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    Subject[PATCH v14 02/11] Add infrastructure for copy offload in block and request layer.
    Date
    We add two new opcode REQ_OP_COPY_SRC, REQ_OP_COPY_DST.
    Since copy is a composite operation involving src and dst sectors/lba,
    each needs to be represented by a separate bio to make it compatible
    with device mapper.
    We expect caller to take a plug and send bio with source information,
    followed by bio with destination information.
    Once the src bio arrives we form a request and wait for destination
    bio. Upon arrival of destination we merge these two bio's and send
    corresponding request down to device driver.

    Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
    Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
    ---
    block/blk-core.c | 7 +++++++
    block/blk-merge.c | 41 +++++++++++++++++++++++++++++++++++++++
    block/blk.h | 16 +++++++++++++++
    block/elevator.h | 1 +
    include/linux/bio.h | 6 +-----
    include/linux/blk_types.h | 10 ++++++++++
    6 files changed, 76 insertions(+), 5 deletions(-)

    diff --git a/block/blk-core.c b/block/blk-core.c
    index 90de50082146..2bcd06686560 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -121,6 +121,8 @@ static const char *const blk_op_name[] = {
    REQ_OP_NAME(ZONE_FINISH),
    REQ_OP_NAME(ZONE_APPEND),
    REQ_OP_NAME(WRITE_ZEROES),
    + REQ_OP_NAME(COPY_SRC),
    + REQ_OP_NAME(COPY_DST),
    REQ_OP_NAME(DRV_IN),
    REQ_OP_NAME(DRV_OUT),
    };
    @@ -796,6 +798,11 @@ void submit_bio_noacct(struct bio *bio)
    if (!q->limits.max_write_zeroes_sectors)
    goto not_supported;
    break;
    + case REQ_OP_COPY_SRC:
    + case REQ_OP_COPY_DST:
    + if (!q->limits.max_copy_sectors)
    + goto not_supported;
    + break;
    default:
    break;
    }
    diff --git a/block/blk-merge.c b/block/blk-merge.c
    index 65e75efa9bd3..bcb55ba48107 100644
    --- a/block/blk-merge.c
    +++ b/block/blk-merge.c
    @@ -158,6 +158,20 @@ static struct bio *bio_split_write_zeroes(struct bio *bio,
    return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs);
    }

    +static struct bio *bio_split_copy(struct bio *bio,
    + const struct queue_limits *lim,
    + unsigned int *nsegs)
    +{
    + *nsegs = 1;
    + if (bio_sectors(bio) <= lim->max_copy_sectors)
    + return NULL;
    + /*
    + * We don't support splitting for a copy bio. End it with EIO if
    + * splitting is required and return an error pointer.
    + */
    + return ERR_PTR(-EIO);
    +}
    +
    /*
    * Return the maximum number of sectors from the start of a bio that may be
    * submitted as a single request to a block device. If enough sectors remain,
    @@ -366,6 +380,12 @@ struct bio *__bio_split_to_limits(struct bio *bio,
    case REQ_OP_WRITE_ZEROES:
    split = bio_split_write_zeroes(bio, lim, nr_segs, bs);
    break;
    + case REQ_OP_COPY_SRC:
    + case REQ_OP_COPY_DST:
    + split = bio_split_copy(bio, lim, nr_segs);
    + if (IS_ERR(split))
    + return NULL;
    + break;
    default:
    split = bio_split_rw(bio, lim, nr_segs, bs,
    get_max_io_size(bio, lim) << SECTOR_SHIFT);
    @@ -922,6 +942,9 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
    if (!rq_mergeable(rq) || !bio_mergeable(bio))
    return false;

    + if (blk_copy_offload_mergable(rq, bio))
    + return true;
    +
    if (req_op(rq) != bio_op(bio))
    return false;

    @@ -951,6 +974,8 @@ enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
    {
    if (blk_discard_mergable(rq))
    return ELEVATOR_DISCARD_MERGE;
    + else if (blk_copy_offload_mergable(rq, bio))
    + return ELEVATOR_COPY_OFFLOAD_MERGE;
    else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
    return ELEVATOR_BACK_MERGE;
    else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
    @@ -1053,6 +1078,20 @@ static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
    return BIO_MERGE_FAILED;
    }

