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    Subject[PATCH 1/2] blkdev: add flush generation counter
    Date
    Callers may use this counter to optimize flushes

    Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
    ---
    block/blk-core.c | 1 +
    block/blk-flush.c | 3 ++-
    include/linux/blkdev.h | 1 +
    3 files changed, 4 insertions(+), 1 deletions(-)

    diff --git a/block/blk-core.c b/block/blk-core.c
    index 074b758..afb5a4b 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -537,6 +537,7 @@ void blk_cleanup_queue(struct request_queue *q)
    spin_unlock_irq(lock);
    mutex_unlock(&q->sysfs_lock);

    + atomic_set(&q->flush_tag, 0);
    /*
    * Drain all requests queued before DYING marking. Set DEAD flag to
    * prevent that q->request_fn() gets invoked after draining finished.
    diff --git a/block/blk-flush.c b/block/blk-flush.c
    index cc2b827..b1adc75 100644
    --- a/block/blk-flush.c
    +++ b/block/blk-flush.c
    @@ -203,7 +203,7 @@ static void flush_end_io(struct request *flush_rq, int error)
    /* account completion of the flush request */
    q->flush_running_idx ^= 1;
    elv_completed_request(q, flush_rq);
    -
    + atomic_inc(&q->flush_tag);
    /* and push the waiting requests to the next stage */
    list_for_each_entry_safe(rq, n, running, flush.list) {
    unsigned int seq = blk_flush_cur_seq(rq);
    @@ -268,6 +268,7 @@ static bool blk_kick_flush(struct request_queue *q)
    q->flush_rq.end_io = flush_end_io;

    q->flush_pending_idx ^= 1;
    + atomic_inc(&q->flush_tag);
    list_add_tail(&q->flush_rq.queuelist, &q->queue_head);
    return true;
    }
    diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    index 78feda9..e079fbd 100644
    --- a/include/linux/blkdev.h
    +++ b/include/linux/blkdev.h
    @@ -416,6 +416,7 @@ struct request_queue {
    unsigned int flush_queue_delayed:1;
    unsigned int flush_pending_idx:1;
    unsigned int flush_running_idx:1;
    + atomic_t flush_tag;
    unsigned long flush_pending_since;
    struct list_head flush_queue[2];
    struct list_head flush_data_in_flight;
    --
    1.7.1


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