linux-kernel - [PATCH 4.12 25/41] blk-mq-pci: add a fallback when pci_irq_get

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Message-Id: <20170822190942.951178747@linuxfoundation.org>
Date:   Tue, 22 Aug 2017 12:13:53 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Omar Sandoval <osandov@...com>, Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.12 25/41] blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL

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

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

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