block: optimise req_bio_endio()

First, get rid of an extra branch and chain error checks. Also reshuffle
it with bio_advance(), so it goes closer to the final check, with that
the compiler loads rq->rq_flags only once, and also doesn't reload
bio->bi_iter.bi_size if bio_advance() didn't actually advanced the iter.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 31d9e61..8b05a8f 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -633,25 +633,23 @@ void blk_mq_free_plug_rqs(struct blk_plug *plug)
 static void req_bio_endio(struct request *rq, struct bio *bio,
                          unsigned int nbytes, blk_status_t error)
 {
-       if (error)
+       if (unlikely(error)) {
                bio->bi_status = error;
-
-       if (unlikely(rq->rq_flags & RQF_QUIET))
-               bio_set_flag(bio, BIO_QUIET);
-
-       bio_advance(bio, nbytes);
-
-       if (req_op(rq) == REQ_OP_ZONE_APPEND && error == BLK_STS_OK) {
+       } else if (req_op(rq) == REQ_OP_ZONE_APPEND) {
                /*
                 * Partial zone append completions cannot be supported as the
                 * BIO fragments may end up not being written sequentially.
                 */
-               if (bio->bi_iter.bi_size)
+               if (bio->bi_iter.bi_size == nbytes)
                        bio->bi_status = BLK_STS_IOERR;
                else
                        bio->bi_iter.bi_sector = rq->__sector;
        }
 
+       bio_advance(bio, nbytes);
+
+       if (unlikely(rq->rq_flags & RQF_QUIET))
+               bio_set_flag(bio, BIO_QUIET);
        /* don't actually finish bio if it's part of flush sequence */
        if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ))
                bio_endio(bio);