[PATCH 4.9 16/27] blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Hellwig <h...@lst.de>

commit c005390374957baacbc38eef96ea360559510aa7 upstream.

While pci_irq_get_affinity should never fail for SMP kernel that
implement the affinity mapping, it will always return NULL in the
UP case, so provide a fallback mapping of all queues to CPU 0 in
that case.

Signed-off-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Omar Sandoval <osan...@fb.com>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 block/blk-mq-pci.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/block/blk-mq-pci.c
+++ b/block/blk-mq-pci.c
@@ -36,12 +36,18 @@ int blk_mq_pci_map_queues(struct blk_mq_
        for (queue = 0; queue < set->nr_hw_queues; queue++) {
                mask = pci_irq_get_affinity(pdev, queue);
                if (!mask)
-                       return -EINVAL;
+                       goto fallback;
 
                for_each_cpu(cpu, mask)
                        set->mq_map[cpu] = queue;
        }
 
        return 0;
+
+fallback:
+       WARN_ON_ONCE(set->nr_hw_queues > 1);
+       for_each_possible_cpu(cpu)
+               set->mq_map[cpu] = 0;
+       return 0;
 }
 EXPORT_SYMBOL_GPL(blk_mq_pci_map_queues);