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    Subject[PATCH 16/16] block: reduce part_stat_lock() scope
    Date
    We only need the stats lock (aka preempt_disable()) for updating the
    states, not for looking up or dropping the hd_struct reference.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
    ---
    block/blk-core.c | 5 +++--
    block/blk-merge.c | 3 ++-
    2 files changed, 5 insertions(+), 3 deletions(-)

    diff --git a/block/blk-core.c b/block/blk-core.c
    index bf2f7d4bc0c1c..a01fb2b508f0e 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -1437,9 +1437,9 @@ void blk_account_io_done(struct request *req, u64 now)
    update_io_ticks(part, jiffies, true);
    part_stat_inc(part, ios[sgrp]);
    part_stat_add(part, nsecs[sgrp], now - req->start_time_ns);
    + part_stat_unlock();

    hd_struct_put(part);
    - part_stat_unlock();
    }
    }

    @@ -1448,8 +1448,9 @@ void blk_account_io_start(struct request *rq)
    if (!blk_do_io_stat(rq))
    return;

    - part_stat_lock();
    rq->part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
    +
    + part_stat_lock();
    update_io_ticks(rq->part, jiffies, false);
    part_stat_unlock();
    }
    diff --git a/block/blk-merge.c b/block/blk-merge.c
    index c3beae5c1be71..f0b0bae075a0c 100644
    --- a/block/blk-merge.c
    +++ b/block/blk-merge.c
    @@ -674,8 +674,9 @@ static void blk_account_io_merge_request(struct request *req)
    if (blk_do_io_stat(req)) {
    part_stat_lock();
    part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
    - hd_struct_put(req->part);
    part_stat_unlock();
    +
    + hd_struct_put(req->part);
    }
    }

    --
    2.26.2
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