for-linus-20190726

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Merge tag 'for-linus-20190726' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:

 - Several io_uring fixes/improvements:
     - Blocking fix for O_DIRECT (me)
     - Latter page slowness for registered buffers (me)
     - Fix poll hang under certain conditions (me)
     - Defer sequence check fix for wrapped rings (Zhengyuan)
     - Mismatch in async inc/dec accounting (Zhengyuan)
     - Memory ordering issue that could cause stall (Zhengyuan)
      - Track sequential defer in bytes, not pages (Zhengyuan)

 - NVMe pull request from Christoph

 - Set of hang fixes for wbt (Josef)

 - Redundant error message kill for libahci (Ding)

 - Remove unused blk_mq_sched_started_request() and related ops (Marcos)

 - drbd dynamic alloc shash descriptor to reduce stack use (Arnd)

 - blkcg ->pd_stat() non-debug print (Tejun)

 - bcache memory leak fix (Wei)

 - Comment fix (Akinobu)

 - BFQ perf regression fix (Paolo)

* tag 'for-linus-20190726' of git://git.kernel.dk/linux-block: (24 commits)
  io_uring: ensure ->list is initialized for poll commands
  Revert "nvme-pci: don't create a read hctx mapping without read queues"
  nvme: fix multipath crash when ANA is deactivated
  nvme: fix memory leak caused by incorrect subsystem free
  nvme: ignore subnqn for ADATA SX6000LNP
  drbd: dynamically allocate shash descriptor
  block: blk-mq: Remove blk_mq_sched_started_request and started_request
  bcache: fix possible memory leak in bch_cached_dev_run()
  io_uring: track io length in async_list based on bytes
  io_uring: don't use iov_iter_advance() for fixed buffers
  block: properly handle IOCB_NOWAIT for async O_DIRECT IO
  blk-mq: allow REQ_NOWAIT to return an error inline
  io_uring: add a memory barrier before atomic_read
  rq-qos: use a mb for got_token
  rq-qos: set ourself TASK_UNINTERRUPTIBLE after we schedule
  rq-qos: don't reset has_sleepers on spurious wakeups
  rq-qos: fix missed wake-ups in rq_qos_throttle
  wait: add wq_has_single_sleeper helper
  block, bfq: check also in-flight I/O in dispatch plugging
  block: fix sysfs module parameters directory path in comment
  ...

