When one sets socket buffer sizes with setsockopt(SO_{SND,RCV}BUF*),
kernel sets coresponding SOCK_SNDBUF_LOCK or SOCK_RCVBUF_LOCK flags on
struct sock. It means that such a socket with explicitly changed buffer
size can not be auto-adjusted by kernel (e.g. if there is free memory
kernel can auto-increase default socket buffers to improve perfomance).
(see tcp_fixup_rcvbuf() and tcp_sndbuf_expand())
CRIU is always changing buf sizes on restore, that means that all
sockets receive lock flags on struct sock and become non-auto-adjusted
after migration. In some cases it can decrease perfomance of network
connections quite a lot.
So let's c/r socket buf locks (SO_BUF_LOCKS), so that sockets for which
auto-adjustment is available does not lose it.
Reviewed-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
e69be16db7