Merge tag 'for-linus-20181102' of git://git.kernel.dk/linux-block

Pull block layer fixes from Jens Axboe:
 "The biggest part of this pull request is the revert of the blkcg
  cleanup series. It had one fix earlier for a stacked device issue, but
  another one was reported. Rather than play whack-a-mole with this,
  revert the entire series and try again for the next kernel release.

  Apart from that, only small fixes/changes.

  Summary:

   - Indentation fixup for mtip32xx (Colin Ian King)

   - The blkcg cleanup series revert (Dennis Zhou)

   - Two NVMe fixes. One fixing a regression in the nvme request
     initialization in this merge window, causing nvme-fc to not work.
     The other is a suspend/resume p2p resource issue (James, Keith)

   - Fix sg discard merge, allowing us to merge in cases where we didn't
     before (Jianchao Wang)

   - Call rq_qos_exit() after the queue is frozen, preventing a hang
     (Ming)

   - Fix brd queue setup, fixing an oops if we fail setting up all
     devices (Ming)"

* tag 'for-linus-20181102' of git://git.kernel.dk/linux-block:
  nvme-pci: fix conflicting p2p resource adds
  nvme-fc: fix request private initialization
  blkcg: revert blkcg cleanups series
  block: brd: associate with queue until adding disk
  block: call rq_qos_exit() after queue is frozen
  mtip32xx: clean an indentation issue, remove extraneous tabs
  block: fix the DISCARD request merge

11 files changed, 166 insertions, 236 deletions

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index d9a7916ff0ab..9fe5952d117d 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -642,7 +642,7 @@ void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
 	uint64_t serial_nr;
 
 	rcu_read_lock();
-	serial_nr = __bio_blkcg(bio)->css.serial_nr;
+	serial_nr = bio_blkcg(bio)->css.serial_nr;
 
 	/*
 	 * Check whether blkcg has changed.  The condition may trigger
@@ -651,7 +651,7 @@ void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
 	if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr))
 		goto out;
 
-	bfqg = __bfq_bic_change_cgroup(bfqd, bic, __bio_blkcg(bio));
+	bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio));
 	/*
 	 * Update blkg_path for bfq_log_* functions. We cache this
 	 * path, and update it here, for the following
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 6075100f03a5..3a27d31fcda6 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4384,7 +4384,7 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
 
 	rcu_read_lock();
 
-	bfqg = bfq_find_set_group(bfqd, __bio_blkcg(bio));
+	bfqg = bfq_find_set_group(bfqd, bio_blkcg(bio));
 	if (!bfqg) {
 		bfqq = &bfqd->oom_bfqq;
 		goto out;
diff --git a/block/bio.c b/block/bio.c
index c27f77befbac..d5368a445561 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -609,9 +609,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
 	bio->bi_iter = bio_src->bi_iter;
 	bio->bi_io_vec = bio_src->bi_io_vec;
 
-	bio_clone_blkg_association(bio, bio_src);
-
-	blkcg_bio_issue_init(bio);
+	bio_clone_blkcg_association(bio, bio_src);
 }
 EXPORT_SYMBOL(__bio_clone_fast);
 
@@ -1956,151 +1954,69 @@ EXPORT_SYMBOL(bioset_init_from_src);
 
