Re: [PATCH V3 1/6] blk-mq: grab .q_usage_counter when queuing request from plug code path

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On Wed, 2019-04-03 at 18:26 +-0800, Ming Lei wrote:
+AD4 However, if request is staggered into plug list, and finally queued
+AD4 from plug code path, the refcount in submission side is actually missed.
+AD4 And we may start to run queue after queue is removed, then kernel oops
+AD4 is triggered.

I don't think that this patch is necessary. blk+AF8-mq+AF8-get+AF8-request() increases
q+AF8-usage+AF8-counter. In other words, as long as at least one request has been
allocated that has not finished it is guaranteed that q+AF8-usage+AF8-counter +AD4 0.
So there is no need for additional protection in blk+AF8-mq+AF8-flush+AF8-plug+AF8-list().

Bart.



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