linux-kernel - [patch] blk-mq: zero out ctx

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Message-ID: <x491u3ecxs0.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 21 Oct 2013 13:57:19 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	jaxboe@...ionio.com, linux-kernel@...r.kernel.org
Subject: [patch] blk-mq: zero out ctx_map during initialization

Hi,

ctx_map may contain random garbage, leading to (potentially chronic but
harmless) false positives in blk_mq_hctx_has_pending.

Note: I have not observed this in practice, just by code inspection.

Signed-off-by: Jeff Moyer <jmoyer@...hat.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 923e9e1..e9be5ed 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1197,7 +1197,7 @@ static int blk_mq_init_hw_queues(struct request_queue *q,
 			break;
 
 		num_maps = ALIGN(nr_cpu_ids, BITS_PER_LONG) / BITS_PER_LONG;
-		hctx->ctx_map = kmalloc_node(num_maps * sizeof(unsigned long),
+		hctx->ctx_map = kzalloc_node(num_maps * sizeof(unsigned long),
 						GFP_KERNEL, node);
 		if (!hctx->ctx_map)
 			break;
--
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