On Sat, Apr 25, 2020 at 07:09:39PM +0200, Christoph Hellwig wrote:
> Don't bother with the on-stack bio list if we know that we directly
> issue to a request based driver that can't re-inject bios.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> block/blk-core.c | 29 +++++++++++++++++++----------
> 1 file changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 732d5b8d3cd25..e8c48203b2c55 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1008,6 +1008,18 @@ generic_make_request_checks(struct bio *bio)
> return false;
> }
>
> +static inline blk_qc_t __direct_make_request(struct bio *bio)
> +{
> + struct request_queue *q = bio->bi_disk->queue;
> + blk_qc_t ret;
> +
> + if (unlikely(bio_queue_enter(bio)))
> + return BLK_QC_T_NONE;
> + ret = blk_mq_make_request(q, bio);
> + blk_queue_exit(q);
> + return ret;
> +}
> +
> static blk_qc_t do_make_request(struct bio *bio,
> struct bio_list bio_list_on_stack[2])
> {
> @@ -1116,7 +1128,10 @@ blk_qc_t generic_make_request(struct bio *bio)
> return BLK_QC_T_NONE;
> }
>
> - return __generic_make_request(bio);
> + if (bio->bi_disk->queue->make_request_fn)
> + return __generic_make_request(bio);
> + return __direct_make_request(bio);
> +
blk_mq_make_request() still calls into generic_make_request(), so bio
may be added to current->bio_list, then looks __direct_make_request()
can't cover recursive bio submission any more.
Thanks,
Ming
