linux-kernel - [PATCH] blk-mq: Avoid memoryless numa node encoded in hctx numa

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Message-Id: <1449055745-14575-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com>
Date:	Wed,  2 Dec 2015 16:59:05 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	<axboe@...nel.dk>
Cc:	<tom.leiming@...il.com>, <linux-block@...r.kernel.org>,
	<nacc@...ux.vnet.ibm.com>, <linux-kernel@...r.kernel.org>,
	<raghavendra.kt@...ux.vnet.ibm.com>
Subject: [PATCH] blk-mq: Avoid memoryless numa node encoded in hctx numa_node

In architecture like powerpc, we can have cpus without any local memory
attached to it (a.k.a memoryless nodes). In such cases cpu to node mapping
can result in memory allocation hints for block hctx->numa_node populated
with node values which does not have real memory.

Instead use local_memory_node(), which is guaranteed to have memory.
local_memory_node is a noop in other architectures that does not support
memoryless nodes.

Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
---
 block/blk-mq-cpumap.c | 2 +-
 block/blk-mq.c        | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

 Validated the patch on a memoryless node powerpc system.

diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 8764c24..d0634bc 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -113,7 +113,7 @@ int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
 
 	for_each_possible_cpu(i) {
 		if (index == mq_map[i])
-			return cpu_to_node(i);
+			return local_memory_node(cpu_to_node(i));
 	}
 
 	return NUMA_NO_NODE;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6ada3b4..74be735 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1794,7 +1794,7 @@ static void blk_mq_init_cpu_queues(struct request_queue *q,
 		 * not, we remain on the home node of the device
 		 */
 		if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
-			hctx->numa_node = cpu_to_node(i);
+			hctx->numa_node = local_memory_node(cpu_to_node(i));
 	}
 }
 
-- 
1.7.11.7

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