blk-cgroup: always terminate io.stat lines

With the removal of seq_get_buf in blkcg_print_one_stat, we
cannot make adding the newline conditional on there being
relevant stats because the name was already written out
unconditionally.
Otherwise we may end up with multiple device names in one
line which is confusing and doesn't follow the nested-keyed
file format.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Fixes: 252c651a4c ("blk-cgroup: stop using seq_get_buf")
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220111083159.42340-1-w.bumiller@proxmox.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

@@ -949,7 +949,6 @@ static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
 {
 	struct blkg_iostat_set *bis = &blkg->iostat;
 	u64 rbytes, wbytes, rios, wios, dbytes, dios;
-	bool has_stats = false;
 	const char *dname;
 	unsigned seq;
 	int i;
@@ -975,14 +974,12 @@ static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
 	} while (u64_stats_fetch_retry(&bis->sync, seq));
 
 	if (rbytes || wbytes || rios || wios) {
-		has_stats = true;
 		seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
 			rbytes, wbytes, rios, wios,
 			dbytes, dios);
 	}
 
 	if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
-		has_stats = true;
 		seq_printf(s, " use_delay=%d delay_nsec=%llu",
 			atomic_read(&blkg->use_delay),
 			atomic64_read(&blkg->delay_nsec));
@@ -994,12 +991,10 @@ static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
 		if (!blkg->pd[i] || !pol->pd_stat_fn)
 			continue;
 
-		if (pol->pd_stat_fn(blkg->pd[i], s))
-			has_stats = true;
+		pol->pd_stat_fn(blkg->pd[i], s);
 	}
 
-	if (has_stats)
-		seq_printf(s, "\n");
+	seq_puts(s, "\n");
 }
 
 static int blkcg_print_stat(struct seq_file *sf, void *v)

block/blk-cgroup.h

@@ -151,7 +151,7 @@ typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
 typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data *pd);
 typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
 typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data *pd);
-typedef bool (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd,
+typedef void (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd,
 				struct seq_file *s);
 
 struct blkcg_policy {

block/blk-iocost.c

@@ -2988,13 +2988,13 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
 	kfree(iocg);
 }
 
-static bool ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
+static void ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
 {
 	struct ioc_gq *iocg = pd_to_iocg(pd);
 	struct ioc *ioc = iocg->ioc;
 
 	if (!ioc->enabled)
-		return false;
+		return;
 
 	if (iocg->level == 0) {
 		unsigned vp10k = DIV64_U64_ROUND_CLOSEST(
@@ -3010,7 +3010,6 @@ static bool ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
 			iocg->last_stat.wait_us,
 			iocg->last_stat.indebt_us,
 			iocg->last_stat.indelay_us);
-	return true;
 }
 
 static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,

block/blk-iolatency.c

@@ -891,7 +891,7 @@ static int iolatency_print_limit(struct seq_file *sf, void *v)
 	return 0;
 }
 
-static bool iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s)
+static void iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s)
 {
 	struct latency_stat stat;
 	int cpu;
@@ -914,17 +914,16 @@ static bool iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s)
 			(unsigned long long)stat.ps.missed,
 			(unsigned long long)stat.ps.total,
 			iolat->rq_depth.max_depth);
-	return true;
 }
 
-static bool iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
+static void iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
 {
 	struct iolatency_grp *iolat = pd_to_lat(pd);
 	unsigned long long avg_lat;
 	unsigned long long cur_win;
 
 	if (!blkcg_debug_stats)
-		return false;
+		return;
 
 	if (iolat->ssd)
 		return iolatency_ssd_stat(iolat, s);
@@ -937,7 +936,6 @@ static bool iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)
 	else
 		seq_printf(s, " depth=%u avg_lat=%llu win=%llu",
 			iolat->rq_depth.max_depth, avg_lat, cur_win);
-	return true;
 }
 
 static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp,