cgroups: add per-thread subsystem callbacks

Add cgroup subsystem callbacks for per-thread attachment in atomic contexts

Add can_attach_task(), pre_attach(), and attach_task() as new callbacks
for cgroups's subsystem interface.  Unlike can_attach and attach, these
are for per-thread operations, to be called potentially many times when
attaching an entire threadgroup.

Also, the old "bool threadgroup" interface is removed, as replaced by
this.  All subsystems are modified for the new interface - of note is
cpuset, which requires from/to nodemasks for attach to be globally scoped
(though per-cpuset would work too) to persist from its pre_attach to
attach_task and attach.

This is a pre-patch for cgroup-procs-writable.patch.

Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 12 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 07371cfdfae..bcaf16ee6ad 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -30,10 +30,8 @@ EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
 static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
 						  struct cgroup *);
-static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
-			      struct task_struct *, bool);
-static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
-			   struct cgroup *, struct task_struct *, bool);
+static int blkiocg_can_attach_task(struct cgroup *, struct task_struct *);
+static void blkiocg_attach_task(struct cgroup *, struct task_struct *);
 static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
 static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 
@@ -46,8 +44,8 @@ static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 struct cgroup_subsys blkio_subsys = {
 	.name = "blkio",
 	.create = blkiocg_create,
-	.can_attach = blkiocg_can_attach,
-	.attach = blkiocg_attach,
+	.can_attach_task = blkiocg_can_attach_task,
+	.attach_task = blkiocg_attach_task,
 	.destroy = blkiocg_destroy,
 	.populate = blkiocg_populate,
 #ifdef CONFIG_BLK_CGROUP
@@ -1616,9 +1614,7 @@ done:
  * of the main cic data structures.  For now we allow a task to change
  * its cgroup only if it's the only owner of its ioc.
  */
-static int blkiocg_can_attach(struct cgroup_subsys *subsys,
-				struct cgroup *cgroup, struct task_struct *tsk,
-				bool threadgroup)
+static int blkiocg_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 {
 	struct io_context *ioc;
 	int ret = 0;
@@ -1633,9 +1629,7 @@ static int blkiocg_can_attach(struct cgroup_subsys *subsys,
 	return ret;
 }
 
-static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
-				struct cgroup *prev, struct task_struct *tsk,
-				bool threadgroup)
+static void blkiocg_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 {
 	struct io_context *ioc;