Patch "blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL" has been added to the 4.12-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL

to the 4.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     blk-mq-pci-add-a-fallback-when-pci_irq_get_affinity-returns-null.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From c005390374957baacbc38eef96ea360559510aa7 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Thu, 17 Aug 2017 12:24:47 +0200
Subject: blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL

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);


Patches currently in stable-queue which might be from hch@lst.de are

queue-4.12/blk-mq-pci-add-a-fallback-when-pci_irq_get_affinity-returns-null.patch