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Subject[PATCH 00/23] proc: Introduce /proc/namespaces/ directory to expose namespaces lineary
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Currently, there is no a way to list or iterate all or subset of namespaces
in the system. Some namespaces are exposed in /proc/[pid]/ns/ directories,
but some also may be as open files, which are not attached to a process.
When a namespace open fd is sent over unix socket and then closed, it is
impossible to know whether the namespace exists or not.

Also, even if namespace is exposed as attached to a process or as open file,
iteration over /proc/*/ns/* or /proc/*/fd/* namespaces is not fast, because
this multiplies at tasks and fds number.

This patchset introduces a new /proc/namespaces/ directory, which exposes
subset of permitted namespaces in linear view:

# ls /proc/namespaces/ -l
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'cgroup:[4026531835]' -> 'cgroup:[4026531835]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'ipc:[4026531839]' -> 'ipc:[4026531839]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026531840]' -> 'mnt:[4026531840]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026531861]' -> 'mnt:[4026531861]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532133]' -> 'mnt:[4026532133]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532134]' -> 'mnt:[4026532134]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532135]' -> 'mnt:[4026532135]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'mnt:[4026532136]' -> 'mnt:[4026532136]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'net:[4026531993]' -> 'net:[4026531993]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'pid:[4026531836]' -> 'pid:[4026531836]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'time:[4026531834]' -> 'time:[4026531834]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'user:[4026531837]' -> 'user:[4026531837]'
lrwxrwxrwx 1 root root 0 Jul 29 16:50 'uts:[4026531838]' -> 'uts:[4026531838]'

Namespace ns is exposed, in case of its user_ns is permitted from /proc's pid_ns.
I.e., /proc is related to pid_ns, so in /proc/namespace we show only a ns, which is

in_userns(pid_ns->user_ns, ns->user_ns).

In case of ns is a user_ns:

in_userns(pid_ns->user_ns, ns).

The patchset follows this steps:

1)A generic counter in ns_common is introduced instead of separate
counters for every ns type (net::count, uts_namespace::kref,
user_namespace::count, etc). Patches [1-8];
2)Patch [9] introduces IDR to link and iterate alive namespaces;
3)Patch [10] is refactoring;
4)Patch [11] actually adds /proc/namespace directory and fs methods;
5)Patches [12-23] make every namespace to use the added methods
and to appear in /proc/namespace directory.

This may be usefull to write effective debug utils (say, fast build
of networks topology) and checkpoint/restore software.
---

Kirill Tkhai (23):
ns: Add common refcount into ns_common add use it as counter for net_ns
uts: Use generic ns_common::count
ipc: Use generic ns_common::count
pid: Use generic ns_common::count
user: Use generic ns_common::count
mnt: Use generic ns_common::count
cgroup: Use generic ns_common::count
time: Use generic ns_common::count
ns: Introduce ns_idr to be able to iterate all allocated namespaces in the system
fs: Rename fs/proc/namespaces.c into fs/proc/task_namespaces.c
fs: Add /proc/namespaces/ directory
user: Free user_ns one RCU grace period after final counter put
user: Add user namespaces into ns_idr
net: Add net namespaces into ns_idr
pid: Eextract child_reaper check from pidns_for_children_get()
proc_ns_operations: Add can_get method
pid: Add pid namespaces into ns_idr
uts: Free uts namespace one RCU grace period after final counter put
uts: Add uts namespaces into ns_idr
ipc: Add ipc namespaces into ns_idr
mnt: Add mount namespaces into ns_idr
cgroup: Add cgroup namespaces into ns_idr
time: Add time namespaces into ns_idr


fs/mount.h | 4
fs/namespace.c | 14 +
fs/nsfs.c | 78 ++++++++
fs/proc/Makefile | 1
fs/proc/internal.h | 18 +-
fs/proc/namespaces.c | 382 +++++++++++++++++++++++++++-------------
fs/proc/root.c | 17 ++
fs/proc/task_namespaces.c | 183 +++++++++++++++++++
include/linux/cgroup.h | 6 -
include/linux/ipc_namespace.h | 3
include/linux/ns_common.h | 11 +
include/linux/pid_namespace.h | 4
include/linux/proc_fs.h | 1
include/linux/proc_ns.h | 12 +
include/linux/time_namespace.h | 10 +
include/linux/user_namespace.h | 10 +
include/linux/utsname.h | 10 +
include/net/net_namespace.h | 11 -
init/version.c | 2
ipc/msgutil.c | 2
ipc/namespace.c | 17 +-
ipc/shm.c | 1
kernel/cgroup/cgroup.c | 2
kernel/cgroup/namespace.c | 25 ++-
kernel/pid.c | 2
kernel/pid_namespace.c | 46 +++--
kernel/time/namespace.c | 20 +-
kernel/user.c | 2
kernel/user_namespace.c | 23 ++
kernel/utsname.c | 23 ++
net/core/net-sysfs.c | 6 -
net/core/net_namespace.c | 18 +-
net/ipv4/inet_timewait_sock.c | 4
net/ipv4/tcp_metrics.c | 2
34 files changed, 746 insertions(+), 224 deletions(-)
create mode 100644 fs/proc/task_namespaces.c

--
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>

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