[Devel] [PATCH v2] mounts: support only shared NFS mounts in inits mount namespace

[Stanislav Kinsburskiy]

The intention of this patch is to define different NFS mount cases and forbid
most ot them.
The reason behind this is that the only mount point we can migrate right now
is:
1) created in init mount namespace
2) shared (because it's default)

All the other cases are not supported by spfs manager so far and migration
attempt can lead to different issues after restore is completed by CRIU.

https://jira.sw.ru/browse/PSBM-66945

v2:
1) Added check that all bind-mounts are in the same shared group for slave
mount. We need this to make sure, that all such mounts will be propagated
correctly.

Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
---
 criu/mount.c |   79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 78 insertions(+), 1 deletion(-)

diff --git a/criu/mount.c b/criu/mount.c
index 6916974..26f3aa5 100644
--- a/criu/mount.c
+++ b/criu/mount.c
@@ -746,6 +746,82 @@ static bool nfs_mount(const struct mount_info *m)
 
 }
 
+static char *mnt_mark(const struct mount_info *m)
+{
+	static char *shared = "shared";
+	static char *private = "private";
+	static char *slave = "slave";
+
+	if (m->flags & MS_SHARED)
+		return shared;
+
+	if (m->flags & MS_SLAVE)
+		return slave;
+
+	return private;
+}
+
+static bool unsupported_nfs_mount(const struct mount_info *m);
+
+static bool unsupported_nfs_bindmounts(const struct mount_info *m)
+{
+	const struct mount_info *bm;
+
+	list_for_each_entry(bm, &m->mnt_bind, mnt_bind) {
+		if (bm->shared_id != m->master_id) {
+			pr_err("Bind-mount %s has another shared "
+					"group, than %s: %d != %d\n",
+					bm->mountpoint, m->mountpoint,
+					bm->shared_id, m->master_id);
+			return true;
+		}
+		if (unsupported_nfs_mount(bm))
+			return true;
+	}
+	return false;
+}
+
+static bool unsupported_nfs_mount(const struct mount_info *m)
+{
+	switch (m->nsid->type) {
+		case NS_ROOT:
+			if (m->flags & MS_SHARED)
+				return false;
+
+			pr_err("NFS mount [%s] in init mount namespace "
+				"is marked as \"%s\".\n",
+				m->mountpoint, mnt_mark(m));
+			pr_err("Only shared NFS mounts in init mount "
+				"namespace are supported yet.\n");
+			break;
+		case NS_OTHER:
+			if (!(m->flags & MS_SLAVE)) {
+				pr_err("NFS mount [%s] in non-init mount "
+					"namespace is marked as \"%s\".\n",
+					m->mountpoint, mnt_mark(m));
+				pr_err("Only slave NFS mounts in non-init "
+					"mount namespace are supported yet.\n");
+				return true;
+			}
+			return unsupported_nfs_bindmounts(m);
+		case NS_CRIU:
+			pr_err("NFS mount [%s] in CRIU namespace is "
+					"unsupported.\n", m->mountpoint);
+			break;
+		case NS_UNKNOWN:
+			pr_err("Unknown NFS mount [%s] namespace type: %d\n",
+					m->mountpoint, m->nsid->type);
+			break;
+		default:
+			pr_err("Invalid NFS mount [%s] namespace type: %d\n",
+					m->mountpoint, m->nsid->type);
+			break;
+	}
+
+
+	return true;
+}
+
 static bool unsupported_mount(const struct mount_info *m)
 {
 	struct mount_info *parent = m->parent;
@@ -760,7 +836,8 @@ static bool unsupported_mount(const struct mount_info *m)
 
 		return true;
 	}
-	return false;
+
+	return nfs_mount(m) ? unsupported_nfs_mount(m) : false;
 }
 
 static int validate_mounts(struct mount_info *info, bool for_dump)