Commit:     57d5f66b86079efac5c9a7843cce2a9bcbe58fb8
Parent:     42614fcde7bfdcbe43a7b17035c167dfebc354dd
Author:     Eric W. Biederman <[EMAIL PROTECTED]>
AuthorDate: Wed Nov 14 17:00:13 2007 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Nov 14 18:45:43 2007 -0800

    pidns: Place under CONFIG_EXPERIMENTAL
    This is my trivial patch to swat innumerable little bugs with a single
    After some intensive review (my apologies for not having gotten to this
    sooner) what we have looks like a good base to build on with the current
    pid namespace code but it is not complete, and it is still much to simple
    to find issues where the kernel does the wrong thing outside of the initial
    pid namespace.
    Until the dust settles and we are certain we have the ABI and the
    implementation is as correct as humanly possible let's keep process ID
    namespaces behind CONFIG_EXPERIMENTAL.
    Allowing us the option of fixing any ABI or other bugs we find as long as
    they are minor.
    Allowing users of the kernel to avoid those bugs simply by ensuring their
    kernel does not have support for multiple pid namespaces.
    [EMAIL PROTECTED]: coding-style cleanups]
    Signed-off-by: Eric W. Biederman <[EMAIL PROTECTED]>
    Cc: Cedric Le Goater <[EMAIL PROTECTED]>
    Cc: Adrian Bunk <[EMAIL PROTECTED]>
    Cc: Jeremy Fitzhardinge <[EMAIL PROTECTED]>
    Cc: Kir Kolyshkin <[EMAIL PROTECTED]>
    Cc: Kirill Korotaev <[EMAIL PROTECTED]>
    Cc: Pavel Emelyanov <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 include/linux/pid_namespace.h |   23 +++++++++++++++++++++++
 init/Kconfig                  |   12 ++++++++++++
 kernel/pid.c                  |    2 ++
 3 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 0135c76..1689e28 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -29,6 +29,7 @@ struct pid_namespace {
 extern struct pid_namespace init_pid_ns;
 static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
        if (ns != &init_pid_ns)
@@ -45,6 +46,28 @@ static inline void put_pid_ns(struct pid_namespace *ns)
                kref_put(&ns->kref, free_pid_ns);
+#else /* !CONFIG_PID_NS */
+#include <linux/err.h>
+static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
+       return ns;
+static inline struct pid_namespace *
+copy_pid_ns(unsigned long flags, struct pid_namespace *ns)
+       if (flags & CLONE_NEWPID)
+               ns = ERR_PTR(-EINVAL);
+       return ns;
+static inline void put_pid_ns(struct pid_namespace *ns)
+#endif /* CONFIG_PID_NS */
 static inline struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
        return tsk->nsproxy->pid_ns;
diff --git a/init/Kconfig b/init/Kconfig
index 5b92e3a..c5b354b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -215,6 +215,18 @@ config USER_NS
          vservers, to use user namespaces to provide different
          user info for different servers.  If unsure, say N.
+config PID_NS
+       bool "PID Namespaces (EXPERIMENTAL)"
+       default n
+       depends on EXPERIMENTAL
+       help
+         Suport process id namespaces.  This allows having multiple
+         process with the same pid as long as they are in different
+         pid namespaces.  This is a building block of containers.
+         Unless you want to work with an experimental feature
+         say N here.
 config AUDIT
        bool "Auditing support"
        depends on NET
diff --git a/kernel/pid.c b/kernel/pid.c
index d1db36b..f815455 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -537,6 +537,7 @@ err_alloc:
        return NULL;
 static struct pid_namespace *create_pid_namespace(int level)
        struct pid_namespace *ns;
@@ -621,6 +622,7 @@ void free_pid_ns(struct kref *kref)
        if (parent != NULL)
+#endif /* CONFIG_PID_NS */
 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
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