cgroup: make rebind_subsystems() handle file additions and removals with proper error handling
Currently, creating and removing cgroup files in the root directory
are handled separately from the actual subsystem binding and unbinding
which happens in rebind_subsystems(). Also, rebind_subsystems() users
aren't handling file creation errors properly. Let's integrate
top_cgroup file handling into rebind_subsystems() so that it's simpler
to use and everyone handles file creation errors correctly.
* On a successful return, rebind_subsystems() is guaranteed to have
created all files of the new subsystems and deleted the ones
belonging to the removed subsystems. After a failure, no file is
created or removed.
* cgroup_remount() no longer needs to make explicit populate/clear
calls as it's all handled by rebind_subsystems(), and it gets proper
error handling automatically.
* cgroup_mount() has been updated such that the root dentry and cgroup
are linked before rebind_subsystems(). Also, the init_cred dancing
and base file handling are moved right above rebind_subsystems()
call and proper error handling for the base files is added. While
at it, add a comment explaining what's going on with the cred thing.
* cgroup_kill_sb() calls rebind_subsystems() to unbind all subsystems
which now implies removing all subsystem files which requires the
directory's i_mutex. Grab it. This means that files on the root
cgroup are removed earlier - they used to be deleted from generic
super_block cleanup from vfs. This doesn't lead to any functional
difference and it's cleaner to do the clean up explicitly for all
files.
Combined with the previous changes, this makes all cgroup file
creation errors handled correctly.
v2: Added comment on init_cred.
v3: Li spotted that cgroup_mount() wasn't freeing tmp_links after base
file addition failure. Fix it by adding free_tmp_links error
handling label.
v4: v3 introduced build bugs which got noticed by Fengguang's awesome
kbuild test robot. Fixed, and shame on me.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
1 file changed
