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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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