blk-cgroup: refactor blkcg_print_stat

Factor out a helper to deal with a single blkcg_gq to make the code a
little bit easier to follow.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210810152623.1796144-1-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

@@ -870,36 +870,23 @@ static void blkcg_fill_root_iostats(void)
 	}
 }
 
-static int blkcg_print_stat(struct seq_file *sf, void *v)
+static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
 {
-	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
-	struct blkcg_gq *blkg;
-
-	if (!seq_css(sf)->parent)
-		blkcg_fill_root_iostats();
-	else
-		cgroup_rstat_flush(blkcg->css.cgroup);
-
-	rcu_read_lock();
-
-	hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
 	struct blkg_iostat_set *bis = &blkg->iostat;
-		const char *dname;
-		char *buf;
 	u64 rbytes, wbytes, rios, wios, dbytes, dios;
-		size_t size = seq_get_buf(sf, &buf), off = 0;
-		int i;
 	bool has_stats = false;
+	const char *dname;
 	unsigned seq;
-
-		spin_lock_irq(&blkg->q->queue_lock);
+	char *buf;
+	size_t size = seq_get_buf(s, &buf), off = 0;
+	int i;
 
 	if (!blkg->online)
-			goto skip;
+		return;
 
 	dname = blkg_dev_name(blkg);
 	if (!dname)
-			goto skip;
+		return;
 
 	/*
 	 * Hooray string manipulation, count is the size written NOT
@@ -930,10 +917,9 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 
 	if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
 		has_stats = true;
-			off += scnprintf(buf+off, size-off,
-					 " use_delay=%d delay_nsec=%llu",
+		off += scnprintf(buf+off, size-off, " use_delay=%d delay_nsec=%llu",
 			atomic_read(&blkg->use_delay),
-					(unsigned long long)atomic64_read(&blkg->delay_nsec));
+			atomic64_read(&blkg->delay_nsec));
 	}
 
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
@@ -952,15 +938,29 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 	if (has_stats) {
 		if (off < size - 1) {
 			off += scnprintf(buf+off, size-off, "\n");
-				seq_commit(sf, off);
+			seq_commit(s, off);
 		} else {
-				seq_commit(sf, -1);
+			seq_commit(s, -1);
 		}
 	}
-	skip:
+}
+
+static int blkcg_print_stat(struct seq_file *sf, void *v)
+{
+	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
+	struct blkcg_gq *blkg;
+
+	if (!seq_css(sf)->parent)
+		blkcg_fill_root_iostats();
+	else
+		cgroup_rstat_flush(blkcg->css.cgroup);
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
+		spin_lock_irq(&blkg->q->queue_lock);
+		blkcg_print_one_stat(blkg, sf);
 		spin_unlock_irq(&blkg->q->queue_lock);
 	}
-
 	rcu_read_unlock();
 	return 0;
 }