blkcg: use CGROUP_WEIGHT_* scale for io.weight on the unified hierarchy

cgroup is trying to make interface consistent across different
controllers.  For weight based resource control, the knob should have
the range [1, 10000] and default to 100.  This patch updates
cfq-iosched so that the weight range conforms.  The internal
calculations have enough range and the widening of the weight range
shouldn't cause any problem.

* blkcg_policy->cpd_bind_fn() is added.  If present, this is invoked
  when blkcg is attached to a hierarchy.

* cfq_cpd_init() is updated to use the new default value on the
  unified hierarchy.

* cfq_cpd_bind() callback is implemented to clear per-blkg configs and
  apply the default config matching the hierarchy type.

* cfqd->root_group->[leaf_]weight initialization in cfq_init_queue()
  is moved into !CONFIG_CFQ_GROUP_IOSCHED block.  cfq_cpd_bind() is
  now responsible for initializing the initial weights when blkcg is
  enabled.

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>

4 files changed, 64 insertions, 16 deletions

diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index bd1ce15d5178..e0975c2cf03d 100644
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -464,7 +464,7 @@ may be specified in any order and not all pairs have to be specified.
 
         The weight setting, currently only available and effective if
         cfq-iosched is in use for the target device.  The weight is
-        between 10 and 1000 and defaults to 500.  The first line
+        between 1 and 10000 and defaults to 100.  The first line
         always contains the default weight in the following format to
         use when per-device setting is missing.
 
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 88bdb73bd5e0..ac8370cb2515 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1143,11 +1143,32 @@ static int blkcg_can_attach(struct cgroup_subsys_state *css,
         return ret;
 }
 
+static void blkcg_bind(struct cgroup_subsys_state *root_css)
+{
+        int i;
+
+        mutex_lock(&blkcg_pol_mutex);
+
+        for (i = 0; i < BLKCG_MAX_POLS; i++) {
+                struct blkcg_policy *pol = blkcg_policy[i];
+                struct blkcg *blkcg;
+
+                if (!pol || !pol->cpd_bind_fn)
+                        continue;
+
+                list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
+                        if (blkcg->cpd[pol->plid])
+                                pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
+        }
+        mutex_unlock(&blkcg_pol_mutex);
+}
+
 struct cgroup_subsys io_cgrp_subsys = {
         .css_alloc = blkcg_css_alloc,
         .css_offline = blkcg_css_offline,
         .css_free = blkcg_css_free,
         .can_attach = blkcg_can_attach,
+        .bind = blkcg_bind,
         .dfl_cftypes = blkcg_files,
         .legacy_cftypes = blkcg_legacy_files,
         .legacy_name = "blkio",
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 0fe721eaff28..04de88463a98 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1522,6 +1522,9 @@ static void cfq_init_cfqg_base(struct cfq_group *cfqg)
 }
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
+static int __cfq_set_weight(struct cgroup_subsys_state *css, u64 val,
+                            bool on_dfl, bool reset_dev, bool is_leaf_weight);
+
 static void cfqg_stats_exit(struct cfqg_stats *stats)
 {
         blkg_rwstat_exit(&stats->merged);
@@ -1578,14 +1581,14 @@ static struct blkcg_policy_data *cfq_cpd_alloc(gfp_t gfp)
 static void cfq_cpd_init(struct blkcg_policy_data *cpd)
 {
         struct cfq_group_data *cgd = cpd_to_cfqgd(cpd);
+        unsigned int weight = cgroup_on_dfl(blkcg_root.css.cgroup) ?
+                              CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;
 
-        if (cpd_to_blkcg(cpd) == &blkcg_root) {
-                cgd->weight = 2 * CFQ_WEIGHT_LEGACY_DFL;
-                cgd->leaf_weight = 2 * CFQ_WEIGHT_LEGACY_DFL;
-        } else {
-                cgd->weight = CFQ_WEIGHT_LEGACY_DFL;
-                cgd->leaf_weight = CFQ_WEIGHT_LEGACY_DFL;
-        }
+        if (cpd_to_blkcg(cpd) == &blkcg_root)
+                weight *= 2;
+
+        cgd->weight = weight;
+        cgd->leaf_weight = weight;
 }
 
 static void cfq_cpd_free(struct blkcg_policy_data *cpd)
@@ -1593,6 +1596,19 @@ static void cfq_cpd_free(struct blkcg_policy_data *cpd)
         kfree(cpd_to_cfqgd(cpd));
 }
 
+static void cfq_cpd_bind(struct blkcg_policy_data *cpd)
+{
+        struct blkcg *blkcg = cpd_to_blkcg(cpd);
+        bool on_dfl = cgroup_on_dfl(blkcg_root.css.cgroup);
+        unsigned int weight = on_dfl ? CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;
+
+        if (blkcg == &blkcg_root)
+                weight *= 2;
+
+        WARN_ON_ONCE(__cfq_set_weight(&blkcg->css, weight, on_dfl, true, false));
+        WARN_ON_ONCE(__cfq_set_weight(&blkcg->css, weight, on_dfl, true, true));
+}
+
 static struct blkg_policy_data *cfq_pd_alloc(gfp_t gfp, int node)
 {
         struct cfq_group *cfqg;
@@ -1742,6 +1758,8 @@ static ssize_t __cfqg_set_weight_device(struct kernfs_open_file *of,
                                         char *buf, size_t nbytes, loff_t off,
                                         bool on_dfl, bool is_leaf_weight)
 {
+        unsigned int min = on_dfl ? CGROUP_WEIGHT_MIN : CFQ_WEIGHT_LEGACY_MIN;
+        unsigned int max = on_dfl ? CGROUP_WEIGHT_MAX : CFQ_WEIGHT_LEGACY_MAX;
         struct blkcg *blkcg = css_to_blkcg(of_css(of));
         struct blkg_conf_ctx ctx;
         struct cfq_group *cfqg;
@@ -1769,7 +1787,7 @@ static ssize_t __cfqg_set_weight_device(struct kernfs_open_file *of,
         cfqgd = blkcg_to_cfqgd(blkcg);
 
