dax: move the dax_read_lock() locking into dax_supported

Move the dax_read_lock/dax_read_unlock pair from the callers into
dax_supported to make it a little easier to use.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/20210826135510.6293-6-hch@lst.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dax/super.c

@@ -219,7 +219,6 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
 	struct request_queue *q;
 	char buf[BDEVNAME_SIZE];
 	bool ret;
-	int id;
 
 	q = bdev_get_queue(bdev);
 	if (!q || !blk_queue_dax(q)) {
@@ -235,10 +234,8 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
 		return false;
 	}
 
-	id = dax_read_lock();
 	ret = dax_supported(dax_dev, bdev, blocksize, 0,
 			i_size_read(bdev->bd_inode) / 512);
-	dax_read_unlock(id);
 
 	put_dax(dax_dev);
 
@@ -356,13 +353,18 @@ EXPORT_SYMBOL_GPL(dax_direct_access);
 bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
 		int blocksize, sector_t start, sector_t len)
 {
-	if (!dax_dev)
-		return false;
+	bool ret = false;
+	int id;
 
-	if (!dax_alive(dax_dev))
+	if (!dax_dev)
 		return false;
 
-	return dax_dev->ops->dax_supported(dax_dev, bdev, blocksize, start, len);
+	id = dax_read_lock();
+	if (dax_alive(dax_dev))
+		ret = dax_dev->ops->dax_supported(dax_dev, bdev, blocksize,
+						  start, len);
+	dax_read_unlock(id);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(dax_supported);
 

drivers/md/dm-table.c

@@ -809,14 +809,9 @@ EXPORT_SYMBOL_GPL(dm_table_set_type);
 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;
+	int blocksize = *(int *) data;
 
-	id = dax_read_lock();
-	rc = !dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len);
-	dax_read_unlock(id);
-
-	return rc;
+	return !dax_supported(dev->dax_dev, dev->bdev, blocksize, start, len);
 }
 
 /* Check devices support synchronous DAX */