Index: b/drivers/nvme/host/pci.c
===================================================================
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2041,41 +2041,42 @@ static int nvme_setup_host_mem(struct nv
 	return ret;
 }
 
-/* irq_queues covers admin queue */
-static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues)
+/*
+ * nirqs is the number of interrupts available for write and read
+ * queues. The core already reserved an interrupt for the admin queue.
+ */
+static void nvme_calc_irq_sets(struct irq_affinity *affd, unsigned int nrirqs)
 {
-	unsigned int this_w_queues = write_queues;
-
-	WARN_ON(!irq_queues);
-
-	/*
-	 * Setup read/write queue split, assign admin queue one independent
-	 * irq vector if irq_queues is > 1.
-	 */
-	if (irq_queues <= 2) {
-		dev->io_queues[HCTX_TYPE_DEFAULT] = 1;
-		dev->io_queues[HCTX_TYPE_READ] = 0;
-		return;
-	}
-
-	/*
-	 * If 'write_queues' is set, ensure it leaves room for at least
-	 * one read queue and one admin queue
-	 */
-	if (this_w_queues >= irq_queues)
-		this_w_queues = irq_queues - 2;
+	struct nvme_dev *dev = affd->priv;
+	unsigned int nr_read_queues;
 
 	/*
-	 * If 'write_queues' is set to zero, reads and writes will share
-	 * a queue set.
-	 */
-	if (!this_w_queues) {
-		dev->io_queues[HCTX_TYPE_DEFAULT] = irq_queues - 1;
-		dev->io_queues[HCTX_TYPE_READ] = 0;
+	 * If there is no interupt available for queues, ensure that
+	 * the default queue is set to 1. The affinity set size is
+	 * also set to one, but the irq core ignores it for this case.
+	 *
+	 * If only one interrupt is available or 'write_queue' == 0, combine
+	 * write and read queues.
+	 *
+	 * If 'write_queues' > 0, ensure it leaves room for at least one read
+	 * queue.
+	 */
+	if (!nrirqs) {
+		nrirqs = 1;
+		nr_read_queues = 0;
+	} else if (nrirqs == 1 || !write_queues) {
+		nr_read_queues = 0;
+	} else if (write_queues >= nrirqs) {
+		nr_read_queues = 1;
 	} else {
-		dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues;
-		dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues - 1;
+		nr_read_queues = nrirqs - write_queues;
 	}
+
+	dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues;
+	affd->set_size[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues;
+	dev->io_queues[HCTX_TYPE_READ] = nr_read_queues;
+	affd->set_size[HCTX_TYPE_READ] = nr_read_queues;
+	affd->nr_sets = nr_read_queues ? 2 : 1;
 }
 
 static int nvme_setup_irqs(struct nvme_dev *dev, unsigned int nr_io_queues)
@@ -2083,10 +2084,9 @@ static int nvme_setup_irqs(struct nvme_d
 	struct pci_dev *pdev = to_pci_dev(dev->dev);
 	struct irq_affinity affd = {
 		.pre_vectors	= 1,
-		.nr_sets	= 2,
+		.calc_sets	= nvme_calc_irq_sets,
+		.priv		= dev,
 	};
-	unsigned int *irq_sets = affd.set_size;
-	int result = 0;
 	unsigned int irq_queues, this_p_queues;
 
 	/*
@@ -2102,51 +2102,12 @@ static int nvme_setup_irqs(struct nvme_d
 	}
 	dev->io_queues[HCTX_TYPE_POLL] = this_p_queues;
 
-	/*
-	 * For irq sets, we have to ask for minvec == maxvec. This passes
-	 * any reduction back to us, so we can adjust our queue counts and
-	 * IRQ vector needs.
-	 */
-	do {
-		nvme_calc_io_queues(dev, irq_queues);
-		irq_sets[0] = dev->io_queues[HCTX_TYPE_DEFAULT];
-		irq_sets[1] = dev->io_queues[HCTX_TYPE_READ];
-		if (!irq_sets[1])
-			affd.nr_sets = 1;
-
-		/*
-		 * If we got a failure and we're down to asking for just
-		 * 1 + 1 queues, just ask for a single vector. We'll share
-		 * that between the single IO queue and the admin queue.
-		 * Otherwise, we assign one independent vector to admin queue.
-		 */
-		if (irq_queues > 1)
-			irq_queues = irq_sets[0] + irq_sets[1] + 1;
+	/* Initialize for the single interrupt case */
+	dev->io_queues[HCTX_TYPE_DEFAULT] = 1;
+	dev->io_queues[HCTX_TYPE_READ] = 0;
 
-		result = pci_alloc_irq_vectors_affinity(pdev, irq_queues,
-				irq_queues,
-				PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
-
-		/*
-		 * Need to reduce our vec counts. If we get ENOSPC, the
-		 * platform should support mulitple vecs, we just need
-		 * to decrease our ask. If we get EINVAL, the platform
-		 * likely does not. Back down to ask for just one vector.
-		 */
-		if (result == -ENOSPC) {
-			irq_queues--;
-			if (!irq_queues)
-				return result;
-			continue;
-		} else if (result == -EINVAL) {
-			irq_queues = 1;
-			continue;
-		} else if (result <= 0)
-			return -EIO;
-		break;
-	} while (1);
-
-	return result;
+	return pci_alloc_irq_vectors_affinity(pdev, 1, irq_queues,
+			      PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
 }
 
 static void nvme_disable_io_queues(struct nvme_dev *dev)
@@ -3021,6 +2982,7 @@ static struct pci_driver nvme_driver = {
 
 static int __init nvme_init(void)
 {
+	BUILD_BUG_ON(IRQ_AFFINITY_MAX_SETS < 2);
 	return pci_register_driver(&nvme_driver);
 }
 
