This patch removes the net_random and net_srandom macros and replaces
them with direct calls to the prandom ones. As new commits only seem to
use prandom_u32 there is no use to keep them around.
This change makes it easier to grep for users of prandom_u32.
Signed-off-by: Aruna-Hewapathirane <aruna.hewapathirane@gmail.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
It is not necessary at all.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
tp->root is a void* pointer, no need to cast it.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
tcf_match_indev() is called in fast path, it is not wise to
search for a netdev by ifindex and then compare by its name,
just compare the ifindex.
Also, dev->name could be changed by user-space, therefore
the match would be always fail, but dev->ifindex could
be consistent.
BTW, this will also save some bytes from the core struct of u32.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It will be needed by the next patch.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Refactor tcf_add_notify() and factor out tcf_del_notify().
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There is no need to store the index separatedly
since tcf_hashinfo is allocated statically too.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is to be compatible with the use of "get_time" (i.e. default
time unit in us) in iproute2 patch for HHF as requested by Stephen.
Signed-off-by: Terry Lam <vtlam@google.com>
Acked-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently, the tx queue were selected implicitly in ndo_dfwd_start_xmit(). The
will cause several issues:
- NETIF_F_LLTX were removed for macvlan, so txq lock were done for macvlan
instead of lower device which misses the necessary txq synchronization for
lower device such as txq stopping or frozen required by dev watchdog or
control path.
- dev_hard_start_xmit() was called with NULL txq which bypasses the net device
watchdog.
- dev_hard_start_xmit() does not check txq everywhere which will lead a crash
when tso is disabled for lower device.
Fix this by explicitly introducing a new param for .ndo_select_queue() for just
selecting queues in the case of l2 forwarding offload. netdev_pick_tx() was also
extended to accept this parameter and dev_queue_xmit_accel() was used to do l2
forwarding transmission.
With this fixes, NETIF_F_LLTX could be preserved for macvlan and there's no need
to check txq against NULL in dev_hard_start_xmit(). Also there's no need to keep
a dedicated ndo_dfwd_start_xmit() and we can just reuse the code of
dev_queue_xmit() to do the transmission.
In the future, it was also required for macvtap l2 forwarding support since it
provides a necessary synchronization method.
Cc: John Fastabend <john.r.fastabend@intel.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: e1000-devel@lists.sourceforge.net
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
drivers/net/ethernet/qlogic/qlcnic/qlcnic_sriov_pf.c
net/ipv6/ip6_tunnel.c
net/ipv6/ip6_vti.c
ipv6 tunnel statistic bug fixes conflicting with consolidation into
generic sw per-cpu net stats.
qlogic conflict between queue counting bug fix and the addition
of multiple MAC address support.
Signed-off-by: David S. Miller <davem@davemloft.net>
action flushing missaccounting
Account only for deleted actions
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Remove unnecessary checks for act->ops
(suggested by Eric Dumazet).
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Proportional Integral controller Enhanced (PIE) is a scheduler to address the
bufferbloat problem.
>From the IETF draft below:
" Bufferbloat is a phenomenon where excess buffers in the network cause high
latency and jitter. As more and more interactive applications (e.g. voice over
IP, real time video streaming and financial transactions) run in the Internet,
high latency and jitter degrade application performance. There is a pressing
need to design intelligent queue management schemes that can control latency and
jitter; and hence provide desirable quality of service to users.
We present here a lightweight design, PIE(Proportional Integral controller
Enhanced) that can effectively control the average queueing latency to a target
value. Simulation results, theoretical analysis and Linux testbed results have
shown that PIE can ensure low latency and achieve high link utilization under
various congestion situations. The design does not require per-packet
timestamp, so it incurs very small overhead and is simple enough to implement
in both hardware and software. "
Many thanks to Dave Taht for extensive feedback, reviews, testing and
suggestions. Thanks also to Stephen Hemminger and Eric Dumazet for reviews and
suggestions. Naeem Khademi and Dave Taht independently contributed to ECN
support.
For more information, please see technical paper about PIE in the IEEE
Conference on High Performance Switching and Routing 2013. A copy of the paper
can be found at ftp://ftpeng.cisco.com/pie/.
Please also refer to the IETF draft submission at
http://tools.ietf.org/html/draft-pan-tsvwg-pie-00
All relevant code, documents and test scripts and results can be found at
ftp://ftpeng.cisco.com/pie/.
For problems with the iproute2/tc or Linux kernel code, please contact Vijay
Subramanian (vijaynsu@cisco.com or subramanian.vijay@gmail.com) Mythili Prabhu
(mysuryan@cisco.com)
Signed-off-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: Mythili Prabhu <mysuryan@cisco.com>
CC: Dave Taht <dave.taht@bufferbloat.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pablo Neira Ayuso says:
====================
netfilter/IPVS updates for net-next
The following patchset contains Netfilter updates for your net-next tree,
they are:
* Add full port randomization support. Some crazy researchers found a way
to reconstruct the secure ephemeral ports that are allocated in random mode
by sending off-path bursts of UDP packets to overrun the socket buffer of
the DNS resolver to trigger retransmissions, then if the timing for the
DNS resolution done by a client is larger than usual, then they conclude
that the port that received the burst of UDP packets is the one that was
opened. It seems a bit aggressive method to me but it seems to work for
them. As a result, Daniel Borkmann and Hannes Frederic Sowa came up with a
new NAT mode to fully randomize ports using prandom.
