for-linus-20191010

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Merge tag 'for-linus-20191010' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:

 - Fix wbt performance regression introduced with the blk-rq-qos
   refactoring (Harshad)

 - Fix io_uring fileset removal inadvertently killing the workqueue (me)

 - Fix io_uring typo in linked command nonblock submission (Pavel)

 - Remove spurious io_uring wakeups on request free (Pavel)

 - Fix null_blk zoned command error return (Keith)

 - Don't use freezable workqueues for backing_dev, also means we can
   revert a previous libata hack (Mika)

 - Fix nbd sysfs mutex dropped too soon at removal time (Xiubo)

* tag 'for-linus-20191010' of git://git.kernel.dk/linux-block:
  nbd: fix possible sysfs duplicate warning
  null_blk: Fix zoned command return code
  io_uring: only flush workqueues on fileset removal
  io_uring: remove wait loop spurious wakeups
  blk-wbt: fix performance regression in wbt scale_up/scale_down
  Revert "libata, freezer: avoid block device removal while system is frozen"
  bdi: Do not use freezable workqueue
  io_uring: fix reversed nonblock flag for link submission

block/blk-rq-qos.c

@@ -160,24 +160,27 @@ bool rq_depth_calc_max_depth(struct rq_depth *rqd)
 	return ret;
 }
 
-void rq_depth_scale_up(struct rq_depth *rqd)
+/* Returns true on success and false if scaling up wasn't possible */
+bool rq_depth_scale_up(struct rq_depth *rqd)
 {
 	/*
 	 * Hit max in previous round, stop here
 	 */
 	if (rqd->scaled_max)
-		return;
+		return false;
 
 	rqd->scale_step--;
 
 	rqd->scaled_max = rq_depth_calc_max_depth(rqd);
+	return true;
 }
 
 /*
  * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
- * had a latency violation.
+ * had a latency violation. Returns true on success and returns false if
+ * scaling down wasn't possible.
  */
-void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
+bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
 {
 	/*
 	 * Stop scaling down when we've hit the limit. This also prevents
@@ -185,7 +188,7 @@ void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
 	 * keep up.
 	 */
 	if (rqd->max_depth == 1)
-		return;
+		return false;
 
 	if (rqd->scale_step < 0 && hard_throttle)
 		rqd->scale_step = 0;
@@ -194,6 +197,7 @@ void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
 
 	rqd->scaled_max = false;
 	rq_depth_calc_max_depth(rqd);
+	return true;
 }
 
 struct rq_qos_wait_data {

block/blk-rq-qos.h

@@ -130,8 +130,8 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,
 		 acquire_inflight_cb_t *acquire_inflight_cb,
 		 cleanup_cb_t *cleanup_cb);
 bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit);
-void rq_depth_scale_up(struct rq_depth *rqd);
+bool rq_depth_scale_up(struct rq_depth *rqd);
-void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle);
+bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle);
 bool rq_depth_calc_max_depth(struct rq_depth *rqd);
 
 void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio);

block/blk-wbt.c

@@ -308,7 +308,8 @@ static void calc_wb_limits(struct rq_wb *rwb)
 
 static void scale_up(struct rq_wb *rwb)
 {
-	rq_depth_scale_up(&rwb->rq_depth);
+	if (!rq_depth_scale_up(&rwb->rq_depth))
+		return;
 	calc_wb_limits(rwb);
 	rwb->unknown_cnt = 0;
 	rwb_wake_all(rwb);
@@ -317,7 +318,8 @@ static void scale_up(struct rq_wb *rwb)
 
 static void scale_down(struct rq_wb *rwb, bool hard_throttle)
 {
-	rq_depth_scale_down(&rwb->rq_depth, hard_throttle);
+	if (!rq_depth_scale_down(&rwb->rq_depth, hard_throttle))
+		return;
 	calc_wb_limits(rwb);
 	rwb->unknown_cnt = 0;
 	rwb_trace_step(rwb, "scale down");

drivers/ata/libata-scsi.c

@@ -4791,27 +4791,6 @@ void ata_scsi_hotplug(struct work_struct *work)
 		return;
 	}
 
