blkio: Take care of cgroup deletion and cfq group reference counting
o One can choose to change elevator or delete a cgroup. Implement group
reference counting so that both elevator exit and cgroup deletion can
take place gracefully.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Nauman Rafique <nauman@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 4f6afd7..0426ab6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -13,6 +13,8 @@
#include <linux/ioprio.h>
#include "blk-cgroup.h"
+extern void cfq_unlink_blkio_group(void *, struct blkio_group *);
+
struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
@@ -28,14 +30,43 @@
spin_lock_irqsave(&blkcg->lock, flags);
rcu_assign_pointer(blkg->key, key);
+ blkg->blkcg_id = css_id(&blkcg->css);
hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
spin_unlock_irqrestore(&blkcg->lock, flags);
}
+static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
+{
+ hlist_del_init_rcu(&blkg->blkcg_node);
+ blkg->blkcg_id = 0;
+}
+
+/*
+ * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
+ * indicating that blk_group was unhashed by the time we got to it.
+ */
int blkiocg_del_blkio_group(struct blkio_group *blkg)
{
- /* Implemented later */
- return 0;
+ struct blkio_cgroup *blkcg;
+ unsigned long flags;
+ struct cgroup_subsys_state *css;
+ int ret = 1;
+
+ rcu_read_lock();
+ css = css_lookup(&blkio_subsys, blkg->blkcg_id);
+ if (!css)
+ goto out;
+
+ blkcg = container_of(css, struct blkio_cgroup, css);
+ spin_lock_irqsave(&blkcg->lock, flags);
+ if (!hlist_unhashed(&blkg->blkcg_node)) {
+ __blkiocg_del_blkio_group(blkg);
+ ret = 0;
+ }
+ spin_unlock_irqrestore(&blkcg->lock, flags);
+out:
+ rcu_read_unlock();
+ return ret;
}
/* called under rcu_read_lock(). */
@@ -97,8 +128,39 @@
static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
+ unsigned long flags;
+ struct blkio_group *blkg;
+ void *key;
+ rcu_read_lock();
+remove_entry:
+ spin_lock_irqsave(&blkcg->lock, flags);
+
+ if (hlist_empty(&blkcg->blkg_list)) {
+ spin_unlock_irqrestore(&blkcg->lock, flags);
+ goto done;
+ }
+
+ blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
+ blkcg_node);
+ key = rcu_dereference(blkg->key);
+ __blkiocg_del_blkio_group(blkg);
+
+ spin_unlock_irqrestore(&blkcg->lock, flags);
+
+ /*
+ * This blkio_group is being unlinked as associated cgroup is going
+ * away. Let all the IO controlling policies know about this event.
+ *
+ * Currently this is static call to one io controlling policy. Once
+ * we have more policies in place, we need some dynamic registration
+ * of callback function.
+ */
+ cfq_unlink_blkio_group(key, blkg);
+ goto remove_entry;
+done:
free_css_id(&blkio_subsys, &blkcg->css);
+ rcu_read_unlock();
kfree(blkcg);
}