blkcg: implement all_blkcgs list

Add all_blkcgs list goes through blkcg->all_blkcgs_node and is
protected by blkcg_pol_mutex.  This will be used to fix
blkcg_policy_data allocation bug.

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 05b893de516bded3ccfafac5d0af93ee7249ea99..42ff436ffaf44ba4850069c998cbc902bdfe8a89 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -46,6 +46,8 @@ struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
 
 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
 
+static LIST_HEAD(all_blkcgs);          /* protected by blkcg_pol_mutex */
+
 static bool blkcg_policy_enabled(struct request_queue *q,
                                 const struct blkcg_policy *pol)
 {
@@ -817,6 +819,10 @@ static void blkcg_css_free(struct cgroup_subsys_state *css)
 {
        struct blkcg *blkcg = css_to_blkcg(css);
 
+       mutex_lock(&blkcg_pol_mutex);
+       list_del(&blkcg->all_blkcgs_node);
+       mutex_unlock(&blkcg_pol_mutex);
+
        if (blkcg != &blkcg_root) {
                int i;
 
@@ -833,6 +839,8 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
        struct cgroup_subsys_state *ret;
        int i;
 
+       mutex_lock(&blkcg_pol_mutex);
+
        if (!parent_css) {
                blkcg = &blkcg_root;
                goto done;
@@ -844,8 +852,6 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                goto free_blkcg;
        }
 
-       mutex_lock(&blkcg_pol_mutex);
-
        for (i = 0; i < BLKCG_MAX_POLS ; i++) {
                struct blkcg_policy *pol = blkcg_policy[i];
                struct blkcg_policy_data *cpd;
@@ -862,7 +868,6 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                BUG_ON(blkcg->pd[i]);
                cpd = kzalloc(pol->cpd_size, GFP_KERNEL);
                if (!cpd) {
-                       mutex_unlock(&blkcg_pol_mutex);
                        ret = ERR_PTR(-ENOMEM);
                        goto free_pd_blkcg;
                }
@@ -871,7 +876,6 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                pol->cpd_init_fn(blkcg);
        }
 
-       mutex_unlock(&blkcg_pol_mutex);
 done:
        spin_lock_init(&blkcg->lock);
        INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
@@ -879,14 +883,17 @@ done:
 #ifdef CONFIG_CGROUP_WRITEBACK
        INIT_LIST_HEAD(&blkcg->cgwb_list);
 #endif
+       list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
+
+       mutex_unlock(&blkcg_pol_mutex);
        return &blkcg->css;
 
 free_pd_blkcg:
        for (i--; i >= 0; i--)
                kfree(blkcg->pd[i]);
-
 free_blkcg:
        kfree(blkcg);
+       mutex_unlock(&blkcg_pol_mutex);
        return ret;
 }
 

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 58cfab80dd707ff28d8b4e12fdf735bc24f7f60b..cf3e7bc22ef398b840fdab60368373a43640e558 100644 (file)
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -47,6 +47,7 @@ struct blkcg {
 
        struct blkcg_policy_data        *pd[BLKCG_MAX_POLS];
 
+       struct list_head                all_blkcgs_node;
 #ifdef CONFIG_CGROUP_WRITEBACK
        struct list_head                cgwb_list;
 #endif