linux/net
Pavel Emelyanov cf7b708c8d Make access to task's nsproxy lighter
When someone wants to deal with some other taks's namespaces it has to lock
the task and then to get the desired namespace if the one exists.  This is
slow on read-only paths and may be impossible in some cases.

E.g.  Oleg recently noticed a race between unshare() and the (sent for
review in cgroups) pid namespaces - when the task notifies the parent it
has to know the parent's namespace, but taking the task_lock() is
impossible there - the code is under write locked tasklist lock.

On the other hand switching the namespace on task (daemonize) and releasing
the namespace (after the last task exit) is rather rare operation and we
can sacrifice its speed to solve the issues above.

The access to other task namespaces is proposed to be performed
like this:

     rcu_read_lock();
     nsproxy = task_nsproxy(tsk);
     if (nsproxy != NULL) {
             / *
               * work with the namespaces here
               * e.g. get the reference on one of them
               * /
     } / *
         * NULL task_nsproxy() means that this task is
         * almost dead (zombie)
         * /
     rcu_read_unlock();

This patch has passed the review by Eric and Oleg :) and,
of course, tested.

[clg@fr.ibm.com: fix unshare()]
[ebiederm@xmission.com: Update get_net_ns_by_pid]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-19 11:53:37 -07:00
..
9p 9p: remove sysctl 2007-10-17 14:35:15 -05:00
802 [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
8021q [8021Q]: transfer dev_id from real device 2007-10-10 16:54:56 -07:00
appletalk [NET]: sparse warning fixes 2007-10-10 16:54:48 -07:00
atm [BR2684]: get rid of broken header code. 2007-10-17 19:39:22 -07:00
ax25 [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
bluetooth [BLUETOOTH]: Make hidp_setup_input() return int 2007-10-10 16:52:39 -07:00
bridge [BRIDGE]: Remove SKB share checks in br_nf_pre_routing(). 2007-10-15 12:26:35 -07:00
core Make access to task's nsproxy lighter 2007-10-19 11:53:37 -07:00
dccp [DCCP]: fix link error with !CONFIG_SYSCTL 2007-10-17 19:33:06 -07:00
decnet [NETFILTER]: Replace sk_buff ** with sk_buff * 2007-10-15 12:26:29 -07:00
econet [NET]: Wrap netdevice hardware header creation. 2007-10-10 16:52:50 -07:00
ethernet [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
ieee80211 [PATCH] ieee80211: fix TKIP QoS bug 2007-10-16 20:58:12 -04:00
ipv4 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2007-10-18 14:40:30 -07:00
ipv6 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2007-10-18 14:40:30 -07:00
ipx [NET]: Make the device list and device lookups per namespace. 2007-10-10 16:49:10 -07:00
irda Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2007-10-18 14:40:30 -07:00
iucv [AF_IUCV]: postpone receival of iucv-packets 2007-10-10 16:54:51 -07:00
key [IPSEC]: Lock state when copying non-atomic fields to user-space 2007-10-10 16:55:02 -07:00
lapb [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
llc [NET]: Introduce and use print_mac() and DECLARE_MAC_BUF() 2007-10-10 16:51:42 -07:00
mac80211 [MAC80211]: only honor IW_SCAN_THIS_ESSID in STA, IBSS, and AP modes 2007-10-17 21:16:16 -07:00
netfilter Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2007-10-18 14:40:30 -07:00
netlabel [NETLINK]: Introduce nested and byteorder flag to netlink attribute 2007-10-10 16:49:16 -07:00
netlink [NETLINK]: Don't leak 'listeners' in netlink_kernel_create() 2007-10-15 12:26:32 -07:00
netrom [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
packet [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
rfkill [RFKILL]: Add support for hardware-only rfkill buttons 2007-10-10 16:54:11 -07:00
rose [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
rxrpc KEYS: Make request_key() and co fundamentally asynchronous 2007-10-17 08:42:57 -07:00
sched [NET]: fix carrier-on bug? 2007-10-17 23:26:43 -07:00
sctp Remove "unsafe" from module struct 2007-10-17 08:42:49 -07:00
sunrpc sysctl: remove broken sunrpc debug binary sysctls 2007-10-18 14:37:22 -07:00
tipc [NET]: Wrap netdevice hardware header creation. 2007-10-10 16:52:50 -07:00
unix sched: affine sync wakeups 2007-10-15 17:00:19 +02:00
wanrouter [NET]: Make /proc/net per network namespace 2007-10-10 16:49:06 -07:00
wireless Driver core: change add_uevent_var to use a struct 2007-10-12 14:51:01 -07:00
x25 [NET]: Make the device list and device lookups per namespace. 2007-10-10 16:49:10 -07:00
xfrm [IPSEC]: Rename mode to outer_mode and add inner_mode 2007-10-17 21:35:51 -07:00
compat.c O_CLOEXEC for SCM_RIGHTS 2007-07-16 09:05:45 -07:00
Kconfig [NET]: Add network namespace clone & unshare support. 2007-10-10 16:52:46 -07:00
Makefile 9p: Reorganization of 9p file system code 2007-07-14 15:13:40 -05:00
nonet.c
socket.c r/o bind mounts: filesystem helpers for custom 'struct file's 2007-10-17 08:43:04 -07:00
sysctl_net.c
TUNABLE