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    Subject[PATCH 1/2] Allow delaying initialization of queue after allocation
    Date
    Export a way to delay initializing a request_queue after allocating it. This
    is needed by device-mapper devices, as they create the queue on device
    creation time, but they decide whether it would use the elevator and requests
    only after first successful table load. Only request-based dm-devices use the
    elevator and requests. Without this either one needs to initialize and free
    the mempool and elevator, if it was a bio-based dm-device or leave it
    allocated, as it is currently done.

    Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>

    ---

    diff --git a/block/blk-core.c b/block/blk-core.c
    index 4b45435..5db0772 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -495,6 +495,8 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
    if (!q)
    return NULL;

    + q->node = node_id;
    +
    q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
    q->backing_dev_info.unplug_io_data = q;
    q->backing_dev_info.ra_pages =
    @@ -569,12 +571,25 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
    if (!q)
    return NULL;

    - q->node = node_id;
    - if (blk_init_free_list(q)) {
    + if (blk_init_allocated_queue(q, rfn, lock)) {
    + blk_put_queue(q);
    kmem_cache_free(blk_requestq_cachep, q);
    return NULL;
    }

    + return q;
    +}
    +EXPORT_SYMBOL(blk_init_queue_node);
    +
    +int blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
    + spinlock_t *lock)
    +{
    + int err = 0;
    +
    + err = blk_init_free_list(q);
    + if (err)
    + goto out;
    +
    /*
    * if caller didn't supply a lock, they get per-queue locking with
    * our embedded lock
    @@ -598,15 +613,20 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
    /*
    * all done
    */
    - if (!elevator_init(q, NULL)) {
    - blk_queue_congestion_threshold(q);
    - return q;
    - }
    + err = elevator_init(q, NULL);
    + if (err)
    + goto free_and_out;

    - blk_put_queue(q);
    - return NULL;
    + blk_queue_congestion_threshold(q);
    +
    + return 0;
    +
    +free_and_out:
    + mempool_destroy(q->rq.rq_pool);
    +out:
    + return err;
    }
    -EXPORT_SYMBOL(blk_init_queue_node);
    +EXPORT_SYMBOL(blk_init_allocated_queue);

    int blk_get_queue(struct request_queue *q)
    {
    diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    index e7cb5db..9552961 100644
    --- a/include/linux/blkdev.h
    +++ b/include/linux/blkdev.h
    @@ -901,6 +901,8 @@ extern void blk_abort_queue(struct request_queue *);
    extern struct request_queue *blk_init_queue_node(request_fn_proc *rfn,
    spinlock_t *lock, int node_id);
    extern struct request_queue *blk_init_queue(request_fn_proc *, spinlock_t *);
    +extern int blk_init_allocated_queue(struct request_queue *q,
    + request_fn_proc *rfn, spinlock_t *lock);
    extern void blk_cleanup_queue(struct request_queue *);
    extern void blk_queue_make_request(struct request_queue *, make_request_fn *);
    extern void blk_queue_bounce_limit(struct request_queue *, u64);


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