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    SubjectRe: [PATCH 2/6] block: allow blk_execute_rq_nowait() to be called form IRQ context
    On Thu, Oct 20, 2011 at 08:56:36PM -0700, Tejun Heo wrote:
    > Currently blk_execute_rq_nowait() directly calls __blk_run_queue() and
    > thus can't be called from IRQ context. This patch updates it to use
    > blk_run_queue_async() instead. This will be used to unexport
    > elv_add_request().
    >
    > This changes how queue is kicked after blk_execute_rq_nowait() but
    > it's hardly a hot path and the effect shouldn't be noticeable.

    It actually very much is a fasthpath for many of it's users, e.g. the
    SCSI tape drivers, the OSD layer and the target scsi passthrough
    backend.

    I don't think blindly adding a context switch here without benchmarking
    is doable. Just add variants that do the workqueue dance or not.



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