         ret = -ERANGE;
-        if (!v || (v >= CFQ_WEIGHT_LEGACY_MIN && v <= CFQ_WEIGHT_LEGACY_MAX)) {
+        if (!v || (v >= min && v <= max)) {
                 if (!is_leaf_weight) {
                         cfqg->dev_weight = v;
                         cfqg->new_weight = v ?: cfqgd->weight;
@@ -1797,15 +1815,17 @@ static ssize_t cfqg_set_leaf_weight_device(struct kernfs_open_file *of,
 }
 
 static int __cfq_set_weight(struct cgroup_subsys_state *css, u64 val,
-                            bool is_leaf_weight)
+                            bool on_dfl, bool reset_dev, bool is_leaf_weight)
 {
+        unsigned int min = on_dfl ? CGROUP_WEIGHT_MIN : CFQ_WEIGHT_LEGACY_MIN;
+        unsigned int max = on_dfl ? CGROUP_WEIGHT_MAX : CFQ_WEIGHT_LEGACY_MAX;
         struct blkcg *blkcg = css_to_blkcg(css);
         struct blkcg_gq *blkg;
         struct cfq_group_data *cfqgd;
         int ret = 0;
 
-        if (val < CFQ_WEIGHT_LEGACY_MIN || val > CFQ_WEIGHT_LEGACY_MAX)
-                return -EINVAL;
+        if (val < min || val > max)
+                return -ERANGE;
 
         spin_lock_irq(&blkcg->lock);
         cfqgd = blkcg_to_cfqgd(blkcg);
@@ -1826,9 +1846,13 @@ static int __cfq_set_weight(struct cgroup_subsys_state *css, u64 val,
                         continue;
 
                 if (!is_leaf_weight) {
+                        if (reset_dev)
+                                cfqg->dev_weight = 0;
                         if (!cfqg->dev_weight)
                                 cfqg->new_weight = cfqgd->weight;
                 } else {
+                        if (reset_dev)
+                                cfqg->dev_leaf_weight = 0;
                         if (!cfqg->dev_leaf_weight)
                                 cfqg->new_leaf_weight = cfqgd->leaf_weight;
                 }
@@ -1842,13 +1866,13 @@ out:
 static int cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
                           u64 val)
 {
-        return __cfq_set_weight(css, val, false);
+        return __cfq_set_weight(css, val, false, false, false);
 }
 
 static int cfq_set_leaf_weight(struct cgroup_subsys_state *css,
                                struct cftype *cft, u64 val)
 {
-        return __cfq_set_weight(css, val, true);
+        return __cfq_set_weight(css, val, false, false, true);
 }
 
 static int cfqg_print_stat(struct seq_file *sf, void *v)
@@ -2135,7 +2159,7 @@ static ssize_t cfq_set_weight_on_dfl(struct kernfs_open_file *of,
         /* "WEIGHT" or "default WEIGHT" sets the default weight */
         v = simple_strtoull(buf, &endp, 0);
         if (*endp == '\0' || sscanf(buf, "default %llu", &v) == 1) {
-                ret = __cfq_set_weight(of_css(of), v, false);
+                ret = __cfq_set_weight(of_css(of), v, true, false, false);
                 return ret ?: nbytes;
         }
 
@@ -4512,9 +4536,9 @@ static int cfq_init_queue(struct request_queue *q, struct elevator_type *e)
                 goto out_free;
 
         cfq_init_cfqg_base(cfqd->root_group);
-#endif
         cfqd->root_group->weight = 2 * CFQ_WEIGHT_LEGACY_DFL;
         cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_LEGACY_DFL;
+#endif
 
         /*
          * Not strictly needed (since RB_ROOT just clears the node and we
@@ -4715,6 +4739,7 @@ static struct blkcg_policy blkcg_policy_cfq = {
         .cpd_alloc_fn           = cfq_cpd_alloc,
         .cpd_init_fn            = cfq_cpd_init,
         .cpd_free_fn            = cfq_cpd_free,
+        .cpd_bind_fn            = cfq_cpd_bind,
 
         .pd_alloc_fn            = cfq_pd_alloc,
         .pd_init_fn             = cfq_pd_init,
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 9a7c4bd45fff..0a5cc7a1109b 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -138,6 +138,7 @@ struct blkcg_gq {
 typedef struct blkcg_policy_data *(blkcg_pol_alloc_cpd_fn)(gfp_t gfp);
 typedef void (blkcg_pol_init_cpd_fn)(struct blkcg_policy_data *cpd);
 typedef void (blkcg_pol_free_cpd_fn)(struct blkcg_policy_data *cpd);
+typedef void (blkcg_pol_bind_cpd_fn)(struct blkcg_policy_data *cpd);
 typedef struct blkg_policy_data *(blkcg_pol_alloc_pd_fn)(gfp_t gfp, int node);
 typedef void (blkcg_pol_init_pd_fn)(struct blkg_policy_data *pd);
 typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
@@ -155,6 +156,7 @@ struct blkcg_policy {
         blkcg_pol_alloc_cpd_fn          *cpd_alloc_fn;
         blkcg_pol_init_cpd_fn           *cpd_init_fn;
         blkcg_pol_free_cpd_fn           *cpd_free_fn;
+        blkcg_pol_bind_cpd_fn           *cpd_bind_fn;
 
         blkcg_pol_alloc_pd_fn           *pd_alloc_fn;
         blkcg_pol_init_pd_fn            *pd_init_fn;