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    Subject[PATCH v5 4/7] block: introduce write-hint to stream-id conversion
    Date
    This patch moves write-hint-to-stream-id conversion in block-layer.
    Earlier this was done by driver (nvme). For user write-hints, conversion
    is of the form "streamid = write-hint - 1". For kernel write-hints,
    streams are allocated in top-to-bottom fashion. This has the effect of
    mapping user-hints to lower range of stream-ids and kernel-hints to upper
    range of stream-ids.
    Conversion takes stream limit (maintained in request queue) into
    account. Write-hints beyond the exposed limit turn to 0.
    A new field 'streamid' has been added in request, while 'write-hint'
    field has been removed. For merging checks, 'bi_write_hint' (of bio) is
    used instead.

    Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
    ---
    block/blk-core.c | 29 ++++++++++++++++++++++++++++-
    block/blk-merge.c | 4 ++--
    drivers/nvme/host/core.c | 7 ++-----
    include/linux/blkdev.h | 2 +-
    4 files changed, 33 insertions(+), 9 deletions(-)

    diff --git a/block/blk-core.c b/block/blk-core.c
    index a55389b..0485c20 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -730,6 +730,33 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
    return false;
    }

    +enum rw_hint blk_write_hint_to_streamid(struct request *req,
    + struct bio *bio)
    +{
    + enum rw_hint streamid, write_hint, nr_streams;
    + struct request_queue *q = req->q;
    +
    + nr_streams = q->limits.nr_streams;
    +
    + write_hint = bio->bi_write_hint;
    +
    + if (!nr_streams || write_hint == WRITE_LIFE_NOT_SET ||
    + write_hint == WRITE_LIFE_NONE)
    + streamid = 0;
    + else if (write_hint < WRITE_LIFE_KERN_MIN) { /*user-space hints*/
    + streamid = write_hint - 1;
    + if (streamid > nr_streams)
    + streamid = 0;
    + } else { /* kernel hints */
    + streamid = write_hint - WRITE_LIFE_KERN_MIN + 1;
    + if (streamid > (nr_streams - BLK_MAX_USER_HINTS))
    + streamid = 0;
    + else
    + streamid = nr_streams - streamid + 1;
    + }
    + return streamid;
    +}
    +
    void blk_init_request_from_bio(struct request *req, struct bio *bio)
    {
    if (bio->bi_opf & REQ_RAHEAD)
    @@ -737,7 +764,7 @@ void blk_init_request_from_bio(struct request *req, struct bio *bio)

    req->__sector = bio->bi_iter.bi_sector;
    req->ioprio = bio_prio(bio);
    - req->write_hint = bio->bi_write_hint;
    + req->streamid = blk_write_hint_to_streamid(req, bio);
    blk_rq_bio_prep(req->q, req, bio);
    }
    EXPORT_SYMBOL_GPL(blk_init_request_from_bio);
    diff --git a/block/blk-merge.c b/block/blk-merge.c
    index 1c9d4f0..1435634 100644
    --- a/block/blk-merge.c
    +++ b/block/blk-merge.c
    @@ -832,7 +832,7 @@ static struct request *attempt_merge(struct request_queue *q,
    * Don't allow merge of different write hints, or for a hint with
    * non-hint IO.
    */
    - if (req->write_hint != next->write_hint)
    + if (req->bio->bi_write_hint != next->bio->bi_write_hint)
    return NULL;

    if (req->ioprio != next->ioprio)
    @@ -964,7 +964,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
    * Don't allow merge of different write hints, or for a hint with
    * non-hint IO.
    */
    - if (rq->write_hint != bio->bi_write_hint)
    + if (rq->bio->bi_write_hint != bio->bi_write_hint)
    return false;

    if (rq->ioprio != bio_prio(bio))
    diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
    index 2c43e12..f3000d9 100644
    --- a/drivers/nvme/host/core.c
    +++ b/drivers/nvme/host/core.c
    @@ -530,12 +530,9 @@ static void nvme_assign_write_stream(struct nvme_ctrl *ctrl,
    struct request *req, u16 *control,
    u32 *dsmgmt)
    {
    - enum rw_hint streamid = req->write_hint;
    + enum rw_hint streamid = req->streamid;

    - if (streamid == WRITE_LIFE_NOT_SET || streamid == WRITE_LIFE_NONE)
    - streamid = 0;
    - else {
    - streamid--;
    + if (streamid != 0) {
    if (WARN_ON_ONCE(streamid > ctrl->nr_streams))
    return;

    diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    index 5b6cb9747..9cf8a40 100644
    --- a/include/linux/blkdev.h
    +++ b/include/linux/blkdev.h
    @@ -216,7 +216,7 @@ struct request {
    unsigned short nr_integrity_segments;
    #endif

    - unsigned short write_hint;
    + unsigned short streamid;
    unsigned short ioprio;

    unsigned int extra_len; /* length of alignment and padding */
    --
    2.7.4
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