block/bfq-iosched.c

@@ -3354,38 +3354,57 @@ static void bfq_dispatch_remove(struct request_queue *q, struct request *rq)
  * there is no active group, then the primary expectation for
  * this device is probably a high throughput.
  *
- * We are now left only with explaining the additional
+ * We are now left only with explaining the two sub-conditions in the
- * compound condition that is checked below for deciding
+ * additional compound condition that is checked below for deciding
- * whether the scenario is asymmetric. To explain this
+ * whether the scenario is asymmetric. To explain the first
- * compound condition, we need to add that the function
+ * sub-condition, we need to add that the function
  * bfq_asymmetric_scenario checks the weights of only
- * non-weight-raised queues, for efficiency reasons (see
+ * non-weight-raised queues, for efficiency reasons (see comments on
- * comments on bfq_weights_tree_add()). Then the fact that
+ * bfq_weights_tree_add()). Then the fact that bfqq is weight-raised
- * bfqq is weight-raised is checked explicitly here. More
+ * is checked explicitly here. More precisely, the compound condition
- * precisely, the compound condition below takes into account
+ * below takes into account also the fact that, even if bfqq is being
- * also the fact that, even if bfqq is being weight-raised,
+ * weight-raised, the scenario is still symmetric if all queues with
- * the scenario is still symmetric if all queues with requests
+ * requests waiting for completion happen to be
- * waiting for completion happen to be
+ * weight-raised. Actually, we should be even more precise here, and
- * weight-raised. Actually, we should be even more precise
+ * differentiate between interactive weight raising and soft real-time
- * here, and differentiate between interactive weight raising
+ * weight raising.
- * and soft real-time weight raising.
+ *
+ * The second sub-condition checked in the compound condition is
+ * whether there is a fair amount of already in-flight I/O not
+ * belonging to bfqq. If so, I/O dispatching is to be plugged, for the
+ * following reason. The drive may decide to serve in-flight
+ * non-bfqq's I/O requests before bfqq's ones, thereby delaying the
+ * arrival of new I/O requests for bfqq (recall that bfqq is sync). If
+ * I/O-dispatching is not plugged, then, while bfqq remains empty, a
+ * basically uncontrolled amount of I/O from other queues may be
+ * dispatched too, possibly causing the service of bfqq's I/O to be
+ * delayed even longer in the drive. This problem gets more and more
+ * serious as the speed and the queue depth of the drive grow,
+ * because, as these two quantities grow, the probability to find no
+ * queue busy but many requests in flight grows too. By contrast,
+ * plugging I/O dispatching minimizes the delay induced by already
+ * in-flight I/O, and enables bfqq to recover the bandwidth it may
+ * lose because of this delay.
  *
  * As a side note, it is worth considering that the above
- * device-idling countermeasures may however fail in the
+ * device-idling countermeasures may however fail in the following
- * following unlucky scenario: if idling is (correctly)
+ * unlucky scenario: if I/O-dispatch plugging is (correctly) disabled
- * disabled in a time period during which all symmetry
+ * in a time period during which all symmetry sub-conditions hold, and
- * sub-conditions hold, and hence the device is allowed to
+ * therefore the device is allowed to enqueue many requests, but at
- * enqueue many requests, but at some later point in time some
+ * some later point in time some sub-condition stops to hold, then it
- * sub-condition stops to hold, then it may become impossible
+ * may become impossible to make requests be served in the desired
- * to let requests be served in the desired order until all
+ * order until all the requests already queued in the device have been
- * the requests already queued in the device have been served.
+ * served. The last sub-condition commented above somewhat mitigates
+ * this problem for weight-raised queues.
  */
 static bool idling_needed_for_service_guarantees(struct bfq_data *bfqd,
 						 struct bfq_queue *bfqq)
 {
 	return (bfqq->wr_coeff > 1 &&
-		bfqd->wr_busy_queues <
+		(bfqd->wr_busy_queues <
-		bfq_tot_busy_queues(bfqd)) ||
+		 bfq_tot_busy_queues(bfqd) ||
+		 bfqd->rq_in_driver >=
+		 bfqq->dispatched + 4)) ||
 		bfq_asymmetric_scenario(bfqd, bfqq);
 }
 

block/blk-cgroup.c

@@ -54,7 +54,7 @@ static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
 
 static LIST_HEAD(all_blkcgs);		/* protected by blkcg_pol_mutex */
 
-static bool blkcg_debug_stats = false;
+bool blkcg_debug_stats = false;
 static struct workqueue_struct *blkcg_punt_bio_wq;
 
 static bool blkcg_policy_enabled(struct request_queue *q,
@@ -944,10 +944,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 					 dbytes, dios);
 		}
 
-		if (!blkcg_debug_stats)
+		if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
-			goto next;
-
-		if (atomic_read(&blkg->use_delay)) {
 			has_stats = true;
 			off += scnprintf(buf+off, size-off,
 					 " use_delay=%d delay_nsec=%llu",
@@ -967,7 +964,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 				has_stats = true;
 			off += written;
 		}
-next:
+
 		if (has_stats) {
 			if (off < size - 1) {
 				off += scnprintf(buf+off, size-off, "\n");

block/blk-iolatency.c

@@ -917,6 +917,9 @@ static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf,
 	unsigned long long avg_lat;
 	unsigned long long cur_win;
 
+	if (!blkcg_debug_stats)
+		return 0;
+
 	if (iolat->ssd)
 		return iolatency_ssd_stat(iolat, buf, size);
 

block/blk-mq-sched.h

@@ -61,15 +61,6 @@ static inline void blk_mq_sched_completed_request(struct request *rq, u64 now)
 		e->type->ops.completed_request(rq, now);
 }
 
-static inline void blk_mq_sched_started_request(struct request *rq)
-{
-	struct request_queue *q = rq->q;
-	struct elevator_queue *e = q->elevator;
-
-	if (e && e->type->ops.started_request)
-		e->type->ops.started_request(rq);
-}
-
 static inline void blk_mq_sched_requeue_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;

block/blk-mq.c

@@ -669,8 +669,6 @@ void blk_mq_start_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;
 
-	blk_mq_sched_started_request(rq);
-
 	trace_block_rq_issue(q, rq);
 
