffer cache KVA storage */

However, des forgot to change the other definition of maxbcache in
<sys/buf.h>:

extern int      maxbcache;              /* Max KVA for buffer cache */

In fact, it's a good thing he didn't.  On sparc64 if you make that
variable a long it causes 32-bit integer overflows elsewhere, which
lead to severe filesystem damage on systems with >12GB RAM.  With the
above bug this is reduced to a hang at boot.

The hang is because maxbcache is not capped to a maximum value on
sparc64, and a loop termination condition never occurs because of a
32-bit integer overflow.  On amd64 it's capped to

/*
 * Ceiling on size of buffer cache (really only effects write queueing,
 * the VM page cache is not effected), can be changed via
 * the kern.maxbcache /boot/loader.conf variable.
 */
#ifndef VM_BCACHE_SIZE_MAX
#define VM_BCACHE_SIZE_MAX      (400 * 1024 * 1024)
#endif

so large-memory amd64 systems never see it.  ia64 and ppc would also
hang at boot with >12GB, I think.

On 5.x, the same hang exists, but you can work around it with the
tunable.  This tunable was broken by the long/int mismatch on 6.0, so
sparc64 systems with >12GB were unusable.

This patch reverts the above int->long change, and adds definitions
for VM_BCACHE_SIZE_MAX and VM_SWZONE_SIZE_MAX on sparc64 copied from
amd64.  Actually, they should probably be added on other architectures
too (ia64, ppc).

Can someone please review?

Kris

Index: kern/subr_param.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/subr_param.c,v
retrieving revision 1.71
diff -u -r1.71 subr_param.c
--- kern/subr_param.c	16 Apr 2005 15:07:41 -0000	1.71
+++ kern/subr_param.c	11 Oct 2005 21:09:01 -0000
_at__at_ -75,8 +75,8 _at__at_
 int	ncallout;			/* maximum # of timer events */
 int	nbuf;
 int	nswbuf;
-long	maxswzone;			/* max swmeta KVA storage */
-long	maxbcache;			/* max buffer cache KVA storage */
+int	maxswzone;			/* max swmeta KVA storage */
+int	maxbcache;			/* max buffer cache KVA storage */
 int	maxpipekva;			/* Limit on pipe KVA */
 u_long	maxtsiz;			/* max text size */
 u_long	dfldsiz;			/* initial data size limit */
_at__at_ -106,11 +106,11 _at__at_
 #ifdef VM_SWZONE_SIZE_MAX
 	maxswzone = VM_SWZONE_SIZE_MAX;
 #endif
-	TUNABLE_LONG_FETCH("kern.maxswzone", &maxswzone);
+	TUNABLE_INT_FETCH("kern.maxswzone", &maxswzone);
 #ifdef VM_BCACHE_SIZE_MAX
 	maxbcache = VM_BCACHE_SIZE_MAX;
 #endif
-	TUNABLE_LONG_FETCH("kern.maxbcache", &maxbcache);
+	TUNABLE_INT_FETCH("kern.maxbcache", &maxbcache);
 
 	maxtsiz = MAXTSIZ;
 	TUNABLE_ULONG_FETCH("kern.maxtsiz", &maxtsiz);
Index: sparc64/include/param.h
===================================================================
RCS file: /home/ncvs/src/sys/sparc64/include/param.h,v
retrieving revision 1.19
diff -u -r1.19 param.h
--- sparc64/include/param.h	20 Nov 2004 02:29:50 -0000	1.19
+++ sparc64/include/param.h	11 Oct 2005 20:54:30 -0000
_at__at_ -110,6 +110,22 _at__at_
 #define KSTACK_GUARD_PAGES	1	/* pages of kstack guard; 0 disables */
 #define PCPU_PAGES		1
 
+/*
+ * Ceiling on amount of swblock kva space, can be changed via
+ * the kern.maxswzone /boot/loader.conf variable.
+ */
+#ifndef VM_SWZONE_SIZE_MAX
+#define VM_SWZONE_SIZE_MAX      (32 * 1024 * 1024)
+#endif
+
+/*
+ * Ceiling on size of buffer cache (really only effects write queueing,
+ * the VM page cache is not effected), can be changed via
+ * the kern.maxbcache /boot/loader.conf variable.
+ */
+#ifndef VM_BCACHE_SIZE_MAX
+#define VM_BCACHE_SIZE_MAX      (400 * 1024 * 1024)
+#endif
 
 /*
  * Mach derived conversion macros
Index: sparc64/include/vmparam.h
===================================================================
RCS file: /home/ncvs/src/sys/sparc64/include/vmparam.h,v
retrieving revision 1.14
diff -u -r1.14 vmparam.h
--- sparc64/include/vmparam.h	27 Dec 2002 19:31:26 -0000	1.14
+++ sparc64/include/vmparam.h	11 Oct 2005 20:54:30 -0000
_at__at_ -171,6 +171,13 _at__at_
 #endif
 
 /*
+ * Ceiling on amount of kmem_map kva space.
+ */
+#ifndef VM_KMEM_SIZE_MAX
+#define VM_KMEM_SIZE_MAX        (400 * 1024 * 1024)
+#endif
+
+/*
  * Initial pagein size of beginning of executable file.
  */
 #ifndef	VM_INITIAL_PAGEIN