lightnvm: pblk: refactor metadata paths

pblk maintains two different metadata paths for smeta and emeta, which
store metadata at the start of the line and at the end of the line,
respectively. Until now, these path has been common for writing and
retrieving metadata, however, as these paths diverge, the common code
becomes less clear and unnecessary complicated.

In preparation for further changes to the metadata write path, this
patch separates the write and read paths for smeta and emeta and
removes the synchronous emeta path as it not used anymore (emeta is
scheduled asynchronously to prevent jittering due to internal I/Os).
Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-gc.c

@@ -148,7 +148,7 @@ static __le64 *get_lba_list_from_emeta(struct pblk *pblk,
 	if (!emeta_buf)
 		return NULL;
 
-	ret = pblk_line_read_emeta(pblk, line, emeta_buf);
+	ret = pblk_line_emeta_read(pblk, line, emeta_buf);
 	if (ret) {
 		pblk_err(pblk, "line %d read emeta failed (%d)\n",
 				line->id, ret);

drivers/lightnvm/pblk-recovery.c

@@ -836,7 +836,7 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 			continue;
 
 		/* Lines that cannot be read are assumed as not written here */
-		if (pblk_line_read_smeta(pblk, line))
+		if (pblk_line_smeta_read(pblk, line))
 			continue;
 
 		crc = pblk_calc_smeta_crc(pblk, smeta_buf);
@@ -906,7 +906,7 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 		line->emeta = emeta;
 		memset(line->emeta->buf, 0, lm->emeta_len[0]);
 
-		if (pblk_line_read_emeta(pblk, line, line->emeta->buf)) {
+		if (pblk_line_emeta_read(pblk, line, line->emeta->buf)) {
 			pblk_recov_l2p_from_oob(pblk, line);
 			goto next;
 		}

drivers/lightnvm/pblk.h

@@ -819,8 +819,8 @@ void pblk_gen_run_ws(struct pblk *pblk, struct pblk_line *line, void *priv,
 		     void (*work)(struct work_struct *), gfp_t gfp_mask,
 		     struct workqueue_struct *wq);
 u64 pblk_line_smeta_start(struct pblk *pblk, struct pblk_line *line);
-int pblk_line_read_smeta(struct pblk *pblk, struct pblk_line *line);
-int pblk_line_read_emeta(struct pblk *pblk, struct pblk_line *line,
+int pblk_line_smeta_read(struct pblk *pblk, struct pblk_line *line);
+int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
 			 void *emeta_buf);
 int pblk_blk_erase_async(struct pblk *pblk, struct ppa_addr erase_ppa);
 void pblk_line_put(struct kref *ref);