 	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
@@ -1960,9 +1958,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 	rq = blk_mq_get_request(q, bio, &data);
 	if (unlikely(!rq)) {
 		rq_qos_cleanup(q, bio);
-		if (bio->bi_opf & REQ_NOWAIT)
+
+		cookie = BLK_QC_T_NONE;
+		if (bio->bi_opf & REQ_NOWAIT_INLINE)
+			cookie = BLK_QC_T_EAGAIN;
+		else if (bio->bi_opf & REQ_NOWAIT)
 			bio_wouldblock_error(bio);
-		return BLK_QC_T_NONE;
+		return cookie;
 	}
 
 	trace_block_getrq(q, bio, bio->bi_opf);

block/blk-rq-qos.c

@@ -202,6 +202,7 @@ static int rq_qos_wake_function(struct wait_queue_entry *curr,
 		return -1;
 
 	data->got_token = true;
+	smp_wmb();
 	list_del_init(&curr->entry);
 	wake_up_process(data->task);
 	return 1;
@@ -244,7 +245,9 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,
 		return;
 
 	prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE);
+	has_sleeper = !wq_has_single_sleeper(&rqw->wait);
 	do {
+		/* The memory barrier in set_task_state saves us here. */
 		if (data.got_token)
 			break;
 		if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
@@ -255,12 +258,14 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,
 			 * which means we now have two. Put our local token
 			 * and wake anyone else potentially waiting for one.
 			 */
+			smp_rmb();
 			if (data.got_token)
 				cleanup_cb(rqw, private_data);
 			break;
 		}
 		io_schedule();
-		has_sleeper = false;
+		has_sleeper = true;
+		set_current_state(TASK_UNINTERRUPTIBLE);
 	} while (1);
 	finish_wait(&rqw->wait, &data.wq);
 }

block/genhd.c

@@ -1969,7 +1969,7 @@ static const struct attribute *disk_events_attrs[] = {
  * The default polling interval can be specified by the kernel
  * parameter block.events_dfl_poll_msecs which defaults to 0
  * (disable).  This can also be modified runtime by writing to
- * /sys/module/block/events_dfl_poll_msecs.
+ * /sys/module/block/parameters/events_dfl_poll_msecs.
  */
 static int disk_events_set_dfl_poll_msecs(const char *val,
 					  const struct kernel_param *kp)

drivers/ata/libahci_platform.c

@@ -408,7 +408,6 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
 	hpriv->mmio = devm_ioremap_resource(dev,
 			      platform_get_resource(pdev, IORESOURCE_MEM, 0));
 	if (IS_ERR(hpriv->mmio)) {
-		dev_err(dev, "no mmio space\n");
 		rc = PTR_ERR(hpriv->mmio);
 		goto err_out;
 	}

drivers/block/drbd/drbd_receiver.c

@@ -5417,7 +5417,7 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	unsigned int key_len;
 	char secret[SHARED_SECRET_MAX]; /* 64 byte */
 	unsigned int resp_size;
-	SHASH_DESC_ON_STACK(desc, connection->cram_hmac_tfm);
+	struct shash_desc *desc;
 	struct packet_info pi;
 	struct net_conf *nc;
 	int err, rv;
@@ -5430,6 +5430,13 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	memcpy(secret, nc->shared_secret, key_len);
 	rcu_read_unlock();
 
+	desc = kmalloc(sizeof(struct shash_desc) +
+		       crypto_shash_descsize(connection->cram_hmac_tfm),
+		       GFP_KERNEL);
+	if (!desc) {
+		rv = -1;
+		goto fail;
+	}
 	desc->tfm = connection->cram_hmac_tfm;
 
 	rv = crypto_shash_setkey(connection->cram_hmac_tfm, (u8 *)secret, key_len);
@@ -5571,7 +5578,10 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	kfree(peers_ch);
 	kfree(response);
 	kfree(right_response);
-	shash_desc_zero(desc);
+	if (desc) {
+		shash_desc_zero(desc);
+		kfree(desc);
+	}
 
 	return rv;
 }

drivers/md/bcache/super.c

@@ -931,6 +931,9 @@ int bch_cached_dev_run(struct cached_dev *dc)
 	if (dc->io_disable) {
 		pr_err("I/O disabled on cached dev %s",
 		       dc->backing_dev_name);
+		kfree(env[1]);
+		kfree(env[2]);
+		kfree(buf);
 		return -EIO;
 	}
 

drivers/nvme/host/core.c

@@ -2311,15 +2311,13 @@ static void nvme_init_subnqn(struct nvme_subsystem *subsys, struct nvme_ctrl *ct
 	memset(subsys->subnqn + off, 0, sizeof(subsys->subnqn) - off);
 }
 
