udp: calculate udp_mem based on low memory instead of all memory

This patch mimics commit 57413ebc
(tcp: calculate tcp_mem based on low memory instead of all memory)

The udp_mem array which contains limits on the total amount of memory
used by UDP sockets is calculated based on nr_all_pages.  On a 32 bits
x86 system, we should base this on the number of lowmem pages.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp.c

@@ -81,6 +81,8 @@
 #include <asm/uaccess.h>
 #include <asm/ioctls.h>
 #include <linux/bootmem.h>
+#include <linux/highmem.h>
+#include <linux/swap.h>
 #include <linux/types.h>
 #include <linux/fcntl.h>
 #include <linux/module.h>
@@ -1751,15 +1753,16 @@ void __init udp_table_init(struct udp_table *table)
 
 void __init udp_init(void)
 {
-	unsigned long limit;
+	unsigned long nr_pages, limit;
 
 	udp_table_init(&udp_table);
 	/* Set the pressure threshold up by the same strategy of TCP. It is a
 	 * fraction of global memory that is up to 1/2 at 256 MB, decreasing
 	 * toward zero with the amount of memory, with a floor of 128 pages.
 	 */
-	limit = min(nr_all_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
-	limit = (limit * (nr_all_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
+	nr_pages = totalram_pages - totalhigh_pages;
+	limit = min(nr_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
+	limit = (limit * (nr_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
 	limit = max(limit, 128UL);
 	sysctl_udp_mem[0] = limit / 4 * 3;
 	sysctl_udp_mem[1] = limit;