1 files changed, 126 insertions, 42 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8dfe62786cd5..40161a3f68d0 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -59,6 +59,23 @@ static struct workqueue_struct *blkcg_punt_bio_wq;
 
 #define BLKG_DESTROY_BATCH_SIZE  64
 
+/**
+ * blkcg_css - find the current css
+ *
+ * Find the css associated with either the kthread or the current task.
+ * This may return a dying css, so it is up to the caller to use tryget logic
+ * to confirm it is alive and well.
+ */
+static struct cgroup_subsys_state *blkcg_css(void)
+{
+	struct cgroup_subsys_state *css;
+
+	css = kthread_blkcg();
+	if (css)
+		return css;
+	return task_css(current, io_cgrp_id);
+}
+
 static bool blkcg_policy_enabled(struct request_queue *q,
 				 const struct blkcg_policy *pol)
 {
@@ -156,6 +173,33 @@ static void blkg_async_bio_workfn(struct work_struct *work)
 }
 
 /**
+ * bio_blkcg_css - return the blkcg CSS associated with a bio
+ * @bio: target bio
+ *
+ * This returns the CSS for the blkcg associated with a bio, or %NULL if not
+ * associated. Callers are expected to either handle %NULL or know association
+ * has been done prior to calling this.
+ */
+struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
+{
+	if (!bio || !bio->bi_blkg)
+		return NULL;
+	return &bio->bi_blkg->blkcg->css;
+}
+EXPORT_SYMBOL_GPL(bio_blkcg_css);
+
+/**
+ * blkcg_parent - get the parent of a blkcg
+ * @blkcg: blkcg of interest
+ *
+ * Return the parent blkcg of @blkcg.  Can be called anytime.
+ */
+static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
+{
+	return css_to_blkcg(blkcg->css.parent);
+}
+
+/**
  * blkg_alloc - allocate a blkg
  * @blkcg: block cgroup the new blkg is associated with
  * @q: request_queue the new blkg is associated with
@@ -254,7 +298,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	struct blkcg_gq *blkg;
 	int i, ret;
 
-	WARN_ON_ONCE(!rcu_read_lock_held());
 	lockdep_assert_held(&q->queue_lock);
 
 	/* request_queue is dying, do not create/recreate a blkg */
@@ -905,7 +948,6 @@ 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;
@@ -931,14 +973,12 @@ 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));
@@ -950,12 +990,10 @@ 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)
@@ -994,6 +1032,13 @@ static struct cftype blkcg_legacy_files[] = {
 	{ }	/* terminate */
 };
 
+#ifdef CONFIG_CGROUP_WRITEBACK
+struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css)
+{
+	return &css_to_blkcg(css)->cgwb_list;
+}
+#endif
+
 /*
  * blkcg destruction is a three-stage process.
  *
@@ -1016,25 +1061,6 @@ static struct cftype blkcg_legacy_files[] = {
  */
 
 /**
- * blkcg_css_offline - cgroup css_offline callback
- * @css: css of interest
- *
- * This function is called when @css is about to go away.  Here the cgwbs are
- * offlined first and only once writeback associated with the blkcg has
- * finished do we start step 2 (see above).
- */
-static void blkcg_css_offline(struct cgroup_subsys_state *css)
-{
-	struct blkcg *blkcg = css_to_blkcg(css);
-
-	/* this prevents anyone from attaching or migrating to this blkcg */
-	wb_blkcg_offline(blkcg);
-
-	/* put the base online pin allowing step 2 to be triggered */
-	blkcg_unpin_online(blkcg);
-}
-
-/**
  * blkcg_destroy_blkgs - responsible for shooting down blkgs
  * @blkcg: blkcg of interest
  *
@@ -1045,7 +1071,7 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
  *
  * This is the blkcg counterpart of ioc_release_fn().
  */
-void blkcg_destroy_blkgs(struct blkcg *blkcg)
+static void blkcg_destroy_blkgs(struct blkcg *blkcg)
 {
 	might_sleep();
 
@@ -1075,6 +1101,57 @@ void blkcg_destroy_blkgs(struct blkcg *blkcg)
 	spin_unlock_irq(&blkcg->lock);
 }
 
