[Devel] [PATCH RH9 01/28] ve/mount: allow pseudosuper to temporary exceed the container limit

[Andrey Zhadchenko]

From: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>

Criu algorithm is (prepare_mnt_ns):
1) Restore all mounts of the CT (from all mntns'es) in single temporary
mount namespace.
2) For each mount namespace of the container recreate it's mounts:
 a) Unshare temporary mntns (mounts are doubled)
 b) Remove with pivot_root all excess mounts

So at some point we have many mntnses of the CT already created with
their mounts and two temporary mount namespaces with mounts copies, that
is ~3x mounts (and may be also some aditional temporary mounts).

When we restore a CT with > 1/3*sysctl_ve_mount_nr mounts we hit the
limit and fail, fix it ignoring the limit at restore stage.

https://jira.sw.ru/browse/PSBM-86511

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>

Acked-by: Cyrill Gorcunov <gorcunov at openvz.org>

(cherry picked from vz7 commit cb5488bae355 ("ve/mount: allow pseudosuper to
temporary exceed the container limit"))

VZ 8 rebase part https://jira.sw.ru/browse/PSBM-127837

Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>

(cherry picked from vz8 commit 454d3b6b7b79d76ce785d21d2c95d2efc173eddc)
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
 fs/namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 0abab30..b2f925a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2811,7 +2811,7 @@ static inline int ve_mount_allowed(void)
 {
 	struct ve_struct *ve = get_exec_env();
 
-	return ve_is_super(ve) ||
+	return ve_is_super(ve) || ve->is_pseudosuper ||
 		atomic_read(&ve->mnt_nr) < (int)sysctl_ve_mount_nr;
 }
 
-- 
1.8.3.1