dm: refactor dm_split_and_process_bio a bit

Remove needless branching and indentation. Leaves code to catch
malformed op_is_zone_mgmt bios (they shouldn't have a payload).
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

@@ -1394,7 +1394,13 @@ static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
 {
 	ci->map = map;
 	ci->io = alloc_io(md, bio);
+	ci->bio = bio;
 	ci->sector = bio->bi_iter.bi_sector;
+	ci->sector_count = bio_sectors(bio);
+
+	/* Shouldn't happen but sector_count was being set to 0 so... */
+	if (WARN_ON_ONCE(op_is_zone_mgmt(bio_op(bio)) && ci->sector_count))
+		ci->sector_count = 0;
 }
 
 /*
@@ -1404,6 +1410,7 @@ static void dm_split_and_process_bio(struct mapped_device *md,
 				     struct dm_table *map, struct bio *bio)
 {
 	struct clone_info ci;
+	struct bio *b;
 	int error = 0;
 
 	init_clone_info(&ci, md, map, bio);
@@ -1411,34 +1418,29 @@ static void dm_split_and_process_bio(struct mapped_device *md,
 	if (bio->bi_opf & REQ_PREFLUSH) {
 		error = __send_empty_flush(&ci);
 		/* dm_io_dec_pending submits any data associated with flush */
-	} else if (op_is_zone_mgmt(bio_op(bio))) {
-		ci.bio = bio;
-		ci.sector_count = 0;
-		error = __split_and_process_bio(&ci);
-	} else {
-		ci.bio = bio;
-		ci.sector_count = bio_sectors(bio);
-		error = __split_and_process_bio(&ci);
-		if (ci.sector_count && !error) {
-			/*
-			 * Remainder must be passed to submit_bio_noacct()
-			 * so that it gets handled *after* bios already submitted
-			 * have been completely processed.
-			 * We take a clone of the original to store in
-			 * ci.io->orig_bio to be used by dm_end_io_acct() and for
-			 * dm_io_dec_pending() to use for completion handling.
-			 */
-			struct bio *b = bio_split(bio, bio_sectors(bio) - ci.sector_count,
-						  GFP_NOIO, &md->queue->bio_split);
-			ci.io->orig_bio = b;
-
-			bio_chain(b, bio);
-			trace_block_split(b, bio->bi_iter.bi_sector);
-			submit_bio_noacct(bio);
-		}
+		goto out;
 	}
-	dm_start_io_acct(ci.io);
 
+	error = __split_and_process_bio(&ci);
+	if (error || !ci.sector_count)
+		goto out;
+
+	/*
+	 * Remainder must be passed to submit_bio_noacct() so it gets handled
+	 * *after* bios already submitted have been completely processed.
+	 * We take a clone of the original to store in ci.io->orig_bio to be
+	 * used by dm_end_io_acct() and for dm_io_dec_pending() to use for
+	 * completion handling.
+	 */
+	b = bio_split(bio, bio_sectors(bio) - ci.sector_count,
+		      GFP_NOIO, &md->queue->bio_split);
+	ci.io->orig_bio = b;
+
+	bio_chain(b, bio);
+	trace_block_split(b, bio->bi_iter.bi_sector);
+	submit_bio_noacct(bio);
+out:
+	dm_start_io_acct(ci.io);
 	/* drop the extra reference count */
 	dm_io_dec_pending(ci.io, errno_to_blk_status(error));
 }