[Bug 35781] kernel32/pipe test fails

https://bugs.winehq.org/show_bug.cgi?id=35781

--- Comment #10 from Austin English  ---
Bisecting the kernel, I found it was introduced by:
root@debian:/mnt/spare_hdd/linux# git bisect good
^[[21;3~eea86af6b1e18d6fa8dc959e3ddc0100f27aff9f is the first bad commit
commit eea86af6b1e18d6fa8dc959e3ddc0100f27aff9f
Author: Daniel Borkmann 
Date:   Wed Jun 19 12:51:20 2013 +0200

net: sock: adapt SOCK_MIN_RCVBUF and SOCK_MIN_SNDBUF

The current situation is that SOCK_MIN_RCVBUF is 2048 + sizeof(struct
sk_buff))
    while SOCK_MIN_SNDBUF is 2048. Since in both cases, skb->truesize is used
for
    sk_{r,w}mem_alloc accounting, we should have both sizes adjusted via
defining a
    TCP_SKB_MIN_TRUESIZE.

Further, as Eric Dumazet points out, the minimal skb truesize in transmit
path is
    SKB_TRUESIZE(2048) after commit f07d960df33c5 ("tcp: avoid frag allocation
for
    small frames"), and tcp_sendmsg() tries to limit skb size to half the
congestion
    window, meaning we try to build two skbs at minimum. Thus, having
SOCK_MIN_SNDBUF
    as 2048 can hit a small regression for some applications setting to low
    SO_SNDBUF / SO_RCVBUF. Note that we define a TCP_SKB_MIN_TRUESIZE, because
    SKB_TRUESIZE(2048) adds SKB_DATA_ALIGN(sizeof(struct skb_shared_info)), but
in
    case of TCP skbs, the skb_shared_info is part of the 2048 bytes allocation
for
    skb->head.

The minor adaption in sk_stream_moderate_sndbuf() is to silence a warning
by
    using a typed max macro, as similarly done in SOCK_MIN_RCVBUF occurences,
that
    would appear otherwise.