blkcg: remove static policy ID enums
Remove BLKIO_POLICY_* enums and let blkio_policy_register() allocate
@pol->plid dynamically on registration. The maximum number of blkcg
policies which can be registered at the same time is defined by
BLKCG_MAX_POLS constant added to include/linux/blkdev.h.
Note that blkio_policy_register() now may fail. Policy init functions
updated accordingly and unnecessary ifdefs removed from cfq_init().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b123152..2d4d7d6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -31,7 +31,7 @@
struct blkio_cgroup blkio_root_cgroup = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
EXPORT_SYMBOL_GPL(blkio_root_cgroup);
-static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
+static struct blkio_policy_type *blkio_policy[BLKCG_MAX_POLS];
struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
{
@@ -67,7 +67,7 @@
if (!blkg)
return;
- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd = blkg->pd[i];
@@ -107,7 +107,7 @@
blkg->refcnt = 1;
cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
struct blkg_policy_data *pd;
@@ -127,7 +127,7 @@
}
/* invoke per-policy init */
- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
if (pol)
@@ -320,7 +320,7 @@
* anyway. If you get hit by a race, retry.
*/
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
- for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkio_policy_type *pol = blkio_policy[i];
if (pol && pol->ops.blkio_reset_group_stats_fn)
@@ -729,46 +729,75 @@
};
EXPORT_SYMBOL_GPL(blkio_subsys);
-void blkio_policy_register(struct blkio_policy_type *blkiop)
+/**
+ * blkio_policy_register - register a blkcg policy
+ * @blkiop: blkcg policy to register
+ *
+ * Register @blkiop with blkcg core. Might sleep and @blkiop may be
+ * modified on successful registration. Returns 0 on success and -errno on
+ * failure.
+ */
+int blkio_policy_register(struct blkio_policy_type *blkiop)
{
struct request_queue *q;
+ int i, ret;
mutex_lock(&blkcg_pol_mutex);
- blkcg_bypass_start();
+ /* find an empty slot */
+ ret = -ENOSPC;
+ for (i = 0; i < BLKCG_MAX_POLS; i++)
+ if (!blkio_policy[i])
+ break;
+ if (i >= BLKCG_MAX_POLS)
+ goto out_unlock;
- BUG_ON(blkio_policy[blkiop->plid]);
- blkio_policy[blkiop->plid] = blkiop;
+ /* register and update blkgs */
+ blkiop->plid = i;
+ blkio_policy[i] = blkiop;
+
+ blkcg_bypass_start();
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop);
-
blkcg_bypass_end();
+ /* everything is in place, add intf files for the new policy */
if (blkiop->cftypes)
WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
-
+ ret = 0;
+out_unlock:
mutex_unlock(&blkcg_pol_mutex);
+ return ret;
}
EXPORT_SYMBOL_GPL(blkio_policy_register);
+/**
+ * blkiop_policy_unregister - unregister a blkcg policy
+ * @blkiop: blkcg policy to unregister
+ *
+ * Undo blkio_policy_register(@blkiop). Might sleep.
+ */
void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
struct request_queue *q;
mutex_lock(&blkcg_pol_mutex);
+ if (WARN_ON(blkio_policy[blkiop->plid] != blkiop))
+ goto out_unlock;
+
+ /* kill the intf files first */
if (blkiop->cftypes)
cgroup_rm_cftypes(&blkio_subsys, blkiop->cftypes);
- blkcg_bypass_start();
-
- BUG_ON(blkio_policy[blkiop->plid] != blkiop);
+ /* unregister and update blkgs */
blkio_policy[blkiop->plid] = NULL;
+ blkcg_bypass_start();
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop);
blkcg_bypass_end();
-
+out_unlock:
mutex_unlock(&blkcg_pol_mutex);
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);