[Lxc-users] [PATCH 1/1] cgroups: fix broken support for deprecated ns cgroup

[Serge Hallyn]

when using ns cgroup, use /cgroup/<init-cgroup> rather than
/cgroup/<init-cgroup>/lxc

At least lxc-start, lxc-stop, lxc-cgroup, lxc-console and lxc-ls work
with this patch.  I've tested this in a 2.6.35 kernel with ns cgroup,
and in a 3.2 kernel without ns cgroup.

Note also that because of the check for container reboot support,
if we're using the ns cgroup we now end up with a /cgroup/<container>/2
cgroup created, empty, by the clone(CLONE_NEWPID).  I'm really not
sure how much time we want to spend cleaning such things up since
ns cgroup is deprecated in kernel.

Signed-off-by: Serge Hallyn <serge at hallyn.com>
---
 src/lxc/cgroup.c  |   60 +++++++++++++++++++++++++++++++---------------------
 src/lxc/lxc-ls.in |    6 ++++-
 2 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/src/lxc/cgroup.c b/src/lxc/cgroup.c
index cc3910a..9af199d 100644
--- a/src/lxc/cgroup.c
+++ b/src/lxc/cgroup.c
@@ -137,6 +137,21 @@ found:
 	return dsg;
 }
 
+static int get_cgroup_flags(struct mntent *mntent)
+{
+	int flags = 0;
+
+
+	if (hasmntopt(mntent, "ns"))
+		flags |= CGROUP_NS_CGROUP;
+
+	if (hasmntopt(mntent, "clone_children"))
+		flags |= CGROUP_CLONE_CHILDREN;
+
+	DEBUG("cgroup %s has flags 0x%x", mntent->mnt_dir, flags);
+	return flags;
+}
+
 static int get_cgroup_mount(const char *subsystem, char *mnt)
 {
 	struct mntent *mntent;
@@ -155,10 +170,12 @@ static int get_cgroup_mount(const char *subsystem, char *mnt)
 			continue;
 		if (!subsystem || hasmntopt_multiple(mntent, subsystem)) {
 			int ret;
-			ret = snprintf(mnt, MAXPATHLEN, "%s%s/lxc",
+			int flags = get_cgroup_flags(mntent);
+			ret = snprintf(mnt, MAXPATHLEN, "%s%s%s",
 				       mntent->mnt_dir,
 				       get_init_cgroup(subsystem, NULL,
-						       initcgroup));
+						       initcgroup),
+				       (flags & CGROUP_NS_CGROUP) ? "" : "/lxc");
 			if (ret < 0 || ret >= MAXPATHLEN)
 				goto fail;
 			fclose(file);
@@ -183,33 +200,26 @@ int lxc_ns_is_mounted(void)
 	return (get_cgroup_mount("ns", buf) == 0);
 }
 
-static int get_cgroup_flags(struct mntent *mntent)
-{
-	int flags = 0;
-
-
-	if (hasmntopt(mntent, "ns"))
-		flags |= CGROUP_NS_CGROUP;
-
-	if (hasmntopt(mntent, "clone_children"))
-		flags |= CGROUP_CLONE_CHILDREN;
-
-	DEBUG("cgroup %s has flags 0x%x", mntent->mnt_dir, flags);
-	return flags;
-}
-
 static int cgroup_rename_nsgroup(const char *mnt, const char *name, pid_t pid)
 {
 	char oldname[MAXPATHLEN];
+	char newname[MAXPATHLEN];
+	int ret;
+
+	ret = snprintf(oldname, MAXPATHLEN, "%s/%d", mnt, pid);
+	if (ret >= MAXPATHLEN)
+		return -1;
 
-	snprintf(oldname, MAXPATHLEN, "%s/%d", mnt, pid);
+	ret = snprintf(newname, MAXPATHLEN, "%s/%s", mnt, name);
+	if (ret >= MAXPATHLEN)
+		return -1;
 
-	if (rename(oldname, name)) {
-		SYSERROR("failed to rename cgroup %s->%s", oldname, name);
+	if (rename(oldname, newname)) {
+		SYSERROR("failed to rename cgroup %s->%s", oldname, newname);
 		return -1;
 	}
 
-	DEBUG("'%s' renamed to '%s'", oldname, name);
+	DEBUG("'%s' renamed to '%s'", oldname, newname);
 
 	return 0;
 }
@@ -321,7 +331,7 @@ static int lxc_one_cgroup_create(const char *name,
 	/* Do we have the deprecated ns_cgroup subsystem? */
 	if (flags & CGROUP_NS_CGROUP) {
 		WARN("using deprecated ns_cgroup");
-		return cgroup_rename_nsgroup(cgparent, cgname, pid);
+		return cgroup_rename_nsgroup(cginit, name, pid);
 	}
 
 	ret = snprintf(clonechild, MAXPATHLEN, "%s/cgroup.clone_children",
@@ -464,9 +474,11 @@ int lxc_one_cgroup_destroy(struct mntent *mntent, const char *name)
 {
 	char cgname[MAXPATHLEN], initcgroup[MAXPATHLEN];
 	char *cgmnt = mntent->mnt_dir;
+	int flags = get_cgroup_flags(mntent);
 
-	snprintf(cgname, MAXPATHLEN, "%s%s/lxc/%s", cgmnt,
-		get_init_cgroup(NULL, mntent, initcgroup), name);
+	snprintf(cgname, MAXPATHLEN, "%s%s%s/%s", cgmnt,
+		get_init_cgroup(NULL, mntent, initcgroup),
+		(flags & CGROUP_NS_CGROUP) ? "" : "/lxc", name);
 	DEBUG("destroying %s\n", cgname);
 	if (recursive_rmdir(cgname)) {
 		SYSERROR("failed to remove cgroup '%s'", cgname);
diff --git a/src/lxc/lxc-ls.in b/src/lxc/lxc-ls.in
index d200509..a1ad642 100644
--- a/src/lxc/lxc-ls.in
+++ b/src/lxc/lxc-ls.in
@@ -33,7 +33,11 @@ if test -n "$active"; then
 	if test -n "$mount_point"; then
 		# get cgroup for init
 		init_cgroup=`cat /proc/1/cgroup | awk -F: '{ print $3 }' | head -1`
-		cd $mount_point/$init_cgroup/lxc
+		if [ ! -d $mount_point/$init_cgroup/lxc  ]; then
+			cd $mount_point/$init_cgroup
+		else
+			cd $mount_point/$init_cgroup/lxc
+		fi
 		ls "$@" -d $active
 	fi
 fi
-- 
1.7.1