+/**
+ * blkcg_pin_online - pin online state
+ * @blkcg_css: blkcg of interest
+ *
+ * While pinned, a blkcg is kept online.  This is primarily used to
+ * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
+ * while an associated cgwb is still active.
+ */
+void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css)
+{
+	refcount_inc(&css_to_blkcg(blkcg_css)->online_pin);
+}
+
+/**
+ * blkcg_unpin_online - unpin online state
+ * @blkcg_css: blkcg of interest
+ *
+ * This is primarily used to impedance-match blkg and cgwb lifetimes so
+ * that blkg doesn't go offline while an associated cgwb is still active.
+ * When this count goes to zero, all active cgwbs have finished so the
+ * blkcg can continue destruction by calling blkcg_destroy_blkgs().
+ */
+void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css)
+{
+	struct blkcg *blkcg = css_to_blkcg(blkcg_css);
+
+	do {
+		if (!refcount_dec_and_test(&blkcg->online_pin))
+			break;
+		blkcg_destroy_blkgs(blkcg);
+		blkcg = blkcg_parent(blkcg);
+	} while (blkcg);
+}
+
+/**
+ * blkcg_css_offline - cgroup css_offline callback
+ * @css: css of interest
+ *
+ * This function is called when @css is about to go away.  Here the cgwbs are
+ * offlined first and only once writeback associated with the blkcg has
+ * finished do we start step 2 (see above).
+ */
+static void blkcg_css_offline(struct cgroup_subsys_state *css)
+{
+	/* this prevents anyone from attaching or migrating to this blkcg */
+	wb_blkcg_offline(css);
+
+	/* put the base online pin allowing step 2 to be triggered */
+	blkcg_unpin_online(css);
+}
+
 static void blkcg_css_free(struct cgroup_subsys_state *css)
 {
 	struct blkcg *blkcg = css_to_blkcg(css);
@@ -1163,8 +1240,7 @@ unlock:
 
 static int blkcg_css_online(struct cgroup_subsys_state *css)
 {
-	struct blkcg *blkcg = css_to_blkcg(css);
-	struct blkcg *parent = blkcg_parent(blkcg);
+	struct blkcg *parent = blkcg_parent(css_to_blkcg(css));
 
 	/*
 	 * blkcg_pin_online() is used to delay blkcg offline so that blkgs
@@ -1172,7 +1248,7 @@ static int blkcg_css_online(struct cgroup_subsys_state *css)
 	 * parent so that offline always happens towards the root.
 	 */
 	if (parent)
-		blkcg_pin_online(parent);
+		blkcg_pin_online(css);
 	return 0;
 }
 
@@ -1201,14 +1277,13 @@ int blkcg_init_queue(struct request_queue *q)
 	preloaded = !radix_tree_preload(GFP_KERNEL);
 
 	/* Make sure the root blkg exists. */
-	rcu_read_lock();
+	/* spin_lock_irq can serve as RCU read-side critical section. */
 	spin_lock_irq(&q->queue_lock);
 	blkg = blkg_create(&blkcg_root, q, new_blkg);
 	if (IS_ERR(blkg))
 		goto err_unlock;
 	q->root_blkg = blkg;
 	spin_unlock_irq(&q->queue_lock);
-	rcu_read_unlock();
 
 	if (preloaded)
 		radix_tree_preload_end();
@@ -1234,7 +1309,6 @@ err_destroy_all:
 	return ret;
 err_unlock:
 	spin_unlock_irq(&q->queue_lock);
-	rcu_read_unlock();
 	if (preloaded)
 		radix_tree_preload_end();
 	return PTR_ERR(blkg);
@@ -1726,7 +1800,6 @@ static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
 void blkcg_maybe_throttle_current(void)
 {
 	struct request_queue *q = current->throttle_queue;
-	struct cgroup_subsys_state *css;
 	struct blkcg *blkcg;
 	struct blkcg_gq *blkg;
 	bool use_memdelay = current->use_memdelay;
@@ -1738,12 +1811,7 @@ void blkcg_maybe_throttle_current(void)
 	current->use_memdelay = false;
 
 	rcu_read_lock();
-	css = kthread_blkcg();
-	if (css)
-		blkcg = css_to_blkcg(css);
-	else
-		blkcg = css_to_blkcg(task_css(current, io_cgrp_id));
-
+	blkcg = css_to_blkcg(blkcg_css());
 	if (!blkcg)
 		goto out;
 	blkg = blkg_lookup(blkcg, q);
@@ -1889,7 +1957,7 @@ void bio_associate_blkg(struct bio *bio)
 	rcu_read_lock();
 
 	if (bio->bi_blkg)
-		css = &bio_blkcg(bio)->css;
+		css = bio_blkcg_css(bio);
 	else
 		css = blkcg_css();
 
@@ -1950,6 +2018,22 @@ void blk_cgroup_bio_start(struct bio *bio)
 	put_cpu();
 }
 
+bool blk_cgroup_congested(void)
+{
+	struct cgroup_subsys_state *css;
+	bool ret = false;
+
+	rcu_read_lock();
+	for (css = blkcg_css(); css; css = css->parent) {
+		if (atomic_read(&css->cgroup->congestion_count)) {
+			ret = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
 static int __init blkcg_init(void)
 {
 	blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",