When a cpu is offline, blk_mq_hctx_notify_dead() is called once for each hctx for the offline cpu. While blk_mq_hctx_notify_dead() is used to splice all ctx->rq_lists[type] to hctx->dispatch, it never checks whether the ctx is already mapped to the hctx. For example, on a VM (with nvme) of 4 cpu, to offline cpu 2 out of the 4 cpu (0-3), blk_mq_hctx_notify_dead() is called once for each io queue hctx: 1st: blk_mq_ctx->cpu = 2 for blk_mq_hw_ctx->queue_num = 3 2nd: blk_mq_ctx->cpu = 2 for blk_mq_hw_ctx->queue_num = 2 3rd: blk_mq_ctx->cpu = 2 for blk_mq_hw_ctx->queue_num = 1 4th: blk_mq_ctx->cpu = 2 for blk_mq_hw_ctx->queue_num = 0 Although blk_mq_ctx->cpu = 2 is only mapped to blk_mq_hw_ctx->queue_num = 2 in this case, its ctx->rq_lists[type] will however be moved to blk_mq_hw_ctx->queue_num = 3 during the 1st call of blk_mq_hctx_notify_dead(). This patch would return and go ahead to next call of blk_mq_hctx_notify_dead() if ctx is not mapped to hctx. Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx> Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx> --- block/blk-mq.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index a935483..9612746 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2219,6 +2219,10 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) enum hctx_type type; hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead); + + if (!cpumask_test_cpu(cpu, hctx->cpumask)) + return 0; + ctx = __blk_mq_get_ctx(hctx->queue, cpu); type = hctx->type; -- 2.7.4