 #ifdef CONFIG_BLK_CGROUP
 
-/**
- * bio_associate_blkg - associate a bio with the a blkg
- * @bio: target bio
- * @blkg: the blkg to associate
- *
- * This tries to associate @bio with the specified blkg.  Association failure
- * is handled by walking up the blkg tree.  Therefore, the blkg associated can
- * be anything between @blkg and the root_blkg.  This situation only happens
- * when a cgroup is dying and then the remaining bios will spill to the closest
- * alive blkg.
- *
- * A reference will be taken on the @blkg and will be released when @bio is
- * freed.
- */
-int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
-{
-	if (unlikely(bio->bi_blkg))
-		return -EBUSY;
-	bio->bi_blkg = blkg_tryget_closest(blkg);
-	return 0;
-}
-
-/**
- * __bio_associate_blkg_from_css - internal blkg association function
- *
- * This in the core association function that all association paths rely on.
- * A blkg reference is taken which is released upon freeing of the bio.
- */
-static int __bio_associate_blkg_from_css(struct bio *bio,
-					 struct cgroup_subsys_state *css)
-{
-	struct request_queue *q = bio->bi_disk->queue;
-	struct blkcg_gq *blkg;
-	int ret;
-
-	rcu_read_lock();
-
-	if (!css || !css->parent)
-		blkg = q->root_blkg;
-	else
-		blkg = blkg_lookup_create(css_to_blkcg(css), q);
-
-	ret = bio_associate_blkg(bio, blkg);
-
-	rcu_read_unlock();
-	return ret;
-}
-
-/**
- * bio_associate_blkg_from_css - associate a bio with a specified css
- * @bio: target bio
- * @css: target css
- *
- * Associate @bio with the blkg found by combining the css's blkg and the
- * request_queue of the @bio.  This falls back to the queue's root_blkg if
- * the association fails with the css.
- */
-int bio_associate_blkg_from_css(struct bio *bio,
-				struct cgroup_subsys_state *css)
-{
-	if (unlikely(bio->bi_blkg))
-		return -EBUSY;
-	return __bio_associate_blkg_from_css(bio, css);
-}
-EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
-
 #ifdef CONFIG_MEMCG
 /**
- * bio_associate_blkg_from_page - associate a bio with the page's blkg
+ * bio_associate_blkcg_from_page - associate a bio with the page's blkcg
  * @bio: target bio
  * @page: the page to lookup the blkcg from
  *
- * Associate @bio with the blkg from @page's owning memcg and the respective
- * request_queue.  If cgroup_e_css returns NULL, fall back to the queue's
- * root_blkg.
- *
- * Note: this must be called after bio has an associated device.
+ * Associate @bio with the blkcg from @page's owning memcg.  This works like
+ * every other associate function wrt references.
  */
-int bio_associate_blkg_from_page(struct bio *bio, struct page *page)
+int bio_associate_blkcg_from_page(struct bio *bio, struct page *page)
 {
-	struct cgroup_subsys_state *css;
-	int ret;
+	struct cgroup_subsys_state *blkcg_css;
 
-	if (unlikely(bio->bi_blkg))
+	if (unlikely(bio->bi_css))
 		return -EBUSY;
 	if (!page->mem_cgroup)
 		return 0;
-
-	rcu_read_lock();
-
-	css = cgroup_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
-
-	ret = __bio_associate_blkg_from_css(bio, css);
-
-	rcu_read_unlock();
-	return ret;
+	blkcg_css = cgroup_get_e_css(page->mem_cgroup->css.cgroup,
+				     &io_cgrp_subsys);
+	bio->bi_css = blkcg_css;
+	return 0;
 }
 #endif /* CONFIG_MEMCG */
 
 /**
- * bio_associate_create_blkg - associate a bio with a blkg from q
- * @q: request_queue where bio is going
+ * bio_associate_blkcg - associate a bio with the specified blkcg
  * @bio: target bio
+ * @blkcg_css: css of the blkcg to associate
+ *
+ * Associate @bio with the blkcg specified by @blkcg_css.  Block layer will
+ * treat @bio as if it were issued by a task which belongs to the blkcg.
  *
- * Associate @bio with the blkg found from the bio's css and the request_queue.
- * If one is not found, bio_lookup_blkg creates the blkg.  This falls back to
- * the queue's root_blkg if association fails.
+ * This function takes an extra reference of @blkcg_css which will be put
+ * when @bio is released.  The caller must own @bio and is responsible for
+ * synchronizing calls to this function.
  */
-int bio_associate_create_blkg(struct request_queue *q, struct bio *bio)
+int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
 {
-	struct cgroup_subsys_state *css;
-	int ret = 0;
-
-	/* someone has already associated this bio with a blkg */
-	if (bio->bi_blkg)
-		return ret;
-
-	rcu_read_lock();
-
-	css = blkcg_css();
-
-	ret = __bio_associate_blkg_from_css(bio, css);
-
-	rcu_read_unlock();
-	return ret;
+	if (unlikely(bio->bi_css))
+		return -EBUSY;
+	css_get(blkcg_css);
+	bio->bi_css = blkcg_css;
+	return 0;
 }
+EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
- * bio_reassociate_blkg - reassociate a bio with a blkg from q
- * @q: request_queue where bio is going
+ * bio_associate_blkg - associate a bio with the specified blkg
  * @bio: target bio
+ * @blkg: the blkg to associate
  *
- * When submitting a bio, multiple recursive calls to make_request() may occur.
- * This causes the initial associate done in blkcg_bio_issue_check() to be
- * incorrect and reference the prior request_queue.  This performs reassociation
- * when this situation happens.
+ * Associate @bio with the blkg specified by @blkg.  This is the queue specific
+ * blkcg information associated with the @bio, a reference will be taken on the
+ * @blkg and will be freed when the bio is freed.
  */
-int bio_reassociate_blkg(struct request_queue *q, struct bio *bio)
+int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
 {
-	if (bio->bi_blkg) {
-		blkg_put(bio->bi_blkg);
-		bio->bi_blkg = NULL;
-	}
-
-	return bio_associate_create_blkg(q, bio);
+	if (unlikely(bio->bi_blkg))
+		return -EBUSY;
+	if (!blkg_try_get(blkg))
+		return -ENODEV;
+	bio->bi_blkg = blkg;
+	return 0;
 }
 