-static void __nvme_release_subsystem(struct nvme_subsystem *subsys)
-{
-	ida_simple_remove(&nvme_subsystems_ida, subsys->instance);
-	kfree(subsys);
-}
-
 static void nvme_release_subsystem(struct device *dev)
 {
-	__nvme_release_subsystem(container_of(dev, struct nvme_subsystem, dev));
+	struct nvme_subsystem *subsys =
+		container_of(dev, struct nvme_subsystem, dev);
+
+	ida_simple_remove(&nvme_subsystems_ida, subsys->instance);
+	kfree(subsys);
 }
 
 static void nvme_destroy_subsystem(struct kref *ref)
@@ -2477,7 +2475,7 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 	mutex_lock(&nvme_subsystems_lock);
 	found = __nvme_find_get_subsystem(subsys->subnqn);
 	if (found) {
-		__nvme_release_subsystem(subsys);
+		put_device(&subsys->dev);
 		subsys = found;
 
 		if (!nvme_validate_cntlid(subsys, ctrl, id)) {

drivers/nvme/host/multipath.c

@@ -12,11 +12,6 @@ module_param(multipath, bool, 0444);
 MODULE_PARM_DESC(multipath,
 	"turn on native support for multiple controllers per subsystem");
 
-inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
-{
-	return multipath && ctrl->subsys && (ctrl->subsys->cmic & (1 << 3));
-}
-
 /*
  * If multipathing is enabled we need to always use the subsystem instance
  * number for numbering our devices to avoid conflicts between subsystems that
@@ -622,7 +617,8 @@ int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 {
 	int error;
 
-	if (!nvme_ctrl_use_ana(ctrl))
+	/* check if multipath is enabled and we have the capability */
+	if (!multipath || !ctrl->subsys || !(ctrl->subsys->cmic & (1 << 3)))
 		return 0;
 
 	ctrl->anacap = id->anacap;

drivers/nvme/host/nvme.h

@@ -485,7 +485,11 @@ extern const struct attribute_group *nvme_ns_id_attr_groups[];
 extern const struct block_device_operations nvme_ns_head_ops;
 
 #ifdef CONFIG_NVME_MULTIPATH
-bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl);
+static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
+{
+	return ctrl->ana_log_buf != NULL;
+}
+
 void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
 			struct nvme_ctrl *ctrl, int *flags);
 void nvme_failover_req(struct request *req);

drivers/nvme/host/pci.c

@@ -2254,9 +2254,7 @@ static int nvme_dev_add(struct nvme_dev *dev)
 	if (!dev->ctrl.tagset) {
 		dev->tagset.ops = &nvme_mq_ops;
 		dev->tagset.nr_hw_queues = dev->online_queues - 1;
-		dev->tagset.nr_maps = 1; /* default */
+		dev->tagset.nr_maps = 2; /* default + read */
-		if (dev->io_queues[HCTX_TYPE_READ])
-			dev->tagset.nr_maps++;
 		if (dev->io_queues[HCTX_TYPE_POLL])
 			dev->tagset.nr_maps++;
 		dev->tagset.timeout = NVME_IO_TIMEOUT;
@@ -3029,6 +3027,8 @@ static const struct pci_device_id nvme_id_table[] = {
 		.driver_data = NVME_QUIRK_LIGHTNVM, },
 	{ PCI_DEVICE(0x1d1d, 0x2601),	/* CNEX Granby */
 		.driver_data = NVME_QUIRK_LIGHTNVM, },
+	{ PCI_DEVICE(0x10ec, 0x5762),   /* ADATA SX6000LNP */
+		.driver_data = NVME_QUIRK_IGNORE_DEV_SUBNQN, },
 	{ PCI_DEVICE_CLASS(PCI_CLASS_STORAGE_EXPRESS, 0xffffff) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2001) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2003) },

fs/block_dev.c

@@ -345,15 +345,24 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	struct bio *bio;
 	bool is_poll = (iocb->ki_flags & IOCB_HIPRI) != 0;
 	bool is_read = (iov_iter_rw(iter) == READ), is_sync;
+	bool nowait = (iocb->ki_flags & IOCB_NOWAIT) != 0;
 	loff_t pos = iocb->ki_pos;
 	blk_qc_t qc = BLK_QC_T_NONE;
-	int ret = 0;
+	gfp_t gfp;
+	ssize_t ret;
 
 	if ((pos | iov_iter_alignment(iter)) &
 	    (bdev_logical_block_size(bdev) - 1))
 		return -EINVAL;
 
