On 2/20/20 2:05 AM, Ming Lei wrote:
On Wed, Feb 19, 2020 at 06:44:35PM -0800, Bart Van Assche wrote:
blk_mq_map_queues() and multiple .map_queues() implementations expect that
set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the number of hardware
Only single queue mapping expects set->map[HCTX_TYPE_DEFAULT].nr_queues
to be set->nr_hw_queues. For multiple mapping, set->nr_hw_queues should
be sum of each mapping's nr_queue.
That's how it should work but that doesn't match what I found in the
kernel tree. Here is an example of a .map_queues() implementation that
depends on .nr_queues being set before it is called:
static int scsi_map_queues(struct blk_mq_tag_set *set)
{
struct Scsi_Host *shost = container_of(set, struct Scsi_Host,
tag_set);
if (shost->hostt->map_queues)
return shost->hostt->map_queues(shost);
return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
}
If shost->hostt->map_queues == NULL, the above function only works
correctly if .nr_queues is set before this function is called.
Additionally, scsi_map_queues() may call e.g. the following function:
static int qla2xxx_map_queues(struct Scsi_Host *shost)
{
int rc;
scsi_qla_host_t *vha = (scsi_qla_host_t *)shost->hostdata;
struct blk_mq_queue_map *qmap =
&shost->tag_set.map[HCTX_TYPE_DEFAULT];
if (USER_CTRL_IRQ(vha->hw) || !vha->hw->mqiobase)
rc = blk_mq_map_queues(qmap);
else
rc = blk_mq_pci_map_queues(qmap, vha->hw->pdev,
vha->irq_offset);
return rc;
}
Both blk_mq_map_queues() and blk_mq_pci_map_queues() assume that
blk_mq_queue_map.nr_queues is set before these functions are called.
Bart.