 /**
@@ -2113,6 +2029,10 @@ void bio_disassociate_task(struct bio *bio)
 		put_io_context(bio->bi_ioc);
 		bio->bi_ioc = NULL;
 	}
+	if (bio->bi_css) {
+		css_put(bio->bi_css);
+		bio->bi_css = NULL;
+	}
 	if (bio->bi_blkg) {
 		blkg_put(bio->bi_blkg);
 		bio->bi_blkg = NULL;
@@ -2120,16 +2040,16 @@ void bio_disassociate_task(struct bio *bio)
 }
 
 /**
- * bio_clone_blkg_association - clone blkg association from src to dst bio
+ * bio_clone_blkcg_association - clone blkcg association from src to dst bio
  * @dst: destination bio
  * @src: source bio
  */
-void bio_clone_blkg_association(struct bio *dst, struct bio *src)
+void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
 {
-	if (src->bi_blkg)
-		bio_associate_blkg(dst, src->bi_blkg);
+	if (src->bi_css)
+		WARN_ON(bio_associate_blkcg(dst, src->bi_css));
 }
-EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
+EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);
 #endif /* CONFIG_BLK_CGROUP */
 
 static void __init biovec_init_slabs(void)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 992da5592c6e..c630e02836a8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -84,37 +84,6 @@ static void blkg_free(struct blkcg_gq *blkg)
 	kfree(blkg);
 }
 
-static void __blkg_release(struct rcu_head *rcu)
-{
-	struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
-
-	percpu_ref_exit(&blkg->refcnt);
-
-	/* release the blkcg and parent blkg refs this blkg has been holding */
-	css_put(&blkg->blkcg->css);
-	if (blkg->parent)
-		blkg_put(blkg->parent);
-
-	wb_congested_put(blkg->wb_congested);
-
-	blkg_free(blkg);
-}
-
-/*
- * A group is RCU protected, but having an rcu lock does not mean that one
- * can access all the fields of blkg and assume these are valid.  For
- * example, don't try to follow throtl_data and request queue links.
- *
- * Having a reference to blkg under an rcu allows accesses to only values
- * local to groups like group stats and group rate limits.
- */
-static void blkg_release(struct percpu_ref *ref)
-{
-	struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
-
-	call_rcu(&blkg->rcu_head, __blkg_release);
-}
-
 /**
  * blkg_alloc - allocate a blkg
  * @blkcg: block cgroup the new blkg is associated with
@@ -141,6 +110,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 	blkg->q = q;
 	INIT_LIST_HEAD(&blkg->q_node);
 	blkg->blkcg = blkcg;
+	atomic_set(&blkg->refcnt, 1);
 
 	/* root blkg uses @q->root_rl, init rl only for !root blkgs */
 	if (blkcg != &blkcg_root) {
@@ -247,11 +217,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 		blkg_get(blkg->parent);
 	}
 
-	ret = percpu_ref_init(&blkg->refcnt, blkg_release, 0,
-			      GFP_NOWAIT | __GFP_NOWARN);
-	if (ret)
-		goto err_cancel_ref;
-
 	/* invoke per-policy init */
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
@@ -284,8 +249,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	blkg_put(blkg);
 	return ERR_PTR(ret);
 
-err_cancel_ref:
-	percpu_ref_exit(&blkg->refcnt);
 err_put_congested:
 	wb_congested_put(wb_congested);
 err_put_css:
@@ -296,7 +259,7 @@ err_free_blkg:
 }
 