-	bio = bio_alloc_bioset(GFP_KERNEL, nr_pages, &blkdev_dio_pool);
+	if (nowait)
+		gfp = GFP_NOWAIT;
+	else
+		gfp = GFP_KERNEL;
+
+	bio = bio_alloc_bioset(gfp, nr_pages, &blkdev_dio_pool);
+	if (!bio)
+		return -EAGAIN;
 
 	dio = container_of(bio, struct blkdev_dio, bio);
 	dio->is_sync = is_sync = is_sync_kiocb(iocb);
@@ -375,7 +384,10 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	if (!is_poll)
 		blk_start_plug(&plug);
 
+	ret = 0;
 	for (;;) {
+		int err;
+
 		bio_set_dev(bio, bdev);
 		bio->bi_iter.bi_sector = pos >> 9;
 		bio->bi_write_hint = iocb->ki_hint;
@@ -383,8 +395,10 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 		bio->bi_end_io = blkdev_bio_end_io;
 		bio->bi_ioprio = iocb->ki_ioprio;
 
-		ret = bio_iov_iter_get_pages(bio, iter);
+		err = bio_iov_iter_get_pages(bio, iter);
-		if (unlikely(ret)) {
+		if (unlikely(err)) {
+			if (!ret)
+				ret = err;
 			bio->bi_status = BLK_STS_IOERR;
 			bio_endio(bio);
 			break;
@@ -399,6 +413,14 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 			task_io_account_write(bio->bi_iter.bi_size);
 		}
 
+		/*
+		 * Tell underlying layer to not block for resource shortage.
+		 * And if we would have blocked, return error inline instead
+		 * of through the bio->bi_end_io() callback.
+		 */
+		if (nowait)
+			bio->bi_opf |= (REQ_NOWAIT | REQ_NOWAIT_INLINE);
+
 		dio->size += bio->bi_iter.bi_size;
 		pos += bio->bi_iter.bi_size;
 
@@ -412,6 +434,11 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 			}
 
 			qc = submit_bio(bio);
+			if (qc == BLK_QC_T_EAGAIN) {
+				if (!ret)
+					ret = -EAGAIN;
+				goto error;
+			}
 
 			if (polled)
 				WRITE_ONCE(iocb->ki_cookie, qc);
@@ -432,8 +459,20 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 			atomic_inc(&dio->ref);
 		}
 
-		submit_bio(bio);
+		qc = submit_bio(bio);
-		bio = bio_alloc(GFP_KERNEL, nr_pages);
+		if (qc == BLK_QC_T_EAGAIN) {
+			if (!ret)
+				ret = -EAGAIN;
+			goto error;
+		}
+		ret += bio->bi_iter.bi_size;
+
+		bio = bio_alloc(gfp, nr_pages);
+		if (!bio) {
+			if (!ret)
+				ret = -EAGAIN;
+			goto error;
+		}
 	}
 
 	if (!is_poll)
@@ -453,13 +492,16 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 	}
 	__set_current_state(TASK_RUNNING);
 
+out:
 	if (!ret)
 		ret = blk_status_to_errno(dio->bio.bi_status);
-	if (likely(!ret))
-		ret = dio->size;
 
 	bio_put(&dio->bio);
 	return ret;
+error:
+	if (!is_poll)
+		blk_finish_plug(&plug);
+	goto out;
 }
 
 static ssize_t

fs/io_uring.c

@@ -202,7 +202,7 @@ struct async_list {
 
 	struct file		*file;
 	off_t			io_end;
-	size_t			io_pages;
+	size_t			io_len;
 };
 
 struct io_ring_ctx {
@@ -333,7 +333,8 @@ struct io_kiocb {
 #define REQ_F_IO_DRAIN		16	/* drain existing IO first */
 #define REQ_F_IO_DRAINED	32	/* drain done */
 #define REQ_F_LINK		64	/* linked sqes */
-#define REQ_F_FAIL_LINK		128	/* fail rest of links */
+#define REQ_F_LINK_DONE		128	/* linked sqes done */
+#define REQ_F_FAIL_LINK		256	/* fail rest of links */
 	u64			user_data;
 	u32			result;
 	u32			sequence;
@@ -429,7 +430,7 @@ static inline bool io_sequence_defer(struct io_ring_ctx *ctx,
 	if ((req->flags & (REQ_F_IO_DRAIN|REQ_F_IO_DRAINED)) != REQ_F_IO_DRAIN)
 		return false;
 
