mq-deadline: the dd->dispatch queue follows a FIFO policy #420
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In the initial implementation, the 'list_add(&rq->queuelist, ...' statement added to the dd_insert_request function was designed to differentiate priorities among various IO-requests within the same linked list. For example, 'Commit 945ffb6 ("mq-deadline: add blk-mq adaptation of the deadline IO scheduler")', introduced this 'list_add' operation to ensure that requests with the at_head flag would always be dispatched before requests without the REQ_TYPE_FS flag. Since 'Commit 7687b38 ("bfq/mq-deadline: remove redundant check for passthrough request")', removed blk_rq_is_passthrough, the dd->dispatch list now contains only requests with the at_head flag. In this context, all at_head requests should be treated as having equal priority, and a first-in-first-out (FIFO) policy better aligns with the current situation. Therefore, replacing list_add with list_add_tail is more appropriate. Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
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Upstream branch: c2f2b01 |
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Pull request for series with
subject: mq-deadline: the dd->dispatch queue follows a FIFO policy
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1031341