UDP memory accounting and limitation (take 8)

Hello,

This is the latest patch set of UDP memory accounting and limitation.

I modified sk_datagram_pages() to avoid using divide instruction.

In addition, I also fixed memory accounting code in udp_recvmsg(), since, in previous takes, the accounting code referred released sk_buff's truesize. The fix can be found in 3rd patch of the patch set.

The patch set is for net-2.6. Please apply.

Changelog take 7 -> take 8:
* sk_datagram_pages(): avoided using divide instruction
* udp_recvmsg(): fixed referring released truesize in accounting

Changelog take 6 -> take 7:
* renamed /proc/sys/net/ipv4/udp_rmem to
/proc/sys/net/ipv4/udp_rmem_min
* renamed /proc/sys/net/ipv4/udp_wmem to
/proc/sys/net/ipv4/udp_wmem_min
* rebased to net-2.6

Changelog take 5 -> take 6:

* removed minimal limit of /proc/sys/net/ipv4/udp_mem
* added udp_init() for default value calculation of parameters
* added /proc/sys/net/ipv4/udp_rmem and /proc/sys/net/ipv4/udp_rmem
* added limitation code to ip_ufo_append_data()
* improved accounting for receiving packet
* fixed typos
* rebased to 2.6.24-rc1

Changelog take 4 -> take 5:

* removing unnessesary EXPORT_SYMBOLs
* adding minimal limit of /proc/sys/net/ipv4/udp_mem
* bugfix of UDP limit affecting protocol other than UDP
* introducing __ip_check_max_skb_pages()
* using CTL_UNNUMBERED
* adding udp_mem usage to Documentation/networking/ip_sysctl.txt

Best regards,
Hideo Aoki

--
Hitachi Computer Products (America) Inc.