-	return req->sequence > ctx->cached_cq_tail + ctx->sq_ring->dropped;
+	return req->sequence != ctx->cached_cq_tail + ctx->sq_ring->dropped;
 }
 
 static struct io_kiocb *io_get_deferred_req(struct io_ring_ctx *ctx)
@@ -632,6 +633,7 @@ static void io_req_link_next(struct io_kiocb *req)
 			nxt->flags |= REQ_F_LINK;
 		}
 
+		nxt->flags |= REQ_F_LINK_DONE;
 		INIT_WORK(&nxt->work, io_sq_wq_submit_work);
 		queue_work(req->ctx->sqo_wq, &nxt->work);
 	}
@@ -1064,8 +1066,44 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
 	 */
 	offset = buf_addr - imu->ubuf;
 	iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);
-	if (offset)
+
-		iov_iter_advance(iter, offset);
+	if (offset) {
+		/*
+		 * Don't use iov_iter_advance() here, as it's really slow for
+		 * using the latter parts of a big fixed buffer - it iterates
+		 * over each segment manually. We can cheat a bit here, because
+		 * we know that:
+		 *
+		 * 1) it's a BVEC iter, we set it up
+		 * 2) all bvecs are PAGE_SIZE in size, except potentially the
+		 *    first and last bvec
+		 *
+		 * So just find our index, and adjust the iterator afterwards.
+		 * If the offset is within the first bvec (or the whole first
+		 * bvec, just use iov_iter_advance(). This makes it easier
+		 * since we can just skip the first segment, which may not
+		 * be PAGE_SIZE aligned.
+		 */
+		const struct bio_vec *bvec = imu->bvec;
+
+		if (offset <= bvec->bv_len) {
+			iov_iter_advance(iter, offset);
+		} else {
+			unsigned long seg_skip;
+
+			/* skip first vec */
+			offset -= bvec->bv_len;
+			seg_skip = 1 + (offset >> PAGE_SHIFT);
+
+			iter->bvec = bvec + seg_skip;
+			iter->nr_segs -= seg_skip;
+			iter->count -= (seg_skip << PAGE_SHIFT);
+			iter->iov_offset = offset & ~PAGE_MASK;
+			if (iter->iov_offset)
+				iter->count -= iter->iov_offset;
+		}
+	}
+
 	return 0;
 }
 
@@ -1120,28 +1158,26 @@ static void io_async_list_note(int rw, struct io_kiocb *req, size_t len)
 	off_t io_end = kiocb->ki_pos + len;
 
 	if (filp == async_list->file && kiocb->ki_pos == async_list->io_end) {
-		unsigned long max_pages;
+		unsigned long max_bytes;
 
 		/* Use 8x RA size as a decent limiter for both reads/writes */
-		max_pages = filp->f_ra.ra_pages;
+		max_bytes = filp->f_ra.ra_pages << (PAGE_SHIFT + 3);
-		if (!max_pages)
+		if (!max_bytes)
-			max_pages = VM_READAHEAD_PAGES;
+			max_bytes = VM_READAHEAD_PAGES << (PAGE_SHIFT + 3);
-		max_pages *= 8;
 
-		/* If max pages are exceeded, reset the state */
+		/* If max len are exceeded, reset the state */
-		len >>= PAGE_SHIFT;
+		if (async_list->io_len + len <= max_bytes) {
-		if (async_list->io_pages + len <= max_pages) {
 			req->flags |= REQ_F_SEQ_PREV;
-			async_list->io_pages += len;
+			async_list->io_len += len;
 		} else {
 			io_end = 0;
-			async_list->io_pages = 0;
+			async_list->io_len = 0;
 		}
 	}
 
 	/* New file? Reset state. */
 	if (async_list->file != filp) {
-		async_list->io_pages = 0;
+		async_list->io_len = 0;
 		async_list->file = filp;
 	}
 	async_list->io_end = io_end;
@@ -1630,6 +1666,8 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	INIT_LIST_HEAD(&poll->wait.entry);
 	init_waitqueue_func_entry(&poll->wait, io_poll_wake);
 