* Add a new classifier to x_tables based on the socket net_cls set via
cgroups. These includes two patches to prepare the field as requested by
Zefan Li. Also from Daniel Borkmann.
* Use prandom instead of get_random_bytes in several locations of the
netfilter code, from Florian Westphal.
* Allow to use the CTA_MARK_MASK in ctnetlink when mangling the conntrack
mark, also from Florian Westphal.
* Fix compilation warning due to unused variable in IPVS, from Geert
Uytterhoeven.
* Add support for UID/GID via nfnetlink_queue, from Valentina Giusti.
* Add IPComp extension to x_tables, from Fan Du.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Zefan Li requested [1] to perform the following cleanup/refactoring:
- Split cgroupfs classid handling into net core to better express a
possible more generic use.
- Disable module support for cgroupfs bits as the majority of other
cgroupfs subsystems do not have that, and seems to be not wished
from cgroup side. Zefan probably might want to follow-up for netprio
later on.
- By this, code can be further reduced which previously took care of
functionality built when compiled as module.
cgroupfs bits are being placed under net/core/netclassid_cgroup.c, so
that we are consistent with {netclassid,netprio}_cgroup naming that is
under net/core/ as suggested by Zefan.
No change in functionality, but only code refactoring that is being
done here.
[1] http://patchwork.ozlabs.org/patch/304825/
Suggested-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: cgroups@vger.kernel.org
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This reverts commit de6fb288b1.
Otherwise we got:
net/sched/cls_cgroup.c:106:29: error: static declaration of ‘net_cls_subsys’ follows non-static declaration
static struct cgroup_subsys net_cls_subsys = {
^
In file included from include/linux/cgroup.h:654:0,
from net/sched/cls_cgroup.c:18:
include/linux/cgroup_subsys.h:35:29: note: previous declaration of ‘net_cls_subsys’ was here
SUBSYS(net_cls)
^
make[2]: *** [net/sched/cls_cgroup.o] Error 1
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
No need to export functions only used in one file.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a new attribute to support 64bit rates so that
tc can use them to break the 32bit limit.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
With TSO/GSO/GRO packets, skb->len doesn't represent
a precise amount of bytes on wire.
This patch replace skb->len with qdisc_pkt_len(skb)
which is more precise.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
In dsmark_drop(), the function name printed by pr_debug
is "dsmark_reset", correct it to "dsmark_drop" by using
__func__ .
BTW, replace the other function names with __func__ .
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Do not use C99 // comments and correct a spelling typo.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is a bug fix. The existing code tries to kill many
birds with one stone: Handling binding of actions to
filters, new actions and replacing of action
attributes. A simple test case to illustrate:
XXXX
moja@fe1:~$ sudo tc actions add action drop index 12
moja@fe1:~$ actions get action gact index 12
action order 1: gact action drop
random type none pass val 0
index 12 ref 1 bind 0
moja@fe1:~$ sudo tc actions replace action ok index 12
moja@fe1:~$ actions get action gact index 12
action order 1: gact action drop
random type none pass val 0
index 12 ref 2 bind 0
XXXX
The above shows the refcounf being wrongly incremented on replace.
There are more complex scenarios with binding of actions to filters
that i am leaving out that didnt work as well...
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When we set burst to 1514 with low rate in userspace,
the kernel get a value of burst that less than 1514,
which doesn't work.
Because it may make some loss when transform burst
to buffer in userspace. This makes burst lose some
bytes, when the kernel transform the buffer back to
burst.
This patch adds two new attributes to support sending
burst/mtu to kernel directly to avoid the loss.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This module shouldn't be randomly exporting symbols
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
list_for_each_entry(a, &act_base, head) doesn't
exit with a = NULL if we reached the end of the list.
tcf_unregister_action(), tc_lookup_action_n() and tc_lookup_action()
need fixes.
Remove tc_lookup_action_id() as its unused and not worth 'fixing'
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 1f747c26c4 ("net_sched: convert tc_action_ops to use struct list_head")
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
list_for_each_entry(t, &tcf_proto_base, head) doesn't
exit with t = NULL if we reached the end of the list.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 3627287463 ("net_sched: convert tcf_proto_ops to use struct
list_head")
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch fixes:
1) pass mask rather than size to tcf_hashinfo_init()
2) the cleanup should be in reversed order in mirred_cleanup_module()
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Fixes: 369ba56787 ("net_sched: init struct tcf_hashinfo at register time")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It already has a NULL pointer check of rtab in qdisc_put_rtab().
Remove the check outside of qdisc_put_rtab().
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It already has a NULL pointer check of rtab in qdisc_put_rtab().
Remove the check outside of qdisc_put_rtab().
