blk-mq: defer to the normal submission path for post-flush requests

Requests with the FUA bit on hardware without FUA support need a post
flush before returning to the caller, but they can still be sent using
the normal I/O path after initializing the flush-related fields and
end I/O handler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230519044050.107790-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 6fb9cf2..7121f9a 100644 (file)
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -432,6 +432,17 @@ bool blk_insert_flush(struct request *rq)
                 * Queue for normal execution.
                 */
                return false;
+       case REQ_FSEQ_DATA | REQ_FSEQ_POSTFLUSH:
+               /*
+                * Initialize the flush fields and completion handler to trigger
+                * the post flush, and then just pass the command on.
+                */
+               blk_rq_init_flush(rq);
+               rq->flush.seq |= REQ_FSEQ_POSTFLUSH;
+               spin_lock_irq(&fq->mq_flush_lock);
+               list_move_tail(&rq->flush.list, &fq->flush_data_in_flight);
+               spin_unlock_irq(&fq->mq_flush_lock);
+               return false;
        default:
                /*
                 * Mark the request as part of a flush sequence and submit it