On 2012/11/13 11:01, Tejun Heo wrote: > While creating a new cgroup, cgroup_create() links the newly allocated > cgroup into various places before trying to create its directory. > Because cgroup life-cycle is tied to the vfs objects, this makes it > impossible to use cgroup_rmdir() for rolling back creation - the > removal logic depends on having full vfs objects. > > This patch moves directory creation above linking and collect linking > operations to one place. This allows directory creation failure to > share error exit path with css allocation failures and any failure > sites afterwards (to be added later) can use cgroup_rmdir() logic to > undo creation. > > It also removes the need to check whether cgroup->dentry is %NULL in > cgroup_path. If a cgroup is visible, its dentry is guaranteed to be > visible too. > I'm afraid this isn't safe. The cgroup is visible to a controller soon after ss->create(), and then the controller might call cgroup_path() while cgrp->dentry is still NULL. This can happen for cpu cgroup I think, and in fact the NULL check was added for this reason IIRC. > Note that this also makes the memory barriers around cgroup->dentry, > which currently is misleadingly using RCU operations, unnecessary. > This will be handled in the next patch. > > While at it, locking BUG_ON() on i_mutex is converted to > lockdep_assert_held(). > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > --- > kernel/cgroup.c | 32 +++++++++++++------------------- > 1 file changed, 13 insertions(+), 19 deletions(-) _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
