linux_dsm_epyc7002/include
Wei Wang 5f56f409b5 net: introduce DST_NOGC in dst_release() to destroy dst based on refcnt
The current mechanism of freeing dst is a bit complicated. dst has its
ref count and when user grabs the reference to the dst, the ref count is
properly taken in most cases except in IPv4/IPv6/decnet/xfrm routing
code due to some historic reasons.

If the reference to dst is always taken properly, we should be able to
simplify the logic in dst_release() to destroy dst when dst->__refcnt
drops from 1 to 0. And this should be the only condition to determine
if we can call dst_destroy().
And as dst is always ref counted, there is no need for a dst garbage
list to hold the dst entries that already get removed by the routing
code but are still held by other users. And the task to periodically
check the list to free dst if ref count become 0 is also not needed
anymore.

This patch introduces a temporary flag DST_NOGC(no garbage collector).
If it is set in the dst, dst_release() will call dst_destroy() when
dst->__refcnt drops to 0. dst_hold_safe() will also check for this flag
and do atomic_inc_not_zero() similar as DST_NOCACHE to avoid double free
issue.
This temporary flag is mainly used so that we can make the transition
component by component without breaking other parts.
This flag will be removed after all components are properly transitioned.

This patch also introduces a new function dst_release_immediate() which
destroys dst without waiting on the rcu when refcnt drops to 0. It will
be used in later patches.

Follow-up patches will correct all the places to properly take ref count
on dst and mark DST_NOGC. dst_release() or dst_release_immediate() will
be used to release the dst instead of dst_free() and its related
functions.
And final clean-up patch will remove the DST_NOGC flag.

Signed-off-by: Wei Wang <weiwan@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-06-17 22:53:59 -04:00
..
acpi Merge branch 'acpica-fixes' 2017-06-15 01:52:32 +02:00
asm-generic
clocksource
crypto
drm drm/dp: start a DPCD based DP sink/branch device quirk database 2017-05-29 13:43:26 +03:00
dt-bindings
keys
kvm
linux mlx5-updates-2017-06-16 2017-06-16 15:22:42 -04:00
math-emu
media [media] media/cec.h: use IS_REACHABLE instead of IS_ENABLED 2017-06-08 16:52:28 -03:00
memory
misc
net net: introduce DST_NOGC in dst_release() to destroy dst based on refcnt 2017-06-17 22:53:59 -04:00
pcmcia
ras
rdma RDMA/SA: Fix kernel panic in CMA request handler flow 2017-06-01 17:20:14 -04:00
rxrpc rxrpc: Implement service upgrade 2017-06-05 14:30:49 +01:00
scsi
soc
sound
target iscsi-target: Fix initial login PDU asynchronous socket close OOPs 2017-05-31 15:12:31 -07:00
trace rxrpc: Add service upgrade support for client connections 2017-06-05 14:30:49 +01:00
uapi net: Add IFLA_XDP_PROG_ID 2017-06-16 11:58:36 -04:00
video
xen