lightnvm: proper error handling for pblk_bio_add_pages

Currently in case of error caused by bio_pc_add_page in
pblk_bio_add_pages two issues occur when calling from
pblk_rb_read_to_bio(). First one is in pblk_bio_free_pages, since we
are trying to free pages not allocated from our mempool. Second one
is the warn from dma_pool_free, that we are trying to free NULL
pointer dma.

This commit fix both issues.
Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@intel.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-core.c

@@ -278,7 +278,9 @@ void pblk_free_rqd(struct pblk *pblk, struct nvm_rq *rqd, int type)
 		return;
 	}
 
-	nvm_dev_dma_free(dev->parent, rqd->meta_list, rqd->dma_meta_list);
+	if (rqd->meta_list)
+		nvm_dev_dma_free(dev->parent, rqd->meta_list,
+				rqd->dma_meta_list);
 	mempool_free(rqd, pool);
 }
 
@@ -316,7 +318,7 @@ int pblk_bio_add_pages(struct pblk *pblk, struct bio *bio, gfp_t flags,
 
 	return 0;
 err:
-	pblk_bio_free_pages(pblk, bio, 0, i - 1);
+	pblk_bio_free_pages(pblk, bio, (bio->bi_vcnt - i), i);
 	return -1;
 }