On 2014/1/28 23:32, Tejun Heo wrote: > cgroup_root_from_opts() checks whether (!opts->subsys_mask && > !opts->none) and returns NULL if so. After that, if allocation fails, > returns ERR_PTR(-ENOMEM). The caller, cgroup_mount(), doesn't treat > NULL as an error but set opts.new_root to NULL; however, later on, > cgroup_set_super() fails with -EINVAL if new_root is NULL. This patch changes mount semantics. If cgroup_root_from_opts() returns NULL, it means we should be looking for existing superblock only. This will fail: # mount -t cgroup -o name=abc xxx /mnt But this is ok: # mount -t cgroup -o none,name=abc xxx /mnt # mkdir /mnt/sub # umount /mnt # mount -t cgroup -o name=abc xxx /mnt <-- this won't work with your patch > > This is one bizarre error handling sequence especially when all other > opts sanity checks including the very close (!opts->subsys_mask && > !opts->name) check are done in parse_cgroupfs_options(). > > Let's move the one-off check in cgroup_root_from_opts() to > parse_cgroupfs_options() where it can be combined with the > (!opts->subsys_mask && !opts->name) check. cgroup_root_from_opts() is > updated to return NULL on memory allocation failure. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