 /**
- * __blkg_lookup_create - lookup blkg, try to create one if not there
+ * blkg_lookup_create - lookup blkg, try to create one if not there
  * @blkcg: blkcg of interest
  * @q: request_queue of interest
  *
@@ -305,11 +268,12 @@ err_free_blkg:
  * that all non-root blkg's have access to the parent blkg.  This function
  * should be called under RCU read lock and @q->queue_lock.
  *
- * Returns the blkg or the closest blkg if blkg_create fails as it walks
- * down from root.
+ * Returns pointer to the looked up or created blkg on success, ERR_PTR()
+ * value on error.  If @q is dead, returns ERR_PTR(-EINVAL).  If @q is not
+ * dead and bypassing, returns ERR_PTR(-EBUSY).
  */
-struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
-				      struct request_queue *q)
+struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+				    struct request_queue *q)
 {
 	struct blkcg_gq *blkg;
 
@@ -321,7 +285,7 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
 	 * we shouldn't allow anything to go through for a bypassing queue.
 	 */
 	if (unlikely(blk_queue_bypass(q)))
-		return q->root_blkg;
+		return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
 
 	blkg = __blkg_lookup(blkcg, q, true);
 	if (blkg)
@@ -329,58 +293,23 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
 
 	/*
 	 * Create blkgs walking down from blkcg_root to @blkcg, so that all
-	 * non-root blkgs have access to their parents.  Returns the closest
-	 * blkg to the intended blkg should blkg_create() fail.
+	 * non-root blkgs have access to their parents.
 	 */
 	while (true) {
 		struct blkcg *pos = blkcg;
 		struct blkcg *parent = blkcg_parent(blkcg);
-		struct blkcg_gq *ret_blkg = q->root_blkg;
-
-		while (parent) {
-			blkg = __blkg_lookup(parent, q, false);
-			if (blkg) {
-				/* remember closest blkg */
-				ret_blkg = blkg;
-				break;
-			}
+
+		while (parent && !__blkg_lookup(parent, q, false)) {
 			pos = parent;
 			parent = blkcg_parent(parent);
 		}
 
 		blkg = blkg_create(pos, q, NULL);
-		if (IS_ERR(blkg))
-			return ret_blkg;
-		if (pos == blkcg)
+		if (pos == blkcg || IS_ERR(blkg))
 			return blkg;
 	}
 }
 
-/**
- * blkg_lookup_create - find or create a blkg
- * @blkcg: target block cgroup
- * @q: target request_queue
- *
- * This looks up or creates the blkg representing the unique pair
- * of the blkcg and the request_queue.
- */
-struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
-				    struct request_queue *q)
-{
-	struct blkcg_gq *blkg = blkg_lookup(blkcg, q);
-	unsigned long flags;
-
-	if (unlikely(!blkg)) {
-		spin_lock_irqsave(q->queue_lock, flags);
-
-		blkg = __blkg_lookup_create(blkcg, q);
-
-		spin_unlock_irqrestore(q->queue_lock, flags);
-	}
-
-	return blkg;
-}
-
 static void blkg_destroy(struct blkcg_gq *blkg)
 {
 	struct blkcg *blkcg = blkg->blkcg;
@@ -424,7 +353,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 	 * Put the reference taken at the time of creation so that when all
 	 * queues are gone, group can be destroyed.
 	 */
-	percpu_ref_kill(&blkg->refcnt);
+	blkg_put(blkg);
 }
 
 /**
@@ -452,6 +381,29 @@ static void blkg_destroy_all(struct request_queue *q)
 }
 
 /*
+ * A group is RCU protected, but having an rcu lock does not mean that one
+ * can access all the fields of blkg and assume these are valid.  For
+ * example, don't try to follow throtl_data and request queue links.
+ *
+ * Having a reference to blkg under an rcu allows accesses to only values
+ * local to groups like group stats and group rate limits.
+ */
+void __blkg_release_rcu(struct rcu_head *rcu_head)
+{
+	struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
+
+	/* release the blkcg and parent blkg refs this blkg has been holding */
+	css_put(&blkg->blkcg->css);
+	if (blkg->parent)
+		blkg_put(blkg->parent);
+
+	wb_congested_put(blkg->wb_congested);
+
+	blkg_free(blkg);
+}
+EXPORT_SYMBOL_GPL(__blkg_release_rcu);
+
+/*
  * The next function used by blk_queue_for_each_rl().  It's a bit tricky
  * because the root blkg uses @q->root_rl instead of its own rl.
  */
@@ -1796,7 +1748,8 @@ void blkcg_maybe_throttle_current(void)
 	blkg = blkg_lookup(blkcg, q);
 	if (!blkg)
 		goto out;
-	if (!blkg_tryget(blkg))
+	blkg = blkg_try_get(blkg);
+	if (!blkg)
 		goto out;
 	rcu_read_unlock();
 
