blkcg: embed struct blkg_policy_data in policy specific data

Currently blkg_policy_data carries policy specific data as char flex
array instead of being embedded in policy specific data.  This was
forced by oddities around blkg allocation which are all gone now.

This patch makes blkg_policy_data embedded in policy specific data -
throtl_grp and cfq_group so that it's more conventional and consistent
with how io_cq is handled.

* blkcg_policy->pdata_size is renamed to ->pd_size.

* Functions which used to take void *pdata now takes struct
  blkg_policy_data *pd.

* blkg_to_pdata/pdata_to_blkg() updated to blkg_to_pd/pd_to_blkg().

* Dummy struct blkg_policy_data definition added.  Dummy
  pdata_to_blkg() definition was unused and inconsistent with the
  non-dummy version - correct dummy pd_to_blkg() added.

* throtl and cfq updated accordingly.

* As dummy blkg_to_pd/pd_to_blkg() are provided,
  blkg_to_cfqg/cfqg_to_blkg() don't need to be ifdef'd.  Moved outside
  ifdef block.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 25 insertions, 12 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 00c7eff66ecf..6a0a17a83862 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -49,6 +49,9 @@ struct tg_stats_cpu {
 };
 
 struct throtl_grp {
+        /* must be the first member */
+        struct blkg_policy_data pd;
+
         /* active throtl group service_tree member */
         struct rb_node rb_node;
 
@@ -120,14 +123,19 @@ static LIST_HEAD(tg_stats_alloc_list);
 static void tg_stats_alloc_fn(struct work_struct *);
 static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
 
+static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
+{
+        return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
+}
+
 static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
 {
-        return blkg_to_pdata(blkg, &blkcg_policy_throtl);
+        return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
 }
 
 static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
 {
-        return pdata_to_blkg(tg);
+        return pd_to_blkg(&tg->pd);
 }
 
 static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
@@ -931,9 +939,10 @@ throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
         }
 }
 
-static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, void *pdata, int off)
+static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
+                                struct blkg_policy_data *pd, int off)
 {
-        struct throtl_grp *tg = pdata;
+        struct throtl_grp *tg = pd_to_tg(pd);
         struct blkg_rwstat rwstat = { }, tmp;
         int i, cpu;
 
@@ -945,7 +954,7 @@ static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, void *pdata, int off)
                         rwstat.cnt[i] += tmp.cnt[i];
         }
 
-        return __blkg_prfill_rwstat(sf, pdata, &rwstat);
+        return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 
 static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
@@ -958,22 +967,26 @@ static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
         return 0;
 }
 
-static u64 tg_prfill_conf_u64(struct seq_file *sf, void *pdata, int off)
+static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
+                              int off)
 {
-        u64 v = *(u64 *)(pdata + off);
+        struct throtl_grp *tg = pd_to_tg(pd);
+        u64 v = *(u64 *)((void *)tg + off);
 
         if (v == -1)
                 return 0;
-        return __blkg_prfill_u64(sf, pdata, v);
+        return __blkg_prfill_u64(sf, pd, v);
 }
 
-static u64 tg_prfill_conf_uint(struct seq_file *sf, void *pdata, int off)
+static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
+                               int off)
 {
-        unsigned int v = *(unsigned int *)(pdata + off);
+        struct throtl_grp *tg = pd_to_tg(pd);
+        unsigned int v = *(unsigned int *)((void *)tg + off);
 
         if (v == -1)
                 return 0;
-        return __blkg_prfill_u64(sf, pdata, v);
+        return __blkg_prfill_u64(sf, pd, v);
 }
 
 static int tg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft,
@@ -1092,7 +1105,7 @@ static struct blkcg_policy blkcg_policy_throtl = {
                 .pd_exit_fn             = throtl_pd_exit,
                 .pd_reset_stats_fn      = throtl_pd_reset_stats,
         },
-        .pdata_size = sizeof(struct throtl_grp),
+        .pd_size = sizeof(struct throtl_grp),
         .cftypes = throtl_files,
 };