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch implements the first size-based qdisc that attempts to
differentiate between small flows and heavy-hitters. The goal is to
catch the heavy-hitters and move them to a separate queue with less
priority so that bulk traffic does not affect the latency of critical
traffic. Currently "less priority" means less weight (2:1 in
particular) in a Weighted Deficit Round Robin (WDRR) scheduler.
In essence, this patch addresses the "delay-bloat" problem due to
bloated buffers. In some systems, large queues may be necessary for
obtaining CPU efficiency, or due to the presence of unresponsive
traffic like UDP, or just a large number of connections with each
having a small amount of outstanding traffic. In these circumstances,
HHF aims to reduce the HoL blocking for latency sensitive traffic,
while not impacting the queues built up by bulk traffic. HHF can also
be used in conjunction with other AQM mechanisms such as CoDel.
To capture heavy-hitters, we implement the "multi-stage filter" design
in the following paper:
C. Estan and G. Varghese, "New Directions in Traffic Measurement and
Accounting", in ACM SIGCOMM, 2002.
Some configurable qdisc settings through 'tc':
- hhf_reset_timeout: period to reset counter values in the multi-stage
filter (default 40ms)
- hhf_admit_bytes: threshold to classify heavy-hitters
(default 128KB)
- hhf_evict_timeout: threshold to evict idle heavy-hitters
(default 1s)
- hhf_non_hh_weight: Weighted Deficit Round Robin (WDRR) weight for
non-heavy-hitters (default 2)
- hh_flows_limit: max number of heavy-hitter flow entries
(default 2048)
Note that the ratio between hhf_admit_bytes and hhf_reset_timeout
reflects the bandwidth of heavy-hitters that we attempt to capture
(25Mbps with the above default settings).
The false negative rate (heavy-hitter flows getting away unclassified)
is zero by the design of the multi-stage filter algorithm.
With 100 heavy-hitter flows, using four hashes and 4000 counters yields
a false positive rate (non-heavy-hitters mistakenly classified as
heavy-hitters) of less than 1e-4.
Signed-off-by: Terry Lam <vtlam@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
drivers/net/ethernet/intel/i40e/i40e_main.c
drivers/net/macvtap.c
Both minor merge hassles, simple overlapping changes.
Signed-off-by: David S. Miller <davem@davemloft.net>
We don't need to maintain our own singly linked list code.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We don't need to maintain our own singly linked list code.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
So that we don't need to play with singly linked list,
and since the code is not on hot path, we can use spinlock
instead of rwlock.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It looks weird to store the lock out of the struct but
still points to a static variable. Just move them into the struct.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
These information can be saved in tcf_exts, and this will
simplify the code.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Currently actions are chained by a singly linked list,
therefore it is a bit hard to add and remove a specific
entry. Convert it to struct list_head so that in the
latter patch we can remove an action without finding
its head.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It is not used.
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Changing name of function as part of making the hash in skbuff to be
generic property, not just for receive path.
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch brings NUMA support and automatic fallback to vmalloc()
in case kmalloc() failed to allocate FQ hash table.
NUMA support depends on XPS being setup for the device before
qdisc allocation. After a XPS change, it might be worth creating
qdisc hierarchy again.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
After commit 95dc19299f ("pkt_sched: give visibility to mq slave
qdiscs") we call disc_list_add() while the device qdisc might be
the noop_qdisc one.
This shows up as duplicates in "tc qdisc show", as all inactive devices
point to noop_qdisc.
Fix this by setting dev->qdisc to the new qdisc before calling
ops->change() in attach_default_qdiscs()
Add a WARN_ON_ONCE() to catch any future similar problem.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It's doing a 64-bit divide which is not supported
on 32-bit architectures in psched_ns_t2l(). The
correct way to do this is to use do_div().
It's introduced by commit cc106e441a
("net: sched: tbf: fix the calculation of max_size")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
It already has a NULL pointer judgment of rtab in qdisc_put_rtab().
Remove the judgment outside of qdisc_put_rtab().
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Now, 32bit rates may be not the true rate.
So use rate_bytes_ps which is from
max(rate32, rate64) to calcualte quantum.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Current max_size is caluated from rate table. Now, the rate table
has been replaced and it's wrong to caculate max_size based on this
rate table. It can lead wrong calculation of max_size.
The burst in kernel may be lower than user asked, because burst may gets
some loss when transform it to buffer(E.g. "burst 40kb rate 30mbit/s")
and it seems we cannot avoid this loss. Burst's value(max_size) based on
rate table may be equal user asked. If a packet's length is max_size, this
packet will be stalled in tbf_dequeue() because its length is above the
burst in kernel so that it cannot get enough tokens. The max_size guards
against enqueuing packet sizes above q->buffer "time" in tbf_enqueue().
To make consistent with the calculation of tokens, this patch add a helper
psched_ns_t2l() to calculate burst(max_size) directly to fix this problem.
After this fix, we can support to using 64bit rates to calculate burst as well.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
SKIP_NONLOCAL hides the control flow. The control flow should be
inlined and expanded explicitly in code so that someone who reads
it can tell the control flow can be changed by the statement.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
