blkcg: replace blkcg_policy->cpd_size with ->cpd_alloc/free_fn() methods

Each active policy has a cpd (blkcg_policy_data) on each blkcg.  The
cpd's were allocated by blkcg core and each policy could request to
allocate extra space at the end by setting blkcg_policy->cpd_size
larger than the size of cpd.

This is a bit unusual but blkg (blkcg_gq) policy data used to be
handled this way too so it made sense to be consistent; however, blkg
policy data switched to alloc/free callbacks.

This patch makes similar changes to cpd handling.
blkcg_policy->cpd_alloc/free_fn() are added to replace ->cpd_size.  As
cpd allocation is now done from policy side, it can simply allocate a
larger area which embeds cpd at the beginning.

As ->cpd_alloc_fn() may be able to perform all necessary
initializations, this patch makes ->cpd_init_fn() optional.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 247c42c..2b4354b 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -817,11 +817,15 @@ static void blkcg_css_free(struct cgroup_subsys_state *css)
        int i;
 
        mutex_lock(&blkcg_pol_mutex);
+
        list_del(&blkcg->all_blkcgs_node);
-       mutex_unlock(&blkcg_pol_mutex);
 
        for (i = 0; i < BLKCG_MAX_POLS; i++)
-               kfree(blkcg->cpd[i]);
+               if (blkcg->cpd[i])
+                       blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
+
+       mutex_unlock(&blkcg_pol_mutex);
+
        kfree(blkcg);
 }
 
@@ -854,11 +858,10 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                 * check if the policy requires any specific per-cgroup
                 * data: if it does, allocate and initialize it.
                 */
-               if (!pol || !pol->cpd_size)
+               if (!pol || !pol->cpd_alloc_fn)
                        continue;
 
-               BUG_ON(blkcg->cpd[i]);
-               cpd = kzalloc(pol->cpd_size, GFP_KERNEL);
+               cpd = pol->cpd_alloc_fn(GFP_KERNEL);
                if (!cpd) {
                        ret = ERR_PTR(-ENOMEM);
                        goto free_pd_blkcg;
@@ -866,7 +869,8 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                blkcg->cpd[i] = cpd;
                cpd->blkcg = blkcg;
                cpd->plid = i;
-               pol->cpd_init_fn(cpd);
+               if (pol->cpd_init_fn)
+                       pol->cpd_init_fn(cpd);
        }
 
        spin_lock_init(&blkcg->lock);
@@ -882,7 +886,8 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 
 free_pd_blkcg:
        for (i--; i >= 0; i--)
-               kfree(blkcg->cpd[i]);
+               if (blkcg->cpd[i])
+                       blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
 free_blkcg:
        kfree(blkcg);
        mutex_unlock(&blkcg_pol_mutex);
@@ -1159,11 +1164,11 @@ int blkcg_policy_register(struct blkcg_policy *pol)
        blkcg_policy[pol->plid] = pol;
 
        /* allocate and install cpd's */
-       if (pol->cpd_size) {
+       if (pol->cpd_alloc_fn) {
                list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
                        struct blkcg_policy_data *cpd;
 
-                       cpd = kzalloc(pol->cpd_size, GFP_KERNEL);
+                       cpd = pol->cpd_alloc_fn(GFP_KERNEL);
                        if (!cpd) {
                                mutex_unlock(&blkcg_pol_mutex);
                                goto err_free_cpds;
@@ -1186,10 +1191,12 @@ int blkcg_policy_register(struct blkcg_policy *pol)
        return 0;
 
 err_free_cpds:
-       if (pol->cpd_size) {
+       if (pol->cpd_alloc_fn) {
                list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
-                       kfree(blkcg->cpd[pol->plid]);
-                       blkcg->cpd[pol->plid] = NULL;
+                       if (blkcg->cpd[pol->plid]) {
+                               pol->cpd_free_fn(blkcg->cpd[pol->plid]);
+                               blkcg->cpd[pol->plid] = NULL;
+                       }
                }
        }
        blkcg_policy[pol->plid] = NULL;
@@ -1222,10 +1229,12 @@ void blkcg_policy_unregister(struct blkcg_policy *pol)
        /* remove cpds and unregister */
        mutex_lock(&blkcg_pol_mutex);
 
-       if (pol->cpd_size) {
+       if (pol->cpd_alloc_fn) {
                list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
-                       kfree(blkcg->cpd[pol->plid]);
-                       blkcg->cpd[pol->plid] = NULL;
+                       if (blkcg->cpd[pol->plid]) {
+                               pol->cpd_free_fn(blkcg->cpd[pol->plid]);
+                               blkcg->cpd[pol->plid] = NULL;
+                       }
                }
        }
        blkcg_policy[pol->plid] = NULL;

diff --cc block/cfq-iosched.c
Simple merge

diff --cc include/linux/blk-cgroup.h
Simple merge