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    Subject[PATCH 12/18] dm: implement copy
    This patch implements basic copy support for device mapper core.
    Individual targets can enable copy support by setting ti->copy_supported.

    Device mapper device advertises copy support if at least one target
    supports copy and for this target, at least one underlying device supports
    copy.

    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

    ---
    drivers/md/dm-table.c | 9 +++++++++
    drivers/md/dm.c | 42 +++++++++++++++++++++++++++++++++++++++---
    include/linux/device-mapper.h | 5 +++++
    3 files changed, 53 insertions(+), 3 deletions(-)

    Index: linux-3.18-rc1/drivers/md/dm.c
    ===================================================================
    --- linux-3.18-rc1.orig/drivers/md/dm.c 2014-10-21 00:46:30.000000000 +0200
    +++ linux-3.18-rc1/drivers/md/dm.c 2014-10-21 00:49:09.000000000 +0200
    @@ -1559,6 +1559,31 @@ static int __send_write_same(struct clon
    return __send_changing_extent_only(ci, get_num_write_same_bios, NULL);
    }

    +static int __send_copy(struct clone_info *ci)
    +{
    + struct dm_target *ti;
    + sector_t bound;
    +
    + ti = dm_table_find_target(ci->map, ci->sector);
    + if (!dm_target_is_valid(ti))
    + return -EIO;
    +
    + if (!ti->copy_supported)
    + return -EOPNOTSUPP;
    +
    + bound = max_io_len(ci->sector, ti);
    +
    + if (unlikely(ci->sector_count > bound))
    + return -EOPNOTSUPP;
    +
    + __clone_and_map_simple_bio(ci, ti, 0, NULL, NULL);
    +
    + ci->sector += ci->sector_count;
    + ci->sector_count = 0;
    +
    + return 0;
    +}
    +
    /*
    * Select the correct strategy for processing a non-flush bio.
    */
    @@ -1572,6 +1597,8 @@ static int __split_and_process_non_flush
    return __send_discard(ci);
    else if (unlikely(bio->bi_rw & REQ_WRITE_SAME))
    return __send_write_same(ci);
    + else if (unlikely(bio->bi_rw & REQ_COPY))
    + return __send_copy(ci);

    ti = dm_table_find_target(ci->map, ci->sector);
    if (!dm_target_is_valid(ti))
    @@ -1656,6 +1683,11 @@ static int dm_merge_bvec(struct request_
    if (!dm_target_is_valid(ti))
    goto out;

    + if (unlikely((bvm->bi_rw & REQ_COPY) != 0)) {
    + if (!ti->copy_supported)
    + goto out_ret_max_size;
    + }
    +
    /*
    * Find maximum amount of I/O that won't need splitting
    */
    @@ -1679,17 +1711,21 @@ static int dm_merge_bvec(struct request_
    * entries. So always set max_size to 0, and the code below allows
    * just one page.
    */
    - else if (queue_max_hw_sectors(q) <= PAGE_SIZE >> 9)
    + else if (likely(!(bvm->bi_rw & REQ_COPY)) &&
    + queue_max_hw_sectors(q) <= PAGE_SIZE >> 9)
    max_size = 0;

    out:
    - dm_put_live_table_fast(md);
    /*
    * Always allow an entire first page
    */
    - if (max_size <= biovec->bv_len && !(bvm->bi_size >> SECTOR_SHIFT))
    + if (likely(!(bvm->bi_rw & REQ_COPY)) &&
    + max_size <= biovec->bv_len && !(bvm->bi_size >> SECTOR_SHIFT))
    max_size = biovec->bv_len;

    +out_ret_max_size:
    + dm_put_live_table_fast(md);
    +
    return max_size;
    }

    Index: linux-3.18-rc1/include/linux/device-mapper.h
    ===================================================================
    --- linux-3.18-rc1.orig/include/linux/device-mapper.h 2014-10-21 00:42:40.000000000 +0200
    +++ linux-3.18-rc1/include/linux/device-mapper.h 2014-10-21 00:49:09.000000000 +0200
    @@ -251,6 +251,11 @@ struct dm_target {
    * Set if this target does not return zeroes on discarded blocks.
    */
    bool discard_zeroes_data_unsupported:1;
    +
    + /*
    + * Set if the target supports XCOPY.
    + */
    + bool copy_supported:1;
    };

    /* Each target can link one of these into the table */
    Index: linux-3.18-rc1/drivers/md/dm-table.c
    ===================================================================
    --- linux-3.18-rc1.orig/drivers/md/dm-table.c 2014-10-21 00:34:45.000000000 +0200
    +++ linux-3.18-rc1/drivers/md/dm-table.c 2014-10-21 00:49:09.000000000 +0200
    @@ -443,6 +443,11 @@ static int dm_set_device_limits(struct d
    q->limits.alignment_offset,
    (unsigned long long) start << SECTOR_SHIFT);

    + if (ti->copy_supported)
    + limits->max_copy_sectors =
    + min_not_zero(limits->max_copy_sectors,
    + bdev_get_queue(bdev)->limits.max_copy_sectors);
    +
    /*
    * Check if merge fn is supported.
    * If not we'll force DM to use PAGE_SIZE or
    @@ -1264,6 +1269,10 @@ combine_limits:
    dm_device_name(table->md),
    (unsigned long long) ti->begin,
    (unsigned long long) ti->len);
    +
    + limits->max_copy_sectors =
    + min_not_zero(limits->max_copy_sectors,
    + ti_limits.max_copy_sectors);
    }

    return validate_hardware_logical_block_alignment(table, limits);


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