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SubjectRe: nfs broken in net-next? -- now in mainline -- bisected: d9f5950f90292f7cc42834338dfd5f44dc4cc4ca
Eric Dumazet wrote:
> Le 13/12/2009 03:41, Yinghai Lu a écrit :
>>>> cause the problem: nfs mount fail.
>>>>
>>>> the setup is:
>>>> 64bit kernel, have all needed drivers in kernel, and boot with
>>>> ip=dhcp, root disk is 256M ramdisk.
>>>> then try to mount nfs....
>>>>
>>> change entries default value from 65536 to 256,
>>> nfs mount will work.
>>>
>> interesting:
>>
>> m:~/dump # grep UDP dmesg.txt
>> [ 28.996034] UDP hash table entries: 65536 (order: 11, 10485760 bytes)
>> [ 29.032364] UDP-Lite hash table entries: 65536 (order: 11, 10485760 bytes)
>>
>> will not work
>>
>> but 32768 will work.
>
> Thanks a lot for this work Yinghai !
> This last bit helped me a lot ...
>
> Hmm, udp_lib_get_port() assumes it can loop at least one time in :
>
> for (last = first + udptable->mask + 1;
> first != last;
> first++) {
> // unit_work
> }
>
> but if udptable->mask == 65535, loop is not entered at all (since last == first)
>
> We should convert it to a do { } while(...); construct, or use 32bit variables
> and (u16) casts.
>
> Thanks
>
> [PATCH] udp: udp_lib_get_port() fix
>
> Now we can have a large udp hash table, udp_lib_get_port() loop
> should be converted to a do {} while (cond) form,
> or we dont enter it at all if hash table size is exactly 65536.
>
> Reported-by: Yinghai Lu <yinghai@kernel.org>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> ---
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 1f95348..f0126fd 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -216,9 +216,8 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
> * force rand to be an odd multiple of UDP_HTABLE_SIZE
> */
> rand = (rand | 1) * (udptable->mask + 1);
> - for (last = first + udptable->mask + 1;
> - first != last;
> - first++) {
> + last = first + udptable->mask + 1;
> + do {
> hslot = udp_hashslot(udptable, net, first);
> bitmap_zero(bitmap, PORTS_PER_CHAIN);
> spin_lock_bh(&hslot->lock);
> @@ -238,7 +237,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
> snum += rand;
> } while (snum != first);
> spin_unlock_bh(&hslot->lock);
> - }
> + } while (++first != last);
> goto fail;
> } else {
> hslot = udp_hashslot(udptable, net, snum);

thanks. that fix the problem.

YH
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