diff --git a/block/blk-core.c b/block/blk-core.c
index bc6ea87d10e0..ce12515f9b9b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -785,6 +785,9 @@ void blk_cleanup_queue(struct request_queue *q)
 	 * prevent that q->request_fn() gets invoked after draining finished.
 	 */
 	blk_freeze_queue(q);
+
+	rq_qos_exit(q);
+
 	spin_lock_irq(lock);
 	queue_flag_set(QUEUE_FLAG_DEAD, q);
 	spin_unlock_irq(lock);
@@ -2432,7 +2435,6 @@ blk_qc_t generic_make_request(struct bio *bio)
 			if (q)
 				blk_queue_exit(q);
 			q = bio->bi_disk->queue;
-			bio_reassociate_blkg(q, bio);
 			flags = 0;
 			if (bio->bi_opf & REQ_NOWAIT)
 				flags = BLK_MQ_REQ_NOWAIT;
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 28f80d227528..38c35c32aff2 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -482,12 +482,34 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio,
 				     spinlock_t *lock)
 {
 	struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
-	struct blkcg_gq *blkg = bio->bi_blkg;
+	struct blkcg *blkcg;
+	struct blkcg_gq *blkg;
+	struct request_queue *q = rqos->q;
 	bool issue_as_root = bio_issue_as_root_blkg(bio);
 
 	if (!blk_iolatency_enabled(blkiolat))
 		return;
 
+	rcu_read_lock();
+	blkcg = bio_blkcg(bio);
+	bio_associate_blkcg(bio, &blkcg->css);
+	blkg = blkg_lookup(blkcg, q);
+	if (unlikely(!blkg)) {
+		if (!lock)
+			spin_lock_irq(q->queue_lock);
+		blkg = blkg_lookup_create(blkcg, q);
+		if (IS_ERR(blkg))
+			blkg = NULL;
+		if (!lock)
+			spin_unlock_irq(q->queue_lock);
+	}
+	if (!blkg)
+		goto out;
+
+	bio_issue_init(&bio->bi_issue, bio_sectors(bio));
+	bio_associate_blkg(bio, blkg);
+out:
+	rcu_read_unlock();
 	while (blkg && blkg->parent) {
 		struct iolatency_grp *iolat = blkg_to_lat(blkg);
 		if (!iolat) {
@@ -708,7 +730,7 @@ static void blkiolatency_timer_fn(struct timer_list *t)
 		 * We could be exiting, don't access the pd unless we have a
 		 * ref on the blkg.
 		 */
-		if (!blkg_tryget(blkg))
+		if (!blkg_try_get(blkg))
 			continue;
 
 		iolat = blkg_to_lat(blkg);
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 42a46744c11b..6b5ad275ed56 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -714,6 +714,31 @@ static void blk_account_io_merge(struct request *req)
 		part_stat_unlock();
 	}
 }
+/*
+ * Two cases of handling DISCARD merge:
+ * If max_discard_segments > 1, the driver takes every bio
+ * as a range and send them to controller together. The ranges
+ * needn't to be contiguous.
+ * Otherwise, the bios/requests will be handled as same as
+ * others which should be contiguous.
+ */
+static inline bool blk_discard_mergable(struct request *req)
+{
+	if (req_op(req) == REQ_OP_DISCARD &&
+	    queue_max_discard_segments(req->q) > 1)
+		return true;
+	return false;
+}
+
+enum elv_merge blk_try_req_merge(struct request *req, struct request *next)
+{
+	if (blk_discard_mergable(req))
+		return ELEVATOR_DISCARD_MERGE;
+	else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
+		return ELEVATOR_BACK_MERGE;
+
+	return ELEVATOR_NO_MERGE;
+}
 
