From f9ab5b5b0f5be506640321d710b0acd3dca6154a Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Wed, 17 Jun 2009 16:26:33 -0700 Subject: [PATCH] cgroups: forbid noprefix if mounting more than just cpuset subsystem The 'noprefix' option was introduced for backwards-compatibility of cpuset, but actually it can be used when mounting other subsystems. This results in possibility of name collision, and now the collision can really happen, because we have 'stat' file in both memory and cpuacct subsystem: # mount -t cgroup -o noprefix,memory,cpuacct xxx /mnt Cgroup will happily mount the 2 subsystems, but only 'stat' file of memory subsys can be seen. We don't want users to use nopreifx, and also want to avoid name collision, so we change to allow noprefix only if mounting just the cpuset subsystem. [akpm@linux-foundation.org: fix shift for cpuset_subsys_id >= 32] Signed-off-by: Li Zefan Cc: Paul Menage Acked-by: KAMEZAWA Hiroyuki Cc: Balbir Singh Acked-by: Dhaval Giani Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/cgroup.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 3fb789f..3737a68 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -843,6 +843,11 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) { char *token, *o = data ?: "all"; + unsigned long mask = (unsigned long)-1; + +#ifdef CONFIG_CPUSETS + mask = ~(1UL << cpuset_subsys_id); +#endif opts->subsys_bits = 0; opts->flags = 0; @@ -887,6 +892,15 @@ static int parse_cgroupfs_options(char *data, } } + /* + * Option noprefix was introduced just for backward compatibility + * with the old cpuset, so we allow noprefix only if mounting just + * the cpuset subsystem. + */ + if (test_bit(ROOT_NOPREFIX, &opts->flags) && + (opts->subsys_bits & mask)) + return -EINVAL; + /* We can't have an empty hierarchy */ if (!opts->subsys_bits) return -EINVAL; -- 2.7.4