+	INIT_LIST_HEAD(&req->list);
+
 	mask = vfs_poll(poll->file, &ipt.pt) & poll->events;
 
 	spin_lock_irq(&ctx->completion_lock);
@@ -1844,6 +1882,10 @@ restart:
 		/* async context always use a copy of the sqe */
 		kfree(sqe);
 
+		/* req from defer and link list needn't decrease async cnt */
+		if (req->flags & (REQ_F_IO_DRAINED | REQ_F_LINK_DONE))
+			goto out;
+
 		if (!async_list)
 			break;
 		if (!list_empty(&req_list)) {
@@ -1891,6 +1933,7 @@ restart:
 		}
 	}
 
+out:
 	if (cur_mm) {
 		set_fs(old_fs);
 		unuse_mm(cur_mm);
@@ -1917,6 +1960,10 @@ static bool io_add_to_prev_work(struct async_list *list, struct io_kiocb *req)
 	ret = true;
 	spin_lock(&list->lock);
 	list_add_tail(&req->list, &list->list);
+	/*
+	 * Ensure we see a simultaneous modification from io_sq_wq_submit_work()
+	 */
+	smp_mb();
 	if (!atomic_read(&list->cnt)) {
 		list_del_init(&req->list);
 		ret = false;

include/linux/blk-cgroup.h

@@ -181,6 +181,7 @@ struct blkcg_policy {
 
 extern struct blkcg blkcg_root;
 extern struct cgroup_subsys_state * const blkcg_root_css;
+extern bool blkcg_debug_stats;
 
 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
 				      struct request_queue *q, bool update_hint);

include/linux/blk_types.h

@@ -311,6 +311,7 @@ enum req_flag_bits {
 	__REQ_RAHEAD,		/* read ahead, can fail anytime */
 	__REQ_BACKGROUND,	/* background IO */
 	__REQ_NOWAIT,           /* Don't wait if request will block */
+	__REQ_NOWAIT_INLINE,	/* Return would-block error inline */
 	/*
 	 * When a shared kthread needs to issue a bio for a cgroup, doing
 	 * so synchronously can lead to priority inversions as the kthread
@@ -345,6 +346,7 @@ enum req_flag_bits {
 #define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
 #define REQ_BACKGROUND		(1ULL << __REQ_BACKGROUND)
 #define REQ_NOWAIT		(1ULL << __REQ_NOWAIT)
+#define REQ_NOWAIT_INLINE	(1ULL << __REQ_NOWAIT_INLINE)
 #define REQ_CGROUP_PUNT		(1ULL << __REQ_CGROUP_PUNT)
 
 #define REQ_NOUNMAP		(1ULL << __REQ_NOUNMAP)
@@ -418,12 +420,13 @@ static inline int op_stat_group(unsigned int op)
 
 typedef unsigned int blk_qc_t;
 #define BLK_QC_T_NONE		-1U
+#define BLK_QC_T_EAGAIN		-2U
 #define BLK_QC_T_SHIFT		16
 #define BLK_QC_T_INTERNAL	(1U << 31)
 
 static inline bool blk_qc_t_valid(blk_qc_t cookie)
 {
-	return cookie != BLK_QC_T_NONE;
+	return cookie != BLK_QC_T_NONE && cookie != BLK_QC_T_EAGAIN;
 }
 
 static inline unsigned int blk_qc_t_to_queue_num(blk_qc_t cookie)

include/linux/elevator.h

@@ -45,7 +45,6 @@ struct elevator_mq_ops {
 	struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
 	bool (*has_work)(struct blk_mq_hw_ctx *);
 	void (*completed_request)(struct request *, u64);
-	void (*started_request)(struct request *);
 	void (*requeue_request)(struct request *);
 	struct request *(*former_request)(struct request_queue *, struct request *);
 	struct request *(*next_request)(struct request_queue *, struct request *);

include/linux/wait.h

@@ -126,6 +126,19 @@ static inline int waitqueue_active(struct wait_queue_head *wq_head)
 	return !list_empty(&wq_head->head);
 }
 
+/**
+ * wq_has_single_sleeper - check if there is only one sleeper
+ * @wq_head: wait queue head
+ *
+ * Returns true of wq_head has only one sleeper on the list.
+ *
+ * Please refer to the comment for waitqueue_active.
+ */
+static inline bool wq_has_single_sleeper(struct wait_queue_head *wq_head)
+{
+	return list_is_singular(&wq_head->head);
+}
+
 /**
  * wq_has_sleeper - check if there are any waiting processes
  * @wq_head: wait queue head