[Devel] [PATCH RHEL9 COMMIT] FD: pidns: virtualize pid_max

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-70.13.1.vz9.16.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-70.13.1.vz9.16.2
------>
commit e08faea5709478392da56e65094a6223e37b22f8
Author: Konstantin Khorenko <khorenko at virtuozzo.com>
Date:   Tue Jun 7 17:41:09 2022 +0300

    FD: pidns: virtualize pid_max
    
    https://jira.sw.ru/browse/PSBM-140308
    
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
    Feature: pidns: virtualize pid_max
---
 .../FeatureDescriptions/pidns-virtualize_pid_max.rst    | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/Virtuozzo/FeatureDescriptions/pidns-virtualize_pid_max.rst b/Documentation/Virtuozzo/FeatureDescriptions/pidns-virtualize_pid_max.rst
new file mode 100644
index 000000000000..2e7ba8f179ba
--- /dev/null
+++ b/Documentation/Virtuozzo/FeatureDescriptions/pidns-virtualize_pid_max.rst
@@ -0,0 +1,17 @@
+=========================
+pidns: virtualize pid_max
+=========================
+
+This feature makes ``kernel.pid_max`` sysctl be per pid namespace
+(instead of a global sysctl by default).
+
+**Q:** Why do we need this feature at all?
+**A:**
+
+1. historically is was implemented to support 32bit containers (pids with the
+   value greater than 2^32 make 32bit userspace go mad)
+2. this feature is needed for Containers online migration: if someone tries to
+   migrate a process with pid XXX to the Hardware Node with pid_max < XXX, the
+   migration will fail without iper-pidns pid_max support
+
+https://jira.sw.ru/browse/PSBM-140308