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Subject[PATCH 4.12 25/41] blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

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

From: Christoph Hellwig <hch@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 <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@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);

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