[PATCH] nvme: create the correct number of queues

Dan Streetman
2016-12-07T22:04:05Z

Change nr_io_queues variable name to nr_queues, as it includes not
only the io queues but also the admin queue in its count; and change
the variable name in functions that it is passed into, for clarity.

Also correct misuses of the nr_queue count:

In the db_bar_size() function, the calculation added 1 to the
nr_io_queues value to account for the admin queue, but since that's
actually already in the nr_queue count, don't add it.

In the nvme_setup_io_queues() function when allocating irq vectors,
it considers the minimum number of queues to be 1, but actually 2
queues are needed; 1 admin queue + at least 1 io queue.

When setting the device's max_qid (maximum queue index id), it's
currently set to nr_io_queues, but since nr_queues counts all
queues, and because max_qid is 0-based and nr_queues is 1-based,
max_qid must be set to nr_queues - 1.

Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
---
drivers/nvme/host/pci.c | 33 +++++++++++++++++----------------
1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index def2285..eff8198 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1007,15 +1007,15 @@ static void nvme_disable_admin_queue(struct nvme_dev *dev, bool shutdown)
spin_unlock_irq(&nvmeq->q_lock);
}

-static int nvme_cmb_qdepth(struct nvme_dev *dev, int nr_io_queues,
+static int nvme_cmb_qdepth(struct nvme_dev *dev, int nr_queues,
int entry_size)
{
int q_depth = dev->q_depth;
unsigned q_size_aligned = roundup(q_depth * entry_size,
dev->ctrl.page_size);

- if (q_size_aligned * nr_io_queues > dev->cmb_size) {
- u64 mem_per_q = div_u64(dev->cmb_size, nr_io_queues);
+ if (q_size_aligned * nr_queues > dev->cmb_size) {
+ u64 mem_per_q = div_u64(dev->cmb_size, nr_queues);
mem_per_q = round_down(mem_per_q, dev->ctrl.page_size);
q_depth = div_u64(mem_per_q, entry_size);

@@ -1387,27 +1387,27 @@ static inline void nvme_release_cmb(struct nvme_dev *dev)
}
}

-static size_t db_bar_size(struct nvme_dev *dev, unsigned nr_io_queues)
+static size_t db_bar_size(struct nvme_dev *dev, unsigned nr_queues)
{
- return 4096 + ((nr_io_queues + 1) * 8 * dev->db_stride);
+ return 4096 + (nr_queues * 8 * dev->db_stride);
}

static int nvme_setup_io_queues(struct nvme_dev *dev)
{
struct nvme_queue *adminq = dev->queues[0];
struct pci_dev *pdev = to_pci_dev(dev->dev);
- int result, nr_io_queues, size;
+ int result, nr_queues, size;

- nr_io_queues = num_online_cpus();
- result = nvme_set_queue_count(&dev->ctrl, &nr_io_queues);
+ nr_queues = num_online_cpus();
+ result = nvme_set_queue_count(&dev->ctrl, &nr_queues);
if (result < 0)
return result;

- if (nr_io_queues == 0)
+ if (nr_queues == 0)
return 0;

if (dev->cmb && NVME_CMB_SQS(dev->cmbsz)) {
- result = nvme_cmb_qdepth(dev, nr_io_queues,
+ result = nvme_cmb_qdepth(dev, nr_queues,
sizeof(struct nvme_command));
if (result > 0)
dev->q_depth = result;
@@ -1415,16 +1415,16 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
nvme_release_cmb(dev);
}

- size = db_bar_size(dev, nr_io_queues);
+ size = db_bar_size(dev, nr_queues);
if (size > 8192) {
iounmap(dev->bar);
do {
dev->bar = ioremap(pci_resource_start(pdev, 0), size);
if (dev->bar)
break;
- if (!--nr_io_queues)
+ if (!--nr_queues)
return -ENOMEM;
- size = db_bar_size(dev, nr_io_queues);
+ size = db_bar_size(dev, nr_queues);
} while (1);
dev->dbs = dev->bar + 4096;
adminq->q_db = dev->dbs;
@@ -1438,11 +1438,12 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
* setting up the full range we need.
*/
pci_free_irq_vectors(pdev);
- nr_io_queues = pci_alloc_irq_vectors(pdev, 1, nr_io_queues,
+ nr_queues = pci_alloc_irq_vectors(pdev, 1, nr_queues,
PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY);
- if (nr_io_queues <= 0)
+ /* we need at least 1 admin queue + 1 io queue */
+ if (nr_queues < 2)
return -EIO;
- dev->max_qid = nr_io_queues;
+ dev->max_qid = nr_queues - 1;

/*
* Should investigate if there's a performance win from allocating
--
2.9.3