dm unstripe: support non-power-of-2 chunk size

Address "FIXME: must support non power of 2 chunk_size, dm-stripe.c does".

Bump target version to indicate change.
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Tested-by: Scott Bauer <Scott.Bauer@intel.com>
Reviewed-by: Scott Bauer <Scott.Bauer@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-unstripe.c

@@ -69,12 +69,6 @@ static int unstripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto err;
 	}
 
-	// FIXME: must support non power of 2 chunk_size, dm-stripe.c does
-	if (!is_power_of_2(uc->chunk_size)) {
-		ti->error = "Non power of 2 chunk_size is not supported yet";
-		goto err;
-	}
-
 	if (kstrtouint(argv[2], 10, &uc->unstripe)) {
 		ti->error = "Invalid stripe number";
 		goto err;
@@ -98,7 +92,7 @@ static int unstripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	uc->unstripe_offset = uc->unstripe * uc->chunk_size;
 	uc->unstripe_width = (uc->stripes - 1) * uc->chunk_size;
-	uc->chunk_shift = fls(uc->chunk_size) - 1;
+	uc->chunk_shift = is_power_of_2(uc->chunk_size) ? fls(uc->chunk_size) - 1 : 0;
 
 	tmp_len = ti->len;
 	if (sector_div(tmp_len, uc->chunk_size)) {
@@ -129,14 +123,18 @@ static sector_t map_to_core(struct dm_target *ti, struct bio *bio)
 {
 	struct unstripe_c *uc = ti->private;
 	sector_t sector = bio->bi_iter.bi_sector;
+	sector_t tmp_sector = sector;
 
 	/* Shift us up to the right "row" on the stripe */
-	sector += uc->unstripe_width * (sector >> uc->chunk_shift);
+	if (uc->chunk_shift)
+		tmp_sector >>= uc->chunk_shift;
+	else
+		sector_div(tmp_sector, uc->chunk_size);
 
-	/* Account for what stripe we're operating on */
-	sector += uc->unstripe_offset;
+	sector += uc->unstripe_width * tmp_sector;
 
-	return sector;
+	/* Account for what stripe we're operating on */
+	return sector + uc->unstripe_offset;
 }
 
 static int unstripe_map(struct dm_target *ti, struct bio *bio)
@@ -185,7 +183,7 @@ static void unstripe_io_hints(struct dm_target *ti,
 
 static struct target_type unstripe_target = {
 	.name = "unstriped",
-	.version = {1, 0, 0},
+	.version = {1, 1, 0},
 	.module = THIS_MODULE,
 	.ctr = unstripe_ctr,
 	.dtr = unstripe_dtr,