lightnvm: pblk: use vmalloc for GC data buffer

For now, we allocate a per I/O buffer for GC data. Since the potential
size of the buffer is 256KB and GC is not in the fast path, do this
allocation with vmalloc. This puts lets pressure on the memory
allocator at no performance cost.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index a654b34..74b8d9d 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -425,16 +425,15 @@
 
 struct bio *pblk_bio_map_addr(struct pblk *pblk, void *data,
 			      unsigned int nr_secs, unsigned int len,
-			      gfp_t gfp_mask)
+			      int alloc_type, gfp_t gfp_mask)
 {
 	struct nvm_tgt_dev *dev = pblk->dev;
-	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 	void *kaddr = data;
 	struct page *page;
 	struct bio *bio;
 	int i, ret;
 
-	if (l_mg->emeta_alloc_type == PBLK_KMALLOC_META)
+	if (alloc_type == PBLK_KMALLOC_META)
 		return bio_map_kern(dev->q, kaddr, len, gfp_mask);
 
 	bio = bio_kmalloc(gfp_mask, nr_secs);
@@ -552,6 +551,7 @@
 {
 	struct nvm_tgt_dev *dev = pblk->dev;
 	struct nvm_geo *geo = &dev->geo;
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 	struct pblk_line_meta *lm = &pblk->lm;
 	void *ppa_list, *meta_list;
 	struct bio *bio;
@@ -589,7 +589,8 @@
 	rq_ppas = pblk_calc_secs(pblk, left_ppas, 0);
 	rq_len = rq_ppas * geo->sec_size;
 
-	bio = pblk_bio_map_addr(pblk, emeta_buf, rq_ppas, rq_len, GFP_KERNEL);
+	bio = pblk_bio_map_addr(pblk, emeta_buf, rq_ppas, rq_len,
+					l_mg->emeta_alloc_type, GFP_KERNEL);
 	if (IS_ERR(bio)) {
 		ret = PTR_ERR(bio);
 		goto free_rqd_dma;