This is a note to let you know that I've just added the patch titled
blk-mq: avoid setting hctx->tags->cpumask before allocation
to the 4.2-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-avoid-setting-hctx-tags-cpumask-before-allocation.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1356aae08338f1c19ce1c67bf8c543a267688fc3 Mon Sep 17 00:00:00 2001
From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Date: Sun, 27 Sep 2015 02:09:19 +0900
Subject: blk-mq: avoid setting hctx->tags->cpumask before allocation
From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
commit 1356aae08338f1c19ce1c67bf8c543a267688fc3 upstream.
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@xxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Ming Lei <tom.leiming@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/blk-mq.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1807,7 +1807,6 @@ static void blk_mq_map_swqueue(struct re
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;
}
@@ -1847,6 +1846,14 @@ static void blk_mq_map_swqueue(struct re
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 blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set)
Patches currently in stable-queue which might be from akinobu.mita@xxxxxxxxx are
queue-4.2/blk-mq-avoid-setting-hctx-tags-cpumask-before-allocation.patch
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