[BUG FIX] fork_init() OOM bug on big highmem machine

[Coywolf Qi Hunt <coywolf@greatcn.org>]

Coywolf Qi Hunt wrote:

> Hello all,
>
> On machine with 16G(or 8G if 4k stacks) or more memory, high 
> max_threads could let system run out of low memory.
> This patch decides max_threads by the amount of low memory instead of 
> the total physical memory.
> Systems without high memory would not be affected. 

This patch should be ok by taking ``max_low_pfn - min_low_pfn'' and also 
becomes more accurate.

On those systems where physical RAM doesn't start at address 0, we 
should initialize min_low_pfn.
Anyway min_low_pfn is already defined on all platforms. The bug of 
forgetting min_low_pfn initialization
on those platforms isn't more severe than this bug.

====================================================================

diff -rup linux-2.6.7/init/main.c linux-2.6.7-cy/init/main.c
--- linux-2.6.7/init/main.c	Wed Jun  9 00:07:40 2004
+++ linux-2.6.7-cy/init/main.c	Thu Jun 17 04:55:54 2004
@@ -467,7 +467,7 @@ asmlinkage void __init start_kernel(void
 	if (efi_enabled)
 		efi_enter_virtual_mode();
 #endif
-	fork_init(num_physpages);
+	fork_init(max_low_pfn - min_low_pfn);
 	proc_caches_init();
 	buffer_init();
 	unnamed_dev_init();
diff -rup linux-2.6.7/kernel/fork.c linux-2.6.7-cy/kernel/fork.c
--- linux-2.6.7/kernel/fork.c	Wed Jun  9 00:07:40 2004
+++ linux-2.6.7-cy/kernel/fork.c	Mon Jun 28 22:55:50 2004
@@ -224,8 +224,8 @@ void __init fork_init(unsigned long memp
 
 	/*
 	 * The default maximum number of threads is set to a safe
-	 * value: the thread structures can take up at most half
-	 * of memory.
+	 * value: the thread structures can take up at most 1/8
+	 * of low memory.
 	 */
 	max_threads = mempages / (THREAD_SIZE/PAGE_SIZE) / 8;
 	/*


-- 
Coywolf Qi Hunt
Admin of http://GreatCN.org and http://LoveCN.org