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The only difference between ->run_work and ->delay_work, is that the latter is used to defer running a queue. This is done by marking the queue stopped, and scheduling ->delay_work to run sometime in the future. While the queue is stopped, direct runs or runs through ->run_work will not run the queue. If we combine the handlers, then we need to handle two things: 1) If a delayed/stopped run is scheduled, then we should not run the queue before that has been completed. 2) If a queue is delayed/stopped, the handler needs to restart the queue. Normally a run of a queue with the stopped bit set would be a no-op. Case 1 is handled by modifying a currently pending queue run to the deadline set by the caller of blk_mq_delay_queue(). Subsequent attempts to queue a queue run will find the work item already pending, and direct runs will see a stopped queue as before. Case 2 is handled by adding a new bit, BLK_MQ_S_START_ON_RUN, that tells the work handler that it should clear a stopped queue and run the handler. Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.