From: Akinobu Mita <akinobu.mita@gmail.com>
Date: Sat, 26 Sep 2015 17:09:19 +0000 (+0900)
Subject: blk-mq: avoid setting hctx->tags->cpumask before allocation
X-Git-Tag: v4.1.12-92~88^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=dd5d896f225498f5445b25d5b13ec0e34e6feeef;p=users%2Fjedix%2Flinux-maple.git

blk-mq: avoid setting hctx->tags->cpumask before allocation

Orabug: 24465370,24464170,24300199

When unmapped hw queue is remapped after CPU topology is changed,
hctx->tags->cpumask has to be set after hctx->tags is setup in
blk_mq_map_swqueue(), otherwise it causes null pointer dereference.

Fixes: f26cdc8536 ("blk-mq: Shared tag enhancements")
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit 1356aae08338f1c19ce1c67bf8c543a267688fc3)
Signed-off-by: Bob Liu <bob.liu@oracle.com>
---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7684b13fd4af..b88e59e4d805 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1754,7 +1754,6 @@ static void blk_mq_map_swqueue(struct request_queue *q,
 		hctx = q->mq_ops->map_queue(q, i);
 
 		cpumask_set_cpu(i, hctx->cpumask);
-		cpumask_set_cpu(i, hctx->tags->cpumask);
 		ctx->index_hw = hctx->nr_ctx;
 		hctx->ctxs[hctx->nr_ctx++] = ctx;
 	}
@@ -1794,6 +1793,14 @@ static void blk_mq_map_swqueue(struct request_queue *q,
 		hctx->next_cpu = cpumask_first(hctx->cpumask);
 		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
 	}
+
+	queue_for_each_ctx(q, ctx, i) {
+		if (!cpu_online(i))
+			continue;
+
+		hctx = q->mq_ops->map_queue(q, i);
+		cpumask_set_cpu(i, hctx->tags->cpumask);
+	}
 }
 
 static void queue_set_hctx_shared(struct request_queue *q, bool shared)