-	/*
-	 * XXX - UGLY HACK
-	 *
-	 * The block layer suspend/resume path is fundamentally broken due
-	 * to freezable kthreads and workqueue and may deadlock if a block
-	 * device gets removed while resume is in progress.  I don't know
-	 * what the solution is short of removing freezable kthreads and
-	 * workqueues altogether.
-	 *
-	 * The following is an ugly hack to avoid kicking off device
-	 * removal while freezer is active.  This is a joke but does avoid
-	 * this particular deadlock scenario.
-	 *
-	 * https://bugzilla.kernel.org/show_bug.cgi?id=62801
-	 * http://marc.info/?l=linux-kernel&m=138695698516487
-	 */
-#ifdef CONFIG_FREEZER
-	while (pm_freezing)
-		msleep(10);
-#endif
-
 	DPRINTK("ENTER\n");
 	mutex_lock(&ap->scsi_scan_mutex);
 

drivers/block/nbd.c

@@ -248,8 +248,8 @@ static void nbd_put(struct nbd_device *nbd)
 	if (refcount_dec_and_mutex_lock(&nbd->refs,
 					&nbd_index_mutex)) {
 		idr_remove(&nbd_index_idr, nbd->index);
-		mutex_unlock(&nbd_index_mutex);
 		nbd_dev_remove(nbd);
+		mutex_unlock(&nbd_index_mutex);
 	}
 }
 

drivers/block/null_blk_zoned.c

@@ -142,8 +142,7 @@ static blk_status_t null_zone_reset(struct nullb_cmd *cmd, sector_t sector)
 		zone->wp = zone->start;
 		break;
 	default:
-		cmd->error = BLK_STS_NOTSUPP;
+		return BLK_STS_NOTSUPP;
-		break;
 	}
 	return BLK_STS_OK;
 }

fs/io_uring.c

@@ -591,14 +591,6 @@ static void io_cqring_add_event(struct io_ring_ctx *ctx, u64 user_data,
 	io_cqring_ev_posted(ctx);
 }
 
-static void io_ring_drop_ctx_refs(struct io_ring_ctx *ctx, unsigned refs)
-{
-	percpu_ref_put_many(&ctx->refs, refs);
-
-	if (waitqueue_active(&ctx->wait))
-		wake_up(&ctx->wait);
-}
-
 static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 				   struct io_submit_state *state)
 {
@@ -646,7 +638,7 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 	req->result = 0;
 	return req;
 out:
-	io_ring_drop_ctx_refs(ctx, 1);
+	percpu_ref_put(&ctx->refs);
 	return NULL;
 }
 
@@ -654,7 +646,7 @@ static void io_free_req_many(struct io_ring_ctx *ctx, void **reqs, int *nr)
 {
 	if (*nr) {
 		kmem_cache_free_bulk(req_cachep, *nr, reqs);
-		io_ring_drop_ctx_refs(ctx, *nr);
+		percpu_ref_put_many(&ctx->refs, *nr);
 		*nr = 0;
 	}
 }
@@ -663,7 +655,7 @@ static void __io_free_req(struct io_kiocb *req)
 {
 	if (req->file && !(req->flags & REQ_F_FIXED_FILE))
 		fput(req->file);
-	io_ring_drop_ctx_refs(req->ctx, 1);
+	percpu_ref_put(&req->ctx->refs);
 	kmem_cache_free(req_cachep, req);
 }
 
@@ -2761,7 +2753,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
 
 	if (link)
 		io_queue_link_head(ctx, link, &link->submit, shadow_req,
-					block_for_last);
+					!block_for_last);
 	if (statep)
 		io_submit_state_end(statep);
 
@@ -2920,8 +2912,12 @@ static void io_finish_async(struct io_ring_ctx *ctx)
 static void io_destruct_skb(struct sk_buff *skb)
 {
 	struct io_ring_ctx *ctx = skb->sk->sk_user_data;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ctx->sqo_wq); i++)
+		if (ctx->sqo_wq[i])
+			flush_workqueue(ctx->sqo_wq[i]);
 
-	io_finish_async(ctx);
 	unix_destruct_scm(skb);
 }
 
@@ -3630,7 +3626,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 		}
 	}
 
-	io_ring_drop_ctx_refs(ctx, 1);
+	percpu_ref_put(&ctx->refs);
 out_fput:
 	fdput(f);
 	return submitted ? submitted : ret;

kernel/freezer.c

@@ -22,12 +22,6 @@ EXPORT_SYMBOL(system_freezing_cnt);
 bool pm_freezing;
 bool pm_nosig_freezing;
 
-/*
- * Temporary export for the deadlock workaround in ata_scsi_hotplug().
- * Remove once the hack becomes unnecessary.
- */
-EXPORT_SYMBOL_GPL(pm_freezing);
-
 /* protects freezing and frozen transitions */
 static DEFINE_SPINLOCK(freezer_lock);
 

mm/backing-dev.c

@@ -239,8 +239,8 @@ static int __init default_bdi_init(void)
 {
 	int err;
 
-	bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
+	bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
-					      WQ_UNBOUND | WQ_SYSFS, 0);
+				 WQ_SYSFS, 0);
 	if (!bdi_wq)
 		return -ENOMEM;