 /*
  * For non-mq, this has to be called with the request spinlock acquired.
@@ -731,12 +756,6 @@ static struct request *attempt_merge(struct request_queue *q,
 	if (req_op(req) != req_op(next))
 		return NULL;
 
-	/*
-	 * not contiguous
-	 */
-	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
-		return NULL;
-
 	if (rq_data_dir(req) != rq_data_dir(next)
 	    || req->rq_disk != next->rq_disk
 	    || req_no_special_merge(next))
@@ -760,11 +779,19 @@ static struct request *attempt_merge(struct request_queue *q,
 	 * counts here. Handle DISCARDs separately, as they
 	 * have separate settings.
 	 */
-	if (req_op(req) == REQ_OP_DISCARD) {
+
+	switch (blk_try_req_merge(req, next)) {
+	case ELEVATOR_DISCARD_MERGE:
 		if (!req_attempt_discard_merge(q, req, next))
 			return NULL;
-	} else if (!ll_merge_requests_fn(q, req, next))
+		break;
+	case ELEVATOR_BACK_MERGE:
+		if (!ll_merge_requests_fn(q, req, next))
+			return NULL;
+		break;
+	default:
 		return NULL;
+	}
 
 	/*
 	 * If failfast settings disagree or any of the two is already
@@ -888,8 +915,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 
 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 {
-	if (req_op(rq) == REQ_OP_DISCARD &&
-	    queue_max_discard_segments(rq->q) > 1)
+	if (blk_discard_mergable(rq))
 		return ELEVATOR_DISCARD_MERGE;
 	else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 		return ELEVATOR_BACK_MERGE;
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 0641533597f1..844a454a7b3a 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -1007,8 +1007,6 @@ void blk_unregister_queue(struct gendisk *disk)
 	kobject_del(&q->kobj);
 	blk_trace_remove_sysfs(disk_to_dev(disk));
 
-	rq_qos_exit(q);
-
 	mutex_lock(&q->sysfs_lock);
 	if (q->request_fn || (q->mq_ops && q->elevator))
 		elv_unregister_queue(q);
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 4bda70e8db48..db1a3a2ae006 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2115,11 +2115,21 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
 }
 #endif
 
+static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
+{
+#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
+	/* fallback to root_blkg if we fail to get a blkg ref */
+	if (bio->bi_css && (bio_associate_blkg(bio, tg_to_blkg(tg)) == -ENODEV))
+		bio_associate_blkg(bio, bio->bi_disk->queue->root_blkg);
+	bio_issue_init(&bio->bi_issue, bio_sectors(bio));
+#endif
+}
+
 bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
 		    struct bio *bio)
 {
 	struct throtl_qnode *qn = NULL;
-	struct throtl_grp *tg = blkg_to_tg(blkg);
+	struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
 	struct throtl_service_queue *sq;
 	bool rw = bio_data_dir(bio);
 	bool throttled = false;
@@ -2138,6 +2148,7 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
 	if (unlikely(blk_queue_bypass(q)))
 		goto out_unlock;
 
+	blk_throtl_assoc_bio(tg, bio);
 	blk_throtl_update_idletime(tg);
 
 	sq = &tg->service_queue;
diff --git a/block/bounce.c b/block/bounce.c
index cf49fe02f65c..36869afc258c 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -276,9 +276,7 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
 		}
 	}
 
-	bio_clone_blkg_association(bio, bio_src);
-
-	blkcg_bio_issue_init(bio);
+	bio_clone_blkcg_association(bio, bio_src);
 
 	return bio;
 }
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 6a3d87dd3c1a..ed41aa978c4a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3759,7 +3759,7 @@ static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
 	uint64_t serial_nr;
 
 	rcu_read_lock();
-	serial_nr = __bio_blkcg(bio)->css.serial_nr;
+	serial_nr = bio_blkcg(bio)->css.serial_nr;
 	rcu_read_unlock();
 
 	/*
@@ -3824,7 +3824,7 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
 	struct cfq_group *cfqg;
 
 	rcu_read_lock();
-	cfqg = cfq_lookup_cfqg(cfqd, __bio_blkcg(bio));
+	cfqg = cfq_lookup_cfqg(cfqd, bio_blkcg(bio));
 	if (!cfqg) {
 		cfqq = &cfqd->oom_cfqq;
 		goto out;