Re: [PATCH 02/14] blk-mq: Fix a potential NULL pointer assignment to hctx tags
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From: Omar Sandoval <osandov@osandov.com>
Date: 2016-09-19 18:34:38
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On Sun, Sep 18, 2016 at 09:37:12AM +0200, Alexander Gordeev wrote:
quoted hunk ↗ jump to hunk
If number of used hardware queues is dynamically decreased then tags corresponding to the newly unused queues are freed. If previously unused hardware queues are then reused again they will start referring the previously freed tags. CC: linux-block@vger.kernel.org Signed-off-by: Alexander Gordeev <redacted> --- block/blk-mq.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/block/blk-mq.c b/block/blk-mq.c index 66505af7..7fa58fe 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c@@ -1995,6 +1995,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, if (hctxs[i]) continue; + if (!set->tags[i]) + break; node = blk_mq_hw_queue_to_node(q->mq_map, i); hctxs[i] = kzalloc_node(sizeof(struct blk_mq_hw_ctx),
In blk_mq_map_swqueue(), we have: /* unmapped hw queue can be remapped after CPU topo changed */ if (!set->tags[i]) set->tags[i] = blk_mq_init_rq_map(set, i); hctx->tags = set->tags[i]; WARN_ON(!hctx->tags); blk_mq_map_swqueue() is called from blk_mq_queue_reinit(), which we call from blk_mq_update_nr_hw_queues(). Is that not enough? This initialization/resizing is a bit of a twisty maze and it's hard to convince myself that it's all correct, so cleanup here is probably valuable. -- Omar