lightnvm: simplify geometry structure

Currently, the device geometry is stored redundantly in the nvm_id and
nvm_geo structures at a device level. Moreover, when instantiating
targets on a specific number of LUNs, these structures are replicated
and manually modified to fit the instance channel and LUN partitioning.

Instead, create a generic geometry around nvm_geo, which can be used by
(i) the underlying device to describe the geometry of the whole device,
and (ii) instances to describe their geometry independently.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
index 2f76128..9eee10f 100644
--- a/drivers/lightnvm/pblk-read.c
+++ b/drivers/lightnvm/pblk-read.c
@@ -563,7 +563,7 @@ int pblk_submit_read_gc(struct pblk *pblk, struct pblk_gc_rq *gc_rq)
 	if (!(gc_rq->secs_to_gc))
 		goto out;
 
-	data_len = (gc_rq->secs_to_gc) * geo->sec_size;
+	data_len = (gc_rq->secs_to_gc) * geo->csecs;
 	bio = pblk_bio_map_addr(pblk, gc_rq->data, gc_rq->secs_to_gc, data_len,
 						PBLK_VMALLOC_META, GFP_KERNEL);
 	if (IS_ERR(bio)) {