cgroup: CGRP_ROOT_SUBSYS_BOUND should be ignored when comparing mount options
1672d04070 ("cgroup: fix cgroupfs_root early destruction path")
introduced CGRP_ROOT_SUBSYS_BOUND which is used to mark completion of
subsys binding on a new root; however, this broke remounts.
cgroup_remount() doesn't allow changing root options via remount and
CGRP_ROOT_SUBSYS_BOUND, which is set on all fully initialized roots,
makes the function reject all remounts.
Fix it by putting the options part in the lower 16 bits of root->flags
and masking the comparions. While at it, make cgroup_remount() emit
an error message explaining why it's rejecting a remount request, so
that it's less of a mystery.
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ad3555b..8db5397 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -276,7 +276,11 @@
CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
- CGRP_ROOT_SUBSYS_BOUND = (1 << 3), /* subsystems finished binding */
+
+ /* mount options live below bit 16 */
+ CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
+
+ CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
};
/*