    +static enum bio_merge_status bio_attempt_copy_offload_merge(struct request *req,
    + struct bio *bio)
    +{
    + if (req->__data_len != bio->bi_iter.bi_size)
    + return BIO_MERGE_FAILED;
    +
    + req->biotail->bi_next = bio;
    + req->biotail = bio;
    + req->nr_phys_segments++;
    + req->__data_len += bio->bi_iter.bi_size;
    +
    + return BIO_MERGE_OK;
    +}
    +
    static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
    struct request *rq,
    struct bio *bio,
    @@ -1073,6 +1112,8 @@ static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
    break;
    case ELEVATOR_DISCARD_MERGE:
    return bio_attempt_discard_merge(q, rq, bio);
    + case ELEVATOR_COPY_OFFLOAD_MERGE:
    + return bio_attempt_copy_offload_merge(rq, bio);
    default:
    return BIO_MERGE_NONE;
    }
    diff --git a/block/blk.h b/block/blk.h
    index 686712e13835..2b3eff2c488f 100644
    --- a/block/blk.h
    +++ b/block/blk.h
    @@ -155,6 +155,20 @@ static inline bool blk_discard_mergable(struct request *req)
    return false;
    }

    +/*
    + * Copy offload sends a pair of bio with REQ_OP_COPY_SRC and REQ_OP_COPY_DST
    + * operation by taking a plug.
    + * Initially SRC bio is sent which forms a request and
    + * waits for DST bio to arrive. Once DST bio arrives
    + * we merge it and send request down to driver.
    + */
    +static inline bool blk_copy_offload_mergable(struct request *req,
    + struct bio *bio)
    +{
    + return (req_op(req) == REQ_OP_COPY_SRC &&
    + bio_op(bio) == REQ_OP_COPY_DST);
    +}
    +
    static inline unsigned int blk_rq_get_max_segments(struct request *rq)
    {
    if (req_op(rq) == REQ_OP_DISCARD)
    @@ -297,6 +311,8 @@ static inline bool bio_may_exceed_limits(struct bio *bio,
    case REQ_OP_DISCARD:
    case REQ_OP_SECURE_ERASE:
    case REQ_OP_WRITE_ZEROES:
    + case REQ_OP_COPY_SRC:
    + case REQ_OP_COPY_DST:
    return true; /* non-trivial splitting decisions */
    default:
    break;
    diff --git a/block/elevator.h b/block/elevator.h
    index 7ca3d7b6ed82..eec442bbf384 100644
    --- a/block/elevator.h
    +++ b/block/elevator.h
    @@ -18,6 +18,7 @@ enum elv_merge {
    ELEVATOR_FRONT_MERGE = 1,
    ELEVATOR_BACK_MERGE = 2,
    ELEVATOR_DISCARD_MERGE = 3,
    + ELEVATOR_COPY_OFFLOAD_MERGE = 4,
    };

    struct blk_mq_alloc_data;
    diff --git a/include/linux/bio.h b/include/linux/bio.h
    index 027ff9ab5d12..9547f31882cf 100644
    --- a/include/linux/bio.h
    +++ b/include/linux/bio.h
    @@ -53,11 +53,7 @@ static inline unsigned int bio_max_segs(unsigned int nr_segs)
    */
    static inline bool bio_has_data(struct bio *bio)
    {
    - if (bio &&
    - bio->bi_iter.bi_size &&
    - bio_op(bio) != REQ_OP_DISCARD &&
    - bio_op(bio) != REQ_OP_SECURE_ERASE &&
    - bio_op(bio) != REQ_OP_WRITE_ZEROES)
    + if (bio && (bio_op(bio) == REQ_OP_READ || bio_op(bio) == REQ_OP_WRITE))
    return true;

    return false;
    diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
    index 0bad62cca3d0..de0ad7a0d571 100644
    --- a/include/linux/blk_types.h
    +++ b/include/linux/blk_types.h
    @@ -394,6 +394,10 @@ enum req_op {
    /* reset all the zone present on the device */
    REQ_OP_ZONE_RESET_ALL = (__force blk_opf_t)17,

    + /* copy offload dst and src operation */
    + REQ_OP_COPY_SRC = (__force blk_opf_t)19,
    + REQ_OP_COPY_DST = (__force blk_opf_t)21,
    +
    /* Driver private requests */
    REQ_OP_DRV_IN = (__force blk_opf_t)34,
    REQ_OP_DRV_OUT = (__force blk_opf_t)35,
    @@ -482,6 +486,12 @@ static inline bool op_is_write(blk_opf_t op)
    return !!(op & (__force blk_opf_t)1);
    }

    +static inline bool op_is_copy(blk_opf_t op)
    +{
    + return ((op & REQ_OP_MASK) == REQ_OP_COPY_SRC ||
    + (op & REQ_OP_MASK) == REQ_OP_COPY_DST);
    +}
    +
    /*
    * Check if the bio or request is one that needs special treatment in the
    * flush state machine.
    --
    2.35.1.500.gb896f729e2
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