dm table: fix DAX iterate_devices based device capability checks

Fix dm_table_supports_dax() and invert logic of both
iterate_devices_callout_fn so that all devices' DAX capabilities are
properly checked.

Fixes: 545ed20e6df6 ("dm: add infrastructure for DAX support")
Cc: [e-mail]
Signed-off-by: Jeffle Xu <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-table.c

···
 EXPORT_SYMBOL_GPL(dm_table_set_type);
 
 /* validate the dax capability of the target device span */
-int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
+int device_not_dax_capable(struct dm_target *ti, struct dm_dev *dev,
 			sector_t start, sector_t len, void *data)
 {
 	int blocksize = *(int *) data, id;
 	bool rc;
 
 	id = dax_read_lock();
-	rc = dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len);
+	rc = !dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len);
 	dax_read_unlock(id);
 
 	return rc;
 }
 
 /* Check devices support synchronous DAX */
-static int device_dax_synchronous(struct dm_target *ti, struct dm_dev *dev,
-				  sector_t start, sector_t len, void *data)
+static int device_not_dax_synchronous_capable(struct dm_target *ti, struct dm_dev *dev,
+					      sector_t start, sector_t len, void *data)
 {
-	return dev->dax_dev && dax_synchronous(dev->dax_dev);
+	return !dev->dax_dev || !dax_synchronous(dev->dax_dev);
 }
 
 bool dm_table_supports_dax(struct dm_table *t,
···
 			return false;
 
 		if (!ti->type->iterate_devices ||
-		    !ti->type->iterate_devices(ti, iterate_fn, blocksize))
+		    ti->type->iterate_devices(ti, iterate_fn, blocksize))
 			return false;
 	}
 
···
 verify_bio_based:
 		/* We must use this table as bio-based */
 		t->type = DM_TYPE_BIO_BASED;
-		if (dm_table_supports_dax(t, device_supports_dax, &page_size) ||
+		if (dm_table_supports_dax(t, device_not_dax_capable, &page_size) ||
 		    (list_empty(devices) && live_md_type == DM_TYPE_DAX_BIO_BASED)) {
 			t->type = DM_TYPE_DAX_BIO_BASED;
 		}
···
 	return false;
 }
 
-static int dm_table_supports_dax_write_cache(struct dm_table *t)
-{
-	struct dm_target *ti;
-	unsigned i;
-
-	for (i = 0; i < dm_table_get_num_targets(t); i++) {
-		ti = dm_table_get_target(t, i);
-
-		if (ti->type->iterate_devices &&
-		    ti->type->iterate_devices(ti,
-				device_dax_write_cache_enabled, NULL))
-			return true;
-	}
-
-	return false;
-}
-
 static int device_is_rotational(struct dm_target *ti, struct dm_dev *dev,
 				sector_t start, sector_t len, void *data)
 {
···
 	}
 	blk_queue_write_cache(q, wc, fua);
 
-	if (dm_table_supports_dax(t, device_supports_dax, &page_size)) {
+	if (dm_table_supports_dax(t, device_not_dax_capable, &page_size)) {
 		blk_queue_flag_set(QUEUE_FLAG_DAX, q);
-		if (dm_table_supports_dax(t, device_dax_synchronous, NULL))
+		if (dm_table_supports_dax(t, device_not_dax_synchronous_capable, NULL))
 			set_dax_synchronous(t->md->dax_dev);
 	}
 	else
 		blk_queue_flag_clear(QUEUE_FLAG_DAX, q);
 
-	if (dm_table_supports_dax_write_cache(t))
+	if (dm_table_any_dev_attr(t, device_dax_write_cache_enabled))
 		dax_write_cache(t->md->dax_dev, true);
 
 	/* Ensure that all underlying devices are non-rotational. */

drivers/md/dm.c

···
 	if (!map)
 		goto out;
 
-	ret = dm_table_supports_dax(map, device_supports_dax, &blocksize);
+	ret = dm_table_supports_dax(map, device_not_dax_capable, &blocksize);
 
 out:
 	dm_put_live_table(md, srcu_idx);

drivers/md/dm.h

···
 struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
 bool dm_table_supports_dax(struct dm_table *t, iterate_devices_callout_fn fn,
 			   int *blocksize);
-int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
+int device_not_dax_capable(struct dm_target *ti, struct dm_dev *dev,
 			   sector_t start, sector_t len, void *data);
 
 void dm_lock_md_type(struct mapped_device *md);