android_kernel_oneplus_msm8998/net
NeilBrown 447383d2ba NFSD/sunrpc: avoid deadlock on TCP connection due to memory pressure.
Since we enabled auto-tuning for sunrpc TCP connections we do not
guarantee that there is enough write-space on each connection to
queue a reply.

If memory pressure causes the window to shrink too small, the request
throttling in sunrpc/svc will not accept any requests so no more requests
will be handled.  Even when pressure decreases the window will not
grow again until data is sent on the connection.
This means we get a deadlock:  no requests will be handled until there
is more space, and no space will be allocated until a request is
handled.

This can be simulated by modifying svc_tcp_has_wspace to inflate the
number of byte required and removing the 'svc_sock_setbufsize' calls
in svc_setup_socket.

I found that multiplying by 16 was enough to make the requirement
exceed the default allocation.  With this modification in place:
   mount -o vers=3,proto=tcp 127.0.0.1:/home /mnt
would block and eventually time out because the nfs server could not
accept any requests.

This patch relaxes the request throttling to always allow at least one
request through per connection.  It does this by checking both
  sk_stream_min_wspace() and xprt->xpt_reserved
are zero.
The first is zero when the TCP transmit queue is empty.
The second is zero when there are no RPC requests being processed.
When both of these are zero the socket is idle and so one more
request can safely be allowed through.

Applying this patch allows the above mount command to succeed cleanly.
Tracing shows that the allocated write buffer space quickly grows and
after a few requests are handled, the extra tests are no longer needed
to permit further requests to be processed.

The main purpose of request throttling is to handle the case when one
client is slow at collecting replies and the send queue gets full of
replies that the client hasn't acknowledged (at the TCP level) yet.
As we only change behaviour when the send queue is empty this main
purpose is still preserved.

Reported-by: Ben Myers <bpm@sgi.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2013-08-01 08:39:16 -04:00
..
9p Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-07-13 17:42:22 -07:00
802
8021q vlan: fix a race in egress prio management 2013-07-18 13:07:13 -07:00
appletalk
atm
ax25
batman-adv
bluetooth Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-07-09 18:24:39 -07:00
bridge bridge: fix some kernel warning in multicast timer 2013-07-06 18:12:47 -07:00
caif
can
ceph libceph: call r_unsafe_callback when unsafe reply is received 2013-07-03 15:32:58 -07:00
core Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-07-18 20:08:47 -07:00
dcb
dccp
decnet
dns_resolver net: strict_strtoul is obsolete, use kstrtoul instead 2013-07-12 16:09:14 -07:00
dsa
ethernet net: Fix sysfs_format_mac() code duplication. 2013-07-16 17:09:22 -07:00
ieee802154
ipv4 ipv4: set transport header earlier 2013-07-16 12:59:28 -07:00
ipv6 ndisc: bool initializations should use true and false 2013-07-16 12:13:31 -07:00
ipx
irda net/irda: fixed style issues in irlan_eth 2013-07-16 12:16:03 -07:00
iucv net: delete __cpuinit usage from all net files 2013-07-14 19:36:58 -04:00
key af_key: fix info leaks in notify messages 2013-06-26 15:15:54 -07:00
l2tp l2tp: make datapath resilient to packet loss when sequence numbers enabled 2013-07-02 16:33:25 -07:00
lapb
llc
mac80211 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-07-09 18:24:39 -07:00
mac802154
mpls
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-07-03 14:55:13 -07:00
netlabel
netlink netlink: fix splat in skb_clone with large messages 2013-06-27 22:44:16 -07:00
netrom
nfc
openvswitch openvswitch: Add Kconfig dependency on GRE-DEMUX. 2013-07-01 13:19:43 -07:00
packet
phonet
rds
rfkill
rose
rxrpc
sched pkt_sched: sch_qfq: remove a source of high packet delay/jitter 2013-07-18 13:02:00 -07:00
sctp net: sctp: confirm route during forward progress 2013-07-09 12:49:56 -07:00
sunrpc NFSD/sunrpc: avoid deadlock on TCP connection due to memory pressure. 2013-08-01 08:39:16 -04:00
tipc net/tipc: use %*phC to dump small buffers in hex form 2013-07-11 17:03:36 -07:00
unix Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-07-09 18:24:39 -07:00
vmw_vsock
wimax
wireless Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next into for-davem 2013-06-28 13:18:21 -04:00
x25 x25: Fix broken locking in ioctl error paths. 2013-07-01 18:15:25 -07:00
xfrm Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2013-06-26 13:23:13 -07:00
compat.c
Kconfig Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-07-09 18:24:39 -07:00
Makefile
nonet.c
socket.c net: rename busy poll socket op and globals 2013-07-10 17:08:27 -07:00
sysctl_net.c