currently if skb does not have enough headroom skb_realloc_headrom is called. It is not optimal because it creates new skb. Unlike skb_realloc_headroom, new helper pskb_realloc_headroom does not allocate a new skb if possible; copies skb->sk on new skb when as needed and frees original skb in case of failures. This helps to simplify ip[6]_finish_output2(), ip6_xmit() and a few other functions in vrf, ax25 and bpf. There are few other cases where this helper can be used but they require an additional investigations. NB: patch "ipv6: use pskb_realloc_headroom in ip6_finish_output2" depends on patch "ipv6: allocate enough headroom in ip6_finish_output2()" submitted separately https://lkml.org/lkml/2021/7/12/732 Vasily Averin (7): skbuff: introduce pskb_realloc_headroom() ipv6: use pskb_realloc_headroom in ip6_finish_output2 ipv6: use pskb_realloc_headroom in ip6_xmit ipv4: use pskb_realloc_headroom in ip_finish_output2 vrf: use pskb_realloc_headroom in vrf_finish_output ax25: use pskb_realloc_headroom bpf: use pskb_realloc_headroom in bpf_out_neigh_v4/6 drivers/net/vrf.c | 14 +++------ include/linux/skbuff.h | 2 ++ net/ax25/ax25_out.c | 13 +++------ net/ax25/ax25_route.c | 13 +++------ net/core/filter.c | 22 +++----------- net/core/skbuff.c | 41 ++++++++++++++++++++++++++ net/ipv4/ip_output.c | 12 ++------ net/ipv6/ip6_output.c | 78 ++++++++++++++++++-------------------------------- 8 files changed, 89 insertions(+), 106 deletions(-) -- 1.8.3.1
