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, 26 insertions, 26 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9975703..3d49552 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -58,11 +58,6 @@ static bool blkcg_policy_enabled(struct request_queue *q,
 	return pol && test_bit(pol->plid, q->blkcg_pols);
 }
 
-static size_t blkg_pd_size(const struct blkcg_policy *pol)
-{
-	return sizeof(struct blkg_policy_data) + pol->pdata_size;
-}
-
 /**
  * blkg_free - free a blkg
  * @blkg: blkg to free
@@ -122,7 +117,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q)
 			continue;
 
 		/* alloc per-policy data and attach it to blkg */
-		pd = kzalloc_node(blkg_pd_size(pol), GFP_ATOMIC, q->node);
+		pd = kzalloc_node(pol->pd_size, GFP_ATOMIC, q->node);
 		if (!pd) {
 			blkg_free(blkg);
 			return NULL;
@@ -346,7 +341,8 @@ static const char *blkg_dev_name(struct blkcg_gq *blkg)
  * cftype->read_seq_string method.
  */
 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
-		       u64 (*prfill)(struct seq_file *, void *, int),
+		       u64 (*prfill)(struct seq_file *,
+				     struct blkg_policy_data *, int),
 		       const struct blkcg_policy *pol, int data,
 		       bool show_total)
 {
@@ -357,7 +353,7 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 	spin_lock_irq(&blkcg->lock);
 	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
 		if (blkcg_policy_enabled(blkg->q, pol))
-			total += prfill(sf, blkg->pd[pol->plid]->pdata, data);
+			total += prfill(sf, blkg->pd[pol->plid], data);
 	spin_unlock_irq(&blkcg->lock);
 
 	if (show_total)
@@ -368,14 +364,14 @@ EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
 /**
  * __blkg_prfill_u64 - prfill helper for a single u64 value
  * @sf: seq_file to print to
- * @pdata: policy private data of interest
+ * @pd: policy private data of interest
  * @v: value to print
  *
- * Print @v to @sf for the device assocaited with @pdata.
+ * Print @v to @sf for the device assocaited with @pd.
  */
-u64 __blkg_prfill_u64(struct seq_file *sf, void *pdata, u64 v)
+u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
 {
-	const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
+	const char *dname = blkg_dev_name(pd->blkg);
 
 	if (!dname)
 		return 0;
@@ -388,12 +384,12 @@ EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
 /**
  * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
  * @sf: seq_file to print to
- * @pdata: policy private data of interest
+ * @pd: policy private data of interest
  * @rwstat: rwstat to print
  *
- * Print @rwstat to @sf for the device assocaited with @pdata.
+ * Print @rwstat to @sf for the device assocaited with @pd.
  */
-u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
+u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 			 const struct blkg_rwstat *rwstat)
 {
 	static const char *rwstr[] = {
@@ -402,7 +398,7 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
 		[BLKG_RWSTAT_SYNC]	= "Sync",
 		[BLKG_RWSTAT_ASYNC]	= "Async",
 	};
-	const char *dname = blkg_dev_name(pdata_to_blkg(pdata));
+	const char *dname = blkg_dev_name(pd->blkg);
 	u64 v;
 	int i;
 
@@ -421,30 +417,31 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, void *pdata,
 /**
  * blkg_prfill_stat - prfill callback for blkg_stat
  * @sf: seq_file to print to
- * @pdata: policy private data of interest
- * @off: offset to the blkg_stat in @pdata
+ * @pd: policy private data of interest
+ * @off: offset to the blkg_stat in @pd
  *
  * prfill callback for printing a blkg_stat.
  */
-u64 blkg_prfill_stat(struct seq_file *sf, void *pdata, int off)
+u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
 {
-	return __blkg_prfill_u64(sf, pdata, blkg_stat_read(pdata + off));
+	return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
 }
 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
 
 /**
  * blkg_prfill_rwstat - prfill callback for blkg_rwstat
  * @sf: seq_file to print to
- * @pdata: policy private data of interest
- * @off: offset to the blkg_rwstat in @pdata
+ * @pd: policy private data of interest
+ * @off: offset to the blkg_rwstat in @pd
  *
  * prfill callback for printing a blkg_rwstat.
  */
-u64 blkg_prfill_rwstat(struct seq_file *sf, void *pdata, int off)
+u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
+		       int off)
 {
-	struct blkg_rwstat rwstat = blkg_rwstat_read(pdata + off);
+	struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
 
-	return __blkg_prfill_rwstat(sf, pdata, &rwstat);
+	return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
 
@@ -733,7 +730,7 @@ int blkcg_activate_policy(struct request_queue *q,
 
 	/* allocate policy_data for all existing blkgs */
 	while (cnt--) {
-		pd = kzalloc_node(blkg_pd_size(pol), GFP_KERNEL, q->node);
+		pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
 		if (!pd) {
 			ret = -ENOMEM;
 			goto out_free;
@@ -832,6 +829,9 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 {
 	int i, ret;
 
+	if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
+		return -EINVAL;
+
 	mutex_lock(&blkcg_pol_mutex);
 
 	/* find an empty slot */